Design Doc 015: Merchant backoffice Routing
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Motivation
==========

A well defined routing will allow users to share backoffice links pointing directly into instance pages (settings, orders, products, etc...)
The backoffice should load from the instance URL and then allow a internal 
rounting of the views with the posibility to accessing them directly when 
sharing a link.


Application rounting
====================

There are 2 type of rounting: external and internal

  external: define how the pathname of the URL will be interpreted to infer
  which instance is being accessed. Also the full URL is used as default when
  no BACKEND_URL exist yet in localStorage. After login, the BACKEND_URL is saved
  in localStorage and the pathname is parsed to infer the instance id.

  internal: define wich view will be rendered. It is implemented using a hash
  routing since 1) the SPA is not server side rendered and 2) the http servers
  doest not need to care about matching all applications URL

Some border cases:
https://bugs.gnunet.org/view.php?id=6811


Application Ready definition
============================

The application is considered ready after

 * the user tried to login.
 * the applicaton checked that the backend url points to a merchant backend
 * the merchant backend response successfully

The backoffice test for $BACKEND_URL/config to define if the $BACKEND_URL is ok.
The application can potentially test if the protocol or version matched. 

While the application is not ready, just the top navigation bar will be shown
with a message in the left and the lang selection option.


Application entry points
========================

When the application is ready to start, it queries the backend to test if the
user can access to the list of instance and decide if the admin panel should be
accesible.

All of this entry points that do not require a paramenter (like $ID) should be
accesbile from the Sidebar.

If the admin panel is accesible, this entry points are available:

 - /instances: Show the list of instances currently created
 - /instance/new: Show a instance creation form
 - /instance/$ID/update: Show a instance modify form and allow updating it

Where admin or not, there is also this entry points:

 - / : redirects to the instance settings page
 - /update: instance setting page, renders a form and allow modifing it
 - /products: list of instance products
 - /product/$ID/update: product modification page
 - /product/new : product creation page
 - /orders : list of instance orders
 - /transfers : list of transfers

Special cases
=============

First time
----------

If the application is loaded for the first time a welcoming message is shown
with the login form (even if the backend doest not need authentication)

Log out
-------

On logout, the application go to the initial state

Unauthorized
------------

For any case that the backend respond 401 the application will render the
login view showing a notification error that the user must check the login
credentials or the backend url

Not found
---------

For any case that the backend respond 404 the application will render a 
custom not found page

Missing default instance
------------------------

If the **user is admin** AND is loading the setting page (/update), product list
(/products), order list (/orders) or transfer list (/transfers) AND **gets a
404** it will tell the user that it need to create a default instance before
proceeding.


Checking for admin rights
=========================

The token and backend url provided may give access to the default instance and
in that case an admin functionality should be accesbile.

This check is done after the query to $BACKEND_URL/config returns 200 validating
that it points to a correct merchant backend. Sidebar with access to the logout
button should be shown after this point.

The user is considered admin if has access to the default instance. This will be
defined after quering $BACKEND_URL/private/instances.

 * HTTP response 200: means that $BACKEND_URL points to default instance and
   user has admin rights 
 * HTTP response 401: means that $BACKEND_URL points to default instance but
   wrong credentials (either no there or invalid). It will render login screen.
 * HTTP response 404: means that $BACKEND_URL its not the default instance and
   will asume that $BACKEND_URL points to a non default instance (since
   $BACKEND_URL/config should have responded 200)
 * HTTP respone with error code: render the error message and the login screen.

When testing for admin rights and if the response is 404, the application will
parse the $BACKEND_URL pathname and expect to match exactly '/instances/$ID'
(optionally ending with a slash) and use $ID as the instance $ID for any
operation that needs it. If fails to infer the instance $ID render an error
message with a login screen.


Credentials
============

All tokens are saved in localStorage with key ``backend-token-$ID``, the default
backend token have the key ``backend-token``.

Default instance user is expected to jump from one instance to another in the
same session so all queries to the backend will be to
``${BACKEND_URL}/instances/${CURRENT_INSTANCE_ID}`` with the ``BACKEND_URL`` provided in
the login form and using the token expected to ``$CURRENT_INSTANCE_ID``. 

Queries from a normal user will be done directly to ``$BACKEND_URL`` and using token
from the login form.