const dayjs = require('dayjs');
const deviceManager = require('../core/deviceManager');
const db = require('../../dbProxy');

/**
 * 任务基类
 * 提供所有任务的通用功能和冲突检测机制
 */
class BaseTask {
    constructor(taskType, config = {}) {
        this.taskType = taskType;
        this.config = {
            // 默认配置
            defaultInterval: 30, // 默认间隔30分钟
            defaultPriority: 5,
            requiresLogin: true, // 是否需要登录状态
            conflictsWith: [],   // 与哪些任务类型冲突
            ...config
        };

        // 任务执行锁 { sn_code: timestamp }
        this.taskLocks = new Map();

        // 最后执行时间缓存 { sn_code: timestamp }
        this.lastExecutionCache = new Map();
    }

    /**
     * Layer 1: 任务类型互斥锁检查
     * 防止同一设备同时添加相同类型的任务
     */
    acquireTaskLock(sn_code) {
        const lockKey = `${sn_code}:${this.taskType}`;
        const now = Date.now();
        const existingLock = this.taskLocks.get(lockKey);

        // 如果存在锁且未超时(5分钟),返回false
        if (existingLock && (now - existingLock) < 5 * 60 * 1000) {
            const remainingTime = Math.ceil((5 * 60 * 1000 - (now - existingLock)) / 1000);
            return {
                success: false,
                reason: `任务 ${this.taskType} 正在添加中,请等待 ${remainingTime} 秒`
            };
        }

        // 获取锁
        this.taskLocks.set(lockKey, now);
        return { success: true };
    }

    /**
     * 释放任务锁
     */
    releaseTaskLock(sn_code) {
        const lockKey = `${sn_code}:${this.taskType}`;
        this.taskLocks.delete(lockKey);
    }

    /**
     * Layer 2: 设备状态检查
     * 检查设备是否在线、是否登录、是否忙碌
     */
    async checkDeviceStatus(sn_code) {
        // 1. 检查设备是否在线
        const device = deviceManager.devices.get(sn_code);
        if (!device) {
            return {
                allowed: false,
                reason: `设备 ${sn_code} 离线(从未发送心跳)`
            };
        }

        // 2. 检查心跳超时
        const offlineThreshold = 3 * 60 * 1000; // 3分钟
        const now = Date.now();
        const lastHeartbeat = device.lastHeartbeat || 0;
        const isOnline = device.isOnline && (now - lastHeartbeat < offlineThreshold);

        if (!isOnline) {
            const offlineMinutes = lastHeartbeat ? Math.round((now - lastHeartbeat) / (60 * 1000)) : '未知';
            return {
                allowed: false,
                reason: `设备 ${sn_code} 离线(最后心跳: ${offlineMinutes}分钟前)`
            };
        }

        // 3. 检查登录状态(如果任务需要)
        if (this.config.requiresLogin && !device.isLoggedIn) {
            return {
                allowed: false,
                reason: `设备 ${sn_code} 未登录平台账号`
            };
        }

        return { allowed: true };
    }

    /**
     * Layer 3: 检查任务队列状态
     * 防止队列中已有相同任务
     */
    async checkTaskQueue(sn_code, taskQueue) {
        // 获取设备队列
        const deviceQueue = taskQueue.deviceQueues.get(sn_code);
        if (!deviceQueue) {
            return { allowed: true };
        }

        // 检查队列中是否有相同类型的待执行任务
        const tasks = deviceQueue.toArray();
        const hasSameTypeTask = tasks.some(task =>
            task.taskType === this.taskType &&
            task.status === 'pending'
        );

        if (hasSameTypeTask) {
            return {
                allowed: false,
                reason: `队列中已存在待执行的 ${this.taskType} 任务`
            };
        }

        return { allowed: true };
    }

    /**
     * Layer 4: 检查任务去重
     * 查询数据库中是否有重复的待执行任务
     */
    async checkDuplicateTask(sn_code) {
        try {
            const { task_status } = db.models;

