REST (Representational State Transfer)
**************************************

.. note::

  This is an experimental feature.

``qx.io.rest.Resource`` allows to encapsulate the specifics of a REST interface. Rather than requesting URLs with a specific HTTP method manually, a resource representing the remote resource is instantiated and **actions** are invoked on this resource. A resource with its actions can be configured declaratively or programatically.

Configuring actions
===================

Given a REST-like interface with URLs that comply to the following pattern.

::

  GET      /photo/{id}
  PUT      /photo/{id}
  DELETE   /photo/{id}

  GET      /photos
  POST     /photos

Note ``{id}`` stands for a placeholder.

This interface comprises of two resources: ``photo`` and ``photos``.

To declare the specifics of the REST interface declaratively, pass a description to the constructor.

::

  // Singular resource
  var photo = new qx.io.rest.Resource({
    // Retrieve photo
    get: {
     method: "GET",
     url: "/photo/{id}"
    },

    // Update photo
    put: {
      method: "POST",
      url: "/photo/{id}"
    },

    // Delete photo
    del: {
      method: "DELETE",
      url: "/photo/{id}"
    }
  });

  // Plural resource
  var photos = new qx.io.rest.Resource({
    // Retrieve list of photos
    get: {
     method: "GET",
     url: "/photos"
    },

    // Create photo
    post: {
      method: "POST",
      url: "/photos"
    }
  });

Or programmatically, for each action.

::

  var photo = new qx.io.rest.Resource();
  photo.map("get", "GET", "/photo/{id}");

Invoking actions
================

Once configured, actions can be invoked. They are invoked by calling a method that is dynamically added to the resource on configuration of the action.

::

  photo.get({id: 1});
  // Alternatively: photo.invoke("get", {id: 1});
  // --> GET /photo/1

  photos.get();
  // Alternatively: photos.invoke("get");
  // --> GET /photos

When an action is invoked, an appropriate request is configured and send automatically.

Parameters
==========

If the URL contains parameters, the position where the parameters should be inserted can be specified by using `URI templates <http://tools.ietf.org/html/draft-gregorio-uritemplate-07>`_. Parameters are optional unless a check is defined. A default value can be provided.

::

  var photo = new qx.io.rest.Resource();
  photo.map("get", "GET", "/photo/{id}/{size=medium}", {id:  qx.io.rest.Resource.REQUIRED});

  photo.get({id: 1, size: "large"});
  // --> GET /photo/1/large

  photo.get({id: 1});
  // --> GET /photo/1/medium

  photo.get();
  // --> Error: Missing parameter 'id'

Events
======

Events are fired by the resource when the request was successful or any kind of error occurred. There are general resource events and action specific events. Handlers receive a ``qx.event.type.Rest`` event that, among other properties, includes the response.

::

  photo.get({id: 1});
  photo.put({id: 1});

  // "success" is fired when any request associated to resource receives a response
  photos.addListener("success", function(e) {
    e.getAction();
    // --> "get" or "put"
  });

  // "getSuccess" is fired when the request associated to the get action receives a response
  photos.addListener("getSuccess", function(e) {
    e.getAction();
    // --> "get"
  });

If the same action should be invoked multiple times and the events fired for each request be handled differently, it is possible to remember the id of the action’s invocation. The ``Rest`` event includes this id.

::

  var getPhotoId = photo.get({id: 1});
  var getLargePhotoId = photo.get({id: 1, size: "large"});
  photo.addListener("getSuccess", function(e) {
    if (e.getId() === getLargePhotoId) {
      // Handle large photo
    }
  });

Helpers
=======

Helpers make it easy to accomplish common tasks when working with requests.

* **refresh(action)** Resend request associated to action. Uses parameters given before.
* **poll(action, params)** Periodically invoke action.
* **longPoll(action)** Use Ajax long-polling to update whenever new data is available.

Data binding
============

A ``qx.data.store.Rest`` store can be attached to an action. Whenever a response is received, the model property of the store is updated with the marshaled response.

::

  var store = new qx.data.store.Rest(photos, "get");
  var list = new qx.ui.form.List();
  var controller = new qx.data.controller.List(null, list);
  store.bind("model", controller, "model");
  photos.longPoll("get");
