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django-api-tools

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Django API Tools is an add-on which allows developers to run RESTful APIs alongside websites using Forms/Templates.

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# Django API Tools #

*Quickstart Guide can be found <a href="#quickstart-guide">here</a>.*

## Overview ##

*Django API Tools is an add-on which allows developers to run RESTful APIs alongside websites using Forms/Templates.*

**Features:**

* Simple integration with an existing project - choose a subset of models to be served by the API.
* RESTful JSON endpoints created for your chosen Django models - no need to hard code URLs.
* Endpoint routing to application specific logic. GET (Read), POST (Create, Update, Deactivate) operations supported by default.
* Supports the addition of custom endpoints.
* Authentication via Django's user auth mechanism; supports login/logout operations as well as custom user permissions on models.

# APIView #

APIView is the add-on's custom class based view. RESTful endpoints are automatically created for each model registered with APIView *(note: these models must subclass APIModel.)*. This allows APIView to take care of routing and responding to requests. A description of the set of URLs created for each registered model can be found in the section <a href="#restful-urls">RESTful URLs</a> below.

The add-on offers developers the flexibility in choosing database models to be exposed by the API, and at a lower level, individual model attributes that can be exposed *(see <a href="#defining-ownership">Defining Ownership below)*.

** We can write views.py using APIView as below:**

```python

from django_api_tools.APIView import APIView
from example.models import Foo, Bar, Profile

class ExampleAPIView(APIView):
    # models can map to custom endpoint names
    registered_endpoints = {
        'f': Foo,
        'bar': Bar,
        'profile': Profile
    }

# Optional attribute:
    # models which allow instances to be created without authentication
    public_create_endpoints = (Profile, )

# Optional attribute:
    # models which allow instances to be updated without authentication
    public_update_endpoints = (Bar, )

# The statement evaluated upon a successful user login    # This should be a subclass of APIModel which can be dictified and returned as JSON
    return_on_login = 'user.profile'
```

** And add support for our new API in urls.py: **

```python
from django.conf.urls import patterns, include, url
from django.views.decorators.csrf import ensure_csrf_cookie
from example.views import PollsAPIView

# An arbitrary URL prefix, which if matched, forwards requests to the APIView
API_PREFIX = 'api'

urlpatterns = patterns('',
    .
    .
    .
    url(r'^{}/'.format(API_PREFIX), ensure_csrf_cookie(ExampleAPIView.as_view())),
)
```

### Logging in ###
``` POST /api/login/ ``` requires the parameters **username** and **password**. If the login is unsuccessful, either as a result of incorrect credentials or an inactive user, the API will return an empty 404 response. A successful login will both set an authenticated session and *dictify* the eval()'d **return_on_login** variable.

**return_on_login**: In many web applications, it is common for a user's profile page to be displayed after a successful login. However, the return_on_login variable provides flexibility over what model should be dictified after a successful login. Note that the model returned must be a subclass of APIModel.

### Logging out ###
``` POST /api/logout/ ``` will delete the user's authenticated session (if logged in), and return an empty 200 response.

### Public Endpoints ###
Applications often require users to sign up. By default, the add-on requires authentication to create or update a model instance. With this default behaviour, APIView would reject any sign up requests, as registering users would  require authentication to complete the process. APIView provides a work around for these kinds of scenarios. Any models registered in **public_create_endpoints** and **public_update_endpoints** are immune from the default behaviour, and allow the public to create or update instances belonging to the models registered.

### RESTful URLs ###

Each model registered with APIView is automatically provided the following URLs *(assuming that the API_PREFIX is 'api')*:

**Get a list of resource instances:**

```GET /api/<endpoint>/?page=n ```

*Where n is an optional integer parameter defaulting to 1.*

Each page of results will return, by default, up to 10 resource instances. Where less than 10 instances are returned for a given page, it is safe to assume that there are no more pages.

*Returns:*

* An array of **short** dictionary objects.
* An empty 404 response for an invalid page number or a request to a non-existent page.

**Get an individual resource:**

``` GET /api/<endpoint>/<instance>/ ```

*Where instance is a unique identifier handled by the specific endpoint. By default, the identifier is treated as a Django model internal id.*

*Returns:*

* A **long** dictionary representation of the model instance.
* An empty 404 response if a model instance can't be found, and a custom request mapping can't be found.

*Notes:*

If no instance is found, APIView will treat the request as a custom request on the endpoint model. It will route the request to the model's ```api_custom_request(cls, request) ``` classmethod. You are free to implement custom requests however you wish.