            // 查询该设备是否有相同类型的pending/running任务
            const existingTask = await task_status.findOne({
                where: {
                    sn_code: sn_code,
                    taskType: this.taskType,
                    status: ['pending', 'running']
                },
                attributes: ['id', 'status', 'taskName']
            });

            if (existingTask) {
                return {
                    allowed: false,
                    reason: `已存在 ${existingTask.status} 状态的任务: ${existingTask.taskName}`
                };
            }

            return { allowed: true };
        } catch (error) {
            console.error(`[${this.taskType}] 检查重复任务失败:`, error);
            // 出错时允许继续,避免阻塞
            return { allowed: true };
        }
    }

    /**
     * Layer 5: 操作类型冲突检测
     * 某些操作类型不能同时执行
     */
    async checkOperationConflict(sn_code, taskQueue) {
        // 如果没有配置冲突类型,直接通过
        if (!this.config.conflictsWith || this.config.conflictsWith.length === 0) {
            return { allowed: true };
        }

        // 检查当前是否有冲突的任务正在执行
        const deviceStatus = taskQueue.deviceStatus.get(sn_code);
        if (deviceStatus && deviceStatus.currentTask) {
            const currentTaskType = deviceStatus.currentTask.taskType;

            if (this.config.conflictsWith.includes(currentTaskType)) {
                return {
                    allowed: false,
                    reason: `与正在执行的任务 ${currentTaskType} 冲突`
                };
            }
        }

        return { allowed: true };
    }

    /**
     * 检查执行间隔
     * 从数据库查询上次成功执行时间,判断是否满足间隔要求
     */
    async checkExecutionInterval(sn_code, intervalMinutes) {
        try {
            const { task_status } = db.models;

            // 先从缓存检查
            const cachedLastExecution = this.lastExecutionCache.get(sn_code);
            const now = Date.now();

            if (cachedLastExecution) {
                const elapsedTime = now - cachedLastExecution;
                const interval_ms = intervalMinutes * 60 * 1000;

                if (elapsedTime < interval_ms) {
                    const remainingMinutes = Math.ceil((interval_ms - elapsedTime) / (60 * 1000));
                    const elapsedMinutes = Math.round(elapsedTime / (60 * 1000));
                    return {
                        allowed: false,
                        reason: `距离上次执行仅 ${elapsedMinutes} 分钟,还需等待 ${remainingMinutes} 分钟(间隔: ${intervalMinutes} 分钟)`,
                        remainingMinutes,
                        elapsedMinutes
                    };
                }
            }

            // 从数据库查询最近一次成功完成的任务
            const lastTask = await task_status.findOne({
                where: {
                    sn_code: sn_code,
                    taskType: this.taskType,
                    status: 'completed'
                },
                order: [['endTime', 'DESC']],
                attributes: ['endTime']
            });

            // 如果存在上次执行记录,检查是否已经过了间隔时间
            if (lastTask && lastTask.endTime) {
                const lastExecutionTime = new Date(lastTask.endTime).getTime();
                const elapsedTime = now - lastExecutionTime;
                const interval_ms = intervalMinutes * 60 * 1000;

                // 更新缓存
                this.lastExecutionCache.set(sn_code, lastExecutionTime);

                if (elapsedTime < interval_ms) {
                    const remainingMinutes = Math.ceil((interval_ms - elapsedTime) / (60 * 1000));
                    const elapsedMinutes = Math.round(elapsedTime / (60 * 1000));
                    return {
                        allowed: false,
                        reason: `距离上次执行仅 ${elapsedMinutes} 分钟,还需等待 ${remainingMinutes} 分钟(间隔: ${intervalMinutes} 分钟)`,
                        remainingMinutes,
                        elapsedMinutes,
                        nextExecutionTime: new Date(lastExecutionTime + interval_ms)
                    };
                }
            }

            return { allowed: true };
        } catch (error) {
            console.error(`[${this.taskType}] 检查执行间隔失败:`, error);
            // 出错时允许继续,避免阻塞
            return { allowed: true };
        }
    }

