const db = require('../DataBase/db')
const path = require('path')
const Logger = require('../../lib/Logger')
const mq = require('.')

class Worker {
    constructor() {
        this.logger = new Logger(
            path.join(__dirname, '../logs/Worker.log'),
            'INFO'
        )

        this.handlers = {}
        this.running = false

        // 队列名
        this.taskQueue = 'task_queue'
        this.resultQueue = 'task_result_queue'

        // channel 名称（避免和别的模块冲突）
        this.channelName = 'worker_channel'
    }

    /**
     * 注册任务处理器
     */
    register(type, handler) {
        this.handlers[type] = handler
        this.logger.info(`注册处理器: ${type}`)
    }

    /**
     * 启动 Worker
     */
    async start() {
        if (this.running) return
        this.running = true

        this.logger.info('Worker 启动中...')

        try {
            const channel = await mq.getChannel(this.channelName)

            // 控制并发（重要）
            await channel.prefetch(5)

            // 确保队列存在
            await channel.assertQueue(this.taskQueue, { durable: true })
            await channel.assertQueue(this.resultQueue, { durable: true })

            // 开始消费
            await channel.consume(
                this.taskQueue,
                async (msg) => {
                    if (!msg) return

                    let content

                    try {
                        content = JSON.parse(msg.content.toString())
                    } catch (err) {
                        this.logger.error('消息解析失败: ' + err.message)
                        channel.ack(msg)
                        return
                    }

                    const { id, type, data } = content

                    this.logger.info(`收到任务: ${id} 类型: ${type}`)

                    const handler = this.handlers[type]

                    if (!handler) {
                        this.logger.error(`未找到处理器: ${type}`)
                        channel.ack(msg)
                        return
                    }

                    try {
                        const result = await handler(data, {
                            db,
                            logger: this.logger
                        })

                        this.logger.info(`任务完成: ${id}`)

                        await this.sendResult(channel, {
                            id,
                            success: true,
                            result
                        })

                        channel.ack(msg)
                    } catch (err) {
                        this.logger.error(`任务失败: ${id} - ${err.stack}`)

                        await this.sendResult(channel, {
                            id,
                            success: false,
                            error: err.message
                        })

                        // 简单策略：失败直接 ack（避免死循环）
                        channel.ack(msg)
                    }
                },
                {
                    noAck: false
                }
            )

            this.logger.info('Worker 启动成功')
        } catch (err) {
            this.logger.error('Worker 启动失败: ' + err.stack)
        }
    }

    /**
     * 发送结果
     */
    async sendResult(channel, data) {
        try {
            channel.sendToQueue(
                this.resultQueue,
                Buffer.from(JSON.stringify(data)),
                { persistent: true }
            )
        } catch (err) {
            this.logger.error('结果发送失败: ' + err.message)
        }
    }

    /**
     * 停止 Worker
     */
    async stop() {
        this.running = false
        await mq.close()
        this.logger.info('Worker 已停止')
    }
}

module.exports = Worker