const fs = require('fs');
const path = require('path');
const db = require('../db');
const logger = require('./logger');

const parsePositiveNumber = (value, fallback) => {
    const num = Number(value);
    return Number.isFinite(num) && num > 0 ? num : fallback;
};

// 磁盘告警阈值（GB），默认 10 GB
const THRESHOLD_GB = parsePositiveNumber(process.env.DISK_ALERT_THRESHOLD_GB, 10);
const THRESHOLD_BYTES = THRESHOLD_GB * 1024 * 1024 * 1024;
// 告警冷却时间（小时），默认 24 小时
const ALERT_COOLDOWN_HOURS = parsePositiveNumber(process.env.DISK_ALERT_COOLDOWN_HOURS, 24);

const getDiskSpace = async (directoryPath) => {
    try {
        // 仅在支持 statfs 的 Node 版本启用
        if (fs.promises.statfs) {
            const stats = await fs.promises.statfs(directoryPath);
            const FreeSpace = stats.bfree * stats.bsize;
            const Size = stats.blocks * stats.bsize;
            return { FreeSpace, Size };
        }

        logger.warn('当前 Node.js 版本不支持 fs.promises.statfs，跳过磁盘检查');
        return { FreeSpace: Number.MAX_SAFE_INTEGER, Size: Number.MAX_SAFE_INTEGER };
    } catch (error) {
        logger.error(`获取磁盘空间失败 [${directoryPath}]: ${error.message}`);
        throw error;
    }
};

const checkDiskSpace = async () => {
    try {
        // 1. 获取上传目录绝对路径
        const uploadDir = process.env.UPLOAD_DIR || 'uploads';
        const absolutePath = path.resolve(uploadDir);

        // 目录不存在时，回退到所在盘符根目录进行检测
        let targetPath = absolutePath;
        try {
            await fs.promises.access(targetPath);
        } catch {
            targetPath = path.parse(absolutePath).root;
        }

        // 2. 获取磁盘空间
        const { FreeSpace } = await getDiskSpace(targetPath);

        // 3. 判断是否低于阈值
        if (FreeSpace < THRESHOLD_BYTES) {
            const root = path.parse(absolutePath).root;
            const freeGB = (FreeSpace / (1024 * 1024 * 1024)).toFixed(2);
            const title = `【系统警告】磁盘空间不足 (${root})`;

            // 4. 冷却期内同标题只发一次
            const cooldownTime = new Date(Date.now() - ALERT_COOLDOWN_HOURS * 60 * 60 * 1000);
            const recentAlert = await db.query(
                `SELECT id FROM notifications
                 WHERE title = $1
                 AND created_at > $2
                 LIMIT 1`,
                [title, cooldownTime]
            );

            if (recentAlert.rows.length === 0) {
                logger.warn(`磁盘空间不足警告: ${root} 剩余 ${freeGB} GB`);

                const content = `系统检测到存储磁盘 (${root}) 剩余空间仅剩 ${freeGB} GB，低于警告阈值 (${THRESHOLD_GB} GB)。\n\n请系统管理员尽快处理：\n1. 清理磁盘空间。\n2. 或配置新的存储路径（如挂载大容量磁盘），并更新配置文件中的 UPLOAD_DIR 参数。`;

                // 尝试获取 ID 最小的 super_admin 作为发布者
                let publisherId = 1;
                const adminRes = await db.query("SELECT id FROM users WHERE role = 'super_admin' ORDER BY id ASC LIMIT 1");
                if (adminRes.rows.length > 0) {
                    publisherId = adminRes.rows[0].id;
                }

                await db.query(
                    'INSERT INTO notifications (title, content, publisher_id, publisher_name, is_top, created_at) VALUES ($1, $2, $3, $4, $5, CURRENT_TIMESTAMP)',
                    [title, content, publisherId, '系统监控', true]
                );

                logger.info('已发布磁盘空间不足警告通知');
            }
        }
    } catch (error) {
        logger.error(`磁盘空间检查失败: ${error.message}`);
    }
};

module.exports = { checkDiskSpace };