initial twilio proxy code

.env-dist

@@ -2,3 +2,6 @@ FXA_OAUTH_ENDPOINT=https://oauth-stable.dev.lcip.org/v1
 FXA_PROFILE_ENDPOINT=https://stable.dev.lcip.org/profile/v1
 SECRET_KEY=
 SENDGRID_API_KEY=
+TWILIO_ACCOUNT_SID=
+TWILIO_AUTH_TOKEN=
+TWILIO_SERVICE_ID=

phones/admin.py

@@ -0,0 +1,10 @@
+from django.contrib import admin
+
+from .models import Session
+
+
+class SessionAdmin(admin.ModelAdmin):
+    pass
+
+
+admin.site.register(Session, SessionAdmin)

phones/apps.py

@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class PhonesConfig(AppConfig):
+    name = 'phones'

phones/migrations/0001_initial.py

@@ -0,0 +1,22 @@
+# Generated by Django 2.2.9 on 2019-12-22 19:53
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Session',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('twilio_sid', models.CharField(max_length=34, unique=True)),
+                ('initiating_proxy_number', models.CharField(max_length=20)),
+            ],
+        ),
+    ]

phones/migrations/0002_session_initiating_real_number.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.2.9 on 2019-12-22 20:47
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('phones', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='session',
+            name='initiating_real_number',
+            field=models.CharField(default='', max_length=20),
+            preserve_default=False,
+        ),
+    ]

phones/migrations/0003_session_initiating_participant_sid.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.2.9 on 2019-12-23 15:14
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('phones', '0002_session_initiating_real_number'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='session',
+            name='initiating_participant_sid',
+            field=models.CharField(default='', max_length=20),
+            preserve_default=False,
+        ),
+    ]

phones/migrations/0004_auto_20191223_1815.py

@@ -0,0 +1,24 @@
+# Generated by Django 2.2.9 on 2019-12-23 18:15
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('phones', '0003_session_initiating_participant_sid'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='session',
+            name='status',
+            field=models.CharField(default='', max_length=20),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name='session',
+            name='initiating_participant_sid',
+            field=models.CharField(max_length=34),
+        ),
+    ]

phones/models.py

@@ -0,0 +1,9 @@
+from django.db import models
+
+
+class Session(models.Model):
+    twilio_sid = models.CharField(max_length=34, unique=True, blank=False)
+    initiating_proxy_number = models.CharField(max_length=20, blank=False)
+    initiating_real_number = models.CharField(max_length=20, blank=False)
+    initiating_participant_sid = models.CharField(max_length=34, blank=False)
+    status = models.CharField(max_length=20, blank=False)

phones/sequence-diagram.mmd

@@ -0,0 +1,17 @@
+sequenceDiagram
+    User->>Relay Phone Number: TXT {minutes}
+    Relay Phone Number->>Proxy Number: Creates {minutes} session
+    Relay Phone Number->>User: TXT {proxy number}
+    User->>3rd Party: give {proxy number} as phone number
+    loop proxied TXT conversation
+        3rd Party->>Proxy Number: TXT
+        Proxy Number->>User: TXT
+        User->>Proxy Number: TXT
+        Proxy Number->>3rd Party: TXT
+    end
+    opt TODO: manual stop
+        User->>Proxy Number: TXT "stop"
+    end
+    opt manual reset
+        User->>Relay Phone Number: TXT "reset"
+    end

phones/tests.py

@@ -0,0 +1,3 @@
+from django.test import TestCase
+
+# Create your tests here.

phones/urls.py

@@ -0,0 +1,9 @@
+from django.urls import path
+
+from . import views
+
+
+urlpatterns = [
+    path('main-twilio-webhook', views.main_twilio_webhook),
+    path('twilio-proxy-out-of-session', views.twilio_proxy_out_of_session),
+]

