send invitation(s) form is ready

18 files changed, 3 insertions, 4435 deletions

diff --git a/public/assets/css/admin.css b/public/assets/css/admin.css
deleted file mode 100644
index 58fcc45..0000000
--- a/public/assets/css/admin.css
+++ /dev/null
@@ -1,124 +0,0 @@
-:root {
-   --class-btn-blue: #337ab7;
-   --class-btn-cyan: #5bc0de;
-   --class-btn-grey: #c9c9c9;
-   --class-btn-grey-light: #c9c9c999;
-}
-
-.office .manage {
-    width: 100%;
-    max-width: 1600px;
-    margin: 0 auto 2em;
-}
-.office .manage.maximized { max-width: 1960px; }
-.office .manage.minimized { max-width: 960px; }
-.office .manage.edit-post { max-width: 1420px; }
-
-.office .edit-post textarea[name=intro] { height: 12vh; }
-.office .edit-post textarea[name=body] {
-   height: calc(100vh - 492px);
-   min-height:320px;
-   font-family: Consolas, 'Ubuntu Mono','Courier New', Courier, monospace;
-   color: #333;
-}
-
-.office .edit-post .post-media button.over-bar { margin: -26px 0 0 0; }
-.office .edit-post .post-media ul {
-   border: 1px solid #ccc;
-   border-radius: 4px;
-   padding: 6px;
-}
-
-.office .edit-post .post-media ul li {
-   border-bottom: 1px solid #ddd;
-   list-style-type: none;
-   padding: 3px 6px;
-
-   display: flex;
-   justify-content: space-between;
-   align-items: center;
-}
-.office .edit-post .post-media ul li:last-child { border-bottom: none ;}
-.office .edit-post .post-media ul li:hover { background: #eee; }
-
-.office .manage h2 {
-   font-size: 20px;
-   color: #445;
-   margin: 20px 0;
-}
-
-.office .manage.edit-post textarea { width: 100% !important;}
-.office .manage.edit-post .select2-selection { min-height: 34px; }
-
-.office .manage.edit-post select#status.published {
-   background-color: #5cb85c;
-   border-color: #4cae4c;
-   color: #fff;
-   text-align: center;
-}
-.office .manage.edit-post select#status option {
-   background: #fff;
-   color: #333;
-}
-
-/* --- optional fields: defaut=hide --- */
-
-.office .edit-post .optional label {
-   margin-bottom: 1em;
-   padding-bottom: .5em;
-   border-bottom: 1px solid var(--class-btn-grey-light)
-}
-.office .edit-post .optional label.show {
-   margin-bottom: unset;
-   border: none;
-}
-
-
-.office .edit-post .optional label:hover {
-   cursor: pointer;
-   color: var(--class-btn-blue);
-}
-.office .edit-post .optional label::after { float: right; content: "+"; }
-.office .edit-post .optional label.show::after { content: "–"; }
-.office .edit-post .optional label + div { display: none; }
-.office .edit-post .optional label.show + div { display: block; }
-
-
-.alert.alert-info.title-bar { min-height: 52px; margin-top: 20px; }
-.alert.alert-info.title-bar button { margin-left: 8px; }
-
-.office .title-bar {
-   display: flex;
-   justify-content: space-between;
-   align-items: center;
-   padding: 8px 8px 8px 16px;
-}
-
-.office .action-btn button { float: right; }
-
-.office .top-bar { padding: 4px 0; }
-
-.office .top-bar .breadcrumb .btn {
-   margin-left: 0;
-   margin-right: 8px;
-   border-radius: 3px;
-   color: var(--class-btn-blue);
-}
-
-.office .top-bar .btn:hover {
-   background-color: var(--class-btn-grey-light);
-}
-.office .top-bar .btn.selected {
-   color: #fff;
-   background-color: var(--class-btn-blue);
-}
-
-
-/* --- dataTables --- */
-
-.office .manage .dataTable tbody tr:hover { background: #f8f8f8; }
-.office .manage .dataTable .dt-actions { width: 48px; text-align: right }
-
-/* --- unpublished posts -- */
-.office .manage .dataTable .fa-eye-slash { color: #999; }
-
diff --git a/public/assets/css/class.css b/public/assets/css/class.css
index d1e7715..6e44227 100644
--- a/public/assets/css/class.css
+++ b/public/assets/css/class.css
@@ -201,4 +201,6 @@ html, body {
 }
 .image-credits a:hover { color: var(--img-credit-hover-color); }
 
-.manage .table tbody tr:hover { background: #eeea; }
\ No newline at end of file
+.manage .table tbody tr:hover { background: #eeea; }
+
+.select2-results__option--selected { display: none; }
\ No newline at end of file
diff --git a/public/assets/css/main.css b/public/assets/css/main.css
deleted file mode 100644
index 016e0ab..0000000
--- a/public/assets/css/main.css
+++ /dev/null
@@ -1,9 +0,0 @@
-:root {
-
-  --wrapperXXS: 816px;
-  --wrapperXS: 984px;
-  --wrapperS: 1142px;
-  --wrapper: 1240px;
-  --wrapperL: 1514px;
-  --wrapperFull: 1920px;
-}
\ No newline at end of file
diff --git a/public/assets/css/normalize.css b/public/assets/css/normalize.css
deleted file mode 100644
index 192eb9c..0000000
--- a/public/assets/css/normalize.css
+++ /dev/null
@@ -1,349 +0,0 @@
-/*! normalize.css v8.0.1 | MIT License | github.com/necolas/normalize.css */
-
-/* Document
-   ========================================================================== */
-
-/**
- * 1. Correct the line height in all browsers.
- * 2. Prevent adjustments of font size after orientation changes in iOS.
- */
-
-html {
-  line-height: 1.15; /* 1 */
-  -webkit-text-size-adjust: 100%; /* 2 */
-}
-
-/* Sections
-   ========================================================================== */
-
-/**
- * Remove the margin in all browsers.
- */
-
-body {
-  margin: 0;
-}
-
-/**
- * Render the `main` element consistently in IE.
- */
-
-main {
-  display: block;
-}
-
-/**
- * Correct the font size and margin on `h1` elements within `section` and
- * `article` contexts in Chrome, Firefox, and Safari.
- */
-
-h1 {
-  font-size: 2em;
-  margin: 0.67em 0;
-}
-
-/* Grouping content
-   ========================================================================== */
-
-/**
- * 1. Add the correct box sizing in Firefox.
- * 2. Show the overflow in Edge and IE.
- */
-
-hr {
-  box-sizing: content-box; /* 1 */
-  height: 0; /* 1 */
-  overflow: visible; /* 2 */
-}
-
-/**
- * 1. Correct the inheritance and scaling of font size in all browsers.
- * 2. Correct the odd `em` font sizing in all browsers.
- */
-
-pre {
-  font-family: monospace, monospace; /* 1 */
-  font-size: 1em; /* 2 */
-}
-
-/* Text-level semantics
-   ========================================================================== */
-
-/**
- * Remove the gray background on active links in IE 10.
- */
-
-a {
-  background-color: transparent;
-}
-
-/**
- * 1. Remove the bottom border in Chrome 57-
- * 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
- */
-
-abbr[title] {
-  border-bottom: none; /* 1 */
-  text-decoration: underline; /* 2 */
-  text-decoration: underline dotted; /* 2 */
-}
-
-/**
- * Add the correct font weight in Chrome, Edge, and Safari.
- */
-
-b,
-strong {
-  font-weight: bolder;
-}
-
-/**
- * 1. Correct the inheritance and scaling of font size in all browsers.
- * 2. Correct the odd `em` font sizing in all browsers.
- */
-
-code,
-kbd,
-samp {
-  font-family: monospace, monospace; /* 1 */
-  font-size: 1em; /* 2 */
-}
-
-/**
- * Add the correct font size in all browsers.
- */
-
-small {
-  font-size: 80%;
-}
-
-/**
- * Prevent `sub` and `sup` elements from affecting the line height in
- * all browsers.
- */
-
-sub,
-sup {
-  font-size: 75%;
-  line-height: 0;
-  position: relative;
-  vertical-align: baseline;
-}
-
-sub {
-  bottom: -0.25em;
-}
-
-sup {
-  top: -0.5em;
-}
-
-/* Embedded content
-   ========================================================================== */
-
-/**
- * Remove the border on images inside links in IE 10.
- */
-
-img {
-  border-style: none;
-}
-
-/* Forms
-   ========================================================================== */
-
-/**
- * 1. Change the font styles in all browsers.
- * 2. Remove the margin in Firefox and Safari.
- */
-
-button,
-input,
-optgroup,
-select,
-textarea {
-  font-family: inherit; /* 1 */
-  font-size: 100%; /* 1 */
-  line-height: 1.15; /* 1 */
-  margin: 0; /* 2 */
-}
-
-/**
- * Show the overflow in IE.
- * 1. Show the overflow in Edge.
- */
-
-button,
-input { /* 1 */
-  overflow: visible;
-}
-
-/**
- * Remove the inheritance of text transform in Edge, Firefox, and IE.
- * 1. Remove the inheritance of text transform in Firefox.
- */
-
-button,
-select { /* 1 */
-  text-transform: none;
-}
-
-/**
- * Correct the inability to style clickable types in iOS and Safari.
- */
-
-button,
-[type="button"],
-[type="reset"],
-[type="submit"] {
-  -webkit-appearance: button;
-}
-
-/**
- * Remove the inner border and padding in Firefox.
- */
-
-button::-moz-focus-inner,
-[type="button"]::-moz-focus-inner,
-[type="reset"]::-moz-focus-inner,
-[type="submit"]::-moz-focus-inner {
-  border-style: none;
-  padding: 0;
-}
-
-/**
- * Restore the focus styles unset by the previous rule.
- */
-
-button:-moz-focusring,
-[type="button"]:-moz-focusring,
-[type="reset"]:-moz-focusring,
-[type="submit"]:-moz-focusring {
-  outline: 1px dotted ButtonText;
-}
-
-/**
- * Correct the padding in Firefox.
- */
-
-fieldset {
-  padding: 0.35em 0.75em 0.625em;
-}
-
-/**
- * 1. Correct the text wrapping in Edge and IE.
- * 2. Correct the color inheritance from `fieldset` elements in IE.
- * 3. Remove the padding so developers are not caught out when they zero out
- *    `fieldset` elements in all browsers.
- */
-
-legend {
-  box-sizing: border-box; /* 1 */
-  color: inherit; /* 2 */
-  display: table; /* 1 */
-  max-width: 100%; /* 1 */
-  padding: 0; /* 3 */
-  white-space: normal; /* 1 */
-}
-
-/**
- * Add the correct vertical alignment in Chrome, Firefox, and Opera.
- */
-
-progress {
-  vertical-align: baseline;
-}
-
-/**
- * Remove the default vertical scrollbar in IE 10+.
- */
-
-textarea {
-  overflow: auto;
-}
-
-/**
- * 1. Add the correct box sizing in IE 10.
- * 2. Remove the padding in IE 10.
- */
-
-[type="checkbox"],
-[type="radio"] {
-  box-sizing: border-box; /* 1 */
-  padding: 0; /* 2 */
-}
-
-/**
- * Correct the cursor style of increment and decrement buttons in Chrome.
- */
-
-[type="number"]::-webkit-inner-spin-button,
-[type="number"]::-webkit-outer-spin-button {
-  height: auto;
-}
-
-/**
- * 1. Correct the odd appearance in Chrome and Safari.
- * 2. Correct the outline style in Safari.
- */
-
-[type="search"] {
-  -webkit-appearance: textfield; /* 1 */
-  outline-offset: -2px; /* 2 */
-}
-
-/**
- * Remove the inner padding in Chrome and Safari on macOS.
- */
-
-[type="search"]::-webkit-search-decoration {
-  -webkit-appearance: none;
-}
-
-/**
- * 1. Correct the inability to style clickable types in iOS and Safari.
- * 2. Change font properties to `inherit` in Safari.
- */
-
-::-webkit-file-upload-button {
-  -webkit-appearance: button; /* 1 */
-  font: inherit; /* 2 */
-}
-
-/* Interactive
-   ========================================================================== */
-
-/*
- * Add the correct display in Edge, IE 10+, and Firefox.
- */
-
-details {
-  display: block;
-}
-
-/*
- * Add the correct display in all browsers.
- */
-
-summary {
-  display: list-item;
-}
-
-/* Misc
-   ========================================================================== */
-
-/**
- * Add the correct display in IE 10+.
- */
-
-template {
-  display: none;
-}
-
-/**
- * Add the correct display in IE 10.
