import json

from channels.generic.websocket import AsyncWebsocketConsumer


class SceneConsumer(AsyncWebsocketConsumer):
    """One connection per open project. Joins the project's group and relays
    scene deltas the server broadcasts (see scenes.views.scene). Read-only:
    edits still go through the PUT endpoint, which is the broadcast source."""

    async def connect(self):
        self.pk = self.scope['url_route']['kwargs']['pk']
        self.group = f'project_{self.pk}'
        await self.channel_layer.group_add(self.group, self.channel_name)
        await self.accept()

    async def disconnect(self, code):
        await self.channel_layer.group_discard(self.group, self.channel_name)

    # broadcast handler: {type: "scene.delta", delta: {...}}
    async def scene_delta(self, event):
        await self.send(text_data=json.dumps(event['delta']))