example.py

# Copyright (C) DATADVANCE, 2010-2021
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"""Simple example of the DjangoChannelsGraphqlWs."""

import pathlib
from collections import defaultdict
from typing import DefaultDict, List

import asgiref
import channels
import channels.auth
import django
import django.contrib.admin
import django.contrib.auth
import django.core.asgi
import graphene
import graphene_django.types

import channels_graphql_ws

# It is OK, Graphene works this way.
# pylint: disable=no-self-use,unsubscriptable-object,invalid-name

# Fake storage for the chat history. Do not do this in production, it
# lives only in memory of the running server and does not persist.
chats: DefaultDict[str, List[str]] = defaultdict(list)


# ---------------------------------------------------------------------- TYPES & QUERIES


class Message(  # type: ignore
    graphene.ObjectType, default_resolver=graphene.types.resolver.dict_resolver
):
    """Message GraphQL type."""

    chatroom = graphene.String()
    text = graphene.String()
    sender = graphene.String()


class User(graphene_django.types.DjangoObjectType):
    """User model to show how to use 'info.context.user'."""

    class Meta:
        """Wrap Django user model."""

        model = django.contrib.auth.get_user_model()


class Query(graphene.ObjectType):
    """Root GraphQL query."""

    history = graphene.List(Message, chatroom=graphene.String())
    user = graphene.Field(User)

    def resolve_history(self, info, chatroom):
        """Return chat history."""
        del info
        return chats[chatroom] if chatroom in chats else []

    def resolve_user(self, info):
        """Provide currently logged in user."""
        if info.context.user.is_authenticated:
            return info.context.user
        return None


# ---------------------------------------------------------------------------- MUTATIONS


class Login(graphene.Mutation, name="LoginPayload"):  # type: ignore
    """Login mutation.

    Login implementation, following the Channels guide:
    https://channels.readthedocs.io/en/latest/topics/authentication.html
    """

    ok = graphene.Boolean(required=True)

    class Arguments:
        """Login request arguments."""

        username = graphene.String(required=True)
        password = graphene.String(required=True)

    def mutate(self, info, username, password):
        """Login request."""

        # Ask Django to authenticate user.
        user = django.contrib.auth.authenticate(username=username, password=password)
        if user is None:
            return Login(ok=False)

        # Use Channels to login, in other words to put proper data to
        # the session stored in the scope. The `info.context` is
        # practically just a wrapper around Channel `self.scope`, but
        # the `login` method requires dict, so use `_asdict`.
        asgiref.sync.async_to_sync(channels.auth.login)(info.context._asdict(), user)
        # Save the session, `channels.auth.login` does not do this.
        info.context.session.save()

        return Login(ok=True)


class SendChatMessage(graphene.Mutation, name="SendChatMessagePayload"):  # type: ignore
    """Send chat message."""

    ok = graphene.Boolean()

    class Arguments:
        """Mutation arguments."""

        chatroom = graphene.String()
        text = graphene.String()

    def mutate(self, info, chatroom, text):
        """Mutation "resolver" - store and broadcast a message."""

        # Use the username from the connection scope if authorized.
        username = (
            info.context.user.username
            if info.context.user.is_authenticated
            else "Anonymous"
        )

        # Store a message.
        chats[chatroom].append({"chatroom": chatroom, "text": text, "sender": username})

        # Notify subscribers.
        OnNewChatMessage.new_chat_message(chatroom=chatroom, text=text, sender=username)

        return SendChatMessage(ok=True)


class Mutation(graphene.ObjectType):
    """Root GraphQL mutation."""

    send_chat_message = SendChatMessage.Field()
    login = Login.Field()


# ------------------------------------------------------------------------ SUBSCRIPTIONS


class OnNewChatMessage(channels_graphql_ws.Subscription):
    """Subscription triggers on a new chat message."""

    sender = graphene.String()
    chatroom = graphene.String()
    text = graphene.String()

    class Arguments:
        """Subscription arguments."""

        chatroom = graphene.String()

    def subscribe(self, info, chatroom=None):
        """Client subscription handler."""
        del info
        # Specify the subscription group client subscribes to.
        return [chatroom] if chatroom is not None else None

    def publish(self, info, chatroom=None):
        """Called to prepare the subscription notification message."""