- */
-
-[hidden] {
-  display: none;
-}
diff --git a/public/assets/js/admin/categories.js b/public/assets/js/admin/categories.js
deleted file mode 100644
index e4d2955..0000000
--- a/public/assets/js/admin/categories.js
+++ /dev/null
@@ -1,288 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var categories = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function category_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-// return children of parent
-// --- -- -- - - -
-function childs_of_parents(list) {
-    // if 'list' is integer then make it an one-item list
-    parents = (Number.isInteger(list)) ? [ list ] : list;
-
-    var childs = [];
-
-    if (parents.length == 0) { return []; }
-
-    parents.forEach( pid => {
-        categories.forEach( el => { if (el.parent == pid) childs.push(el.id)});
-    });
-
-    var grandchilds = childs_of_parents(childs);
-
-    return childs.concat(grandchilds);
-}
-
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var del, edit;
-
-    del = "";
-
-    edit = [
-        '<button type="button" class="btn btn-sm btn-warning"',
-            'data-bs-toggle="modal" data-bs-target="#manageCategory"',
-            'data-id="'+ id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    return edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    
-    /** init selec2 element (used to specify parent-category)
-     * --- -- -- - - -
-     */
-    $("#parent_id").select2({
-        placeholder: 'Γονική Κατηγορία',
-        dropdownParent: $('#manageCategory'),
-        width: '100%',
-        // dropdownParent: "#manageCategory"   // ref: https://github.com/select2/select2-bootstrap-theme/issues/41
-    });
-
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/admin/api/categories")
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            categories.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                categories.push({
-                    id: parseInt(el.rec.id),
-                    label: el.rec.label,
-                    breadcrumb: el.breadcrumb.replaceAll('\t', ' / '),
-                    parent: parseInt(el.rec.parent),
-                    actions: create_actions_html(el.rec.id)
-                });
-            });
-
-            // sort by breadcrumb
-            categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-categories').dataTable().fnClearTable();
-            $('#dt-categories').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-categories').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: categories,
-                ordering: false,
-                columns: [
-                    { data: 'breadcrumb' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-    init_table();   // init table on first run
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#manageCategory').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-        // ---
-        $('#manageCategory .modal-title').html(             // modal title
-            (id) ? 'Ενημέρωση Κατηγορίας' : 'Δημιουργία Κατηγορίας'
-        );
-        $('#manageCategory form input[name=id]').val( id );     // category id (hidden)
-        $('#manageCategory form input[name=label]').val(    // category label
-            (id) ? category_record(id).label : ""
-        );
-        prepare_parents_element(id);        // prepare <select> for parents
-    })
-
-    /** prepare_parents_element()
-     * ---
-     * @param id (int) : id of selected category
-     * -> Get all posible parents
-     * -> call set_parent_options() to render the options
-     */
-    function prepare_parents_element(id) {
-        var parents = [];
-
-        if (id) {   // get all possible parents
-
-            // id-category and subcategories are fobiden parents
-            var forbiden = childs_of_parents(id);
-            forbiden.push(id);
-
-            // filter catogories adn prepare parents
-            categories.forEach( el => {
-                if (!forbiden.includes(el.id))  {
-                    parents.push({
-                        id: el.id,
-                        breadcrumb: el.breadcrumb,
-                    });
-                }
-            });
-            set_parent_options(parents, category_record(id).parent);
-
-
-        } else {    // new record; all categories are possible parrents
-            categories.forEach( el => {
-                parents.push({
-                    id: el.id,
-                    breadcrumb: el.breadcrumb,
-                });
-            })
-            set_parent_options(parents, -1);
-        }
-    }
-
-    /** set_parent_options()
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-    function set_parent_options(parents, selected) {
-        // sort parents by breadcrumb
-        parents.sort( compare_breadcrumb );
-
-        // remove any olded options from select2
-        $('#parent_id option').each(function() { $(this).remove(); });
-
-        // first option is the root category
-        $('#parent_id').append('<option value="0">Root</option>')
-
-        // add all other parent options
-        parents.forEach( i => {
-            $('#parent_id').append(`<option value="${i.id}">${i.breadcrumb}</option>`);
-        });
-
-        if (selected == -1) {   // new category; remove any parent pre-selection
-            $('#parent_id').val(null).trigger('change');
-
-        } else {    // category exists; choose selected parent
-            $('#parent_id').val(selected).trigger('change');
-        }
-    }
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            label: $('#manageCategory form input[name=label]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/admin/api/categories/' + ((data.id == 0)  ? 'add' : 'update');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/admin/edit_lesson.js b/public/assets/js/admin/edit_lesson.js
deleted file mode 100644
index 367c3b7..0000000
--- a/public/assets/js/admin/edit_lesson.js
+++ /dev/null
@@ -1,600 +0,0 @@
-/** NOTE:
- * depricated code for tag-system is commented-out and kept in the source-code
- * as case-study; the code is operational;
- */
-
-
-// Globals
-// -----------------------------------------------------------------------------
-
-// NOTE:
-// Variable `entity_id` is defined before evaluating this script
-// id (int) : the id of edited post (or 0 if new post)
-
-var lesson;
-
-var id = (entity_id == 0) ? false : entity_id;
-
-var categories = [
-    // Nope! root can not be a post's category ... { id: 0 , label: 'Ρίζα (root)' }
-];
-
-var privileges = [
-    { id: 0, label: '_Δημόσιο_'}
-];
-
-var files = [];     // array of { id:.., title:.., type:.., path:.. } records
-
-// TODO: support tags
-// var tags = [];      // array of integers
-
-
-// an alternative--id when a lesson_id not exists (needed for file-upload)
-// ... consist of a 6-digit date string + random number up to 999
-const yymmdd = new Date().toISOString().slice(2, 10).replaceAll('-','');
-var rnd999 = Math.floor(Math.random() * 1000);
-var altID = (id == 0) ? ( yymmdd +'-'+ rnd999.toString() ) : id;
-
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-// return course record by course-id
-// --- -- -- - - -
-function course_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-
-
-// Modal HTML Creators
-// -----------------------------------------------------------------------------
-
-const modal_header = (title) => {
-    return [
-        '<div class="modal-header">',
-            '<h4 class="modal-title" id="myModalLabel">',
-                title,
-            '</h4>',
-            '<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close">',
-                '<span aria-hidden="true"></span>',
-            '</button>',
-        '</div>'
-    ].join('\n');
-}
-
-
-const upload_file_form = () => {
-    return [
-        '<form method="POST" id="file_upload_form" name="upload_file_form">',
-
-            '<div class="modal-body">',
-
-                '<input type="hidden" name="folder" value="'+ altID +'">',
-
-                '<div class="form-group">',
-                    '<label for="title">Τίτλος/Περιγραφή για το Αρχείο</label>',
-                    '<input type="text" class="form-control " value="" name="title" id="title" placeholder="Τίτλος για το Αρχείο" required="">',
-                '</div>',
-
-                '<div class="form-group">',
-                    '<label class="control-label" for="file">Εισαγωγή Αρχείου</label>',
-                    '<input class="form-control" type="file" id="file" name="file" required="">',
-                '</div>',
-
-            '</div>',
-
-            '<div class="modal-footer">',
-                '<div class="row" style="width: 50%;">',
-                    '<div class="form-actions">',
-                        '<div class="col col-4">',
-                            '<buton type="button" class="btn btn-default js-modal-close col-12" data-bs-dismiss="modal">',
-                                'Κλείσιμο',
-                            '</button>',
-                        '</div>',
-                        '<div class="col-8">',
-                            '<button class="btn btn-success col-12" type="submit">Καταχώριση</button>',
-                        '</div>',
-                    '</div>',
-                '</div>',
-            '</div>',
-
-        '</form>'
-    ].join('\n');
-}
-
-
-const preview_article = (title, intro, body) => {
-    return [
-        '<div class="modal-body">',
-            '<div class="post">',
-
-                '<h2>'+ title +'</h2>',
-
-                ((intro == '') ? '' : ('<div class="intro">'+ intro +'</div>')),
-
-                '<div class="article-body">',
-                    marked.parse(body, { sanitize: true }),
-                '</div>',
-             
-            '</div>',
-        '</div>',
-        '<div class="modal-footer">',
-            '<div class="row" style="width: 50%;">',
-                '<div class="form-actions">',
-                    '<div class="col-md-4 col-md-offset-4 col-6 col-offset-3">',
-                        '<buton type="button" class="btn btn-default js-modal-close col-12" data-bs-dismiss="modal">',
-                            'Κλείσιμο',
-                        '</button>',
-                    '</div>',
-                '</div>',
-            '</div>',
-        '</div>'
-    ].join('\n');
-}
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-
-    // inti category (select2)
-    // ...
-    $("#course_id").select2({
-        placeholder: 'Κεφάλαιο',
-        width: '100%'
-    });
-
-    // inti category (select2)
-    // ...
-    $("#privilege_id").select2({
-        placeholder: 'Επίπεδο Πρόσβασης',
-        width: '100%'
-    });
-
-
-    /** DEPRICATED: (tag system)
-     * 
-     * // init tags (select2)
-     * // ...
-     * $('#tags').select2({
-     *     placeholder: 'Ετικέτες (tags/keywords)',
-     *     width: '100%',
-     *     tags: true
-     * });
-     */
-
-    /**  DEPRICATED:
-     * 
-     * // TINY-MCE EDITOR
-     * init editor (tiny MCE)
-     * tinymce.init({
-     *     selector: 'form textarea[name=body]',
-     *     language: 'el',
-     *     menubar: true
-     * });
-     */
-
-
-    /** preload content
-     * --- -- -- - - -
-     * get post
-     * get categories
-     * get tags
-     * update content (form-elements)
-     */
-    if (id) {   // if an `id` is given, load post .. then init_form
-
-        $.getJSON( "/admin/api/lesson/" + id )
-        .done( function (data) {
-            lesson = data;            // keep post
-
-            // update fields' values
-            $('input[name=id]').val(lesson.id);           // id
-            $('input[name=title]').val(lesson.title);     // title
-            $('textarea[name=intro]').val(lesson.intro);  // intro
-            $('textarea[name=body]').val(lesson.body);    // body
-            $('select[name=status]').val(
-                (lesson.status == 0) ? '0' : "one"
-                ).trigger('change');
-            // $('input[name=status]').prop(               // status
-            //     'checked',
-            //     ((lesson.status==1)? true : false))
-            // .trigger('change');
-
-            // $('#post-info').html('Δημιουργία: '+post.creation_date+'<br>Τελευταία Ενημέρωση: '+ post.update_date);
-
-            // parse media files; then draw
-            if (lesson.medias_json != null) {
-                files = JSON.parse(lesson.medias_json);
-            }
-            draw_files_list();      // then draw the files list
-            
-            init_form_values();     // init all (other) values
-        });
-
-    } else {    // else ... just init_form
-        init_form_values();
-    }
-
-
-
-    /**
-     * load categories and tags;
-     * if not a new post (id!=0) update form elemnts with post's values
-     */
-    function init_form_values() {
-
-        $.when(     // when loaded posts and categories
-
-            $.getJSON( "/admin/api/categories" ),
-
-            $.getJSON( "/admin/api/privileges" )
-
-        ).done( function( categories_response, privileges_response ) {
-
-            // construct categories data
-            // ---
-            Object.keys(categories_response[0]).forEach( key => {
-                cat = categories_response[0][key];
-                categories.push({
-                    id: cat.rec.id,
-                    label: cat.breadcrumb.replaceAll('\t', ' / ')
-                });
-            });
-            categories.sort( compare_label );  // sort categories by breadcrumb
-
-            /** DEPRICATED: (tag system)
-             * 
-             * // construct tags data
-             * // ---
-             * Object.keys(tags_response[0]).forEach( key => {
-             *     tag = tags_response[0][key];
-             *     tags.push({
-             *         id: tag.id,
-             *         label: tag.name
-             *     });
-             * });
-             */
-
-            // construct provileges data
-            // ---
-            Object.keys(privileges_response[0]).forEach( key => {
-                priv = privileges_response[0][key];
-                privileges.push({
-                    id: priv.id,
-                    label: priv.label
-                });
-            });
-            privileges.sort( compare_label );  // sort categories by breadcrumb
-
-            // pass categories and tags options onto select2 elements
-            // --- -- -- - - -
-            if (id == 0) {
-                set_parent_options( $('#course_id'), categories );
-                set_parent_options( $('#privilege_id'), privileges );
-
-            } else {
-                // setup category_id options; select post's chosen category-id
-                set_parent_options( $('#course_id'), categories, lesson.course_id );
-
-                /*** DEPRICATED: (tag system)
-                 * 
-                 * // parse selected tags
-                 * // ---
