# -*- coding: utf-8 -*-
"""
Graceful Shutdown Manager für geordnetes Herunterfahren.

Ermöglicht das kontrollierte Stoppen von Services mit Timeouts
und Abhängigkeitsberücksichtigung.
"""

from __future__ import annotations

import asyncio
import signal
import sys
from dataclasses import dataclass, field
from datetime import datetime
from enum import Enum, auto
from typing import TYPE_CHECKING, Any, Callable, Coroutine

from trixy_core.service.enums import ServicePriority, ServiceState

if TYPE_CHECKING:
    from trixy_core.service.iservice import IService


class ShutdownPhase(Enum):
    """
    Phasen des Shutdown-Prozesses.
    """

    NOT_STARTED = auto()
    """Shutdown noch nicht gestartet."""

    PRE_SHUTDOWN = auto()
    """Vorbereitungsphase - Hooks werden ausgeführt."""

    STOPPING_SERVICES = auto()
    """Services werden gestoppt."""

    POST_SHUTDOWN = auto()
    """Aufräumphase - Finale Hooks."""

    COMPLETED = auto()
    """Shutdown abgeschlossen."""

    FAILED = auto()
    """Shutdown mit Fehlern beendet."""


class ShutdownReason(Enum):
    """
    Grund für den Shutdown.
    """

    NORMAL = auto()
    """Normaler Shutdown durch Benutzeranforderung."""

    SIGNAL = auto()
    """Shutdown durch Signal (SIGTERM, SIGINT)."""

    ERROR = auto()
    """Shutdown durch kritischen Fehler."""

    TIMEOUT = auto()
    """Shutdown durch Timeout."""

    MANUAL = auto()
    """Manueller Shutdown durch API."""


@dataclass
class ShutdownResult:
    """
    Ergebnis eines Service-Shutdowns.
    """

    service_name: str
    """Name des Services."""

    success: bool
    """Ob der Shutdown erfolgreich war."""

    duration: float
    """Dauer in Sekunden."""

    error: Exception | None = None
    """Fehler, falls aufgetreten."""

    timed_out: bool = False
    """Ob ein Timeout aufgetreten ist."""

    def __str__(self) -> str:
        """String-Repräsentation."""
        status = "OK" if self.success else "FAILED"
        if self.timed_out:
            status = "TIMEOUT"
        return f"{self.service_name}: {status} ({self.duration:.3f}s)"


@dataclass
class ShutdownReport:
    """
    Gesamtbericht des Shutdown-Prozesses.
    """

    reason: ShutdownReason
    """Grund für den Shutdown."""

    phase: ShutdownPhase
    """Endphase des Shutdowns."""

    started_at: datetime
    """Startzeitpunkt."""

    completed_at: datetime | None = None
    """Endzeitpunkt."""

    results: list[ShutdownResult] = field(default_factory=list)
    """Ergebnisse pro Service."""

    errors: list[str] = field(default_factory=list)
    """Allgemeine Fehler."""

    @property
    def duration(self) -> float:
        """Gesamtdauer in Sekunden."""
        if self.completed_at is None:
            return 0.0
        return (self.completed_at - self.started_at).total_seconds()

    @property
    def success(self) -> bool:
        """Ob der gesamte Shutdown erfolgreich war."""
        return (
            self.phase == ShutdownPhase.COMPLETED
            and all(r.success for r in self.results)
        )

    @property
    def failed_services(self) -> list[str]:
        """Liste der fehlgeschlagenen Services."""
        return [r.service_name for r in self.results if not r.success]

    def to_dict(self) -> dict[str, Any]:
        """Konvertiert in ein Dictionary."""
        return {
            "reason": self.reason.name,
            "phase": self.phase.name,
            "success": self.success,
            "duration": self.duration,
            "started_at": self.started_at.isoformat(),
            "completed_at": self.completed_at.isoformat() if self.completed_at else None,
            "services": [
                {
                    "name": r.service_name,
                    "success": r.success,
                    "duration": r.duration,
                    "timed_out": r.timed_out,
                    "error": str(r.error) if r.error else None,
                }
                for r in self.results
            ],
            "failed_services": self.failed_services,
            "errors": self.errors,
        }


