# -*- coding: utf-8 -*-
"""任务队列服务

基于 PostgreSQL task_queue 表实现 FIFO 队列，支持：
- enqueue：入队，自动分配 position（当前最大 + 1）
- dequeue：取出 position 最小的 pending 任务
- reorder：调整任务在队列中的位置
- delete：删除 pending 任务
- process_loop：后台协程，队列非空且无运行中任务时自动取出执行

所有操作按 site_id 过滤，实现门店隔离。
"""

from __future__ import annotations

import asyncio
import json
import logging
import platform
import uuid
from dataclasses import dataclass, field
from typing import Any

from ..database import get_connection
from ..schemas.tasks import TaskConfigSchema

logger = logging.getLogger(__name__)

# CHANGE 2026-03-07 | 实例标识：用于多后端实例共享同一 DB 时的任务隔离
# 背景：发现有另一台机器（宿主机 D 盘）的后端也在消费同一个 task_queue，
# 导致任务被错误实例执行。通过 enqueued_by 列实现"谁入队谁消费"。
_INSTANCE_ID = platform.node()

# 后台循环轮询间隔（秒）
POLL_INTERVAL_SECONDS = 2


@dataclass
class QueuedTask:
    """队列任务数据对象"""

    id: str
    site_id: int
    config: dict[str, Any]
    status: str
    position: int
    created_at: Any = None
    started_at: Any = None
    finished_at: Any = None
    exit_code: int | None = None
    error_message: str | None = None
    schedule_id: str | None = None


class TaskQueue:
    """基于 PostgreSQL 的任务队列"""

    def __init__(self) -> None:
        self._running = False
        self._loop_task: asyncio.Task | None = None

    # ------------------------------------------------------------------
    # 入队
    # ------------------------------------------------------------------

    def enqueue(self, config: TaskConfigSchema, site_id: int, schedule_id: str | None = None) -> str:
        """将任务配置入队，自动分配 position。

        Args:
            config: 任务配置
            site_id: 门店 ID（门店隔离）
            schedule_id: 关联的调度任务 ID（可选）

        Returns:
            新创建的队列任务 ID（UUID 字符串）
        """
        task_id = str(uuid.uuid4())
        config_json = config.model_dump(mode="json")

        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # 取当前该门店 pending 任务的最大 position，新任务排在末尾
                cur.execute(
                    """
                    SELECT COALESCE(MAX(position), 0)
                    FROM task_queue
                    WHERE site_id = %s AND status = 'pending'
                    """,
                    (site_id,),
                )
                max_pos = cur.fetchone()[0]
                new_pos = max_pos + 1

                # CHANGE 2026-03-07 | 写入 enqueued_by 实现多实例任务隔离
                cur.execute(
                    """
                    INSERT INTO task_queue (id, site_id, config, status, position, schedule_id, enqueued_by)
                    VALUES (%s, %s, %s, 'pending', %s, %s, %s)
                    """,
                    (task_id, site_id, json.dumps(config_json), new_pos, schedule_id, _INSTANCE_ID),
                )
            conn.commit()
        finally:
            conn.close()

        logger.info("任务入队 [%s] site_id=%s position=%s schedule_id=%s", task_id, site_id, new_pos, schedule_id)
        return task_id

    # ------------------------------------------------------------------
    # 出队
    # ------------------------------------------------------------------

    def dequeue(self, site_id: int) -> QueuedTask | None:
        """取出 position 最小的 pending 任务，将其状态改为 running。

        Args:
            site_id: 门店 ID

        Returns:
            QueuedTask 或 None（队列为空时）
        """
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # CHANGE 2026-03-07 | 只消费本实例入队的任务（enqueued_by 匹配）
                # 背景：多后端实例共享同一 DB 时，防止 A 实例消费 B 实例入队的任务
                cur.execute(
                    """
                    SELECT id, site_id, config, status, position,
                           created_at, started_at, finished_at,
                           exit_code, error_message, schedule_id
                    FROM task_queue
                    WHERE site_id = %s AND status = 'pending'
                      AND (enqueued_by = %s OR enqueued_by IS NULL)
                    ORDER BY position ASC
                    LIMIT 1
                    FOR UPDATE SKIP LOCKED
                    """,
                    (site_id, _INSTANCE_ID),
                )
                row = cur.fetchone()
                if row is None:
                    conn.commit()
                    return None

                task = QueuedTask(
                    id=str(row[0]),
                    site_id=row[1],
                    config=row[2] if isinstance(row[2], dict) else json.loads(row[2]),
                    status=row[3],
                    position=row[4],
                    created_at=row[5],
                    started_at=row[6],
                    finished_at=row[7],
                    exit_code=row[8],
                    error_message=row[9],
                    schedule_id=str(row[10]) if row[10] else None,
                )

