"""Stream watchdog — monitor mediamtx paths + emit MQTT events + dispatch overlays.

Phase 1 resilience (issue #3): controller poll'ит /v3/paths/list на mediamtx.
Если ожидаемый path исчез/появился — публикует MQTT events + опционально
показывает icon overlay (e.g. "🔇 audio offline").

Полагается ONLY на observable state mediamtx — не lazy на ffmpeg внутреннее
состояние pipeline.
"""

from __future__ import annotations

import asyncio
import time
from typing import TYPE_CHECKING

import httpx
import structlog
from pydantic import BaseModel, Field

from .overlays import TextOverlay

if TYPE_CHECKING:
    from .dispatch import CommandDispatcher

log = structlog.get_logger()


class WatchedPath(BaseModel):
    """Один stream path для monitoring."""

    mediamtx_path: str = Field(description="Имя path в mediamtx (например 'live-audio')")
    instance: str = Field(description="cuda-grid instance — для overlay/MQTT context")
    label: str = Field(description="Human-readable name для events/overlays")
    overlay_when_lost: bool = Field(default=False,
        description="Показывать text overlay 'OFFLINE' когда path lost")
    overlay_id: str = Field(default="watchdog_offline",
        description="Overlay id если overlay_when_lost=true")


class WatchdogCfg(BaseModel):
    enabled: bool = False
    mediamtx_api_url: str = Field(default="http://cuda-grid-mediamtx:9997",
        description="mediamtx control API base URL")
    poll_interval_sec: float = Field(default=5.0, ge=1.0, le=60.0)
    lost_threshold_sec: float = Field(default=10.0, ge=2.0, le=120.0,
        description="Path missing > N sec → emit lost event")
    paths: list[WatchedPath] = []


class StreamWatchdog:
    def __init__(self, cfg: WatchdogCfg, dispatcher: "CommandDispatcher",
                 mqtt_publish_event=None) -> None:
        self.cfg = cfg
        self.dispatcher = dispatcher
        self._publish_event = mqtt_publish_event  # async callback (instance, kind, data)
        self._task: asyncio.Task | None = None
        # state per path: { path_name: { last_seen_ts, current_lost } }
        self._path_state: dict[str, dict] = {}

    async def start(self) -> None:
        if not self.cfg.enabled or not self.cfg.paths:
            return
        self._task = asyncio.create_task(self._loop())
        log.info("watchdog.started", paths=[p.mediamtx_path for p in self.cfg.paths])

    async def stop(self) -> None:
        if self._task:
            self._task.cancel()
            try:
                await self._task
            except asyncio.CancelledError:
                pass
            self._task = None

    async def _loop(self) -> None:
        while True:
            try:
                await self._poll_once()
                await asyncio.sleep(self.cfg.poll_interval_sec)
            except asyncio.CancelledError:
                raise
            except Exception as e:
                log.error("watchdog.poll_fail", error=str(e))
                await asyncio.sleep(self.cfg.poll_interval_sec)

    async def _poll_once(self) -> None:
        try:
            async with httpx.AsyncClient(timeout=3.0) as client:
                r = await client.get(f"{self.cfg.mediamtx_api_url}/v3/paths/list")
                r.raise_for_status()
                data = r.json()
        except Exception as e:
            log.warning("watchdog.mediamtx_api_fail", error=str(e))
            return

        # mediamtx /v3/paths/list — { items: [{name, ready, ...}] }
        active_paths = {
            item["name"]: item for item in data.get("items", [])
            if item.get("ready", False)
        }

        now = time.time()
        for wp in self.cfg.paths:
            state = self._path_state.setdefault(wp.mediamtx_path, {
                "last_seen": 0, "current_lost": False,
            })

            if wp.mediamtx_path in active_paths:
                # Path жив — recently seen
                state["last_seen"] = now
                if state["current_lost"]:
                    # Restored
                    state["current_lost"] = False
                    await self._on_restored(wp)
            else:
                # Path не активен — check threshold
                age = now - state["last_seen"]
                if age >= self.cfg.lost_threshold_sec and not state["current_lost"]:
                    state["current_lost"] = True
                    await self._on_lost(wp)

    async def _on_lost(self, wp: WatchedPath) -> None:
        log.warning("watchdog.stream_lost", path=wp.mediamtx_path, label=wp.label)
        if self._publish_event:
            await self._publish_event(
                wp.instance, "stream_lost",
                {"path": wp.mediamtx_path, "label": wp.label},
            )
        if wp.overlay_when_lost:
            ov = TextOverlay(
                id=wp.overlay_id,
                cell=None,            # absolute on output frame
                x=0.35, y=0.92,       # внизу по центру
                text=f"⚠ {wp.label} OFFLINE",
                font_size=32,
                color="#FF4040",
                opacity=1.0,
                z_order=30,
            )
            await self.dispatcher.handle(wp.instance, "overlay.add", ov.model_dump_json())

    async def _on_restored(self, wp: WatchedPath) -> None:
        log.info("watchdog.stream_restored", path=wp.mediamtx_path, label=wp.label)
        if self._publish_event:
            await self._publish_event(
                wp.instance, "stream_restored",
                {"path": wp.mediamtx_path, "label": wp.label},
            )
        if wp.overlay_when_lost:
            await self.dispatcher.handle(wp.instance, "overlay.remove", wp.overlay_id)