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Build read receipts using Django

  • Samuel Ogundipe
May 30th, 2017
A basic understanding of Django and Vue.js is needed to follow this tutorial.

Today, we will make a read receipt framework for your chat app with Django and Pusher.

Setting up Django

First, we need to install the Python Django library if we don't already have it. To install Django, we run:

    pip install django

After installing Django, it’s time to create our project. Open up a terminal, and create a new project using the following command:

    django-admin startproject pusher_message

In the above command, we created a new project called pusher_message. The next step will be to create an app inside our new project. To do that, let’s run the following commands:

    //change directory into the pusher_message directory
    cd pusher_message
    //create a new app where all our logic would live
    django-admin startapp message

Once we are done setting up the new app, we need to tell Django about our new application, so we will go into our pusher_message\settings.py and add the message app to our installed apps as seen below:

    INSTALLED_APPS = [
        'django.contrib.admin',
        'django.contrib.auth',
        'django.contrib.contenttypes',
        'django.contrib.sessions',
        'django.contrib.messages',
        'django.contrib.staticfiles',
        'message'
    ]

After doing the above, it’s time for us to run the application and see if all went well. In our terminal shell, we run:

    python manage.py runserver

If we navigate our browser to http://localhost:8000, we should see the following:

read-receipts-django-first-page

Set up an app on Pusher

At this point, Django is ready and set up. We now need to set up Pusher, as well as grab our app credentials. We need to sign up on Pusher and create a new app, and also copy our secret, application key and application id.

read-receipts-django-create-app

The next step is to install the required libraries:

    pip install pusher

In the above bash command, we installed one package, pusher. This is the official Pusher library for Python, which we will be using to trigger and send our messages to Pusher.

Creating our application

First, let us create a model class, which will generate our database structure. Let's open up message\models.py and replace the content with the following:

    from django.db import models

    from django.contrib.auth.models import User
    # Create your models here.
    class Conversation(models.Model):
        user = models.ForeignKey(User, on_delete=models.CASCADE)
        message = models.CharField(blank=True, null=True, max_length=225)
        status = models.CharField(blank=True, null=True, max_length=225)
        created_at = models.DateTimeField(auto_now=True)

In the above block of code, we defined a model called Conversation. The conversation table consists of the following fields:

  • A field to link the message to the user that created it
  • A field to store the message
  • A field to store the status of the message
  • A filed to store the date and time the message was created

Running migrations

We need to make migrations and also run them, so our database table can be created. To do that, let us run the following in our terminal:

    python manage.py makemigrations

    python manage.py migrate

Creating our views

In Django, the views do not necessarily refer to the HTML structure of our application. In fact, we can see it as our Controller as referred to in some other frameworks. Let us open up our views.py in our message folder and replace the content with the following:

    from django.shortcuts import render
    from django.contrib.auth.decorators import login_required
    from django.views.decorators.csrf import csrf_exempt
    from pusher import Pusher
    from .models import *
    from django.http import JsonResponse, HttpResponse

    # instantiate pusher
    pusher = Pusher(app_id=u'XXX_APP_ID', key=u'XXX_APP_KEY', secret=u'XXX_APP_SECRET', cluster=u'XXX_APP_CLUSTER')
    # Create your views here.
    #add the login required decorator, so the method cannot be accessed withour login
    @login_required(login_url='login/')
    def index(request):
        return render(request,"chat.html");

    #use the csrf_exempt decorator to exempt this function from csrf checks
    @csrf_exempt
    def broadcast(request):
        # collect the message from the post parameters, and save to the database
        message = Conversation(message=request.POST.get('message', ''), status='', user=request.user);
        message.save();
        # create an dictionary from the message instance so we can send only required details to pusher
        message = {'name': message.user.username, 'status': message.status, 'message': message.message, 'id': message.id}
        #trigger the message, channel and event to pusher
        pusher.trigger(u'a_channel', u'an_event', message)
        # return a json response of the broadcasted message
        return JsonResponse(message, safe=False)

    #return all conversations in the database
    def conversations(request):
        data = Conversation.objects.all()
        # loop through the data and create a new list from them. Alternatively, we can serialize the whole object and send the serialized response 
        data = [{'name': person.user.username, 'status': person.status, 'message': person.message, 'id': person.id} for person in data]
        # return a json response of the broadcasted messgae
        return JsonResponse(data, safe=False)

    #use the csrf_exempt decorator to exempt this function from csrf checks
    @csrf_exempt
    def delivered(request, id):

        message = Conversation.objects.get(pk=id);
        # verify it is not the same user who sent the message that wants to trigger a delivered event
        if request.user.id != message.user.id:
            socket_id = request.POST.get('socket_id', '')
            message.status = 'Delivered';
            message.save();
            message = {'name': message.user.username, 'status': message.status, 'message': message.message, 'id': message.id}
            pusher.trigger(u'a_channel', u'delivered_message', message, socket_id)
            return HttpResponse('ok');
        else:
            return HttpResponse('Awaiting Delivery');

