Introduction
============
The *fragalysis-backend* codebase (https://github.com/xchem/fragalysis-backend) contains the python code used on the
back-end of fragalysis (https://fragalysis.diamond.ac.uk) and controls:

- Models - the database table definitions for the postgres database that serves fragalysis data
- Views - the Django Rest Framework views that handle which data can be served to either the front-end or a user, and
  how it is served to them
- Media - serving of files via views and nginx (see
  https://docs.djangoproject.com/en/3.1/howto/static-files/deployment/#serving-static-files-from-a-dedicated-server)
- Tasks - some tasks for uploading files via a user-facing page
- Templates - some templates to allow users to upload certain files

If you understand all of the concepts briefly mentioned here, you may want to go ahead and
:ref:`setup your developer stack <stack-setup>`

For Newbies
-----------
If you are unfamiliar with django or RESTful APIs, and are hoping to develop fragalysis backend, we recommend that you
start by familiarising yourself with the following:

- Django:
   - overview: https://www.djangoproject.com/start/overview/
   - tutorial: https://docs.djangoproject.com/en/3.1/intro/tutorial01/
- Model, View, Controller software design pattern:
   - wiki: https://en.wikipedia.org/wiki/Model–view–controller
   - tutorial: https://blog.codinghorror.com/understanding-model-view-controller/
- RESTful APIs:
   - wiki: https://en.wikipedia.org/wiki/Representational_state_transfer
   - restfulapi.net: https://restfulapi.net
- Django Rest Framework: https://www.django-rest-framework.org

Once you feel like you understand these concepts, a good thing to do is :ref:`setup your developer stack <stack-setup>`

Context
-------
This section aims to briefly describe the context of the back-end code in terms of the data serverd to the front-end
application.

The image below shows a target page from fragalysis (https://fragalysis.diamond.ac.uk/viewer/react/preview/target/Mpro)
and highlights it's 3 main functions:

1. Serving crystallographic data
2. Allowing a user to navigate the data in 3D
3. Serving 2D and 3D information relating to new molecule designs

The image also highlights some of the data-types associated with these functionalities

.. image:: ../context.jpg

This data is all contained within a number of database tables in the backend codebase, defined by django *Models*; and
served to the frontend via. RESTful endpoints, defined through Django and Django Rest Framework *Views*.

Although it could, the backend does not directly handle the loading (upload of data to fragalysis server and processing
to put into database) of **most** data - this is done by the loader (https://github.com/xchem/fragalysis-loader).

The rest of the documentation attempts to present code-level documentation and tutorials to the developer within the
context described here.

1. Crystallographic data:
    - links
2. Computed data:
    - links
3. API (Restful) - data
    - links
4. Serving media - files
    - links

The Stack
---------
The fragalysis stack is very intentionally split up into many components, each with its own codebase. This documentation
only covers the backend, as described in the introduction.