-                 * var selected_tag_ids = [];
-                 * if (post.tags_json != null) {
-                 *     var selected_tags = JSON.parse(post.tags_json);
-                 *     selected_tags.forEach( itag => { selected_tag_ids.push(itag.id); })
-                 * }
-                 */
-
-                // setup tags options; select post's chosen tags
-                set_parent_options( $('#privilege_id'), privileges, lesson.privilege_id );
-
-                // DEPRICATED: ALSO: if tags selectd, show tags field
-                // if (selected_tag_ids.length != 0) { $('.optional label[for=tags]').addClass('show'); }
-            }
-
-        });
-
-    }
-
-
-    /** set_parent_options()
-     * 
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * 
-     * NOTE:
-     * the targer <select> should be a select2 control
-     * 
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-    function set_parent_options(selector, list, selected_value = false) {
-
-        list.forEach( li => {   // attach options into <select> control
-            selector.append(`<option value="${li.id}">${li.label}</option>`);
-        });
-
-        if (selected_value !== false) {     // mark selected option(s)
-            selector.val(selected_value).trigger('change');
-        }
-        else { selector.val(null).trigger('change'); }
-    }
-
-
-    /** draw_files_list
-     * --- -- -- - - -
-     */
-    function draw_files_list() {
-        var li_list = [];
-        var ref_icon, ref_class;
-
-        files.forEach( item => {
-            var copy = [    // copy button
-                '<button type="button" class="btn btn-xs btn-default js-copy"',
-                    ' data-url="' + item.path +'"',
-                    ' data-type="' + item.type + '"',
-                    '>',
-                    '<i class="far fa-clone"></i>',
-                '</button>'
-            ].join('');
-
-            var del = [    // delete button
-                '<button type="button" class="btn btn-xs btn-danger js-delete"',
-                    'data-id="' + item.id + '">',
-                    '<i class="fas fa-trash-alt"></i>',
-                '</button>'
-            ].join('');
-            var option = [  // li html
-                '<li>',
-                    '<div class="text">' + item.label + '</div>',
-                    '<div class="actions">',
-                        copy, ' ',  del,
-                    '</div>',
-                '</li>'
-            ].join('');
-            li_list.push(option);   // push to li_list
-        });
-        $('#files_list').html( li_list.join('\n') );
-
-    }
-
-
-
-    // When form's action-buttons are clicked
-    // -------------------------------------------------------------------------
-
-
-    // form submit
-    // --- -- -- - - -
-    $('.edit-post form').submit( event => {
-        event.preventDefault();
-
-        /** DEPRICATED:
-         * 
-         ### TAG SYSTEM
-         # // rearrange tags to old and new ones
-         # // ---
-         # var old_tags = [];
-         # var new_tags = [];
-         # var tags = $('#tags').select2('data');      
-         # tags.forEach( t => {
-         #     if (!parseInt(t.id)) {
-         #          new_tags.push(t.text);
-         #     } else {    old_tags.push(t.id); }
-         # })
-         */
-
-        var attachments = [];
-        // attachments (array) of "`media_id`;`reference`" strings
-        files.forEach( f => { attachments.push( f.id ) });
-
-        // prepare data to POST
-        // ---
-        var data = {
-            id: parseInt($('.edit-post form input[name=id]').val()),
-            title: $('.edit-post form input[name=title]').val(),
-            course_id: parseInt($('#course_id').select2('data')[0].id),
-            intro: $('.edit-post form textarea[name=intro]').val(),
-            body: $('.edit-post form textarea[name=body]').val(),
-            status: ( ($('select[name=status]').val() == "0") ? 0 : 1 ),
-            privilege_id: parseInt($('#privilege_id').select2('data')[0].id),
-            // tags: old_tags,
-            // new_tags: new_tags,
-            media: attachments
-        };
-
-        // select action url (add or update)
-        // ---
-        var request = '/admin/api/lesson/' + ((data.id == 0) ? 'add' : 'update');
-
-        // send POST (ajax) request
-        $.post(request, data)
-        .done(function( data ) {
-            // console.log(data);
-            window.location.href = '/admin/lessons';      // seems ok; bach to articles
-        });       
-
-    });
-
-
-    // go-back (to lessons)
-    // --- -- -- - - -
-    $('#go-back').click( event => {
-        if (confirm('Θέλετε να ακυρώσετε τις όποιες αλλαγές και να φύγτε από τη σελίδα;')) {
-            window.location.href = '/admin/lessons';
-        }
-    });
-
-
-    // copy url button
-    // --- -- -- - - -
-    $('.admin-container').on('click', 'button.js-copy', function (e) {
-        var copytext = '';   // default: copy nothing
-
-        if ($(this).data('id') !== undefined) {
-            copytext = window.location.origin +'/lesson/' + $(this).data('id');
-        }
-
-        if ($(this).data('url') !== undefined) {
-            copytext = window.location.origin + '/serve/file/' + $(this).data('url') + '?type=' + $(this).data('type');
-        }
-        
-        navigator.clipboard
-        .writeText(copytext)
-        .then(() => {   // notify the copy event
-            $(this).addClass('copied');
-            setTimeout( () => { $(this).removeClass('copied'); }, 700);
-            console.log(copytext, ' copied!');
-        })
-        .catch(() => {
-            console.log("error on coping text");
-        });
-    });
-
-
-
-    // delete (remove) file button
-    // --- -- -- - - -
-    $('.admin-container').on('click', 'button.js-delete', function (e) {
-        console.log('delete!');
-        var media_id = $(this).data('id');
-
-        // remove from files array the one with id == media_id
-        // ---
-        var temp = [];
-        files.forEach( it => { if (it.id != media_id) temp.push(it); });
-
-        files = temp;           // re-define files
-        draw_files_list();      // then re-draw files list
-    });
-
-
-   
-    /** DEPRICATED:
-     * 
-     # // show|hide file as referece button
-     # // --- -- -- - - -
-     # $('.admin-container').on('click', 'button.js-reference', function (e) {
-     #     var id = $(this).data('id');
-     #
-     #     // toggle reference attribute of item with `id` = id
-     #     // ---
-     #     var temp = [];
-     #     files.forEach( it => {
-     #         if (it.id == id) {
-     #             it.reference = (it.reference==0) ? 1 : 0;
-     #         }
-     #         temp.push(it)
-     #     });
-     #
-     #     files = temp;           // re-define files
-     #     draw_files_list();      // then re-draw files list
-     # });
-     */
-
-
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#editorModal').on('show.bs.modal', event => {
-        let button = $(event.relatedTarget);    // Button that triggered the modal
-        let action = button.data('action');     // action
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-
-        switch (action) {
-            case 'upload_file':
-                $("#editorModal .modal-content").html(
-                    modal_header('Εισαγωγή Αρχείου') + upload_file_form()
-                );
-                break;
-            
-                case 'preview':
-                    let preview = preview_article(
-                        $('.edit-post form input[name=title]').val(),
-                        $('.edit-post form textarea[name=intro]').val(),
-                        $('.edit-post form textarea[name=body]').val()
-                    );
-                    $("#editorModal .modal-content").html( modal_header('Προεπισκόπηση') + preview);
-                    break;
-
-            default:
-                // do nothing
-        }
-
-    });
-
-
-
-    /** submit upload file event
-     * -------------------------------------------------------------------------
-     */
-    $('#editorModal').on('submit', 'form[name=upload_file_form]', function (event) {
-        event.preventDefault();
-
-        // create the FormData object
-        // --- -- -- - - -
-        var fd = new FormData(document.getElementById('file_upload_form'));
-
-        // post the form (via ajax)
-        $.ajax({
-            url: '/admin/api/file_upload',
-            type: 'POST',
-            data: fd,
-            contentType: false,
-            processData: false,
-            dataType: 'json',
-            success: function(response) {   // on success
-
-                if (response.success) {      
-                    files.push({    // ... update files array
-                        id: response.id,
-                        label: response.title,
-                        path: response.path,
-                        type: response.type
-                    });
-                    draw_files_list();                   
-
-                    $('#editorModal').modal('hide');
-
-                } else {
-                    console.log('File not uploaded');
-                }
-            }
-        });
-    });
-
-
-    // TODO:
-    // disable links while previewing the article
-    // OR add a target="_blank"
-
-
-});
-
diff --git a/public/assets/js/admin/edit_page.js b/public/assets/js/admin/edit_page.js
deleted file mode 100644
index ec0e84e..0000000
--- a/public/assets/js/admin/edit_page.js
+++ /dev/null
@@ -1,382 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-
-// NOTE:
-// Variable `entity_id` is defined before evaluating this script
-// id (int) : the id of edited post (or 0 if new post)
-
-var page;
-
-var id = (entity_id == 0) ? false : entity_id;
-
-var files = [];     // array of { id:.., title:.., type:.., path:.. } records
-
-// TODO: support tags
-// var tags = [];      // array of integers
-
-
-
-// an alternative--id when a page_id not exists (needed for file-upload)
-// ... consist of a 6-digit date string + random number up to 999
-const yymmdd = new Date().toISOString().slice(2, 10).replaceAll('-','');
-var rnd999 = Math.floor(Math.random() * 1000);
-var altID = (id == 0) ? ( yymmdd +'-'+ rnd999.toString() ) : id;
-
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-// return course record by course-id
-// --- -- -- - - -
-function course_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-
-
-// Modal HTML Creators
-// -----------------------------------------------------------------------------
-
-const modal_header = (title) => {
-    return [
-        '<div class="modal-header">',
-            '<h4 class="modal-title" id="myModalLabel">',
-                title,
-            '</h4>',
-            '<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close">',
-                '<span aria-hidden="true"></span>',
-            '</button>',
-        '</div>'
-    ].join('\n');
-}
-
-
-const upload_file_form = () => {
-    return [
-        '<form method="POST" id="file_upload_form" name="upload_file_form">',
-
-            '<div class="modal-body">',
-
-                '<input type="hidden" name="folder" value="'+ altID +'">',
-
-                '<div class="form-group">',
-                    '<label for="title">Τίτλος/Περιγραφή για το Αρχείο</label>',
-                    '<input type="text" class="form-control " value="" name="title" id="title" placeholder="Τίτλος για το Αρχείο" required="">',
-                '</div>',
-
-                '<div class="form-group">',
-                    '<label class="control-label" for="file">Εισαγωγή Αρχείου</label>',
-                    '<input class="form-control" type="file" id="file" name="file" required="">',
-                '</div>',
-
-            '</div>',
-
-            '<div class="modal-footer">',
-                '<div class="row" style="width: 50%;">',
-                    '<div class="form-actions">',
-                        '<div class="col col-4">',
-                            '<buton type="button" class="btn btn-default js-modal-close col-12" data-bs-dismiss="modal">',
-                                'Κλείσιμο',
-                            '</button>',
-                        '</div>',
-                        '<div class="col-8">',
-                            '<button class="btn btn-success col-12" type="submit">Καταχώριση</button>',
-                        '</div>',
-                    '</div>',
-                '</div>',
-            '</div>',
-
-        '</form>'
-    ].join('\n');
-}
-
-
-const preview_article = (title, body) => {
-    return [
-        '<div class="modal-body">',
-            '<div class="post">',
-
-                '<h2>'+ title +'</h2>',
-
-                '<div class="article-body">',
-                    marked.parse(body, { sanitize: true }),
-                '</div>',
-             
-            '</div>',
-        '</div>',
-        '<div class="modal-footer">',
-            '<div class="row" style="width: 50%;">',
-                '<div class="form-actions">',
-                    '<div class="col-md-4 col-md-offset-4 col-6 col-offset-3">',
-                        '<buton type="button" class="btn btn-default js-modal-close col-12" data-bs-dismiss="modal">',
-                            'Κλείσιμο',
-                        '</button>',
-                    '</div>',
-                '</div>',
-            '</div>',
-        '</div>'
-    ].join('\n');
-}
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    /** preload content
-     * --- -- -- - - -
-     * get page
-     * update content (form-elements)
-     */
-    if (id) {   // if an `id` is given, load post .. then init_form
-
-        $.getJSON( "/admin/api/page/" + id )
-        .done( function (data) {
-            page = data;            // keep post
-
-            // update fields' values
-            $('input[name=id]').val(page.id);           // id
-            $('input[name=title]').val(page.title);     // title
-            $('textarea[name=body]').val(page.body);    // body
-            $('select[name=status]').val(
-                (page.status == 0) ? '0' : "one"
-                ).trigger('change');
-
-            // $('#post-info').html('Δημιουργία: '+post.creation_date+'<br>Τελευταία Ενημέρωση: '+ post.update_date);
-
-            // parse media files; then draw
-            if (page.medias_json != null) {
-                files = JSON.parse(page.medias_json);
-            }
-            draw_files_list();      // then draw the files list          
-
-        });
-
-    }
-
-
-    /** draw_files_list
-     * --- -- -- - - -
-     */
-    function draw_files_list() {
-        var li_list = [];
-        var ref_icon, ref_class;
-
-        files.forEach( item => {
-            var copy = [    // copy button
-                '<button type="button" class="btn btn-xs btn-default js-copy"',