@dataclass
class ShutdownConfig:
    """
    Konfiguration für den Shutdown-Manager.
    """

    default_timeout: float = 30.0
    """Standard-Timeout pro Service in Sekunden."""

    total_timeout: float = 120.0
    """Maximale Gesamtzeit für Shutdown."""

    force_after_timeout: bool = True
    """Ob nach Timeout forciert wird."""

    parallel_shutdown: bool = False
    """Ob Services parallel gestoppt werden (wenn möglich)."""

    respect_dependencies: bool = True
    """Ob Abhängigkeiten beim Shutdown berücksichtigt werden."""

    service_timeouts: dict[str, float] = field(default_factory=dict)
    """Individuelle Timeouts pro Service."""

    register_signals: bool = True
    """Ob Signal-Handler registriert werden."""


class GracefulShutdownManager:
    """
    Manager für geordnetes Herunterfahren von Services.

    Stoppt Services in umgekehrter Startreihenfolge unter
    Berücksichtigung von Abhängigkeiten und Timeouts.

    Example:
        manager = GracefulShutdownManager(service_container)

        # Normaler Shutdown
        report = await manager.shutdown()

        # Mit Hooks
        manager.add_pre_shutdown_hook(save_state)
        manager.add_post_shutdown_hook(cleanup)

        # Signal-Handler automatisch registrieren
        manager.register_signal_handlers()
    """

    def __init__(
        self,
        services: dict[str, "IService"] | None = None,
        config: ShutdownConfig | None = None,
    ) -> None:
        """
        Initialisiert den Shutdown-Manager.

        Args:
            services: Dictionary der Services (Name → Service).
            config: Shutdown-Konfiguration.
        """
        self._services = services or {}
        self._config = config or ShutdownConfig()
        self._phase = ShutdownPhase.NOT_STARTED
        self._reason: ShutdownReason | None = None

        self._pre_hooks: list[Callable[[], Coroutine[Any, Any, None]]] = []
        self._post_hooks: list[Callable[[ShutdownReport], Coroutine[Any, Any, None]]] = []

        self._shutdown_lock = asyncio.Lock()
        self._shutdown_event = asyncio.Event()

        if self._config.register_signals:
            self._register_default_signals()

    @property
    def phase(self) -> ShutdownPhase:
        """Aktuelle Shutdown-Phase."""
        return self._phase

    @property
    def is_shutting_down(self) -> bool:
        """Prüft, ob ein Shutdown läuft."""
        return self._phase not in (
            ShutdownPhase.NOT_STARTED,
            ShutdownPhase.COMPLETED,
            ShutdownPhase.FAILED,
        )

    def set_services(self, services: dict[str, "IService"]) -> None:
        """
        Setzt die zu verwaltenden Services.

        Args:
            services: Dictionary der Services.
        """
        self._services = services

    def add_pre_shutdown_hook(
        self,
        hook: Callable[[], Coroutine[Any, Any, None]],
    ) -> None:
        """
        Fügt einen Pre-Shutdown-Hook hinzu.

        Args:
            hook: Async-Funktion die vor dem Shutdown ausgeführt wird.
        """
        self._pre_hooks.append(hook)

    def add_post_shutdown_hook(
        self,
        hook: Callable[[ShutdownReport], Coroutine[Any, Any, None]],
    ) -> None:
        """
        Fügt einen Post-Shutdown-Hook hinzu.

        Args:
            hook: Async-Funktion die nach dem Shutdown ausgeführt wird.
        """
        self._post_hooks.append(hook)

    def get_timeout_for_service(self, service_name: str) -> float:
        """
        Gibt den Timeout für einen Service zurück.

        Args:
            service_name: Name des Services.

