"""Replay orphan watchdog for in-flight replay actions.

This module watches `_retry_pending` and re-pushes actions that were
dispatched by the server but never acknowledged by the Windows agent.
"""

from __future__ import annotations

import asyncio
import contextlib
import logging
import os
import time
from typing import Any, Callable, Dict, List, Optional, Tuple


logger = logging.getLogger(__name__)


def _env_bool(name: str, default: str) -> bool:
    return os.environ.get(name, default).strip().lower() in {
        "1",
        "true",
        "yes",
        "on",
    }


def _env_float(name: str, default: float) -> float:
    try:
        return float(os.environ.get(name, str(default)))
    except (TypeError, ValueError):
        logger.warning("Watchdog: invalid env %s, fallback=%s", name, default)
        return default


def _env_int(name: str, default: int) -> int:
    try:
        return int(os.environ.get(name, str(default)))
    except (TypeError, ValueError):
        logger.warning("Watchdog: invalid env %s, fallback=%s", name, default)
        return default


def _env_max_resends(default: int) -> int:
    raw = os.environ.get("RPA_WATCHDOG_MAX_RESENDS")
    if raw is None or not str(raw).strip():
        raw = os.environ.get("RPA_WATCHDOG_MAX_RETRIES")
    try:
        return int(raw) if raw is not None else default
    except (TypeError, ValueError):
        logger.warning("Watchdog: invalid max resend env, fallback=%s", default)
        return default


WATCHDOG_ENABLED = _env_bool("RPA_WATCHDOG_ENABLED", "1")
WATCHDOG_SCAN_INTERVAL_S = _env_float("RPA_WATCHDOG_SCAN_INTERVAL_S", 10.0)
WATCHDOG_ORPHAN_TIMEOUT_S = _env_float("RPA_WATCHDOG_ORPHAN_TIMEOUT_S", 45.0)
WATCHDOG_MAX_RESENDS = _env_max_resends(2)
WATCHDOG_REPUSH_POSITION = (
    os.environ.get("RPA_WATCHDOG_REPUSH_POSITION", "head").strip().lower()
)


_metrics_lock = asyncio.Lock()
_metrics: Dict[str, Any] = {
    "orphans_detected_total": 0,
    "orphans_resent_total": 0,
    "orphans_giveup_total": 0,
    "scans_total": 0,
    "scans_failed_total": 0,
    "last_scan_ts": 0.0,
    "last_scan_duration_ms": 0.0,
    "current_in_flight_count": 0,
    "current_orphan_count": 0,
}


async def _bump(key: str, delta: int = 1) -> None:
    async with _metrics_lock:
        _metrics[key] = _metrics.get(key, 0) + delta


def get_metrics_snapshot() -> Dict[str, Any]:
    return dict(_metrics)


SseNotifier = Callable[[str, str], None]


class ReplayWatchdog:
    """Background coroutine that re-pushes orphaned replay actions."""

    def __init__(
        self,
        retry_pending: Dict[str, Dict[str, Any]],
        replay_queues: Dict[str, List[Dict[str, Any]]],
        async_lock_factory: Callable[[], Any],
        sse_notifier: Optional[SseNotifier] = None,
    ) -> None:
        self._retry_pending = retry_pending
        self._replay_queues = replay_queues
        self._async_lock = async_lock_factory
        self._sse_notifier = sse_notifier
        self._task: Optional[asyncio.Task] = None
        self._stopped = asyncio.Event()

    async def start(self) -> None:
        if not WATCHDOG_ENABLED:
            logger.info("[WATCHDOG] disabled via RPA_WATCHDOG_ENABLED=0")
            return
        if self._task is not None and not self._task.done():
            logger.warning("[WATCHDOG] already started")
            return
        self._stopped.clear()
        self._task = asyncio.create_task(self._run(), name="replay_watchdog")
        logger.info(
            "[WATCHDOG] started scan=%.1fs orphan_timeout=%.1fs max_resends=%d repush=%s",
            WATCHDOG_SCAN_INTERVAL_S,
            WATCHDOG_ORPHAN_TIMEOUT_S,
            WATCHDOG_MAX_RESENDS,
            WATCHDOG_REPUSH_POSITION,
        )

    async def stop(self, timeout_s: float = 5.0) -> None:
        if self._task is None:
            return
        self._stopped.set()
        self._task.cancel()
        try:
            await asyncio.wait_for(self._task, timeout=timeout_s)
        except asyncio.CancelledError:
            pass
        except asyncio.TimeoutError:
            logger.warning("[WATCHDOG] stop timeout after %.1fs", timeout_s)
        except Exception:
            logger.exception("[WATCHDOG] unexpected stop error")
        self._task = None
        logger.info("[WATCHDOG] stopped")

    async def _run(self) -> None:
        try:
            while not self._stopped.is_set():
                try:
                    await asyncio.wait_for(
                        self._stopped.wait(),
                        timeout=WATCHDOG_SCAN_INTERVAL_S,
                    )
                    break
                except asyncio.TimeoutError:
                    pass

                try:
                    await self._scan_once()
                except Exception:
                    await _bump("scans_failed_total")
                    logger.exception("[WATCHDOG] scan failed")
        except asyncio.CancelledError:
            logger.info("[WATCHDOG] cancelled")
            raise
        finally:
            logger.info("[WATCHDOG] loop terminated")