-                    ' data-url="' + item.path +'"',
-                    ' data-type="' + item.type + '"',
-                    '>',
-                    '<i class="far fa-clone"></i>',
-                '</button>'
-            ].join('');
-
-            var del = [    // delete button
-                '<button type="button" class="btn btn-xs btn-danger js-delete"',
-                    'data-id="' + item.id + '">',
-                    '<i class="fas fa-trash-alt"></i>',
-                '</button>'
-            ].join('');
-            var option = [  // li html
-                '<li>',
-                    '<div class="text">' + item.label + '</div>',
-                    '<div class="actions">',
-                        copy, ' ',  del,
-                    '</div>',
-                '</li>'
-            ].join('');
-            li_list.push(option);   // push to li_list
-        });
-        $('#files_list').html( li_list.join('\n') );
-
-    }
-
-
-
-    // When form's action-buttons are clicked
-    // -------------------------------------------------------------------------
-
-
-    // form submit
-    // --- -- -- - - -
-    $('.edit-page form').submit( event => {
-        event.preventDefault();
-
-        var attachments = [];
-        // attachments (array) of "`media_id`;`reference`" strings
-        files.forEach( f => { attachments.push( f.id ) });
-
-        // prepare data to POST
-        // ---
-        var data = {
-            id: parseInt($('.edit-page form input[name=id]').val()),
-            title: $('.edit-page form input[name=title]').val(),
-            body: $('.edit-page form textarea[name=body]').val(),
-            status: ( ($('select[name=status]').val() == "0") ? 0 : 1 ),
-            media: attachments
-        };
-
-        // select action url (add or update)
-        // ---
-        var request = '/admin/api/page/' + ((data.id == 0) ? 'add' : 'update');
-
-        // send POST (ajax) request
-        $.post(request, data)
-        .done(function( data ) {
-            console.log(data);
-            window.location.href = '/admin/pages';      // seems ok; bach to articles
-        });       
-
-    });
-
-
-    // go-back (to pages)
-    // --- -- -- - - -
-    $('#go-back').click( event => {
-        if (confirm('Θέλετε να ακυρώσετε τις όποιες αλλαγές και να φύγτε από τη σελίδα;')) {
-            window.location.href = '/admin/pages';
-        }
-    });
-
-
-    // copy url button
-    // --- -- -- - - -
-    $('.admin-container').on('click', 'button.js-copy', function (e) {
-        var copytext = '';   // default: copy nothing
-
-        if ($(this).data('id') !== undefined) {
-            copytext = window.location.origin +'/page/' + $(this).data('id');
-        }
-
-        if ($(this).data('url') !== undefined) {
-            copytext = window.location.origin + '/serve/file/' + $(this).data('url') + '?type=' + $(this).data('type');
-        }
-        
-        navigator.clipboard
-        .writeText(copytext)
-        .then(() => {   // notify the copy event
-            $(this).addClass('copied');
-            setTimeout( () => { $(this).removeClass('copied'); }, 700);
-            console.log(copytext, ' copied!');
-        })
-        .catch(() => {
-            console.log("error on coping text");
-        });
-    });
-
-
-
-    // delete (remove) file button
-    // --- -- -- - - -
-    $('.admin-container').on('click', 'button.js-delete', function (e) {
-        console.log('delete!');
-        var media_id = $(this).data('id');
-
-        // remove from files array the one with id == media_id
-        // ---
-        var temp = [];
-        files.forEach( it => { if (it.id != media_id) temp.push(it); });
-
-        files = temp;           // re-define files
-        draw_files_list();      // then re-draw files list
-    });
-
-
-   
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#editorModal').on('show.bs.modal', event => {
-        let button = $(event.relatedTarget);    // Button that triggered the modal
-        let action = button.data('action');     // action
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-
-        switch (action) {
-            case 'upload_file':
-                $("#editorModal .modal-content").html(
-                    modal_header('Εισαγωγή Αρχείου') + upload_file_form()
-                );
-                break;
-            
-                case 'preview':
-                    let preview = preview_article(
-                        $('.edit-page form input[name=title]').val(),
-                        $('.edit-page form textarea[name=body]').val()
-                    );
-                    $("#editorModal .modal-content").html( modal_header('Προεπισκόπηση') + preview);
-                    break;
-
-            default:
-                // do nothing
-        }
-
-    });
-
-
-
-    /** submit upload file event
-     * -------------------------------------------------------------------------
-     */
-    $('#editorModal').on('submit', 'form[name=upload_file_form]', function (event) {
-        event.preventDefault();
-
-        // create the FormData object
-        // --- -- -- - - -
-        var fd = new FormData(document.getElementById('file_upload_form'));
-
-        // post the form (via ajax)
-        $.ajax({
-            url: '/admin/api/file_upload',
-            type: 'POST',
-            data: fd,
-            contentType: false,
-            processData: false,
-            dataType: 'json',
-            success: function(response) {   // on success
-
-                if (response.success) {      
-                    files.push({    // ... update files array
-                        id: response.id,
-                        label: response.title,
-                        path: response.path,
-                        type: response.type
-                    });
-                    draw_files_list();                   
-
-                    $('#editorModal').modal('hide');
-
-                } else {
-                    console.log('File not uploaded');
-                }
-            }
-        });
-    });
-
-
-    // TODO:
-    // disable links while previewing the article
-    // OR add a target="_blank"
-
-
-});
-
diff --git a/public/assets/js/admin/files.js b/public/assets/js/admin/files.js
deleted file mode 100644
index e100b30..0000000
--- a/public/assets/js/admin/files.js
+++ /dev/null
@@ -1,302 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var privileges = [ { id: 0, label: 'Δημόσιο' } ];
-var files = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-
-// return file record by file-id
-// --- -- -- - - -
-function privilege_record(id) {
-    var record = 0;
-    files.forEach(el => { if (el.id == id) record = el; });  
-    return record;
-}
-
-
-/** privilege(id) 
- * label of privilege with
- * @param id (int)
- */
-function privilege_(id) {
-    let reply = false;
-    privileges.forEach( pri => { if (pri.id == id) reply = pri.label; });
-    return reply;
-}
-
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var del, edit;
-
-    del = "";
-
-    edit = [
-        '<button type="button" class="btn btn-sm btn-warning"',
-            'data-bs-toggle="modal" data-bs-target="#manageFiles"',
-            'data-id="'+ id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    return edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    
-    /** init selec2 element (used to specify parent-category)
-     * --- -- -- - - -
-     */
-    $("#privilege_id").select2({
-        placeholder: 'Επίπεδο πρόσβασης',
-        dropdownParent: $('#manageFiles'),
-        width: '100%',
-    });
-
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/admin/api/files")
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            files.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                files.push({
-                    id: el.id,
-                    label: el.label,
-                    path: el.path,
-                    type: el.type,
-                    privilege_id: ((el.privilege_id == null) ? 0 : el.privilege_id),
-                    privilege: privilege_( ((el.privilege_id == null) ? 0 : el.privilege_id) ),
-                    actions: create_actions_html(el.id)
-                });
-            });
-
-            // sort by breadcrumb
-            // categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-files').dataTable().fnClearTable();
-            $('#dt-files').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-files').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: files,
-                ordering: false,
-                columns: [
-                    { data: 'id' },
-                    { data: 'label' },
-                    { data: 'path' },
-                    { data: 'type' },
-                    { data: 'privilege' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-
-
-
-    $.getJSON( "/admin/api/privileges" )
-    .done( function( response ) {
-
-        // construct provileges data
-        // ---
-        response.forEach( el => {
-            privileges.push({
-                id: el.id,
-                label: el.label
-            });
-        });
-        privileges.sort( compare_label );  // sort categories by breadcrumb
-
-        init_table();   // init table on first run
-    });
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#managePrivileges').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-        // ---
-        $('#managePrivileges .modal-title').html(             // modal title
-            (id) ? 'Ενημέρωση Επιπέδου Πρόσβασης' : 'Δημιουργία Επιπέδου Πρόσβασης'
-        );
-        $('#managePrivileges form input[name=id]').val( id );     // category id (hidden)
-        $('#managePrivileges form input[name=label]').val(    // category label
-            (id) ? privilege_record(id).label : ""
-        );
-        prepare_included_element(id);        // prepare <select> for parents
-    })
-
-    /** prepare_included_element()
-     * ---
-     * @param id (int) : id of selected privilege
-     * -> Get all posible included privileges
-     * -> call set_included_options() to render the options
-     */
-    function prepare_included_element(id) {
-        var may_included = [];
-
-        if (id) {   // get all possible parents
-
-            // TODO: 
-            // specify forbiden privilege IDs for being included
-
-            // filter privileges adn prepare possible included privileges
-            privileges.forEach( el => {
-                if (id != el.id)  {
-                    may_included.push({
-                        id: el.id,
-                        label: el.label
-                    });
-                }
-            });
-            console.log(may_included);
-            set_included_options(may_included, privilege_record(id).included_id);
-
-
-        } else {    // new record; all categories are possible parrents
-            privileges.forEach( el => {
-                may_included.push({
-                    id: el.id,
-                    label: el.label,
-                });
-            })
-            set_included_options(may_included, -1);
-        }
-    }
-
-    /** set_included_options()
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * @param may_included (array): array of possible included privileges
-     * @param selected (int): selected included privilege
-     */
-    function set_included_options(may_included, selected) {
-        // sort parents by breadcrumb
-        // parents.sort( compare_breadcrumb );
-
-        // remove any olded options from select2
-        $('#included_id option').each(function() { $(this).remove(); });
-
-        // first option is the root category
-        $('#included_id').append('<option value="0">— κανένα —</option>')
-
-        // add all other parent options
-        may_included.forEach( i => {
-            $('#included_id').append(`<option value="${i.id}">${i.label}</option>`);
-        });
-
-        if (selected == -1) {   // new category; remove any parent pre-selection
-            $('#included_id').val(0).trigger('change');
-
-        } else {    // category exists; choose selected parent
-            $('#included_id').val(selected).trigger('change');
-        }
-    }
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            label: $('#manageCategory form input[name=label]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/admin/api/category/' + ((data.id == 0)  ? 'add' : 'update');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/admin/lessons.js b/public/assets/js/admin/lessons.js
deleted file mode 100644
index 1a08875..0000000
--- a/public/assets/js/admin/lessons.js
+++ /dev/null
@@ -1,364 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var categories = [];
-var privileges = [ { id: 0, label: 'Δημόσιο' } ];
-var lessons = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function lesson_record(id) {
-    var record = 0;
-    lessons.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-/** course(id) 
- * label of course with
- * @param id (int)
- */
-function course_(id) {
-    let reply = false;
-    categories.forEach( cat => { if (cat.id == id) reply = cat.label; })
-    return reply;
-}
-
-/** privilege(id) 
- * label of privilege with
- * @param id (int)
- */
-function privilege_(id) {
-    let reply = false;
-    privileges.forEach( pri => { if (pri.id == id) reply = pri.label; });
-    return reply;
-}
-
-
-//// return children of parent
-//// --- -- -- - - -
-//function childs_of_parents(list) {
-//    // if 'list' is integer then make it an one-item list
-//    parents = (Number.isInteger(list)) ? [ list ] : list;
-//
-//    var childs = [];
-//
-//    if (parents.length == 0) { return []; }
-//
-//    parents.forEach( pid => {
-//        categories.forEach( el => { if (el.parent == pid) childs.push(el.id)});
-//    });
-//
-//    var grandchilds = childs_of_parents(childs);
-//
-//    return childs.concat(grandchilds);
-//}
-
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(el) {
-
-    var pub, del, edit;
-
-    // preapre [show|hide]-file as reference
-    if (el.status == 1) {
-        pub = '<span class="btn btn-sm"><i class="fas fa-eye"></i></span>';
-
-    } else {
-        pub = '<span class="btn btn-sm"><i class="fas fa-eye-slash"></i></span>';
-    }
-
-    del = "";
-
-    fast_edit = [
-        '<button type="button" class="btn btn-sm btn-light"',
-            'data-bs-toggle="modal" data-bs-target="#manageLessons"',
-            'data-id="'+ el.id +'">',
-            '<i class="fa-solid fa-bolt"></i>',
-        '</button>'
-    ].join('\n');
-
-    edit = [
-        '<a type="button" class="btn btn-sm btn-warning "',
-            'href="/admin/edit_lesson/'+ el.id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</a>'
-    ].join('\n');
-
-    return pub +' '+ fast_edit +' '+ edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-
-    // inti category (select2)
-    // ...