        Returns:
            Timeout in Sekunden.
        """
        return self._config.service_timeouts.get(
            service_name,
            self._config.default_timeout,
        )

    def _register_default_signals(self) -> None:
        """Registriert Standard-Signal-Handler."""
        try:
            loop = asyncio.get_running_loop()
        except RuntimeError:
            # Kein Event-Loop läuft - Handler später registrieren
            return

        if sys.platform == "win32":
            # Windows: add_signal_handler nicht verfügbar
            for sig in (signal.SIGINT, signal.SIGTERM):
                signal.signal(sig, lambda s, f, _loop=loop: _loop.call_soon_threadsafe(
                    lambda _s=s: asyncio.create_task(self._signal_handler(_s))
                ))
        else:
            # Unix-Signale
            for sig in (signal.SIGTERM, signal.SIGINT):
                loop.add_signal_handler(
                    sig,
                    lambda s=sig: asyncio.create_task(
                        self._signal_handler(s)
                    ),
                )

    async def _signal_handler(self, sig: signal.Signals) -> None:
        """
        Handler für System-Signale.

        Args:
            sig: Empfangenes Signal.
        """
        await self.shutdown(ShutdownReason.SIGNAL)

    def _get_shutdown_order(self) -> list[str]:
        """
        Berechnet die Shutdown-Reihenfolge.

        Returns:
            Liste von Service-Namen in Shutdown-Reihenfolge.
        """
        if not self._config.respect_dependencies:
            # Einfach nach Priorität sortieren (umgekehrt)
            return sorted(
                self._services.keys(),
                key=lambda n: (
                    -self._services[n].PRIORITY,  # Höhere Priorität zuerst stoppen
                    n,
                ),
            )

        # Topologische Sortierung mit Abhängigkeiten
        # Services ohne Abhängige zuerst stoppen

        dependents: dict[str, set[str]] = {name: set() for name in self._services}

        for name, service in self._services.items():
            for dep in service.DEPENDENCIES:
                if dep in dependents:
                    dependents[dep].add(name)

        result: list[str] = []
        remaining = set(self._services.keys())

        while remaining:
            # Finde Services ohne laufende Abhängige
            can_stop = [
                name
                for name in remaining
                if not (dependents[name] & remaining)
            ]

            if not can_stop:
                # Zyklische Abhängigkeit - Rest nach Priorität
                can_stop = sorted(
                    remaining,
                    key=lambda n: (-self._services[n].PRIORITY, n),
                )

            # Nach Priorität sortieren (höhere zuerst)
            can_stop.sort(key=lambda n: (-self._services[n].PRIORITY, n))

            for name in can_stop:
                result.append(name)
                remaining.discard(name)

        return result

    async def _stop_service(
        self,
        service: "IService",
        timeout: float,
    ) -> ShutdownResult:
        """
        Stoppt einen einzelnen Service.

        Args:
            service: Der zu stoppende Service.
            timeout: Timeout in Sekunden.

        Returns:
            Ergebnis des Shutdowns.
        """
        start_time = datetime.now()
        name = service.name

        try:
            # Pre-Stop Hook
            await asyncio.wait_for(
                service.on_pre_stop(),
                timeout=timeout / 3,
            )

            # Stop
            await asyncio.wait_for(
                service.stop(),
                timeout=timeout / 3,
            )

            # Post-Stop Hook
            await asyncio.wait_for(
                service.on_post_stop(),
                timeout=timeout / 3,
            )

            duration = (datetime.now() - start_time).total_seconds()
            return ShutdownResult(
                service_name=name,
                success=True,
                duration=duration,
            )

        except asyncio.TimeoutError:
            duration = (datetime.now() - start_time).total_seconds()
            return ShutdownResult(
                service_name=name,
                success=False,
                duration=duration,
                timed_out=True,
            )

        except Exception as e:
            duration = (datetime.now() - start_time).total_seconds()
            return ShutdownResult(
                service_name=name,
                success=False,
                duration=duration,
                error=e,
            )

    async def _run_pre_hooks(self) -> list[str]:
        """
        Führt Pre-Shutdown-Hooks aus.