                # 更新状态为 running
                cur.execute(
                    """
                    UPDATE task_queue
                    SET status = 'running', started_at = NOW()
                    WHERE id = %s
                    """,
                    (task.id,),
                )
            conn.commit()
        finally:
            conn.close()

        task.status = "running"
        logger.info("任务出队 [%s] site_id=%s", task.id, site_id)
        return task

    # ------------------------------------------------------------------
    # 重排
    # ------------------------------------------------------------------

    def reorder(self, task_id: str, new_position: int, site_id: int) -> None:
        """调整任务在队列中的位置。

        仅允许对 pending 状态的任务重排。将目标任务移到 new_position，
        其余 pending 任务按原有相对顺序重新编号。

        Args:
            task_id: 要移动的任务 ID
            new_position: 目标位置（1-based）
            site_id: 门店 ID
        """
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # 获取该门店所有 pending 任务，按 position 排序
                cur.execute(
                    """
                    SELECT id FROM task_queue
                    WHERE site_id = %s AND status = 'pending'
                    ORDER BY position ASC
                    """,
                    (site_id,),
                )
                rows = cur.fetchall()
                task_ids = [str(r[0]) for r in rows]

                if task_id not in task_ids:
                    conn.commit()
                    return

                # 从列表中移除目标任务，再插入到新位置
                task_ids.remove(task_id)
                # new_position 是 1-based，转为 0-based 索引并 clamp
                insert_idx = max(0, min(new_position - 1, len(task_ids)))
                task_ids.insert(insert_idx, task_id)

                # 按新顺序重新分配 position（1-based 连续编号）
                for idx, tid in enumerate(task_ids, start=1):
                    cur.execute(
                        "UPDATE task_queue SET position = %s WHERE id = %s",
                        (idx, tid),
                    )
            conn.commit()
        finally:
            conn.close()

        logger.info(
            "任务重排 [%s] → position=%s site_id=%s",
            task_id, new_position, site_id,
        )

    # ------------------------------------------------------------------
    # 删除
    # ------------------------------------------------------------------

    def delete(self, task_id: str, site_id: int) -> bool:
        """删除 pending 状态的任务。

        Args:
            task_id: 任务 ID
            site_id: 门店 ID

        Returns:
            True 表示成功删除，False 表示任务不存在或非 pending 状态。
        """
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    DELETE FROM task_queue
                    WHERE id = %s AND site_id = %s AND status = 'pending'
                    """,
                    (task_id, site_id),
                )
                deleted = cur.rowcount > 0
            conn.commit()
        finally:
            conn.close()

        if deleted:
            logger.info("任务删除 [%s] site_id=%s", task_id, site_id)
        else:
            logger.warning(
                "任务删除失败 [%s] site_id=%s（不存在或非 pending）",
                task_id, site_id,
            )
        return deleted

    # ------------------------------------------------------------------
    # 查询
    # ------------------------------------------------------------------

    def list_pending(self, site_id: int) -> list[QueuedTask]:
        """列出指定门店的所有 pending 任务（仅限本实例入队的），按 position 升序。"""
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # CHANGE 2026-03-07 | 只列出本实例入队的 pending 任务
                cur.execute(
                    """
                    SELECT id, site_id, config, status, position,
                           created_at, started_at, finished_at,
                           exit_code, error_message
                    FROM task_queue
                    WHERE site_id = %s AND status = 'pending'
                      AND (enqueued_by = %s OR enqueued_by IS NULL)
                    ORDER BY position ASC
                    """,
                    (site_id, _INSTANCE_ID),
                )
                rows = cur.fetchall()
            conn.commit()
        finally:
            conn.close()

        return [
            QueuedTask(
                id=str(r[0]),
                site_id=r[1],
                config=r[2] if isinstance(r[2], dict) else json.loads(r[2]),
                status=r[3],
                position=r[4],
                created_at=r[5],
                started_at=r[6],
                finished_at=r[7],
                exit_code=r[8],
                error_message=r[9],
            )
            for r in rows
        ]

