"""
线程安全的账号池 —— 最空闲优先调度 + RAII Guard。
"""

import logging
import threading
import time

logger = logging.getLogger(__name__)


class AccountPool:
    """线程安全的账号池，实现最空闲优先（most-idle-first）选择策略。"""

    def __init__(self):
        self._lock = threading.Lock()
        self._accounts = []

    def load(self, accounts: list):
        """用配置中的账号列表初始化池（startup 时调用）。"""
        with self._lock:
            self._accounts = []
            for acct in accounts:
                self._accounts.append({
                    **acct,
                    "_busy": False,
                    "_last_released": 0.0,
                })
            logger.info(f"[AccountPool] 加载了 {len(self._accounts)} 个账号")

    def acquire(self, exclude_ids=None):
        """最空闲优先选择一个非忙碌账号。

        返回 (account_dict, guard) 或 (None, None)。
        guard 在 `with` / `__exit__` 时自动释放账号。
        """
        if exclude_ids is None:
            exclude_ids = []

        with self._lock:
            now = time.time()
            best = None
            for acct in self._accounts:
                if acct["_busy"]:
                    continue
                acc_id = acct.get("email", "").strip() or acct.get("mobile", "").strip()
                if acc_id and acc_id in exclude_ids:
                    continue
                idle_time = now - acct.get("_last_released", 0)
                if best is None or idle_time > best[0]:
                    best = (idle_time, acct)

            if best is None:
                return None, None

            acct = best[1]
            acct["_busy"] = True
            guard = AccountGuard(acct, self)
            logger.info(f"[AccountPool] 分配账号: {self._identifier(acct)}")
            return acct, guard

    def release(self, account):
        """将账号放回池中（由 AccountGuard 或手动调用）。"""
        with self._lock:
            account["_busy"] = False
            account["_last_released"] = time.time()
            logger.info(f"[AccountPool] 释放账号: {self._identifier(account)}")

    def all_accounts(self):
        """返回所有账号的浅拷贝（用于健康检查等遍历）。"""
        with self._lock:
            return list(self._accounts)

    def available_count(self):
        """返回当前空闲账号数。"""
        with self._lock:
            return sum(1 for a in self._accounts if not a["_busy"])

    @staticmethod
    def _identifier(account):
        return account.get("email", "").strip() or account.get("mobile", "").strip()


class AccountGuard:
    """RAII 账号守卫 —— 离开作用域时自动释放账号。"""

    def __init__(self, account, pool: AccountPool):
        self.account = account
        self._pool = pool

    def __enter__(self):
        return self.account

    def __exit__(self, exc_type, exc_val, exc_tb):
        self._pool.release(self.account)
        return False


# 全局单例
account_pool = AccountPool()