        Returns:
            Liste von Fehlermeldungen.
        """
        errors: list[str] = []

        for hook in self._pre_hooks:
            try:
                await asyncio.wait_for(
                    hook(),
                    timeout=self._config.default_timeout,
                )
            except asyncio.TimeoutError:
                errors.append(f"Pre-Hook Timeout: {hook.__name__}")
            except Exception as e:
                errors.append(f"Pre-Hook Fehler ({hook.__name__}): {e}")

        return errors

    async def _run_post_hooks(self, report: ShutdownReport) -> list[str]:
        """
        Führt Post-Shutdown-Hooks aus.

        Args:
            report: Der Shutdown-Report.

        Returns:
            Liste von Fehlermeldungen.
        """
        errors: list[str] = []

        for hook in self._post_hooks:
            try:
                await asyncio.wait_for(
                    hook(report),
                    timeout=self._config.default_timeout,
                )
            except asyncio.TimeoutError:
                errors.append(f"Post-Hook Timeout: {hook.__name__}")
            except Exception as e:
                errors.append(f"Post-Hook Fehler ({hook.__name__}): {e}")

        return errors

    async def shutdown(
        self,
        reason: ShutdownReason = ShutdownReason.NORMAL,
    ) -> ShutdownReport:
        """
        Führt einen geordneten Shutdown durch.

        Args:
            reason: Grund für den Shutdown.

        Returns:
            Bericht über den Shutdown.
        """
        async with self._shutdown_lock:
            if self.is_shutting_down:
                # Bereits im Shutdown
                await self._shutdown_event.wait()
                return ShutdownReport(
                    reason=reason,
                    phase=self._phase,
                    started_at=datetime.now(),
                    completed_at=datetime.now(),
                    errors=["Shutdown bereits in Bearbeitung"],
                )

            self._reason = reason
            self._shutdown_event.clear()

            report = ShutdownReport(
                reason=reason,
                phase=ShutdownPhase.PRE_SHUTDOWN,
                started_at=datetime.now(),
            )

            try:
                # Phase 1: Pre-Hooks
                self._phase = ShutdownPhase.PRE_SHUTDOWN
                hook_errors = await self._run_pre_hooks()
                report.errors.extend(hook_errors)

                # Phase 2: Services stoppen
                self._phase = ShutdownPhase.STOPPING_SERVICES
                shutdown_order = self._get_shutdown_order()

                if self._config.parallel_shutdown:
                    # Paralleles Stoppen (nur wenn keine Abhängigkeiten)
                    tasks = []
                    for name in shutdown_order:
                        service = self._services.get(name)
                        if service and service.state == ServiceState.RUNNING:
                            timeout = self.get_timeout_for_service(name)
                            tasks.append(self._stop_service(service, timeout))

                    if tasks:
                        results = await asyncio.gather(*tasks, return_exceptions=True)
                        for result in results:
                            if isinstance(result, ShutdownResult):
                                report.results.append(result)
                            elif isinstance(result, Exception):
                                report.errors.append(str(result))
                else:
                    # Sequentielles Stoppen
                    for name in shutdown_order:
                        service = self._services.get(name)
                        if service and service.state == ServiceState.RUNNING:
                            timeout = self.get_timeout_for_service(name)
                            result = await self._stop_service(service, timeout)
                            report.results.append(result)

                # Phase 3: Post-Hooks
                self._phase = ShutdownPhase.POST_SHUTDOWN
                post_errors = await self._run_post_hooks(report)
                report.errors.extend(post_errors)

                # Abschluss
                self._phase = ShutdownPhase.COMPLETED
                report.phase = ShutdownPhase.COMPLETED

            except Exception as e:
                self._phase = ShutdownPhase.FAILED
                report.phase = ShutdownPhase.FAILED
                report.errors.append(f"Kritischer Fehler: {e}")

            finally:
                report.completed_at = datetime.now()
                self._shutdown_event.set()

            return report

    async def wait_for_shutdown(self) -> None:
        """Wartet auf das Ende des Shutdowns."""
        await self._shutdown_event.wait()

    def request_shutdown(
        self,
        reason: ShutdownReason = ShutdownReason.MANUAL,
    ) -> None:
        """
        Fordert einen Shutdown an (nicht-blockierend).

        Args:
            reason: Grund für den Shutdown.
        """
        asyncio.create_task(self.shutdown(reason))