phones/views.py

@@ -0,0 +1,140 @@
+from decouple import config
+from phonenumbers import parse, format_number
+from phonenumbers import PhoneNumberFormat
+from twilio.rest import Client
+from twilio.twiml.messaging_response import MessagingResponse
+
+from django.core.exceptions import MultipleObjectsReturned
+from django.http import HttpResponse, HttpResponseNotFound
+from django.shortcuts import render
+from django.views.decorators.csrf import csrf_exempt
+
+from .models import Session
+
+
+account_sid = config('TWILIO_ACCOUNT_SID', None)
+auth_token = config('TWILIO_AUTH_TOKEN', None)
+client = Client(account_sid, auth_token)
+service = client.proxy.services(config('TWILIO_SERVICE_ID'))
+
+
+PROMPT_MESSAGE = "For how many minutes do you need a relay number?"
+
+
+@csrf_exempt
+def main_twilio_webhook(request):
+    resp = MessagingResponse()
+    from_num = request.POST['From']
+    body = request.POST['Body'].lower()
+
+    if body == 'reset':
+        from_num_sessions = Session.objects.filter(
+            initiating_real_number=from_num
+        )
+        for session in from_num_sessions:
+            service.sessions(session.twilio_sid).update(status='closed')
+        from_num_sessions.delete()
+        resp.message(
+            "Relay session reset. \n%s" % PROMPT_MESSAGE
+        )
+        return HttpResponse(resp)
+
+    # TODO: remove this check; allow users to have multiple sessions at once?
+    if body != 'reset':
+        existing_sessions = Session.objects.filter(
+            initiating_real_number=from_num
+        )
+        if existing_sessions:
+            pretty_proxy = format_number(
+                parse(existing_sessions[0].initiating_proxy_number),
+                PhoneNumberFormat.NATIONAL
+            )
+            resp.message(
+                "You already have a relay number: \n%s. \n"
+                "Reply 'reset' to reset it." % pretty_proxy
+            )
+            return HttpResponse(resp)
+
+    try:
+        ttl_minutes = int(body)
+    except ValueError:
+        resp.message(PROMPT_MESSAGE)
+        return HttpResponse(resp)
+
+    session = service.sessions.create(ttl=ttl_minutes*60,)
+    participant = service.sessions(session.sid).participants.create(
+        identifier=from_num
+    )
+    proxy_num = participant.proxy_identifier
+
+    # store this half-way open session in our local DB,
+    # so when the next number texts the proxy number,
+    # we can add them as the 2nd participant and open the session
+    Session.objects.create(
+        twilio_sid = session.sid,
+        initiating_proxy_number=proxy_num,
+        initiating_real_number=from_num,
+        initiating_participant_sid=participant.sid,
+        status='waiting-for-party',
+    )
+
+    # reply back with the number and minutes it will live
+    pretty_from = format_number(parse(from_num), PhoneNumberFormat.NATIONAL)
+    pretty_proxy = format_number(parse(proxy_num), PhoneNumberFormat.NATIONAL)
+    resp.message(
+        '%s will forward to this number for %s minutes' %
+        (pretty_proxy, ttl_minutes)
+    )
+    return HttpResponse(resp)
+
+
+@csrf_exempt
+def twilio_proxy_out_of_session(request):
+    """
+    By design, Relay doesn't know who the 2nd participant is before they text
+    the 1st participant.
+
+    Twilio requires both participants be added to a session before either can
+    communicate with the other. When the 2nd participant sends their first text
+    to a 1st participant, it triggers an "out-of-session" hook.
+
+    So, we use this to add the 2nd participant to the existing session, relay
+    the 2nd participant's message, and the 2 parties can begin communicating
+    thru the proxy number.
+
+    TODO: detect real out-of-session messages - i.e., not first messages
+    """
+    resp = MessagingResponse()
+
+    try:
+        db_session = Session.objects.get(
+            initiating_proxy_number=request.POST['To'],
+            status='waiting-for-party',
+        )
+    except (Session.DoesNotExist, MultipleObjectsReturned) as e:
+        print(e)
+        resp.message('The person you are trying to reach is unavailable.')
+        return HttpResponse(resp)
+
+    twilio_session = service.sessions(db_session.twilio_sid).fetch()
+    if (twilio_session.status in ['closed', 'failed', 'unknown']):
+        error_message = ('Twilio session %s status: %s' %
+                         (db_session.twilio_sid, twilio_session.status))
+        print(error_message)
+        return HttpResponseNotFound(error_message)
+
+    from_num = request.POST['From']
+    new_participant = service.sessions(twilio_session.sid).participants.create(
+        identifier=from_num
+    )
+    db_session.status = 'connected-to-party'
+    db_session.save()
+    # Now that we've added the 2nd participant,
+    # send their first message to the 1st participant
+    message = (
+        service.sessions(twilio_session.sid)
+        .participants(db_session.initiating_participant_sid)
+        .message_interactions.create(body=request.POST['Body'])
+    )
+
+    return HttpResponse(status=201, content="Created")

privaterelay/settings.py

@@ -62,6 +62,7 @@ INSTALLED_APPS = [
     'allauth.socialaccount.providers.fxa',
 
     'emails.apps.EmailsConfig',
+    'phones.apps.PhonesConfig',
 ]
 
 MIDDLEWARE = [

privaterelay/urls.py

@@ -24,5 +24,6 @@ urlpatterns = [
     path('admin/', admin.site.urls),
     path('accounts/', include('allauth.urls')),
     path('emails/', include('emails.urls')),
+    path('phones/', include('phones.urls')),
     path('', views.home),
 ]

requirements.txt

@@ -1,8 +1,10 @@
-Django==2.2.2
+Django==2.2.9
 django-allauth==0.39.1
 django-csp==3.5
 django-heroku==0.3.1
 django-referrer-policy==1.0
 gunicorn==19.9.0
+phonenumbers==8.11.1
 python-decouple==3.1
 sendgrid==6.0.5
+twilio==6.35.1