-    $("#privilege_id").select2({
-        placeholder: 'Επίπεδο Πρόσβασης',
-        dropdownParent: $('#manageLessons'),
-        width: '100%'
-    });
-    
-    /** init selec2 element (used to specify parent-category)
-     * --- -- -- - - -
-     */
-    $("#course_id").select2({
-        placeholder: 'Κεφάλαιο',
-        dropdownParent: $('#manageLessons'),
-        width: '100%',
-    });
-
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/admin/api/lessons")
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            lessons.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                lessons.push({
-                    id: parseInt(el.id),
-                    title: el.title,
-                    course_id: el.course_id,
-                    course: course_(el.course_id),
-                    privilege_id: el.privilege_id,
-                    privilege: privilege_(el.privilege_id),
-                    actions: create_actions_html(el)
-                });
-            });
-
-            // sort by breadcrumb
-            // categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-lessons').dataTable().fnClearTable();
-            $('#dt-lessons').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-lessons').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: lessons,
-                ordering: false,
-                columns: [
-                    { data: 'id' },
-                    { data: 'title' },
-                    { data: 'course' },
-                    { data: 'privilege' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-
-
-    $.when(     // when loaded posts and categories
-
-        $.getJSON( "/admin/api/categories" ),
-
-        $.getJSON( "/admin/api/privileges" )
-
-    ).done( function( categories_response, privileges_response ) {
-
-        // construct categories data
-        // ---
-        Object.keys(categories_response[0]).forEach( key => {
-            cat = categories_response[0][key];
-            categories.push({
-                id: cat.rec.id,
-                label: cat.breadcrumb.replaceAll('\t', ' / ')
-            });
-        });
-        categories.sort( compare_label );  // sort categories by breadcrumb
-
-        // construct provileges data
-        // ---
-        Object.keys(privileges_response[0]).forEach( key => {
-            priv = privileges_response[0][key];
-            privileges.push({
-                id: priv.id,
-                label: priv.label
-            });
-        });
-        privileges.sort( compare_label );  // sort categories by breadcrumb
-
-        set_parent_options( $('#course_id'), categories );
-        set_parent_options( $('#privilege_id'), privileges );
-
-        init_table();   // init table on first run
-    });
-
-
-    /** set_parent_options()
-     * 
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * 
-     * NOTE:
-     * the targer <select> should be a select2 control
-     * 
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-    function set_parent_options(selector, list, selected_value = false) {
-
-        list.forEach( li => {   // attach options into <select> control
-            selector.append(`<option value="${li.id}">${li.label}</option>`);
-        });
-
-        if (selected_value !== false) {     // mark selected option(s)
-            selector.val(selected_value).trigger('change');
-        }
-        else { selector.val(null).trigger('change'); }
-    }
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#manageLesson').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        //// update modal literature
-        //// ---
-        //$('#manageCategory .modal-title').html(             // modal title
-        //    (id) ? 'Ενημέρωση Κατηγορίας' : 'Δημιουργία Κατηγορίας'
-        //);
-        //$('#manageCategory form input[name=id]').val( id );     // category id (hidden)
-        //$('#manageCategory form input[name=label]').val(    // category label
-        //    (id) ? category_record(id).label : ""
-        //);
-        //prepare_parents_element(id);        // prepare <select> for parents
-    })
-
-
-    /** set_parent_options()
-     * 
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * 
-     * NOTE:
-     * the targer <select> should be a select2 control
-     * 
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-        function set_parent_options(selector, list, selected_value = false) {
-
-            list.forEach( li => {   // attach options into <select> control
-                selector.append(`<option value="${li.id}">${li.label}</option>`);
-            });
-    
-            if (selected_value !== false) {     // mark selected option(s)
-                selector.val(selected_value).trigger('change');
-            }
-            else { selector.val(null).trigger('change'); }
-        }
-    
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            label: $('#manageCategory form input[name=label]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/admin/api/categories/' + ((data.id == 0)  ? 'add' : 'update');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/admin/pages.js b/public/assets/js/admin/pages.js
deleted file mode 100644
index 4aa02ca..0000000
--- a/public/assets/js/admin/pages.js
+++ /dev/null
@@ -1,240 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var categories = [];
-var privileges = [ { id: 0, label: 'Δημόσιο' } ];
-var pages = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function page_record(id) {
-    var record = 0;
-    pages.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(el) {
-
-    var pub, del, edit;
-
-    // preapre [show|hide]-file as reference
-    if (el.status == 1) {
-        pub = '<span class="btn btn-sm"><i class="fas fa-eye"></i></span>';
-
-    } else {
-        pub = '<span class="btn btn-sm"><i class="fas fa-eye-slash"></i></span>';
-    }
-
-    del = "";
-
-    fast_edit = [
-        '<button type="button" class="btn btn-sm btn-light"',
-            'data-bs-toggle="modal" data-bs-target="#managePages"',
-            'data-id="'+ el.id +'">',
-            '<i class="fa-solid fa-bolt"></i>',
-        '</button>'
-    ].join('\n');
-
-    edit = [
-        '<a type="button" class="btn btn-sm btn-warning "',
-            'href="/admin/edit_page/'+ el.id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</a>'
-    ].join('\n');
-
-    return pub +' '+ fast_edit +' '+ edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-   
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/admin/api/pages")
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            pages.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                pages.push({
-                    id: parseInt(el.id),
-                    title: el.title,
-                    actions: create_actions_html(el)
-                });
-            });
-
-            // sort by breadcrumb
-            // categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-pages').dataTable().fnClearTable();
-            $('#dt-pages').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-pages').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: pages,
-                ordering: false,
-                columns: [
-                    { data: 'id' },
-                    { data: 'title' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-    init_table();   // init table on first run
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#managePages').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        //// update modal literature
-        //// ---
-        //$('#manageCategory .modal-title').html(             // modal title
-        //    (id) ? 'Ενημέρωση Κατηγορίας' : 'Δημιουργία Κατηγορίας'
-        //);
-        //$('#manageCategory form input[name=id]').val( id );     // category id (hidden)
-        //$('#manageCategory form input[name=label]').val(    // category label
-        //    (id) ? category_record(id).label : ""
-        //);
-        //prepare_parents_element(id);        // prepare <select> for parents
-    })
-
-
-    /** set_parent_options()
-     * 
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * 
-     * NOTE:
-     * the targer <select> should be a select2 control
-     * 
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-        function set_parent_options(selector, list, selected_value = false) {
-
-            list.forEach( li => {   // attach options into <select> control
-                selector.append(`<option value="${li.id}">${li.label}</option>`);
-            });
-    
-            if (selected_value !== false) {     // mark selected option(s)
-                selector.val(selected_value).trigger('change');
-            }
-            else { selector.val(null).trigger('change'); }
-        }
-    
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            label: $('#manageCategory form input[name=label]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/admin/api/categories/' + ((data.id == 0)  ? 'add' : 'update');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/admin/panel.js b/public/assets/js/admin/panel.js
deleted file mode 100644
index 24b465e..0000000
--- a/public/assets/js/admin/panel.js
+++ /dev/null
@@ -1 +0,0 @@
-console.log('Admin Panel!');
\ No newline at end of file
diff --git a/public/assets/js/admin/privileges.js b/public/assets/js/admin/privileges.js
deleted file mode 100644
index e4355c5..0000000
--- a/public/assets/js/admin/privileges.js
+++ /dev/null
@@ -1,291 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var privileges = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-/*
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-*/
-
-// return category record by category-id
-// --- -- -- - - -
-function privilege_record(id) {
-    var record = 0;
-    privileges.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-/*
-// return children of parent
-// --- -- -- - - -
-function childs_of_parents(list) {
-    // if 'list' is integer then make it an one-item list
-    parents = (Number.isInteger(list)) ? [ list ] : list;
-
-    var childs = [];
-
-    if (parents.length == 0) { return []; }
-
-    parents.forEach( pid => {
-        categories.forEach( el => { if (el.parent == pid) childs.push(el.id)});
-    });
-
-    var grandchilds = childs_of_parents(childs);
-
-    return childs.concat(grandchilds);
-}
-*/
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var del, edit;
-
-    del = "";
-
-    edit = [
-        '<button type="button" class="btn btn-sm btn-warning"',
-            'data-bs-toggle="modal" data-bs-target="#managePrivileges"',
-            'data-id="'+ id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    return edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    
-    /** init selec2 element (used to specify parent-category)
-     * --- -- -- - - -
-     */
-    $("#included_id").select2({
-        placeholder: 'Περιλαμβάνει τα δικαιώματα της',
-        dropdownParent: $('#managePrivileges'),
-        width: '100%',
-        // dropdownParent: "#manageCategory"   // ref: https://github.com/select2/select2-bootstrap-theme/issues/41
-    });
-
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/admin/api/privileges")
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            privileges.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                privileges.push({
-                    id: el.id,
-                    label: el.label,
-                    includes: ((el.includes == null) ? [] : el.includes),
-                    included_id: ((el.included_id == null) ? 0 : el.included_id),
-                    actions: create_actions_html(el.id)
-                });
-            });
-
-            // sort by breadcrumb
-            // categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-privileges').dataTable().fnClearTable();
-            $('#dt-privileges').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-privileges').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: privileges,
-                ordering: false,
-                columns: [
-                    { data: 'id' },
-                    { data: 'label' },
-                    { data: 'includes' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-    init_table();   // init table on first run
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#managePrivileges').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-        // ---
-        $('#managePrivileges .modal-title').html(             // modal title
-            (id) ? 'Ενημέρωση Επιπέδου Πρόσβασης' : 'Δημιουργία Επιπέδου Πρόσβασης'
-        );
-        $('#managePrivileges form input[name=id]').val( id );     // category id (hidden)
-        $('#managePrivileges form input[name=label]').val(    // category label
-            (id) ? privilege_record(id).label : ""
-        );
-        prepare_included_element(id);        // prepare <select> for parents
-    })
-
-    /** prepare_included_element()
-     * ---
-     * @param id (int) : id of selected privilege
-     * -> Get all posible included privileges
-     * -> call set_included_options() to render the options
-     */
-    function prepare_included_element(id) {
-        var may_included = [];
-
-        if (id) {   // get all possible parents
-
-            // TODO: 
-            // specify forbiden privilege IDs for being included
-
-            // filter privileges adn prepare possible included privileges
-            privileges.forEach( el => {
-                if (id != el.id)  {
-                    may_included.push({
-                        id: el.id,
-                        label: el.label
-                    });
-                }
-            });
-            console.log(may_included);
-            set_included_options(may_included, privilege_record(id).included_id);
-
-
-        } else {    // new record; all categories are possible parrents
-            privileges.forEach( el => {
-                may_included.push({
-                    id: el.id,
-                    label: el.label,
-                });
-            })
-            set_included_options(may_included, -1);
-        }
-    }
-
-    /** set_included_options()
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * @param may_included (array): array of possible included privileges
-     * @param selected (int): selected included privilege
-     */
-    function set_included_options(may_included, selected) {
-        // sort parents by breadcrumb
-        // parents.sort( compare_breadcrumb );
-
-        // remove any olded options from select2
-        $('#included_id option').each(function() { $(this).remove(); });
-
-        // first option is the root category
-        $('#included_id').append('<option value="0">— κανένα —</option>')
-
-        // add all other parent options
-        may_included.forEach( i => {
-            $('#included_id').append(`<option value="${i.id}">${i.label}</option>`);
-        });
-
-        if (selected == -1) {   // new category; remove any parent pre-selection
-            $('#included_id').val(0).trigger('change');
-
-        } else {    // category exists; choose selected parent
-            $('#included_id').val(selected).trigger('change');
-        }
-    }
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            label: $('#manageCategory form input[name=label]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/admin/api/category/' + ((data.id == 0)  ? 'add' : 'update');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/classroom.js b/public/assets/js/classroom.js
deleted file mode 100644
index b1947f8..0000000
--- a/public/assets/js/classroom.js
+++ /dev/null
@@ -1,27 +0,0 @@
-$(document).ready(function() {
-
-
-    /** Categories Menu Toggler
-     * -------------------------------------------------------------------------
-     */
-    $('.toggler').click(function(e) {
-        e.preventDefault();
-
-        // inner div (contains children of this category)
-        var inner = $(this).parent().parent().find("ul.inner").first();
-
-        // toggle 'show' class on/off
-        if (inner.hasClass('show')) {
-            inner.removeClass('show');
-            inner.slideUp(350);
-            $(this).html("+");
-        } else {
-            inner.addClass('show');
-            inner.slideDown(350);
-            $(this).html("–");
-        }
-    });
-
-
-
-});
diff --git a/public/assets/js/edit-post.js b/public/assets/js/edit-post.js
deleted file mode 100644
index 49446ce..0000000
--- a/public/assets/js/edit-post.js
+++ /dev/null
@@ -1,612 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-
-// NOTE:
-// Variable `id` is defined before evaluating this script
-// id (int) : the id of edited post (or 0 if new post)
-
-var post;
-var categories = [
-    // Nope! root can not be a post's category ... { id: 0 , label: 'Ρίζα (root)' }
-];
-var tags = [];      // array of integers
-var files = [];     // array of { id:.., title:.., type:.., path:.. } records
-
-const files_root = 'https://cdn.sklavenitis.co.gr/';    // files root firectory
-
-
-
-var pageUrl = new URL(window.location.href);
-
-// an alternative--id when a post id not exists (needed for file-upload)
-// ... consist of a 6-digit date string + random number up to 999
-const yymmdd = new Date().toISOString().slice(2, 10).replaceAll('-','');
-var rnd999 = Math.floor(Math.random() * 1000);
-var altID = (id == 0) ? ( yymmdd +'-'+ rnd999.toString() ) : id;
-
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// function for sorting an array by 'label' attribute
-// --- -- -- - - -
-function compare_label (a,b) {
-    if ( a.label < b.label ) { return -1; }
-    if ( a.label > b.label ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function category_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-
-
-// Modal HTML Creators
-// -----------------------------------------------------------------------------
-
-const modal_header = (title) => {
-    return [
-        '<div class="modal-header">',
-            '<button type="button" class="close" data-dismiss="modal" aria-label="Close">',
-                '<span aria-hidden="true">&times;</span>',
-            '</button>',
-            '<h4 class="modal-title" id="myModalLabel">',
-                title,
-            '</h4>',
-        '</div>'
-    ].join('\n');
-}
-
-
-const upload_file_form = () => {
-    return [
-        '<form method="POST" id="file_upload_form" name="upload_file_form">',
-
-            '<div class="modal-body">',
-
-                '<input type="hidden" name="folder" value="'+ altID +'">',
-
-                '<div class="form-group">',
-                    '<label for="title">Τίτλος/Περιγραφή για το Αρχείο</label>',
-                    '<input type="text" class="form-control " value="" name="title" id="title" placeholder="Τίτλος για το Αρχείο" required="">',
-                '</div>',
-
-                '<div class="row">',
-
-                    '<div class="form-group col-md-7">',
-                        '<label class="control-label" for="file">Εισαγωγή Αρχείου</label>',
-                        '<input class="form-control" type="file" id="file" name="file" required="">',
-                    '</div>',
-
-                    '<div class="form-group col-md-5">',
-                        '<label class="control-label" for="category_id">Είδος</label>',
-                        '<select class="form-control" id="reference" name="reference" required="">',
-                            '<option"></option>',
-                            '<option value="1">Παραπομπή (εμφανίζεται)</option>',
-                            '<option value="0">Βοηθητικό αρχείο (κρυφό)</option>',
-                        '</select>',
-                    '</div>',
-
-                '</div>',
-
-            '</div>',
-
-            '<div class="modal-footer">',
-                '<div class="row">',
-                    '<div class="form-actions">',
-                        '<div class="col-lg-3 col-lg-offset-6 col-md-4 col-md-offset-4 col-xs-6">',
-                            '<buton type="button" class="btn btn-default js-modal-close col-xs-12" data-dismiss="modal">',
-                                'Κλείσιμο',
-                            '</button>',
-                        '</div>',
-                        '<div class="col-lg-3 col-md-4 col-xs-6">',
-                            '<button class="btn btn-success col-xs-12" type="submit">Καταχώριση</button>',
-                        '</div>',
-                    '</div>',
-                '</div>',
-            '</div>',
-
-        '</form>'
-    ].join('\n');
-}
-
-
-const preview_article = (title, intro, body) => {
-    return [
-        '<div class="modal-body">',
-            '<div class="post">',
-
-                '<h2>'+ title +'</h2>',
-
-                ((intro == '') ? '' : ('<div class="intro">'+ intro +'</div>')),
-
-                '<div class="article-body">',
-                    marked.parse(body, { sanitize: true }),
-                '</div>',
-             
-            '</div>',
-        '</div>',
-        '<div class="modal-footer">',
-            '<div class="row">',
-                '<div class="form-actions">',
-                    '<div class="col-md-4 col-md-offset-4 col-xs-6 col-xs-offset-3">',
-                        '<buton type="button" class="btn btn-default js-modal-close col-xs-12" data-dismiss="modal">',
-                            'Κλείσιμο',
-                        '</button>',
-                    '</div>',
-                '</div>',
-            '</div>',
-        '</div>'
-    ].join('\n');
-}
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-
-    // inti category (select2)
-    // ...