In the code above, we have defined four main functions which are:

  • index
  • broadcast
  • conversation
  • delivered

In the index function, we added the login required decorator, and we also passed the login URL argument which does not exist yet, as we will need to create it in the urls.py file. Also, we rendered a default template called chat.html which we will also create soon. In the broadcast function, we retrieved the content of the message being sent, saved it into our database, we finally trigger a Pusher request passing in our message dictionary, as well as a channel and event name. In the conversations function, we simply grab all conversations and return them as a JSON response Finally, we have the delivered function, which is the function which takes care of our read receipt feature. In this function, we get the conversation by the ID supplied to us, we then verify that the user who wants to trigger the delivered event isn’t the user who sent the message in the first place. Also, we pass in the socket_id so that Pusher does not broadcast the event back to the person who triggered it. The socket_id stands as an identifier for the socket connection that triggered the event.

Populating the urls.py

Let us open up our pusher_message\urls.py file and replace with the following:

    """pusher_message URL Configuration

    The `urlpatterns` list routes URLs to views. For more information please see:
        https://docs.djangoproject.com/en/1.11/topics/http/urls/
    Examples:
    Function views
        1. Add an import:  from my_app import views
        2. Add a URL to urlpatterns:  url(r'^$', views.home, name='home')
    Class-based views
        1. Add an import:  from other_app.views import Home
        2. Add a URL to urlpatterns:  url(r'^$', Home.as_view(), name='home')
    Including another URLconf
        1. Import the include() function: from django.conf.urls import url, include
        2. Add a URL to urlpatterns:  url(r'^blog/', include('blog.urls'))
    """
    from django.conf.urls import url
    from django.contrib import admin
    from django.contrib.auth import views
    from message.views import *

    urlpatterns = [
        url(r'^$', index),
        url(r'^admin/', admin.site.urls),
        url(r'^login/$', views.login, {'template_name': 'login.html'}), 
        url(r'^logout/$', views.logout, {'next_page': '/login'}),
        url(r'^conversation$', broadcast),
        url(r'^conversations/$', conversations),
        url(r'^conversations/(?P<id>[-\w]+)/delivered$',delivered)
    ]

What has changed in this file? We have added 6 new routes to the file. We have defined the entry point, and have assigned it to our index function. Next, we defined the login URL, which the login_required decorator would try to access to authenticate users. We have used the default auth function to handle it but passed in our own custom template for login, which we will create soon. Next, we defined the routes for the conversation message trigger, all conversations, and finally the delivered conversation.

Creating the HTML files

Now we will need to create two HTML pages, so our application can run smoothly. We have referenced two HTML pages in the course of building the application which are:

  • login.html
  • chat.html

Let us create a new folder in our messages folder called templates. Next, we create a file called login.html in our templates folder and replace it with the following:

    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
      {% if form.errors %}

    <center><p>Your username and password didn't match. Please try again.</p></center>
    {% endif %}

    {% if next %}
        {% if user.is_authenticated %}

    <center><p>Your account doesn't have access to this page. To proceed,
        please login with an account that has access.</p></center>
        {% else %}

    <center><p>Please login to see this page.</p></center>
        {% endif %}
    {% endif %}

    <div class="container">
        <div class="row">
            <div class="col-md-4 col-md-offset-4">
                <div class="login-panel panel panel-default">
                    <div class="panel-heading">
                        <h3 class="panel-title">Please Sign In</h3>
                    </div>
                    <div class="panel-body">
                        <form method="post" action="">
    {% csrf_token %}

                            <p class="bs-component">
                                <table>
                                    <tr>
                                        <td>{{ form.username.label_tag }}</td>
                                        <td>{{ form.username }}</td>
                                    </tr>
                                    <tr>
                                        <td>{{ form.password.label_tag }}</td>
                                        <td>{{ form.password }}</td>
                                    </tr>
                                </table>
                            </p>
                            <p class="bs-component">
                                <center>
                                    <input class="btn btn-success btn-sm" type="submit" value="login" />
                                </center>
                            </p>
                            <input type="hidden" name="next" value="{{ next }}" />
                        </form>
                    </div>
                </div>
            </div>
        </div>
    </div>

Next, let us create the `chat.html` file and replace it with the following:

     <html>
        <head>
            <title>
            </title>
        </head>
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"/>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.3.2/vue.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.16.1/axios.min.js"></script>
        <script src="//js.pusher.com/4.0/pusher.min.js"></script>
        <style>
            .chat
    {
        list-style: none;
        margin: 0;
        padding: 0;
    }

