import json
from channels.generic.websocket import AsyncJsonWebsocketConsumer
from channels.db import database_sync_to_async
from django.core.serializers.json import DjangoJSONEncoder
from .basic import execute_data_query

class DataConsumer(AsyncJsonWebsocketConsumer):
    async def encode_json(self, content):
        """
        Encode the given content as JSON, using Django's encoder
        to handle dates, decimals, etc.
        """
        return json.dumps(content, cls=DjangoJSONEncoder)

    async def connect(self):
        self.subscribed_groups = set()
        self.subscription_params = {}  # e.g., {'Product': {'filter': '...', 'values': '...'}}
        await self.accept()

    async def disconnect(self, close_code):
        for group_name in self.subscribed_groups:
            await self.channel_layer.group_discard(group_name, self.channel_name)

    async def receive_json(self, content):
        action = content.get("action")
        if action == "subscribe":
            await self.handle_subscribe(content.get("payload", {}), content.get("request_id"))

    async def handle_subscribe(self, payload, request_id):
        model_name = payload.get("name")
        params = payload.get("params", {})

        if not model_name:
            await self.send_json({"type": "error", "request_id": request_id, "message": "Model name is required."})
            return

        # Store subscription params for this client
        self.subscription_params[model_name] = params

        # Run the initial data query
        data = await database_sync_to_async(execute_data_query)(model_name, params)

        # Send the initial result back to the client
        await self.send_json({
            "type": "subscription_response",
            "request_id": request_id,
            "data": data
        })

        # Join the group using a lowercase model name to match the signal
        group_name = f"model_{model_name.lower()}_updates"
        if group_name not in self.subscribed_groups:
            await self.channel_layer.group_add(group_name, self.channel_name)
            self.subscribed_groups.add(group_name)

    async def realtime_update(self, event):
        # Move imports inside the method to prevent AppRegistryNotReady error on startup
        import ast
        from django.db.models import Q
        from .views import get_serializer

        payload = event["payload"]
        record = payload["record"]
        model_name_lower = payload["name"]
        model_name_capitalized = model_name_lower.capitalize()

        # 1. Get this client's subscription parameters for the specific model
        client_params = self.subscription_params.get(model_name_capitalized)
        if not client_params:
            return  # This client is not subscribed to this model.

        # 2. Check if the updated record matches the client's filter
        filter_str = client_params.get('filter')
        if filter_str:
            try:
                Model, _ = get_serializer(model_name_lower)
                if not Model:
                    return

                filter_q = Q()
                filter_dict = ast.literal_eval(filter_str)
                for key, value in filter_dict.items():
                    filter_q.add(Q(**{key: value}), Q.AND)

                matches = await database_sync_to_async(
                    Model.objects.filter(pk=record["id"]).filter(filter_q).exists
                )()

                if not matches:
                    return  # Record does not match the client's filter, so don't send.
            except Exception:
                return # Fail silently if filter is invalid or DB check fails.

        # 3. Create a tailored payload, respecting the 'values' parameter
        payload_for_client = payload.copy()
        values_str = client_params.get('values')
        if values_str:
            requested_values = values_str.split(',')
            # The record from the signal contains all fields. Filter it down.
            filtered_record = {key: record.get(key) for key in requested_values if key in record}
            payload_for_client['record'] = filtered_record

        # 4. Send the final, tailored payload to the client
        await self.send_json({
            "type": "realtime_update",
            "payload": payload_for_client
        })