    async def _scan_once(self) -> Dict[str, int]:
        t0 = time.time()
        await _bump("scans_total")

        resent = 0
        gaveup = 0
        skipped = 0
        in_flight = 0
        orphans = 0

        orphan_targets: List[Tuple[str, Dict[str, Any]]] = []
        async with self._async_lock():
            for action_id, info in list(self._retry_pending.items()):
                dispatched_at = info.get("dispatched_at", 0.0) or 0.0
                if dispatched_at <= 0:
                    skipped += 1
                    continue
                age = t0 - dispatched_at
                in_flight += 1
                if age < WATCHDOG_ORPHAN_TIMEOUT_S:
                    continue
                orphans += 1
                orphan_targets.append((action_id, dict(info)))

        for action_id, info in orphan_targets:
            await _bump("orphans_detected_total")
            resent_count = int(info.get("resent_count", 0) or 0)

            if resent_count >= WATCHDOG_MAX_RESENDS:
                async with self._async_lock():
                    self._retry_pending.pop(action_id, None)
                age_total = t0 - float(info.get("first_dispatched_at", t0) or t0)
                logger.error(
                    "[BUS] lea:dispatch_orphan_giveup action_id=%s resent=%d age_total=%.1fs "
                    "session=%s machine=%s replay=%s",
                    action_id,
                    resent_count,
                    age_total,
                    info.get("session_id", "?"),
                    info.get("machine_id", "?"),
                    info.get("replay_id", "?"),
                )
                gaveup += 1
                await _bump("orphans_giveup_total")
                continue

            session_id = info.get("session_id")
            machine_id = info.get("machine_id", "default")
            action = info.get("dispatched_action") or info.get("action")
            if not session_id or not isinstance(action, dict):
                logger.warning(
                    "[WATCHDOG] invalid schema for %s session_id=%r action_type=%s",
                    action_id,
                    session_id,
                    type(action).__name__,
                )
                async with self._async_lock():
                    self._retry_pending.pop(action_id, None)
                continue

            async with self._async_lock():
                existing = self._retry_pending.get(action_id)
                if existing is None:
                    logger.debug(
                        "[WATCHDOG] %s acked between snapshot and resend; skip",
                        action_id,
                    )
                    continue
                queue = self._replay_queues.setdefault(session_id, [])
                if WATCHDOG_REPUSH_POSITION == "tail":
                    queue.append(dict(action))
                else:
                    queue.insert(0, dict(action))
                existing["resent_count"] = resent_count + 1
                existing["last_resent_at"] = time.time()
                existing["dispatched_at"] = 0.0

            age_total = t0 - float(info.get("first_dispatched_at", t0) or t0)
            logger.warning(
                "[BUS] lea:dispatch_orphan_resent action_id=%s resent=%d/%d age=%.1fs "
                "session=%s machine=%s replay=%s",
                action_id,
                resent_count + 1,
                WATCHDOG_MAX_RESENDS,
                age_total,
                session_id,
                machine_id,
                info.get("replay_id", "?"),
            )
            resent += 1
            await _bump("orphans_resent_total")

            if self._sse_notifier is not None:
                try:
                    self._sse_notifier(session_id, machine_id)
                except Exception as exc:
                    logger.debug("[WATCHDOG] sse notifier failed: %s", exc)

        elapsed_ms = (time.time() - t0) * 1000.0
        async with _metrics_lock:
            _metrics["last_scan_ts"] = t0
            _metrics["last_scan_duration_ms"] = elapsed_ms
            _metrics["current_in_flight_count"] = in_flight
            _metrics["current_orphan_count"] = orphans
            scans_total = _metrics["scans_total"]

        if orphans or gaveup:
            logger.info(
                "[METRIC] watchdog scan=%d orphans=%d resent=%d gaveup=%d "
                "in_flight=%d skipped=%d elapsed_ms=%.1f",
                scans_total,
                orphans,
                resent,
                gaveup,
                in_flight,
                skipped,
                elapsed_ms,
            )

        return {
            "orphans": orphans,
            "resent": resent,
            "gaveup": gaveup,
            "skipped": skipped,
            "in_flight": in_flight,
        }


_singleton: Optional[ReplayWatchdog] = None


def get_or_create_watchdog(
    retry_pending: Dict[str, Dict[str, Any]],
    replay_queues: Dict[str, List[Dict[str, Any]]],
    async_lock_factory: Callable[[], Any],
    sse_notifier: Optional[SseNotifier] = None,
) -> ReplayWatchdog:
    global _singleton
    if _singleton is None:
        _singleton = ReplayWatchdog(
            retry_pending=retry_pending,
            replay_queues=replay_queues,
            async_lock_factory=async_lock_factory,
            sse_notifier=sse_notifier,
        )
    return _singleton


@contextlib.asynccontextmanager
async def watchdog_lifespan(
    retry_pending: Dict[str, Dict[str, Any]],
    replay_queues: Dict[str, List[Dict[str, Any]]],
    async_lock_factory: Callable[[], Any],
    sse_notifier: Optional[SseNotifier] = None,
):
    watchdog = get_or_create_watchdog(
        retry_pending=retry_pending,
        replay_queues=replay_queues,
        async_lock_factory=async_lock_factory,
        sse_notifier=sse_notifier,
    )
    await watchdog.start()
    try:
        yield watchdog
    finally:
        await watchdog.stop()