        # The `self` contains payload delivered from the `broadcast()`.
        new_msg_chatroom = self["chatroom"]
        new_msg_text = self["text"]
        new_msg_sender = self["sender"]

        # Method is called only for events on which client explicitly
        # subscribed, by returning proper subscription groups from the
        # `subscribe` method. So he either subscribed for all events or
        # to particular chatroom.
        assert chatroom is None or chatroom == new_msg_chatroom

        # Avoid self-notifications.
        if (
            info.context.user.is_authenticated
            and new_msg_sender == info.context.user.username
        ):
            return OnNewChatMessage.SKIP

        return OnNewChatMessage(
            chatroom=chatroom, text=new_msg_text, sender=new_msg_sender
        )

    @classmethod
    def new_chat_message(cls, chatroom, text, sender):
        """Auxiliary function to send subscription notifications.

        It is generally a good idea to encapsulate broadcast invocation
        inside auxiliary class methods inside the subscription class.
        That allows to consider a structure of the `payload` as an
        implementation details.
        """
        cls.broadcast(
            group=chatroom,
            payload={"chatroom": chatroom, "text": text, "sender": sender},
        )


class Subscription(graphene.ObjectType):
    """GraphQL subscriptions."""

    on_new_chat_message = OnNewChatMessage.Field()


# ----------------------------------------------------------- GRAPHQL WEBSOCKET CONSUMER


def demo_middleware(next_middleware, root, info, *args, **kwds):
    """Demo GraphQL middleware.

    For more information read:
    https://docs.graphene-python.org/en/latest/execution/middleware/#middleware
    """
    # Skip Graphiql introspection requests, there are a lot.
    if (
        info.operation.name is not None
        and info.operation.name.value != "IntrospectionQuery"
    ):
        print("Demo middleware report")
        print("    operation :", info.operation.operation)
        print("    name      :", info.operation.name.value)

    # Invoke next middleware.
    return next_middleware(root, info, *args, **kwds)


class MyGraphqlWsConsumer(channels_graphql_ws.GraphqlWsConsumer):
    """Channels WebSocket consumer which provides GraphQL API."""

    async def on_connect(self, payload):
        """Handle WebSocket connection event."""

        # Use auxiliary Channels function `get_user` to replace an
        # instance of `channels.auth.UserLazyObject` with a native
        # Django user object (user model instance or `AnonymousUser`)
        # It is not necessary, but it helps to keep resolver code
        # simpler. Cause in both HTTP/WebSocket requests they can use
        # `info.context.user`, but not a wrapper. For example objects of
        # type Graphene Django type `DjangoObjectType` does not accept
        # `channels.auth.UserLazyObject` instances.
        # https://github.com/datadvance/DjangoChannelsGraphqlWs/issues/23
        self.scope["user"] = await channels.auth.get_user(self.scope)

    schema = graphene.Schema(query=Query, mutation=Mutation, subscription=Subscription)
    middleware = [demo_middleware]


# ------------------------------------------------------------------------- ASGI ROUTING

# NOTE: Please note `channels.auth.AuthMiddlewareStack` wrapper, for
# more details about Channels authentication read:
# https://channels.readthedocs.io/en/latest/topics/authentication.html
application = channels.routing.ProtocolTypeRouter(
    {
        "http": django.core.asgi.get_asgi_application(),
        "websocket": channels.auth.AuthMiddlewareStack(
            channels.routing.URLRouter(
                [django.urls.path("graphql/", MyGraphqlWsConsumer.as_asgi())]
            )
        ),
    }
)

# -------------------------------------------------------------------- URL CONFIGURATION
def graphiql(request):
    """Trivial view to serve the `graphiql.html` file."""
    del request
    graphiql_filepath = pathlib.Path(__file__).absolute().parent / "graphiql.html"
    with open(graphiql_filepath) as f:
        return django.http.response.HttpResponse(f.read())


urlpatterns = [
    django.urls.path("", graphiql),
    django.urls.path("admin", django.contrib.admin.site.urls),
]