"""storage_monitor.py — 磁盘配额检查与后台定时任务。"""

import asyncio
import logging
import shutil
from pathlib import Path

from app.config import settings

logger = logging.getLogger(__name__)


# ------------------------------------------------------------------ #
# 磁盘统计工具
# ------------------------------------------------------------------ #

def _dir_size(path: Path) -> int:
    """递归计算目录占用字节数；目录不存在返回 0。"""
    if not path.exists():
        return 0
    return sum(f.stat().st_size for f in path.rglob("*") if f.is_file())


def get_storage_info() -> dict:
    """
    扫描 tmp/ 目录，返回存储统计信息：
    {
        disk_total_bytes, disk_used_bytes,
        tmp_total_bytes, quota_bytes, quota_exceeded,
        active_users, per_user_quota_bytes,
        users: [{ user_id, used_bytes, quota_exceeded }]
    }
    """
    tmp_path = Path(settings.temp_dir)
    disk = shutil.disk_usage(tmp_path if tmp_path.exists() else ".")
    disk_total = disk.total
    disk_used = disk.used

    quota_bytes = int(disk_total * settings.disk_quota_ratio)
    tmp_total = _dir_size(tmp_path)
    quota_exceeded = tmp_total > quota_bytes

    # 遍历用户子目录（tmp/{user_id}/）
    users: list[dict] = []
    if tmp_path.exists():
        for user_dir in sorted(tmp_path.iterdir()):
            if not user_dir.is_dir():
                continue
            used = _dir_size(user_dir)
            if used > 0:
                users.append({"user_id": user_dir.name, "used_bytes": used})

    active_users = len(users)
    per_user_quota = (quota_bytes // active_users) if active_users > 0 else quota_bytes

    for u in users:
        u["quota_exceeded"] = u["used_bytes"] > per_user_quota

    return {
        "disk_total_bytes": disk_total,
        "disk_used_bytes": disk_used,
        "tmp_total_bytes": tmp_total,
        "quota_bytes": quota_bytes,
        "quota_exceeded": quota_exceeded,
        "active_users": active_users,
        "per_user_quota_bytes": per_user_quota,
        "users": users,
    }


# ------------------------------------------------------------------ #
# 配额检查（导出后调用 / 定时任务共用）
# ------------------------------------------------------------------ #

def check_quota(user_id: str) -> str | None:
    """
    检查存储配额，返回用户侧 warning 文本；无超限时返回 None。
    同时将管理员级别超限情况写入日志。
    """
    info = get_storage_info()

    # 全局超限 → 记录管理员日志
    if info["quota_exceeded"]:
        logger.warning(
            "[存储告警] tmp/ 总占用 %d bytes 超过配额 %d bytes（磁盘 %.0f%%）",
            info["tmp_total_bytes"],
            info["quota_bytes"],
            settings.disk_quota_ratio * 100,
        )

    # 检查当前用户是否超个人配额
    user_entry = next((u for u in info["users"] if u["user_id"] == user_id), None)
    if user_entry and user_entry["quota_exceeded"]:
        logger.warning(
            "[存储告警] 用户 %s 占用 %d bytes 超过均分配额 %d bytes",
            user_id,
            user_entry["used_bytes"],
            info["per_user_quota_bytes"],
        )
        return "您的存储空间已超出限额，请删除旧文件释放空间"

    return None


# ------------------------------------------------------------------ #
# 后台定时任务
# ------------------------------------------------------------------ #

async def _periodic_check(interval_seconds: int = 1800) -> None:
    """每 interval_seconds 秒（默认 30 分钟）执行一次全量磁盘检查。"""
    while True:
        await asyncio.sleep(interval_seconds)
        try:
            info = get_storage_info()
            if info["quota_exceeded"]:
                logger.warning(
                    "[定时检查] tmp/ 总占用 %d bytes 超过配额 %d bytes",
                    info["tmp_total_bytes"],
                    info["quota_bytes"],
                )
            for u in info["users"]:
                if u["quota_exceeded"]:
                    logger.warning(
                        "[定时检查] 用户 %s 占用 %d bytes 超过均分配额 %d bytes",
                        u["user_id"],
                        u["used_bytes"],
                        info["per_user_quota_bytes"],
                    )
        except Exception:
            logger.exception("[定时检查] 磁盘检查异常")


def start_background_monitor() -> asyncio.Task:
    """在当前事件循环中启动后台定时任务，返回 Task 对象。"""
    return asyncio.create_task(_periodic_check())