"""MQTT subscriber + publisher loop.

Topics:
  Subscribed:
    cuda_grid/cmd/<instance>/layout/set            — payload = layout name
    cuda_grid/cmd/<instance>/<future commands>     — Phase 4+
    homeassistant/status                           — HA online → republish discovery

  Published (per instance):
    cuda_grid/state/<instance>/layout              — текущий layout (retained)
    cuda_grid/event/<instance>/layout_switched     — {from, to, reason}

  Global:
    cuda_grid/state/online                         — LWT (online/offline)
"""

from __future__ import annotations

import asyncio
import json
from typing import Awaitable, Callable

import aiomqtt
import structlog

from .config import Config
from .frigate_bridge import FrigateBridge
from .ha_discovery import availability_topic, discovery_payloads
from .state import ControllerState

log = structlog.get_logger()

CommandHandler = Callable[[str, str, str], Awaitable[None]]
# args: (instance_name, command_kind, payload_str)


class MqttLoop:
    def __init__(
        self,
        cfg: Config,
        state: ControllerState,
        command_handler: CommandHandler,
        frigate_bridge: FrigateBridge | None = None,
    ) -> None:
        self.cfg = cfg
        self.state = state
        self.command_handler = command_handler
        self.frigate_bridge = frigate_bridge
        self._client: aiomqtt.Client | None = None
        self._stop = asyncio.Event()

    async def run(self) -> None:
        """Main loop — connect + subscribe + dispatch. Re-connect при разрыве."""
        avail = availability_topic()
        while not self._stop.is_set():
            try:
                async with aiomqtt.Client(
                    hostname=self.cfg.broker.host,
                    port=self.cfg.broker.port,
                    username=self.cfg.broker.username,
                    password=self.cfg.broker.password,
                    identifier=self.cfg.broker.client_id,
                    keepalive=self.cfg.broker.keepalive_sec,
                    will=aiomqtt.Will(
                        topic=avail, payload=b"offline", qos=1, retain=True
                    ),
                ) as client:
                    self._client = client
                    log.info("mqtt.connected", host=self.cfg.broker.host)

                    # online + HA Discovery
                    await client.publish(avail, b"online", qos=1, retain=True)
                    if self.cfg.ha_discovery.enabled:
                        await self._publish_ha_discovery()

                    # Subscribe commands per instance
                    for inst in self.cfg.instances:
                        await client.subscribe(
                            f"cuda_grid/cmd/{inst.name}/+/+", qos=1
                        )
                    # HA status — republish discovery если HA рестартанул
                    await client.subscribe("homeassistant/status", qos=0)
                    # Frigate topics для bridge
                    if self.frigate_bridge:
                        for t in self.frigate_bridge.topics_to_subscribe():
                            await client.subscribe(t, qos=0)
                            log.info("mqtt.frigate.subscribed", topic=t)

                    async for msg in client.messages:
                        await self._handle_message(msg)
            except aiomqtt.MqttError as e:
                log.warning("mqtt.disconnected", error=str(e))
                self._client = None
                await asyncio.sleep(5)

    async def _publish_ha_discovery(self) -> None:
        assert self._client is not None
        payloads = discovery_payloads(self.cfg.ha_discovery, self.cfg.instances)
        for topic, payload in payloads:
            await self._client.publish(topic, payload.encode(), qos=1, retain=True)
        log.info("mqtt.ha_discovery.published", count=len(payloads))

    async def _handle_message(self, msg: aiomqtt.Message) -> None:
        topic = str(msg.topic)
        try:
            payload = msg.payload.decode() if isinstance(msg.payload, (bytes, bytearray)) else str(msg.payload)
        except Exception:
            payload = repr(msg.payload)

        if topic == "homeassistant/status" and payload == "online":
            log.info("mqtt.ha.restarted — republish discovery")
            if self.cfg.ha_discovery.enabled:
                await self._publish_ha_discovery()
            return

        # cuda_grid/cmd/<instance>/<scope>/<action>
        parts = topic.split("/")
        if len(parts) >= 5 and parts[0] == "cuda_grid" and parts[1] == "cmd":
            instance, scope, action = parts[2], parts[3], parts[4]
            kind = f"{scope}.{action}"  # e.g. "layout.set", "overlay.add"
            await self.command_handler(instance, kind, payload)
            return

        # Frigate bridge
        if self.frigate_bridge and topic.startswith(self.frigate_bridge.cfg.base_topic + "/"):
            await self.frigate_bridge.handle_message(topic, payload)
            return

        log.warning("mqtt.unknown_topic", topic=topic, payload=payload)

    async def publish_state(self, instance: str, scope: str, value: str, retain: bool = True) -> None:
        """Publish state — `cuda_grid/state/<instance>/<scope>`."""
        if self._client is None:
            return
        await self._client.publish(
            f"cuda_grid/state/{instance}/{scope}",
            value.encode(),
            qos=1,
            retain=retain,
        )

    async def publish_event(self, instance: str, event_kind: str, data: dict) -> None:
        """Publish event (non-retained) — `cuda_grid/event/<instance>/<kind>`."""
        if self._client is None:
            return
        await self._client.publish(
            f"cuda_grid/event/{instance}/{event_kind}",
            json.dumps(data).encode(),
            qos=0,
            retain=False,
        )

    async def stop(self) -> None:
        self._stop.set()