    def has_running(self, site_id: int) -> bool:
        """检查指定门店是否有本实例的 running 状态任务。"""
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # CHANGE 2026-03-07 | 只检查本实例的 running 任务
                cur.execute(
                    """
                    SELECT EXISTS(
                        SELECT 1 FROM task_queue
                        WHERE site_id = %s AND status = 'running'
                          AND (enqueued_by = %s OR enqueued_by IS NULL)
                    )
                    """,
                    (site_id, _INSTANCE_ID),
                )
                result = cur.fetchone()[0]
            conn.commit()
        finally:
            conn.close()
        return result

    # ------------------------------------------------------------------
    # 后台处理循环
    # ------------------------------------------------------------------

    async def process_loop(self) -> None:
        """后台协程：队列非空且无运行中任务时，自动取出并执行。

        循环逻辑：
        1. 查询所有有 pending 任务的 site_id
        2. 对每个 site_id，若无 running 任务则 dequeue 并执行
        3. 等待 POLL_INTERVAL_SECONDS 后重复
        """
        # 延迟导入避免循环依赖
        from .task_executor import task_executor

        self._running = True
        logger.info(
            "TaskQueue process_loop 启动 (instance_id=%s，仅消费本实例入队的任务)",
            _INSTANCE_ID,
        )

        while self._running:
            try:
                await self._process_once(task_executor)
            except Exception:
                logger.exception("process_loop 迭代异常")

            await asyncio.sleep(POLL_INTERVAL_SECONDS)

        logger.info("TaskQueue process_loop 停止")

    async def _process_once(self, executor: Any) -> None:
        """单次处理：扫描所有门店的 pending 队列并执行。"""
        # CHANGE 2026-03-09 | 每次轮询先回收僵尸 running 任务
        self._recover_zombie_tasks()

        site_ids = self._get_pending_site_ids()

        for site_id in site_ids:
            if self.has_running(site_id):
                continue

            task = self.dequeue(site_id)
            if task is None:
                continue

            config = TaskConfigSchema(**task.config)
            execution_id = str(uuid.uuid4())

            logger.info(
                "process_loop 自动执行 [%s] queue_id=%s site_id=%s",
                execution_id, task.id, site_id,
            )

            # 异步启动执行（不阻塞循环）
            asyncio.create_task(
                self._execute_and_update(
                    executor, config, execution_id, task.id, site_id,
                    schedule_id=task.schedule_id,
                )
            )

    async def _execute_and_update(
        self,
        executor: Any,
        config: TaskConfigSchema,
        execution_id: str,
        queue_id: str,
        site_id: int,
        schedule_id: str | None = None,
    ) -> None:
        """执行任务并更新队列状态。"""
        try:
            await executor.execute(
                config=config,
                execution_id=execution_id,
                queue_id=queue_id,
                site_id=site_id,
                schedule_id=schedule_id,
            )
            # 执行完成后根据 executor 的结果更新 task_queue 状态
            self._update_queue_status_from_log(queue_id)
        except Exception:
            logger.exception("队列任务执行异常 [%s]", queue_id)
            self._mark_failed(queue_id, "执行过程中发生未捕获异常")
        finally:
            # CHANGE 2026-03-09 | 兜底：确保 task_queue 不会卡在 running
            # 背景：_update_execution_log 内部异常（如 duration_ms integer 溢出）
            # 被吞掉后，_update_queue_status_from_log 读到的 execution_log 仍是
            # running，导致 task_queue 永远卡住，后续任务全部排队。
            self._ensure_not_stuck_running(queue_id)


    def _get_pending_site_ids(self) -> list[int]:
        """获取所有有 pending 任务的 site_id 列表（仅限本实例入队的）。"""
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                # CHANGE 2026-03-07 | 只查本实例入队的 pending 任务
                cur.execute(
                    """
                    SELECT DISTINCT site_id FROM task_queue
                    WHERE status = 'pending'
                      AND (enqueued_by = %s OR enqueued_by IS NULL)
                    """,
                    (_INSTANCE_ID,),
                )
                rows = cur.fetchall()
            conn.commit()
        finally:
            conn.close()
        return [r[0] for r in rows]

