# -*- coding: utf-8 -*-
# Copyright (c) 2025 relakkes@gmail.com
#
# This file is part of MediaCrawler project.
# Repository: https://github.com/NanmiCoder/MediaCrawler/blob/main/api/monitor/scheduler.py
# GitHub: https://github.com/NanmiCoder
# Licensed under NON-COMMERCIAL LEARNING LICENSE 1.1
#
# 声明：本代码仅供学习和研究目的使用。使用者应遵守以下原则：
# 1. 不得用于任何商业用途。
# 2. 使用时应遵守目标平台的使用条款和robots.txt规则。
# 3. 不得进行大规模爬取或对平台造成运营干扰。
# 4. 应合理控制请求频率，避免给目标平台带来不必要的负担。
# 5. 不得用于任何非法或不当的用途。
#
# 详细许可条款请参阅项目根目录下的LICENSE文件。
# 使用本代码即表示您同意遵守上述原则和LICENSE中的所有条款。

"""Background scheduler for monitor tasks.

One asyncio loop polls for due tasks and hands them to the runner. A plain loop
is enough here: there is exactly one process, one global crawler subprocess, and
therefore no concurrency to coordinate -- a cron-style library would add a
dependency without adding a capability.

Scheduling is **fixed-delay**, not fixed-rate: ``next_run_at`` is set from the
moment a run starts, so a slow run cannot make its task fire back-to-back.
"""

import asyncio
import random
from datetime import datetime
from typing import Optional

from sqlalchemy import select

from tools.time_util import get_current_timestamp

from ..services import crawler_manager
from . import app_settings
from .db import get_session
from .models import MonitorRun, MonitorTask, RUN_INTERRUPTED, RUN_RUNNING
from .runner import execute_task
from .settings import get_cookie

POLL_INTERVAL_SECONDS = 20
# Spread tasks sharing an interval so they do not all come due on the same tick.
JITTER_SECONDS = 60

_MS_PER_MINUTE = 60_000


class MonitorScheduler:
    """Polls the task table and runs whatever is due."""

    def __init__(self) -> None:
        self._loop_task: Optional[asyncio.Task] = None
        self._stopping = asyncio.Event()
        # Avoids logging "no cookie" on every single tick.
        self._warned_no_cookie = False

    async def start(self) -> None:
        if self._loop_task is not None and not self._loop_task.done():
            return
        self._stopping.clear()
        self._loop_task = asyncio.create_task(self._run_loop())

    async def stop(self) -> None:
        self._stopping.set()
        if self._loop_task is not None:
            self._loop_task.cancel()
            try:
                await self._loop_task
            except asyncio.CancelledError:
                pass
            self._loop_task = None

    async def _run_loop(self) -> None:
        try:
            await self.recover()
        except Exception as exc:  # pragma: no cover - defensive
            print(f"[monitor.scheduler] recovery failed: {exc}")

        while not self._stopping.is_set():
            try:
                await self.tick()
            except Exception as exc:  # pragma: no cover - keep the loop alive
                print(f"[monitor.scheduler] tick failed: {exc}")
            await asyncio.sleep(POLL_INTERVAL_SECONDS)

    async def recover(self) -> None:
        """Clean up state left behind by a server restart.

        A run still marked ``running`` cannot be running -- its subprocess died
        with the previous process. Marking it interrupted stops it from blocking
        the UI as a phantom in-flight run.
        """
        async with get_session() as session:
            stale = (
                await session.scalars(
                    select(MonitorRun).where(MonitorRun.status == RUN_RUNNING)
                )
            ).all()
            for run in stale:
                run.status = RUN_INTERRUPTED
                run.finished_at = get_current_timestamp()
            if stale:
                print(
                    f"[monitor.scheduler] marked {len(stale)} interrupted run(s) "
                    f"left over from a previous process"
                )

    async def tick(self) -> None:
        """Run one due task, if the crawler is free and we are in the active window."""
        # The crawler subprocess is a global singleton, so a manual crawl and a
        # monitor run cannot overlap. Returning without advancing next_run_at
        # leaves the task due, and it is picked up on a later tick.
        if crawler_manager.is_busy():
            return

        async with get_session() as session:
            if not await self._within_active_hours(session):
                # Deliberately does not advance next_run_at: the task simply runs
                # when the window next opens, rather than being skipped for a day.
                return

        await self._run_due_task()

    async def _within_active_hours(self, session) -> bool:
        """Whether scheduled runs are allowed right now (local time)."""
        start, end = await app_settings.active_hours(session)
        hour = datetime.now().hour
        if start <= end:
            return start <= hour <= end
        # Window wraps past midnight, e.g. 22 -> 6.
        return hour >= start or hour <= end

    async def _run_due_task(self) -> None:
        async with get_session() as session:
            task = await session.scalar(
                select(MonitorTask)
                .where(
                    MonitorTask.enabled.is_(True),
                    MonitorTask.next_run_at.is_not(None),
                    MonitorTask.next_run_at <= get_current_timestamp(),
                )
                .order_by(MonitorTask.next_run_at)
                .limit(1)
            )

            if task is None:
                return

            # No cookie means every run would report an auth failure. Leave the
            # task due rather than advancing: it starts working the moment the
            # user pastes one.
            cookie = await get_cookie(session)
            if not cookie:
                if not self._warned_no_cookie:
                    print(
                        "[monitor.scheduler] no XHS cookie configured; "
                        "scheduled tasks will not run until one is set"
                    )
                    self._warned_no_cookie = True
                return
            self._warned_no_cookie = False

            # Advance before running so a crash mid-run cannot cause an immediate
            # re-fire, and so a long outage coalesces into a single run instead
            # of one run per missed interval.
            task.next_run_at = (
                get_current_timestamp()
                + task.interval_minutes * _MS_PER_MINUTE
                + random.randint(0, JITTER_SECONDS) * 1000
            )
            task_id = task.id

        try:
            await execute_task(task_id, trigger="scheduled")
        except Exception as exc:
            print(f"[monitor.scheduler] task {task_id} failed: {exc}")


# Global singleton, mirroring the crawler_manager pattern.
monitor_scheduler = MonitorScheduler()