**Custom request Type 2:**

```GET /api/<endpoint>/<instance>/<custom_field>/<custom_field2>/.../.../```

*Where there can be an arbitrary number of custom fields.*

*Returns:*

* An empty 404 response by default, unless code handling the custom request has been implemented.

**Create a new resource:**

```POST /api/<endpoint>/```

*Notes:*

The create request is routed to the endpoint's implementation of ``api_create(cls, request)``.

*Returns:*

* A **long** dictionary representation of the created model instance.
* An empty 404 response if an instance could not be created.

**Update an existing resource:**

```POST /api/<endpoint>/<instance>/```

*Notes:*

The update request is routed to the endpoint's implementation of ``api_update(self, request)``.

*Returns:*

* A **long** dictionary representation of the updated model instance.
* An empty 404 response if updating failed.

# APIModel #
APIModel is the add-on's custom abstract model class. Each model registered with APIView must be a subclass of APIModel and implement the abstract methods *is_owner*, *api_create* and *api_update*.

APIModel handles the *dictification* of instances, that is, creating a dictionary representation of the model instance *(see <a href="#dictification">Dictification</a> for a more detailed explanation*).

## Defining Ownership ##
Django API Tools allow model attributes to be divided into three authentication levels:

* Those that can be viewed by the public
* Those that only registered users of the application can view
* Those that can only be viewed by the owner(s) of a particular model instance.

Django API Tools use Django's standard user authentication system. Thus, much of the authentication revolves around extracting the **request_user** (request.user) and testing the users' authentication level against a model instance.

Django API Tools assumes that the underlying application can deduce, from the request user, the ownership status that particular user has over a given model instance.

**We highly recommend that your application has a model (inheriting from APIModel) with a 1:1 mapping to User.**

In the examples below we call this model *Profile*:
```python
class Profile(APIModel):
    user = models.OneToOneField(User, unique=True, related_name='profile')
```

Having this kind of setup provides a mechanism for extending Django's user model; we can add application-specific fields to Profile, such as *eye_colour*, which can then be extracted from a request via the notation ```request.user.profile.eye_colour```. Furthermore, having this setup provides a basis for authenticating "owners" of model instances.

Sub-classes of APIModel must implement the abstract method ```is_owner(self, request_user)```.

### Example 1: No ownership ###

Suppose we he had an application with a "Wall" which could be read from, written to, and modified by the public.
In this scenario, for any user, APIModel would always return True.

```python
class Wall(APIModel):
    .
    .
    .
    def is_owner(self, request_user):
        return True
```

### Example 2: Individual user ownership ###

Suppose our application was changed, such that each "Wall" now had an individual owner.
We could change ```is_owner``` to return True if the requesting user is the owner of the Wall.

```python
class Profile(APIModel):
    user = models.OneToOneField(User, unique=True, related_name='profile')

class Wall(APIModel):
    owner = models.ForeignKey(Profile, related_name='walls')
    .
    .
    .
    def is_owner(self, request_user):
        return request_user.profile == self.owner
```

### Example 3: Group ownership ###

We could change our application further so that each "Wall" is owned by a "Group", and that Groups consist of Profiles.
```is_owner``` would now return True if the requesting user is a member of the Group which owns the Wall.

```python
class Group(APIModel):
    .
    .
    .

class Profile(APIModel):
    user = models.OneToOneField(User, unique=True, related_name='profile')
    group = models.ForeignKey(Group, related_name='members')

class Wall(APIModel):
    owner = models.ForeignKey(Profile, related_name='walls')
    group = models.ForeignKey(Group, related_name='walls')
    .
    .
    .
    def is_owner(self, request_user):
        return request_user.profile.group == self.group
```

## Dictification ##

Dictification is the process of creating a dictionary representation of a model instance.
Although this process is largely taken care of by the underlying APIModel class, subclasses of APIModel must specify what attributes should be used.