-    $("#category_id").select2({
-        placeholder: 'Γονική Κατηγορία',
-        width: '100%'
-    });
-
-
-    // init tags (select2)
-    // ...
-    $('#tags').select2({
-        placeholder: 'Ετικέτες (tags/keywords)',
-        width: '100%',
-        tags: true
-    });
-
-
-    // init editor (tiny MCE)
-    // tinymce.init({
-    //     selector: 'form textarea[name=body]',
-    //     language: 'el',
-    //     menubar: true
-    // });
-    // --- -- -- - - -
-
-
-    /** preload content
-     * --- -- -- - - -
-     * get post
-     * get categories
-     * get tags
-     * update content (form-elements)
-     */
-    if (id) {   // if an `id` is given, load post .. then init_form
-
-        $.getJSON( "/wiki/ajax", { action: "get_post", id: id } )
-        .done( function (data) {
-            post = data;            // keep post
-
-            // update fields' values
-            $('input[name=id]').val(post.id);           // id
-            $('input[name=title]').val(post.title);     // title
-            $('textarea[name=intro]').val(post.intro);  // intro
-            $('textarea[name=body]').val(post.body);    // body         
-            $('input[name=status]').prop(               // status
-                'checked',
-                ((post.status==1)? true : false))
-            .trigger('change');
-
-            $('#post-info').html('Δημιουργία: '+post.creation_date+'<br>Τελευταία Ενημέρωση: '+ post.update_date);
-
-            $('#delete').prop( "disabled", false );     // enable delete button
-
-            // if intro exist, show intro (optinal) field
-            if ((post.intro != null) && (post.intro != '')) {
-                $('.optional label[for=intro]').addClass('show');   // unhide section
-            }
-
-            // parse media files; then draw
-            if (post.medias_json != null) {
-                files = JSON.parse(post.medias_json);
-                $('.optional label[for=media]').addClass('show');   // unhide section
-            }
-            draw_files_list();      // then draw the files list
-            
-            init_form_values();     // init all (other) values
-        });
-
-    } else {    // else ... just init_form
-        $('#delete').prop( "disabled", true );     // disable delete button for new post attempt
-        // depricated $('select[name=status').val('0').trigger('change'); // pre-selecd unpublished
-        init_form_values();
-    }
-
-
-
-    /**
-     * load categories and tags;
-     * if not a new post (id!=0) update form elemnts with post's values
-     */
-    function init_form_values() {
-
-        $.when(     // when loaded posts and categories
-
-            $.getJSON( "/wiki/ajax", { action: "get_categories_array", exclude: '0' } ),
-
-            $.getJSON( "/wiki/ajax", { action: "get_all_tags" } )
-
-        ).done( function( categories_response, tags_response ) {
-
-            // construct categories data
-            // ---
-            Object.keys(categories_response[0]).forEach( key => {
-                cat = categories_response[0][key];
-                categories.push({
-                    id: cat.rec.id,
-                    label: cat.breadcrumb.replaceAll('\t', ' / ')
-                });
-            });
-            categories.sort( compare_label );  // sort categories by breadcrumb
-
-            // construct tags data
-            // ---
-            Object.keys(tags_response[0]).forEach( key => {
-                tag = tags_response[0][key];
-                tags.push({
-                    id: tag.id,
-                    label: tag.name
-                });
-            });
-
-            // pass categories and tags options onto select2 elements
-            // --- -- -- - - -
-            if (id == 0) {
-                set_parent_options( $('#category_id'), categories );
-                set_parent_options( $('#tags'), tags );
-
-            } else {
-                // setup category_id options; select post's chosen category-id
-                set_parent_options( $('#category_id'), categories, post.category_id );
-
-                // parse selected tags
-                // ---
-                var selected_tag_ids = [];
-                if (post.tags_json != null) {
-                    var selected_tags = JSON.parse(post.tags_json);
-                    selected_tags.forEach( itag => { selected_tag_ids.push(itag.id); })
-                }
-                // setup tags options; select post's chosen tags
-                set_parent_options( $('#tags'), tags, selected_tag_ids );
-
-                // ALSO: if tags selectd, show tags field
-                if (selected_tag_ids.length != 0) { $('.optional label[for=tags]').addClass('show'); }
-            }
-
-        });
-
-    }
-
-
-    /** set_parent_options()
-     * 
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * 
-     * NOTE:
-     * the targer <select> should be a select2 control
-     * 
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-    function set_parent_options(selector, list, selected_value = false) {
-
-        list.forEach( li => {   // attach options into <select> control
-            selector.append(`<option value="${li.id}">${li.label}</option>`);
-        });
-
-        if (selected_value !== false) {     // mark selected option(s)
-            selector.val(selected_value).trigger('change');
-        }
-        else { selector.val(null).trigger('change'); }
-    }
-
-
-    /** draw_files_list
-     * --- -- -- - - -
-     */
-    function draw_files_list() {
-        var li_list = [];
-        var ref_icon, ref_class;
-
-        files.forEach( item => {
-            // preapre [show|hide]-file as reference
-            if (item.reference == 1) {
-                ref_icon = '<i class="fas fa-eye"></i>';
-                ref_class = 'btn-default';
-    
-            } else {
-                ref_icon = '<i class="fas fa-eye-slash"></i>';
-                ref_class = 'btn-disabled';
-            }
-
-            var copy = [    // copy button
-                '<button type="button" class="btn btn-xs btn-default js-copy"',
-                    'data-url="' + item.path + '">',
-                    '<i class="far fa-clone"></i>',
-                '</button>'
-            ].join('');
-            var ref = [   // show|hide (is_reference)
-                '<button type="button" class="btn btn-xs '+ ref_class +' js-reference"',
-                    'data-id="' + item.id + '">',
-                    ref_icon,
-                '</button>'
-            ].join('');
-            var del = [    // delete button
-                '<button type="button" class="btn btn-xs btn-danger js-delete"',
-                    'data-id="' + item.id + '">',
-                    '<i class="fas fa-trash-alt"></i>',
-                '</button>'
-            ].join('');
-            var option = [  // li html
-                '<li>',
-                    '<div class="text">' + item.title + '</div>',
-                    '<div class="actions">',
-                        ref, ' ', copy, ' ',  del,
-                    '</div>',
-                '</li>'
-            ].join('');
-            li_list.push(option);   // push to li_list
-        });
-        $('#files_list').html( li_list.join('\n') );
-
-    }
-
-
-
-    // When form's action-buttons are clicked
-    // -------------------------------------------------------------------------
-
-
-    // form submit
-    // --- -- -- - - -
-    $('.edit-post form').submit( event => {
-        event.preventDefault();
-
-        // rearrange tags to old and new ones
-        // ---
-        var old_tags = [];
-        var new_tags = [];
-        var tags = $('#tags').select2('data');      
-        tags.forEach( t => {
-            if (!parseInt(t.id)) {
-                 new_tags.push(t.text);
-            } else {    old_tags.push(t.id); }
-        })
-
-        var attachments = [];
-        // attachments (array) of "`media_id`;`reference`" strings
-        files.forEach( f => { attachments.push( f.id +';'+ f.reference ) });
-
-        // prepare data to POST
-        // ---
-        var data = {
-            id: parseInt($('.edit-post form input[name=id]').val()),
-            title: $('.edit-post form input[name=title]').val(),
-            category_id: parseInt($('#category_id').select2('data')[0].id),
-            intro: $('.edit-post form textarea[name=intro]').val(),
-            body: $('.edit-post form textarea[name=body]').val(),
-            status: (($('input[name=status]').is(":checked")) ? 1 : 0),
-            tags: old_tags,
-            new_tags: new_tags,
-            media: attachments
-        };
-
-        // select action url (add or update)
-        // ---
-        var request = '/wiki/ajax?action=' + ((data.id == 0) ? 'add_post' : 'update_post');
-
-        // send POST (ajax) request
-        $.post(request, data)
-        .done(function( data ) {
-            window.location.href = '/wiki/admin?action=posts';      // seems ok; bach to articles
-        });       
-
-    });
-
-
-    // go-back (to posts)
-    // --- -- -- - - -
-    $('#go-back').click( event => {
-        window.location.href = '/wiki/admin?action=posts';
-    });
-
-
-    // delete
-    // --- -- -- - - -
-    $('#delete').click( event => {
-        // ask before deletion
-        swal({
-            title: 'Είστε βέβαιος;',
-            html: "Ζητήσατε να διαγραφεί το άρθρο.<br>Παρακαλώ επιβεβαιώστε την διαγραφή.<br>ΠΡΟΣΟΧΗ: Δεν θα έχετε την δυνατότητα αναίρεσης!",
-            type: 'warning',
-            showCancelButton: true,
-            confirmButtonColor: '#3085d6',
-            cancelButtonColor: '#d33',
-            cancelButtonText: 'Ακύρωση',
-            confirmButtonText: 'Ναι, να διαγραφεί',
-            showLoaderOnConfirm: true,
-            preConfirm: function() {
-                return new Promise(function(resolve) {
-                    $.getJSON( "/wiki/ajax", { action: "delete_post", id: id } )
-                    .done( function (data) {
-                        // return to posts-administration
-                        window.location.href = '/wiki/admin?action=posts';
-                    });
-                });
-            }, 
-            allowOutsideClick: false
-        }).catch(swal.noop);
-
-    });
-
-
-
-    // copy url button
-    // --- -- -- - - -
-    $('.wiki').on('click', 'button.js-copy', function (e) {
-        var copytext = '';   // default: copy nothing
-
-        if ($(this).data('id') !== undefined) {
-            copytext = pageUrl.origin +'/wiki/post?id=' + $(this).data('id');
-        }
-
-        if ($(this).data('url') !== undefined) {
-            copytext = files_root + $(this).data('url');
-        }
-        
-        navigator.clipboard
-        .writeText(copytext)
-        .then(() => {   // notify the copy event
-            $(this).addClass('copied');
-            setTimeout( () => { $(this).removeClass('copied'); }, 700);
-        })
-        .catch(() => {
-            console.log("error on coping text");
-        });
-    });
-
-
-
-    // delete (remove) file button
-    // --- -- -- - - -
-    $('.wiki').on('click', 'button.js-delete', function (e) {
-        var media_id = $(this).data('id');
-
-        // remove from files array the one with id == media_id
-        // ---
-        var temp = [];
-        files.forEach( it => { if (it.id != media_id) temp.push(it); });
-
-        files = temp;           // re-define files
-        draw_files_list();      // then re-draw files list
-    });
-
-
-
-    
-
-    // show|hide file as referece button
-    // --- -- -- - - -
-    $('.wiki').on('click', 'button.js-reference', function (e) {
-        var id = $(this).data('id');
-        
-        // toggle reference attribute of item with `id` = id
-        // ---
-        var temp = [];
-        files.forEach( it => {
-            if (it.id == id) {
-                it.reference = (it.reference==0) ? 1 : 0;
-            }
-            temp.push(it)
-        });
-
-        files = temp;           // re-define files
-        draw_files_list();      // then re-draw files list
-    });
-
-
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#editorModal').on('show.bs.modal', event => {
-        let button = $(event.relatedTarget);    // Button that triggered the modal
-        let action = button.data('action');     // action