    /**
     * 检查时间范围限制
     * @param {Object} timeRange - 时间范围配置 {start_time: '09:00', end_time: '18:00', workdays_only: 1}
     */
    checkTimeRange(timeRange) {
        if (!timeRange || !timeRange.start_time || !timeRange.end_time) {
            return { allowed: true, reason: '未配置时间范围' };
        }

        const now = new Date();
        const currentHour = now.getHours();
        const currentMinute = now.getMinutes();
        const currentTime = currentHour * 60 + currentMinute;

        // 解析开始时间和结束时间
        const [startHour, startMinute] = timeRange.start_time.split(':').map(Number);
        const [endHour, endMinute] = timeRange.end_time.split(':').map(Number);
        const startTime = startHour * 60 + startMinute;
        const endTime = endHour * 60 + endMinute;

        // 检查是否仅工作日
        if (timeRange.workdays_only == 1) {
            const dayOfWeek = now.getDay();
            if (dayOfWeek === 0 || dayOfWeek === 6) {
                return { allowed: false, reason: '当前是周末,不在允许的时间范围内' };
            }
        }

        // 检查当前时间是否在时间范围内
        if (startTime <= endTime) {
            // 正常情况: 09:00 - 18:00
            if (currentTime < startTime || currentTime >= endTime) {
                return {
                    allowed: false,
                    reason: `当前时间不在允许的时间范围内 (${timeRange.start_time} - ${timeRange.end_time})`
                };
            }
        } else {
            // 跨天情况: 22:00 - 06:00
            if (currentTime < startTime && currentTime >= endTime) {
                return {
                    allowed: false,
                    reason: `当前时间不在允许的时间范围内 (${timeRange.start_time} - ${timeRange.end_time})`
                };
            }
        }

        return { allowed: true, reason: '在允许的时间范围内' };
    }

    /**
     * 综合检查 - 执行所有层级的检查
     * @param {string} sn_code - 设备SN码
     * @param {Object} taskQueue - 任务队列实例
     * @param {Object} options - 额外选项
     * @returns {Object} { allowed: boolean, reason: string }
     */
    async canExecuteTask(sn_code, taskQueue, options = {}) {
        const checks = [
            { name: 'Layer1-任务锁', fn: () => this.acquireTaskLock(sn_code) },
            { name: 'Layer2-设备状态', fn: () => this.checkDeviceStatus(sn_code) },
            { name: 'Layer3-队列检查', fn: () => this.checkTaskQueue(sn_code, taskQueue) },
            { name: 'Layer4-任务去重', fn: () => this.checkDuplicateTask(sn_code) },
            { name: 'Layer5-操作冲突', fn: () => this.checkOperationConflict(sn_code, taskQueue) }
        ];

        // 逐层检查
        for (const check of checks) {
            const result = await check.fn();
            if (!result.allowed) {
                console.log(`[${this.taskType}] ${check.name} 未通过: ${result.reason}`);
                return result;
            }
        }

        return { allowed: true };
    }

    /**
     * 清理任务锁(定期清理过期锁)
     */
    cleanupExpiredLocks() {
        const now = Date.now();
        const timeout = 5 * 60 * 1000; // 5分钟超时

        for (const [lockKey, timestamp] of this.taskLocks.entries()) {
            if (now - timestamp > timeout) {
                this.taskLocks.delete(lockKey);
            }
        }
    }

    /**
     * 获取任务名称(子类可覆盖)
     */
    getTaskName(params) {
        return `${this.taskType} 任务`;
    }

    /**
     * 验证任务参数(子类必须实现)
     */
    validateParams(params) {
        throw new Error('子类必须实现 validateParams 方法');
    }

    /**
     * 执行任务的具体逻辑(子类必须实现)
     */
    async execute(sn_code, params) {
        throw new Error('子类必须实现 execute 方法');
    }
}

module.exports = BaseTask;