From 47cbb529f5723b246125ae083a193e11481b89ef Mon Sep 17 00:00:00 2001
From: George Halkiadakis <gchalkiadakis@sklavenitis.co.gr>
Date: Sun, 12 Mar 2023 07:01:30 +0200
Subject: initializing classroom structure using anom framework

---
 helpers/design_patterns.php | 104 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 helpers/design_patterns.php

(limited to 'helpers/design_patterns.php')

diff --git a/helpers/design_patterns.php b/helpers/design_patterns.php
new file mode 100644
index 0000000..d66ffa9
--- /dev/null
+++ b/helpers/design_patterns.php
@@ -0,0 +1,104 @@
+<?php
+/** proxy
+ * implements the proxy design pattern
+ * 
+ * uses: Registry::cache
+ * 
+ * algorithm:
+ * - 1: proxy gets (Class::method, Arguments) and calculates a unique key
+ * - 2: if a valid Cache for the triplete's key exists, it is served immediately
+ * - 3: otherwise calls Class::Method(Arguments), caches then serves response
+ * 
+ * @param $class_method (array): a 2 (string) items array in the form
+ *    : [ 'fully\qualifies\ClassName' , 'methodName' ]
+ *    : Using the ClassName::class notation is strongly recommended.
+ * @param $args: array of arguments (passed to the Class::Method())
+ * @param $ttl: time (in sec) where the data will remain valid (not expired)
+ * @param $options: bitwise flags*
+ * ---
+ * @return $data (mixed)
+ * 
+ * (*) option flags
+ * all option flags represend non default behaviour of proxy
+ * ---
+ * PROXY_CACHE_ERRORS : cache value even if callback returns error
+ * PROXY_IGNORE_CACHE : ignore if cache exist; get result from callback
+ * PROXY_DO_NOT_CACHE : do not cache the result (even if from callback)
+ */
+function proxy(array $callable, array $args, int $ttl, int $options=0)
+{   
+    // resolve option flags
+    $cache_errors = ($options&PROXY_CACHE_ERRORS) ? true : false;
+    $ignore_cache = ($options&PROXY_IGNORE_CACHE) ? true : false;
+    $do_not_cache = ($options&PROXY_DO_NOT_CACHE) ? true : false;
+
+    // we're gonna use cache;
+    $cache = Registry::use('cache');
+
+
+    // check validity of callable argument
+    // -------------------------------------------------------------------------
+    if ((!is_callable($callable)) || (!is_array($callable))) {
+
+        throw new Exception(
+            'Proxy\'s first parameter has to be a callable array [fully\\qualified\\ClassName, method], passed:'.print_r($callable, true)
+        );
+
+    }
+
+    // create a unique key
+    // -------------------------------------------------------------------------
+    list($class, $method) = $callable;
+    $key = sha1(
+        $class .':'. $method .':'. json_encode(
+            $args, JSON_UNESCAPED_LINE_TERMINATORS|JSON_UNESCAPED_UNICODE
+        )
+    );
+
+    // search cache if data for this key exist
+    // -------------------------------------------------------------------------
+    if (!$ignore_cache) {
+        $data = $cache->get($key);
+
+    } else { $data = false; }   // ignore cache? pass false
+
+
+    if ($data !== false) {      // if exists, serve cached data
+
+        // if cashed data exist
+        // ---------------------------------------------------------------------
+        # if (!PRODUCTION)   Benchmark::add_spot('proxy-cached');
+        if ($data == '_ERROR_')   return false;   // previous cached error
+        else return $data;  // previous cache ()
+
+
+    } else {    // else (not exist)...
+
+        // no data on cache -> get data from Class::method( arguments )
+        // ---------------------------------------------------------------------
+        $data = call_user_func_array($callable, $args);
+
+        // handle newly created data
+        // ---------------------------------------------------------------------
+
+        // if faulty data, return false
+        if ($data == false) {
+
+            if ($cache_errors && !$do_not_cache)   {   // cache the error
+                $cache->set($key, '_ERROR_', $ttl);
+            }
+
+            # if (!PRODUCTION)   Benchmark::add_spot('proxy-new-error');
+            return false;
+        }
+
+        // store to cache
+        if (!$do_not_cache) {
+            $cache->set($key, $data, $ttl);
+        }
+
+        # if (!PRODUCTION)   Benchmark::add_spot('proxy-new');
+        return $data;   // serve data
+    }
+
+}
-- 
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