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-
-        switch (action) {
-            case 'upload_file':
-                $("#editorModal .modal-content").html(
-                    modal_header('Εισαγωγή Αρχείου') + upload_file_form()
-                );
-                break;
-            
-                case 'preview':
-                    let preview = preview_article(
-                        $('.edit-post form input[name=title]').val(),
-                        $('.edit-post form textarea[name=intro]').val(),
-                        $('.edit-post form textarea[name=body]').val()
-                    );
-                    $("#editorModal .modal-content").html( modal_header('Προεπισκόπηση') + preview);
-                    break;
-
-            default:
-                // do nothing
-        }
-
-    });
-
-
-
-    /** submit upload file event
-     * -------------------------------------------------------------------------
-     */
-    $('#editorModal').on('submit', 'form[name=upload_file_form]', function (event) {
-        event.preventDefault();
-
-        // create the FormData object
-        // --- -- -- - - -
-        var fd = new FormData(document.getElementById('file_upload_form'));
-
-        // post the form (via ajax)
-        $.ajax({
-            url: '/wiki/ajax?action=file_upload',
-            type: 'POST',
-            data: fd,
-            contentType: false,
-            processData: false,
-            dataType: 'json',
-            success: function(response) {   // on success
-
-                if (response.success) {      
-                    files.push({    // ... update files array
-                        id: response.id,
-                        title: response.title,
-                        path: response.path,
-                        type: response.type,
-                        reference: $('#reference').val()
-                    });
-                    draw_files_list();                   
-
-                    $('#editorModal').modal('hide');
-
-                } else {
-                    console('File not uploaded');
-                }
-            }
-        });
-    });
-
-
-    // TODO:
-    // disable links while previewing the article
-    // OR add a target="_blank"
-
-
-});
-
diff --git a/public/assets/js/lesson-features.js b/public/assets/js/lesson-features.js
deleted file mode 100644
index 189b301..0000000
--- a/public/assets/js/lesson-features.js
+++ /dev/null
@@ -1,218 +0,0 @@
-const valid_codeblocks = [      // supported sort-code keys
-    'youtube',
-    'spotify',
-    'spotify-track',
-    'world-data',
-    'vimeo',
-    'dailymotion'
-];
-
-
-const symbol_escapes = [
-    { esc: '&gt;',    chr: '>' },
-    { esc: '&lt;',    chr: '<' },
-    { esc: '&amp;',   chr: '&' },
-    { esc: '&quot;',  chr: '\"' },
-    { esc: '&apos;',  chr: '\'' },
-    { esc: '&euro;',  chr: '€' },
-    { esc: '&copy;',  chr: '©' },
-    { esc: '&reg;',   chr: '®' }
-];
-
-
-var youtube_template = ( id => {
-    return '<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/'+ id +'?rel=0&controls=0" title="YouTube video player" frameborder="0" allow="clipboard-write; encrypted-media; picture-in-picture; web-share" allowfullscreen></iframe>';
-}); 
-
-
-var spotify_template = ( id => {
-    return '<iframe style="border-radius:12px" src="https://open.spotify.com/embed/episode/'+ id +'?utm_source=generator" width="100%" height="152" frameBorder="0" allowfullscreen="" allow="autoplay; clipboard-write; encrypted-media; fullscreen; picture-in-picture" loading="lazy"></iframe>';
-});
-
-var spotify_track = ( id => {
-    return '<iframe style="border-radius:12px" src="https://open.spotify.com/embed/track/'+ id +'?utm_source=generator" width="100%" height="152" frameBorder="0" allowfullscreen="" allow="autoplay; clipboard-write; encrypted-media; fullscreen; picture-in-picture" loading="lazy"></iframe>';
-});
-
-var owid_template = ( id => {       // our world in data (explorer)
-    return '<iframe src="https://ourworldindata.org/explorers/'+ id +'?zoomToSelection=true&hideControls=true" loading="lazy" style="width: 100%; height: 480px; border: 0px none;"></iframe>'
-});
-
-var vimeo_template = ( id => {
-    return '<div style="padding:56.25% 0 0 0;position:relative;"><iframe src="https://player.vimeo.com/video/'+ id +'?h=2e7bdb3901&title=0&byline=0&portrait=0" style="position:absolute;top:0;left:0;width:100%;height:100%;" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen></iframe></div><script src="https://player.vimeo.com/api/player.js"></script>'
-});
-
-var dailymotion_template = ( id => {
-    return '<div style="position:relative;padding-bottom:56.25%;height:0;overflow:hidden;"> <iframe style="width:100%;height:100%;position:absolute;left:0px;top:0px;overflow:hidden" frameborder="0" type="text/html" src="https://www.dailymotion.com/embed/video/'+ id +'" width="100%" height="100%" allowfullscreen title="Dailymotion Video Player" > </iframe> </div>'
-});
-
-
-
-/** inject_codeblocks
- * --- -- -- - - -
- * 
- * NOTE:
- * a short-code is a mustache block of 3 parametres:
- * {{ object = someID ; some label description }}
- * ex. `{{product=1507175; Coca Cola Zero}}`
- * 
- * The short-code is parsed to a code-block:
- * an `a` modal-toggler link with certain data-attributes (+label), ex:
- * `<a class='modal-toggler view-product' data-id='1507175'>Coca Cola Zero</a>`
- * 
- * @param code (string): original content html with short-codes
- * @returns (string): html content with code-blocks
- */
-function inject_codeblocks(code) {
-    // isolate all mustache blocks
-    const regexp = /{{(.*?)}}/g;        // regex makes multiple-matching easier
-    const matches = [...code.matchAll(regexp)];
-        // console.log(matches);
-    
-    var output = code;      // use a copy of (source) code
-
-    console.log(matches);
-      
-    matches.forEach( match => {
-      // parse (every) match
-        // NOTE:
-        // match array has 3 items; example:
-        // match[0] : `{{youtube=6EA-MIYY1bg}}`
-        // match[1] : `youtube=6EA-MIYY1bg`
-        // match[3] : the (source) code string
-
-      // let blockparts = unescaped_str( match[1] ).trim().split('=');
-      let blockparts = match[1].trim().split('=');
-      let target = blockparts[0].toLowerCase();
-      let id = blockparts[1];
-      // let label = escaped_str(blockparts[1]);
-      if (valid_codeblocks.includes(target)) {
-
-        var codeblock = '';
-
-        console.log(target, id);
-
-        switch (target) {
-
-            case 'youtube':
-                codeblock = youtube_template(id);
-                break;
-            
-            case 'spotify':
-                codeblock = spotify_template(id);
-                break;
-
-            case 'spotify-track':
-                codeblock = spotify_track(id);
-                break;
-
-            case 'world-data':
-                codeblock = owid_template(id);
-                break;
-
-            case 'vimeo':
-                codeblock = vimeo_template(id);
-                break;
-
-            case 'dailymotion':
-                codeblock = dailymotion_template(id);
-                break;
-                
-            default:
-                codeblock = id;
-
-        }
-
-        output = output.replaceAll(match[0], codeblock);
-
-      }
-    });
-    
-    return output;
-}
-
-
-// pair of function to escepe/unescape special html symbols
-// --- -- -- - - -
-function unescaped_str(txt) {
-    symbol_escapes.forEach( pair => { txt = txt.replaceAll(pair.esc, pair.chr); })
-    return txt;
-}
-
-function escaped_str(txt) {
-    symbol_escapes.forEach( pair => { txt = txt.replaceAll(pair.chr, pair.esc); })
-    return txt;
-}
-
-
-$(document).ready(function() {
-
-
-    /** translate short-codes to code-blocks
-     * -------------------------------------------------------------------------
-     */ 
-    var content = $('.main-content .article-body').html();       // get code with shorts
-    $('.main-content .article-body').html( inject_codeblocks(content) ); // put code with blocks
-    
-
-    
-    /** modal listeners
-     * -------------------------------------------------------------------------
-     */  
-/* DEPRICATED: not needed
-    // open store modal listener
-    // --- -- -- - - -
-    $(document).on('click', '.js-get_store', function (e) {
-        e.preventDefault();
-        var id = $(this).data('id');    // id for requesting content via ajax
-
-        $('#dynamic-content').html('');
-        $('#modal-loader').show();
-
-        $.ajax({
-            url: '/libs/modals/modalStore.php',
-            type: 'POST',
-            cache: false,
-            data: 'id=' + id,
-            dataType: 'html'
-        })
-        .done(function (data) {
-            $('#dynamic-content').html('');
-            $('#dynamic-content').html(data);
-            $('#modal-loader').hide();
-        })
-        .fail(function () {
-            $('#dynamic-content').html('<i class="glyphicon glyphicon-info-sign"></i> Υπήρξε κάποιο πρόβλημα, παρακαλώ προσπαθήστε ξανά.');
-            $('#modal-loader').hide();
-        });
-    });
-
-    // open product modal listener
-    // ---
-    $(document).on('click', '.js-get_product', function (e) {
-        e.preventDefault();
-        var id = $(this).data('id');    // id for requesting content via ajax
-
-        $('#dynamic-product').html('');
-        $('#modal-loader').show();
-        
-        $.ajax({
-            url: '/products/ajax/get_product_full',
-            cache: false,
-            type: 'POST',
-            data: { id: id },
-            dataType: 'html'
-        })
-        .done(function (data) {
-            $('#dynamic-product').html('');
-            $('#dynamic-product').html(data);
-            $('#modal-loader').hide();
-
-        })
-        .fail(function () {
-            $('#dynamic-product').html('<i class="glyphicon glyphicon-info-sign"></i> Υπήρξε κάποιο πρόβλημα, παρακαλώ προσπαθήστε ξανά.');
-            $('#modal-loader').hide();
-
-        });
-    });
-*/
-});
diff --git a/public/assets/js/manage-category.js b/public/assets/js/manage-category.js
deleted file mode 100644
index 85a4851..0000000
--- a/public/assets/js/manage-category.js
+++ /dev/null
@@ -1,287 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var categories = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// array.indexOf polyfill
-// --- -- -- - - -
-if (!Array.prototype.indexOf)
-{
-  Array.prototype.indexOf = function(elt /*, from*/)
-  {
-    var len = this.length >>> 0;
-
-    var from = Number(arguments[1]) || 0;
-    from = (from < 0)
-         ? Math.ceil(from)
-         : Math.floor(from);
-    if (from < 0)
-      from += len;
-
-    for (; from < len; from++)
-    {
-      if (from in this &&
-          this[from] === elt)
-        return from;
-    }
-    return -1;
-  };
-}
-
-
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function category_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-
-// return children of parent
-// --- -- -- - - -
-function childs_of_parents(list) {
-    // if 'list' is integer then make it an one-item list
-    parents = (Number.isInteger(list)) ? [ list ] : list;
-
-    var childs = [];
-
-    if (parents.length == 0) { return []; }
-
-    parents.forEach( pid => {
-        categories.forEach( el => { if (el.parent == pid) childs.push(el.id)});
-    });
-
-    var grandchilds = childs_of_parents(childs);
-
-    return childs.concat(grandchilds);
-}
-
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var del, edit;
-
-    del = "";
-
-    edit = [
-        '<button type="button" class="btn btn-xs btn-warning"',
-            'data-toggle="modal" data-target="#manageCategory"',
-            'data-id="'+ id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    return edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    
-    /** init selec2 element (used to specify parent-category)
-     * --- -- -- - - -
-     */
-    $("#parent_id").select2({
-        placeholder: 'Γονική Κατηγορία',
-        width: '100%',
-        // dropdownParent: "#manageCategory"   // ref: https://github.com/select2/select2-bootstrap-theme/issues/41
-    });
-
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/wiki/ajax", { action: "get_categories_array", exclude: '0' } )
-        .done(function( json ) {
-            // then ...