### Long & Short Dictionaries ###

There are two types of dictification:

* Short - A partial dictionary representation of an object. Only dictifies attributes listed in the *short_description_fields*.
* Long - A full dictionary representation of an object. Dictifies attributes listed in both *short_description_fields* and *long_description_fields*.

```python
class Choice(APIModel):
    text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

short_description_fields = (id, )
    long_description_fields = (text, votes, )

```

```
c = Choice.obects.create(text='foo')

c.dictify_short()
>> {"id":1}

c.dictify_long()
>> {"id": 1, "text": "foo", "votes": 0}
```

### Foreign Model attributes ###

In a typical web application, some models will be related to other models.
API add-on supports both short and long dictification of related models:

*  Related - prefix "rel_short" or "rel_long"
*  One-to-One - prefix "onetoone_short" or "onetoone_long"
*  Foreign Key - prefix "fk_short" or "fk_long"
*  Many-to-Many - prefix "m2m_short" or "m2m_long"

```python
class Choice(APIModel):
    text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

short_description_fields = (id, )
    long_description_fields = (text, votes, rel_long_foos)

class Foo(APIModel):
    choice = models.ForeignKey(Choice, related_name='foos')
    text = models.CharField(max_length=200)

short_description_fields = (id, )
    long_description_fields = (text, fk_long_choice)
```

Upon dictification, APIModel would recognise the attribute *rel_long_bars* as a related key named bars, and create a long dictification of the related model. If instead the attribute was named *rel_short_bars*, the related model would only be dictified as a short dictionary.

```python
c = Choice.objects.create(text='foo')
f = Foo.objects.create(text='foo', choice=c)

f.dictify_short()
>> {"id":1}

f.dictify_long()
>> {"id": 1, "text": "foo",
      "choice": {"id", "text": "foo", "votes": 0}
   }

c.dictify_short()
>> {"id": 1}

c.dictify_long()
>> {"id", "text": "foo", "votes": 0,
      "foos":[
        {"id": 1, "text": "foo"}
      ]
   }

```

# Quickstart Guide #

``` sudo pip install django_api_tools ```

The quickstart guide adapts the model setup found in the <a href="https://docs.djangoproject.com/en/dev/intro/tutorial01/">Django Tutorial</a>, illustrating how you can set up and use Django API Tools in an application.

We adapt **views.py** to use the Class-based APIView:
```python

from django_api_tools.APIView import APIView
from polls.models import Question, Choice, Profile

class PollsAPIView(APIView):
    # models can map to custom endpoint names
    registered_endpoints = {
        'question': Question,
        'choice': Choice,
        'profile': Profile
    }

# models which allow instances to be created by the public
    public_create_endpoints = (Profile, )

# models which allow instances to be updated by the public
    public_update_endpoints = (Choice, )

# the endpoint instance whose JSON dictionary should be returned upon a successful user login
    return_on_login = 'user.profile'
```

We next hook up the **urls.py** to our class-based view:

```python
from django.conf.urls import patterns, include, url
from django.views.decorators.csrf import ensure_csrf_cookie
from polls.views import PollsAPIView

urlpatterns = patterns('',
    url(r'^api/', ensure_csrf_cookie(PollsAPIView.as_view())),
)
```

*Note that your API URLs don't necessarily have to start with /api/.*

Finally, we must create our **models.py**

```python
from datetime import datetime

from django_api_tools.APIModel import APIModel

from django.db import models
from django.contrib.auth.models import User

class Profile(APIModel):
    user = models.OneToOneField(User, unique=True, related_name='profile')

def is_owner(self, request_user):
      return request_user.profile == self.user

@classmethod
    def api_create(cls, request):
      # first create a user
      user = User.objects.create(username=request.POST['username', email=request.POST['email'], password=request.POST['password'])

# next create the profile object
      profile = Profile.objects.create(user=user)

# login code
      user = authenticate(username=user.username, password=user.password)
      login(request, user)

# return the object to be dictified
      return profile

def api_update(self, request):
        # APIModel provides default code for deactivation,
        # so it's wise to call the super api_update even
        # if you don't have any update logic yourself
        if self.is_owner(request.user):
            return super(Profile, self).api_update(request)

# Empty return if the request user didn't have proper permissions
        return None

class Question(APIModel):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

public_fields = ('id', 'question_text', 'pub_date')

def is_owner(self, request_user):
        # No ownership in this basic model setup, so everyone is treated as an owner
        return True

@classmethod
    def api_create(cls, request):
        question = Question.objects.create(question_text=request.POST['question'], pub_date=datetime.now())
        return question

# Empty return if the request user didn't have proper permissions
        return None

class Choice(APIModel):
    question = models.ForeignKey(Question)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)
    owner = models.ForeignKey(Profile, related_name='choices')

def is_owner(self, request_user):
      return request_user.profile == self.owner

@classmethod
    def api_create(cls, request):
        choice = Choice.objects.create(choice_text=request.POST['text'], owner=request.user)
        return choice

def api_update(self, request):
        if request.POST['vote']:
            self.votes += 1
        if self.is_owner(request.user):
            return super(Profile, self).api_update(request)

# Empty return if the request user didn't have proper permissions
        return None
```

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