    def _update_queue_status_from_log(self, queue_id: str) -> None:
        """从 task_execution_log 读取执行结果，同步到 task_queue 记录。"""
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    SELECT status, finished_at, exit_code, error_log
                    FROM task_execution_log
                    WHERE queue_id = %s
                    ORDER BY started_at DESC
                    LIMIT 1
                    """,
                    (queue_id,),
                )
                row = cur.fetchone()
                if row:
                    cur.execute(
                        """
                        UPDATE task_queue
                        SET status = %s, finished_at = %s,
                            exit_code = %s, error_message = %s
                        WHERE id = %s
                        """,
                        (row[0], row[1], row[2], row[3], queue_id),
                    )
            conn.commit()
        finally:
            conn.close()

    def _mark_failed(self, queue_id: str, error_message: str) -> None:
        """将队列任务标记为 failed。"""
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    UPDATE task_queue
                    SET status = 'failed', finished_at = NOW(),
                        error_message = %s
                    WHERE id = %s
                    """,
                    (error_message, queue_id),
                )
            conn.commit()
        finally:
            conn.close()

    def _ensure_not_stuck_running(self, queue_id: str) -> None:
        """兜底检查：如果 task_queue 仍是 running，强制标记 failed。

        CHANGE 2026-03-09 | 防止 _update_execution_log 内部异常导致
        task_queue 永远卡在 running 状态。
        """
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                cur.execute(
                    "SELECT status FROM task_queue WHERE id = %s",
                    (queue_id,),
                )
                row = cur.fetchone()
                if row and row[0] == "running":
                    logger.warning(
                        "兜底修正：task_queue [%s] 执行完毕但仍为 running，"
                        "强制标记 failed",
                        queue_id,
                    )
                    cur.execute(
                        """
                        UPDATE task_queue
                        SET status = 'failed', finished_at = NOW(),
                            error_message = %s
                        WHERE id = %s AND status = 'running'
                        """,
                        (
                            "[兜底修正] 执行流程结束但状态未同步，"
                            "可能因 execution_log 更新失败",
                            queue_id,
                        ),
                    )
            conn.commit()
        except Exception:
            logger.exception("_ensure_not_stuck_running 异常 [%s]", queue_id)
        finally:
            conn.close()

    def _recover_zombie_tasks(self, max_running_minutes: int = 180) -> None:
        """恢复僵尸 running 任务：超过阈值时间仍为 running 的任务强制标记 failed。

        CHANGE 2026-03-09 | 在 process_loop 每次轮询时调用，作为最后防线。
        场景：后端进程崩溃/重启后，之前的 running 任务永远不会被更新。
        """
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    UPDATE task_queue
                    SET status = 'failed', finished_at = NOW(),
                        error_message = %s
                    WHERE status = 'running'
                      AND (enqueued_by = %s OR enqueued_by IS NULL)
                      AND started_at < NOW() - INTERVAL '%s minutes'
                    RETURNING id
                    """,
                    (
                        f"[僵尸回收] running 超过 {max_running_minutes} 分钟，"
                        "自动标记 failed",
                        _INSTANCE_ID,
                        max_running_minutes,
                    ),
                )
                recovered = cur.fetchall()
                if recovered:
                    ids = [r[0] for r in recovered]
                    logger.warning(
                        "僵尸回收：%d 个 running 任务超时，已标记 failed: %s",
                        len(ids), ids,
                    )
            conn.commit()
        except Exception:
            logger.exception("_recover_zombie_tasks 异常")
        finally:
            conn.close()

    # ------------------------------------------------------------------
    # 生命周期
    # ------------------------------------------------------------------

    def start(self) -> None:
        """启动后台处理循环（在 FastAPI lifespan 中调用）。"""
        if self._loop_task is None or self._loop_task.done():
            self._loop_task = asyncio.create_task(self.process_loop())
            logger.info("TaskQueue 后台循环已启动")

    async def stop(self) -> None:
        """停止后台处理循环。"""
        self._running = False
        if self._loop_task and not self._loop_task.done():
            self._loop_task.cancel()
            try:
                await self._loop_task
            except asyncio.CancelledError:
                pass
        self._loop_task = None
        logger.info("TaskQueue 后台循环已停止")


# 全局单例
task_queue = TaskQueue()