# -*- coding: utf-8 -*-
"""下载/播客任务登记。

与原实现的唯一差异：不依赖请求上下文（flask.g），请求级账本键由 Billing 显式携带。
其余（归属、容量闸、task_id 白名单与碰撞换新、账本承接与撞名重试）逐条对齐。
"""
import logging
import re
import uuid
from collections.abc import Callable
from typing import Any

from core.config import MAX_ACTIVE_TASKS_PER_USER, MAX_TERMINAL_TASKS, MAX_TOTAL_TASKS
from core.state import DOWNLOAD_TASKS, DOWNLOAD_TASKS_LOCK
from web.billing import Billing

logger = logging.getLogger('web.tasks')

_TASK_ID_RE = re.compile(r'^[A-Za-z0-9_-]{1,32}$')


async def register_download_task(billing: Billing, task: dict[str, Any],
                                 task_id_hint: str = '') -> str | None:
    """任务登记：失败返回错误描述，成功返回 None。task['task_id'] 为最终 id。"""
    user_id = billing.user.id
    task['user_id'] = user_id
    task['billing_reserved'] = billing.need

    with DOWNLOAD_TASKS_LOCK:
        tid = (task_id_hint or '').strip() or uuid.uuid4().hex[:12]
        if not _TASK_ID_RE.match(tid):
            tid = uuid.uuid4().hex[:12]
        while tid in DOWNLOAD_TASKS:
            tid = uuid.uuid4().hex[:12]
        active = sum(1 for t in DOWNLOAD_TASKS.values()
                     if t.get('user_id') == user_id
                     and t.get('status') in ('queued', 'running', 'paused'))
        if active >= MAX_ACTIVE_TASKS_PER_USER:
            return f'您有 {active} 个任务正在进行，请等待完成或取消后再提交'
        active_total = sum(1 for t in DOWNLOAD_TASKS.values()
                           if t.get('status') in ('queued', 'running', 'paused'))
        if active_total >= MAX_TOTAL_TASKS:
            return '当前任务队列已满，请稍后再试'
        if len(DOWNLOAD_TASKS) - active_total >= MAX_TERMINAL_TASKS:
            return '当前任务队列已满，请稍后再试'
        task['task_id'] = tid
        DOWNLOAD_TASKS[tid] = task

    # 账本承接（撞名重试）
    try:
        renamed = await billing.rename_to(tid)
        retries = 0
        while not renamed and retries < 5:
            retries += 1
            with DOWNLOAD_TASKS_LOCK:
                DOWNLOAD_TASKS.pop(tid, None)
                tid = uuid.uuid4().hex[:12]
                while tid in DOWNLOAD_TASKS:
                    tid = uuid.uuid4().hex[:12]
                task['task_id'] = tid
                DOWNLOAD_TASKS[tid] = task
            renamed = await billing.rename_to(tid)
        if not renamed:
            raise RuntimeError('任务账本键撞名，请重新提交')
        billing.ledger_key = tid
    except Exception:
        with DOWNLOAD_TASKS_LOCK:
            if DOWNLOAD_TASKS.get(tid) is task:
                DOWNLOAD_TASKS.pop(tid, None)
        raise
    return None


async def start_task(task_id: str, worker: Callable, args: tuple = ()) -> str | None:
    """启动 worker 线程（复用 services 的 _start_task_thread，失败收敛终态并退费）。"""
    import asyncio

    import services.runtime as services
    return await asyncio.to_thread(services._start_task_thread, task_id, worker, args)