    .chat li
    {
        margin-bottom: 10px;
        padding-bottom: 5px;
        border-bottom: 1px dotted #B3A9A9;
    }

    .chat li.left .chat-body
    {
        margin-left: 60px;
    }

    .chat li.right .chat-body
    {
        margin-right: 60px;
    }


    .chat li .chat-body p
    {
        margin: 0;
        color: #777777;
    }

    .panel .slidedown .glyphicon, .chat .glyphicon
    {
        margin-right: 5px;
    }

    .panel-body
    {
        overflow-y: scroll;
        height: 250px;
    }

    ::-webkit-scrollbar-track
    {
        -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3);
        background-color: #F5F5F5;
    }

    ::-webkit-scrollbar
    {
        width: 12px;
        background-color: #F5F5F5;
    }

    ::-webkit-scrollbar-thumb
    {
        -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,.3);
        background-color: #555;
    }

        </style>
        <body>
            <div class="container" id="app">
        <div class="row">
            <div class="col-md-12">
                <div class="panel panel-primary">
                    <div class="panel-heading">
                        <span class="glyphicon glyphicon-comment"></span> Chat

                    </div>
                    <div class="panel-body">
                        <ul class="chat" id="chat" >
                           <li class="left clearfix" v-for="data in conversations">
                            <span class="chat-img pull-left" >
                               <img :src="'http://placehold.it/50/55C1E7/fff&amp;text='+data.name" alt="User Avatar" class="img-circle"/> 
                            </span>
                                <div class="chat-body clearfix">
                                    <div class="header">
                                        <strong class="primary-font" v-html="data.name">  </strong> <small class="pull-right text-muted" v-html="data.status"></small>
                                    </div>
                                    <p v-html="data.message">

                                    </p>
                                </div>
                            </li>
                        </ul>
                    </div>
                    <div class="panel-footer">
                        <div class="input-group">
                            <input id="btn-input" v-model="message" class="form-control input-sm" placeholder="Type your message here..." type="text">
                            <span class="input-group-btn">
                                <button class="btn btn-warning btn-sm" id="btn-chat" @click="sendMessage()">
                                    Send</button>
                            </span>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
    </body>
    </html>

Vue component and Pusher bindings

That’s it! Now, whenever a new message is delivered, it will be broadcast and we can listen using our channel to update the status in realtime. Below is our Example component written using Vue.js Please note: In the Vue component below, a new function called **queryParams** was defined to serialize our POST body so it can be sent as x-www-form-urlencoded to the server in place of as a payload. We did this because Django cannot handle requests coming in as** payload.

    <script>
        var pusher = new Pusher('XXX_APP_KEY',{
          cluster: 'XXX_APP_CLUSTER'
        });
        var socketId = null;
        pusher.connection.bind('connected', function() {
            socketId = pusher.connection.socket_id;

        });

        var my_channel = pusher.subscribe('a_channel');
        var config = { headers: { 'Content-Type': 'application/x-www-form-urlencoded' } };
        new Vue({
            el: "#app",
            data: {
                    'message': '',
                    'conversations': []
            },
            mounted() {
                this.getConversations();
                this.listen();

            },
            methods: {
                sendMessage() {
                    axios.post('/conversation', this.queryParams({message: this.message}), config)
                        .then(response => {
                            this.message = '';
                        });
                },
                getConversations() {
                    axios.get('/conversations').then((response) => {
                        this.conversations = response.data;
                        this.readall();
                    });  
                },
                listen() {
                    my_channel.bind("an_event", (data)=> {
                        this.conversations.push(data);
                        axios.post('/conversations/'+ data.id +'/delivered', this.queryParams({socket_id: socketId}));
                    })

                     my_channel.bind("delivered_message", (data)=> {
                        for(var i=0; i < this.conversations.length; i++){
                            if (this.conversations[i].id == data.id){
                                this.conversations[i].status = data.status;
                            }
                        }

                    })
                },
                readall(){

                      for(var i=0; i < this.conversations.length; i++){
                            if(this.conversations[i].status=='Sent'){
                                axios.post('/conversations/'+ this.conversations[i].id +'/delivered');
                            }
                        }

                },
                queryParams(source) {
                    var array = [];

                    for(var key in source) {
                        array.push(encodeURIComponent(key) + "=" + encodeURIComponent(source[key]));
                    }

                    return array.join("&");
                    }
            }
        });
    </script>

Below is the image demonstrating what we have built:

read-receipts-django-demo

Conclusion

In this article, we have covered how to create a read receipt framework using Django and Pusher. We have gone through exempting certain functions from CSRF checks, as well as exempting the broadcaster from receiving an event they triggered.

  • Channels

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