-
-            // reset categories
-            categories.length = 0;
-
-            // construct (new) categories data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                categories.push({
-                    id: parseInt(el.rec.id),
-                    title: el.rec.title,
-                    breadcrumb: el.breadcrumb.replaceAll('\t', ' / '),
-                    parent: parseInt(el.rec.parent),
-                    actions: create_actions_html(el.rec.id)
-                });
-            });
-
-            // sort by breadcrumb
-            categories.sort( compare_breadcrumb );
-
-            // destroy previous datatable table instances
-            $('#dt-categories').dataTable().fnClearTable();
-            $('#dt-categories').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-categories').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: categories,
-                ordering: false,
-                columns: [
-                    { data: 'breadcrumb' },
-                    { data: 'actions' }
-                ]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-    init_table();   // init table on first run
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#manageCategory').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-        // ---
-        $('#manageCategory .modal-title').html(             // modal title
-            (id) ? 'Ενημέρωση Κατηγορίας' : 'Δημιουργία Κατηγορίας'
-        );
-        $('#manageCategory form input[name=id]').val( id );     // category id (hidden)
-        $('#manageCategory form input[name=title]').val(    // category title
-            (id) ? category_record(id).title : ""
-        );
-        prepare_parents_element(id);        // prepare <select> for parents
-    })
-
-    /** prepare_parents_element()
-     * ---
-     * @param id (int) : id of selected category
-     * -> Get all posible parents
-     * -> call set_parent_options() to render the options
-     */
-    function prepare_parents_element(id) {
-        var parents = [];
-
-        if (id) {   // get all possible parents
-
-            // id-category and subcategories are fobiden parents
-            var forbiden = childs_of_parents(id);
-            forbiden.push(id);
-
-            // filter catogories adn prepare parents
-            categories.forEach( el => {
-                if (!forbiden.includes(el.id))  {
-                    parents.push({
-                        id: el.id,
-                        breadcrumb: el.breadcrumb,
-                    });
-                }
-            });
-            set_parent_options(parents, category_record(id).parent);
-
-
-        } else {    // new record; all categories are possible parrents
-            categories.forEach( el => {
-                parents.push({
-                    id: el.id,
-                    breadcrumb: el.breadcrumb,
-                });
-            })
-            set_parent_options(parents, -1);
-        }
-    }
-
-    /** set_parent_options()
-     * -> create options for parents <select>
-     * -> choose selected parent
-     * @param parents (array): array of parents
-     * @param selected (int): selected parent
-     */
-    function set_parent_options(parents, selected) {
-        // sort parents by breadcrumb
-        parents.sort( compare_breadcrumb );
-
-        // remove any olded options from select2
-        $('#parent_id option').each(function() { $(this).remove(); });
-
-        // first option is the root category
-        $('#parent_id').append('<option value="0">Root</option>')
-
-        // add all other parent options
-        parents.forEach( i => {
-            $('#parent_id').append(`<option value="${i.id}">${i.breadcrumb}</option>`);
-        });
-
-        if (selected == -1) {   // new category; remove any parent pre-selection
-            $('#parent_id').val(null).trigger('change');
-
-        } else {    // category exists; choose selected parent
-            $('#parent_id').val(selected).trigger('change');
-        }
-    }
-
-
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            title: $('#manageCategory form input[name=title]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/wiki/ajax?action=' + ((data.id == 0)  ? 'add_category' : 'update_category');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});
diff --git a/public/assets/js/manage-posts.js b/public/assets/js/manage-posts.js
deleted file mode 100644
index 028c773..0000000
--- a/public/assets/js/manage-posts.js
+++ /dev/null
@@ -1,177 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var categories = [];
-var posts = [];
-var table;
-
-var pageUrl = new URL(window.location.href);
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-// function for sorting an array by 'breadcrumb' attribute
-// --- -- -- - - -
-function compare_breadcrumb (a,b) {
-    if ( a.breadcrumb < b.breadcrumb ) { return -1; }
-    if ( a.breadcrumb > b.breadcrumb ) { return 1; }
-    return 0;
-}
-
-// return category record by category-id
-// --- -- -- - - -
-function category_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var copy, edit;
-
-    edit = [
-        '<button type="button" class="btn btn-xs btn-warning js-edit"',
-            'data-id="'+ id +'">',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    copy = [
-        '<button type="button" class="btn btn-xs btn-dafault js-copy"',
-            'data-id="'+ id +'">',
-            '<i class="far fa-clone"></i>',
-        '</button>'
-    ].join('\n');
-
-    return copy +' '+ edit;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    /** init_table for 1st time
-     * --- -- -- - - -
-     * get posts + categories
-     * constuct posts + categories array
-     * render dataTable
-     */
-    // function init_table() {
-
-        $.when(     // when loaded posts and categories
-
-            $.getJSON( "/wiki/ajax", { action: "all_posts_props" } ),
-
-            $.getJSON( "/wiki/ajax", { action: "get_categories_array", exclude: '0' } )
-
-        ).done( function( posts_response, categories_response ) {
-
-            // each response is an array of 3 items:
-            // [0] => data (array)
-            // [1] => [success|fail]
-            // [2] => xhr object
-
-            // construct categories data
-            Object.keys(categories_response[0]).forEach( key => {
-                cat = categories_response[0][key];
-                categories.push({
-                    id: cat.rec.id,
-                    breadcrumb: cat.breadcrumb.replaceAll('\t', ' / ')
-                });
-            });
-
-            // construct posts data
-            Object.keys(posts_response[0]).forEach( key => {
-                po = posts_response[0][key];
-                posts.push({
-                    id: po.id,
-                    title: po.title,
-                    category: category_record(po.category_id).breadcrumb,
-                    updated: po.update_date,
-                    status: ((po.status == 1) ? '<i class="fas fa-eye"></i>' : '<i class="fas fa-eye-slash"></i>'),
-                    actions: create_actions_html(po.id)
-                });
-            });
-
-            // (re-)create categories datatable
-            table = $('#dt-posts').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },
-                data: posts,
-                order: [[2, 'desc']],
-                columns: [
-                    { data: 'title' },
-                    { data: 'category' },
-                    {   // update date
-                        data: 'updated',
-                        render: {
-                            _: function (data, row, full) { return data; },
-                            display: function (data, row, full) { return mini_date(data); }
-                        }
-                    },
-                    { data: 'status' },
-                    { data: 'actions', width: '64px' }
-                ],
-                columnDefs: [{
-                    'targets': [3,4],
-                    'orderable': false
-                }]
-            });
-
-       });
-
-
-    function mini_date(d){
-        let yy = d.substring(2,4);      // year 2digit
-        let mo = d.substring(5,7);      // month
-        let dd = d.substring(8,10);     // dat
-        let h = d.substring(11,13);     // hour
-        let m = d.substring(14,16);     // minute
-        return dd +'/'+ mo +'/'+ yy +' '+ h +':'+ m;
-    }
-
-
-
-    /** When user ckicks button
-     * -------------------------------------------------------------------------
-     */
-
-
-    /** on(click, .edit-btn)
-     * --- -- -- - - -
-     * We need to attach the event handler to some element
-     * higher up in the DOM tree that will remain present;
-     * so the handled attached on #dt-posts
-     * 
-     * get post-id ; load editpost
-    */
-    $('#dt-posts').on('click', 'button.js-edit', function (e) {
-
-        var id = $(this).data('id');
-        window.location.href = '/wiki/admin?action=editpost&id=' + id
-
-    });
-
-
-    $('#dt-posts').on('click', 'button.js-copy', function (e) {
-        var postUrl = pageUrl.origin +'/wiki/post?id=' + $(this).data('id');
-        
-        navigator.clipboard
-        .writeText(postUrl)
-        .then(() => {
-            $(this).addClass('copied');
-            setTimeout( () => { $(this).removeClass('copied'); }, 700);
-        })
-        .catch(() => {
-            console.log("error on coping text");
-        });
-    });
-
-
-});
diff --git a/public/assets/js/manage-tags.js b/public/assets/js/manage-tags.js
deleted file mode 100644
index c287849..0000000
--- a/public/assets/js/manage-tags.js
+++ /dev/null
@@ -1,163 +0,0 @@
-// Globals
-// -----------------------------------------------------------------------------
-var tags = [];
-var table;
-
-
-
-// Supplamentary functions
-// -----------------------------------------------------------------------------
-
-
-
-// return category record by category-id
-// --- -- -- - - -
-function category_record(id) {
-    var record = 0;
-    categories.forEach(el => { if (el.id == id) record = el; });
-   
-    return record;
-}
-
-// create actions html (edit and delete buttons)
-// --- -- -- - - -
-function create_actions_html(id) {
-
-    var del, edit;
-
-    del = [
-        '<button type="button" class="btn btn-xs btn-danger"',
-            'data-toggle="modal" data-target="#manageCategory"',
-            'data-id="'+ id +'" disabled>',
-            '<i class="fas fa-times"></i>',
-        '</button>'
-    ].join('\n');
-
-    edit = [
-        '<button type="button" class="btn btn-xs btn-warning"',
-            'data-toggle="modal" data-target="#manageCategory"',
-            'data-id="'+ id +'" disabled>',
-            '<i class="fas fa-pencil-alt"></i>',
-        '</button>'
-    ].join('\n');
-
-    return edit +' '+ del;
-}
-
-
-
-$(document).ready(function() {
-
-    // When document is ready
-    // -------------------------------------------------------------------------
-
-    
-    
-    /** init_table
-     * --- -- -- - - -
-     * get categories
-     * constuct categories array
-     * render dataTable 
-     */
-    function init_table() {
-
-        // get all categories from server (ajax)
-        $.getJSON( "/wiki/ajax", { action: "tags_stats" } )
-        .done(function( json ) {
-            // then ...
-
-            // reset tags
-            tags.length = 0;
-
-            // construct tags data
-            Object.keys(json).forEach( key => {
-                el = json[key];
-                tags.push({
-                    id: parseInt(el.id),
-                    title: el.name,
-                    counter: parseInt(el.totals),
-                    actions: create_actions_html(el.id)
-                });
-            });
-
-            // destroy previous datatable table instances
-            $('#dt-tags').dataTable().fnClearTable();
-            $('#dt-tags').dataTable().fnDestroy();
-
-            // (re-)create categories datatable
-            table = $('#dt-tags').DataTable({
-                language: { url: '/libs/DataTables/localization/Greek.json' },           
-                data: tags,
-                order: [[1, 'desc']],
-                columns: [
-                    { data: 'title' },
-                    { data: 'counter' },
-                    { data: 'actions', width: '64px' }
-                ],
-                columnDefs: [{
-                    'targets': [2],
-                    'orderable': false
-                }]
-            });
-
-        })
-        .fail(function( jqxhr, textStatus, error ) {
-            console.log( "Request Failed (" + error +")" );
-        });
-
-    }
-    init_table();   // init table on first run
-
-
-
-    /** When modal show-up
-     * -------------------------------------------------------------------------
-     * ... prepare the manage-category form 
-     * ... update select2 with possible parents
-     */
-    $('#manageCategory').on('show.bs.modal', event => {
-        var button = $(event.relatedTarget);        // Button that triggered the modal
-        var id = parseInt( button.data('id') );     // category_id from data-id
-        // var modal = $(this);    // modal object     
-        
-        // update modal literature
-        // ---
-        $('#manageCategory .modal-title').html(             // modal title
-            (id) ? 'Ενημέρωση Κατηγορίας' : 'Δημιουργία Κατηγορίας'
-        );
-        $('#manageCategory form input[name=id]').val( id );     // category id (hidden)
-        $('#manageCategory form input[name=title]').val(    // category title
-            (id) ? category_record(id).title : ""
-        );
-        prepare_parents_element(id);        // prepare <select> for parents
-    })
-
-
-    // When form is submited
-    // -------------------------------------------------------------------------
-
-    $('#manageCategory form').submit( event => {
-        event.preventDefault();
-
-        // prepare data to POST
-        var data = {
-            id: parseInt($('#manageCategory form input[name=id]').val()),
-            title: $('#manageCategory form input[name=title]').val(),
-            parent_id: parseInt($('#parent_id').select2('data')[0].id)
-        };
-
-        // select action url (add or update)
-        var request = '/wiki/ajax?action=' + ((data.id == 0)  ? 'add_category' : 'update_category');
-
-        // send POST request
-        $.post(request, data)
-        .done(function( data ) {
-
-            $('#manageCategory').modal('hide');     // when done, close modal
-
-            init_table();       // reload table of categories
-        });       
-
-    });
-
-});