## Server-Client contract

Servers can serve content in 2 major formats: text/html and json (and links to many more content types)

Clients/browsers can handle content in many more ways; they can just passive render the content or they
can grow their proccessing and logic to become a smart engine or heavy application.

These 2 factors need to cooperate smoothly. So, it is necessary to pre-define:
- what a server serves
- what a borwser/client procceses

This contract:
- allows development sharing in separate teams
- sets clear rules for each development group
- helps developing an ecosystem of reliable tools that can be reused and extended
- helps to detect malfunctions and apply fixes and optimizations
- makes the project manageable and scalable


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## The Contract

A cotract is recommended to include as less as possible rules;

Of course there might be page-types that need special handling; Such pages are

- product pages

- product categories pages



### Rule #1: Default rule


On the server side:

- Server serves main content in html format; all non-user-based content is constucted and served in html format

On the client side:

- Client/browser requests the user-based content via ajax; (*still to be determinid the format of the replies*)



### Product Pages

 
apache:
serves product -> product: { id, title, prices:{ s1:{..}, s2:{..}, ... }, images:{...} }

browser:
check cookie(store) = s#
-> use product.prices.s# to draw prices


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