import datetime
import logging
import threading
import time
from collections import deque
from collections.abc import Callable
from dataclasses import dataclass, field
from multiprocessing.synchronize import Event as MpEvent

from frigate.notices import raise_notice
from frigate.object_detection.base import ObjectDetectProcess
from frigate.util.process import FrigateProcess
from frigate.util.services import restart_frigate

logger = logging.getLogger(__name__)

MAX_RESTARTS = 5
RESTART_WINDOW_S = 60


@dataclass
class MonitoredProcess:
    """A process monitored by the watchdog for automatic restart."""

    name: str
    process: FrigateProcess
    factory: Callable[[], FrigateProcess]
    on_restart: Callable[[FrigateProcess], None] | None = None
    restart_timestamps: deque[float] = field(
        default_factory=lambda: deque(maxlen=MAX_RESTARTS)
    )
    clean_exit_logged: bool = False

    def is_restarting_too_fast(self, now: float) -> bool:
        while (
            self.restart_timestamps
            and now - self.restart_timestamps[0] > RESTART_WINDOW_S
        ):
            self.restart_timestamps.popleft()
        return len(self.restart_timestamps) >= MAX_RESTARTS


class FrigateWatchdog(threading.Thread):
    def __init__(
        self,
        detectors: dict[str, ObjectDetectProcess],
        stop_event: MpEvent,
    ):
        super().__init__(name="frigate_watchdog")
        self.detectors = detectors
        self.stop_event = stop_event
        self._monitored: list[MonitoredProcess] = []

    def register(
        self,
        name: str,
        process: FrigateProcess,
        factory: Callable[[], FrigateProcess],
        on_restart: Callable[[FrigateProcess], None] | None = None,
    ) -> None:
        """Register a FrigateProcess for monitoring and automatic restart."""
        self._monitored.append(
            MonitoredProcess(
                name=name,
                process=process,
                factory=factory,
                on_restart=on_restart,
            )
        )

    def _check_process(self, entry: MonitoredProcess) -> None:
        if entry.process.is_alive():
            return

        exitcode = entry.process.exitcode
        if exitcode == 0:
            if not entry.clean_exit_logged:
                logger.info("Process %s exited cleanly, not restarting", entry.name)
                entry.clean_exit_logged = True
            return

        logger.warning(
            "Process %s (PID %s) exited with code %s",
            entry.name,
            entry.process.pid,
            exitcode,
        )

        now = datetime.datetime.now().timestamp()

        if entry.is_restarting_too_fast(now):
            logger.error(
                "Process %s restarting too frequently (%d times in %ds), backing off",
                entry.name,
                MAX_RESTARTS,
                RESTART_WINDOW_S,
            )
            return

        try:
            entry.process.close()
            new_process = entry.factory()
            new_process.start()

            entry.process = new_process
            entry.restart_timestamps.append(now)

            if entry.on_restart:
                entry.on_restart(new_process)

            logger.info("Restarted %s (PID %s)", entry.name, new_process.pid)
        except Exception:
            logger.exception("Failed to restart %s", entry.name)

    def _check_detectors(self) -> None:
        now = datetime.datetime.now().timestamp()

        for name, detector in self.detectors.items():
            detection_start = detector.detection_start.value  # type: ignore[attr-defined]
            # issue https://github.com/python/typeshed/issues/8799
            # from mypy 0.981 onwards
            if detection_start > 0.0 and now - detection_start > 10:
                logger.info(
                    "Detection appears to be stuck. Restarting detection process..."
                )
                detector.start_or_restart()
                raise_notice("detector_stuck", scope=name, params={"detector": name})
            elif (
                detector.detect_process is not None
                and not detector.detect_process.is_alive()
            ):
                logger.info("Detection appears to have stopped. Exiting Frigate...")
                restart_frigate()

    def run(self) -> None:
        time.sleep(10)
        while not self.stop_event.wait(10):
            self._check_detectors()

            for entry in self._monitored:
                self._check_process(entry)

        logger.info("Exiting watchdog...")