const { EventEmitter } = require('eventemitter3');
const PQueue = require('p-queue').default;
const got = require('./got').default;
const fs = require('fs-extra');
const path = require('path');
const { exec } = require('child_process');
const { promisify } = require('util');
const execAsync = promisify(exec);

class grb2DownloadManager extends EventEmitter {
    constructor(options = {}) {
        super();

        // 配置默认选项
        this.options = {
            concurrency: options.concurrency || 10,
            retryCount: options.retryCount || 3,
            retryDelay: options.retryDelay || 5000,
            wgrib2Path: options.wgrib2Path || path.join(__dirname, "../wgrib2/wgrib2.exe"),
            ...options
        };

        // 下载队列
        this.queue = new PQueue({
            concurrency: this.options.concurrency,
            autoStart: false
        });

        // 状态管理
        this.status = 'idle'; // idle, downloading, paused, stopped
        this.pendingTasks = [];
        this.activeTasks = new Map();
        this.completedTasks = [];
        this.failedTasks = [];

        // 事件类型
        this.EVENTS = {
            STATUS_CHANGE: 'statusChange',
            TASK_ADDED: 'taskAdded',
            TASK_START: 'taskStart',
            TASK_PROGRESS: 'taskProgress',
            TASK_COMPLETE: 'taskComplete',
            TASK_SKIP: 'taskSkip',
            TASK_ERROR: 'taskError',
            QUEUE_EMPTY: 'queueEmpty',
            ALL_COMPLETE: 'allComplete'
        };

        // 绑定方法
        this.start = this.start.bind(this);
        this.pause = this.pause.bind(this);
        this.resume = this.resume.bind(this);
        this.stop = this.stop.bind(this);
        this.addTasks = this.addTasks.bind(this);

        console.log('气象文件下载器初始化完成');
        console.log(`最大并发数: ${this.options.concurrency}`);
    }

    // 设置状态
    setStatus(status) {
        if (this.status !== status) {
            this.status = status;
            this.emit(this.EVENTS.STATUS_CHANGE, status);

            const statusMap = {
                'idle': '空闲',
                'downloading': '下载中',
                'paused': '已暂停',
                'stopped': '已停止'
            };

            console.log(`下载器状态变更为: ${statusMap[status] || status}`);
        }
    }

    // 检查文件是否存在并使用wgrib2验证
    async validateFile(filePath, fileName) {
        const fullPath = path.join(filePath, fileName);

        try {
            // 检查文件是否存在
            const exists = await fs.pathExists(fullPath);
            if (!exists) {
                console.log(`文件不存在: ${fullPath}`);
                return false;
            }

            // 检查文件大小，如果文件大小为0，则直接返回无效
            const stats = await fs.stat(fullPath);
            if (stats.size === 0) {
                console.log(`文件为空: ${fileName}`);
                return false;
            }

            // 使用wgrib2验证文件
            console.log(`正在验证文件: ${fileName}`);
            const { stdout, stderr } = await execAsync(`${this.options.wgrib2Path} "${fullPath}"`);

            // 如果wgrib2有输出，通常表示文件有效
            if (stdout && stdout.length > 0) {
                console.log(`文件验证成功: ${fileName}`);
                return true;
            } else {
                console.log(`文件验证失败: ${fileName}`);
                return false;
            }
        } catch (error) {
            console.log(`文件验证出错: ${fileName}`, error.message);
            return false;
        }
    }

    // 下载文件
    async downloadFile(task, retryCount = 0) {
        const { url, filePath, fileName } = task;
        const fullPath = path.join(filePath, fileName);

        // 确保目录存在
        await fs.ensureDir(filePath);

        try {
            console.log(`开始下载: ${fileName}`);

            const downloadStream = got.stream(url);

            // 使用got的流式下载API
            // const downloadStream = got(url, {
            //     isStream: true,
            //     timeout: 300000, // 5分钟超时
            //     retry: 0 // 禁用内置重试，因为我们自己实现了重试逻辑
            // });
            const fileWriterStream = fs.createWriteStream(fullPath);

            // 返回Promise以便等待下载完成
            return new Promise((resolve, reject) => {
                let downloadedBytes = 0;
                let totalBytes = 0;

                // 监听下载进度
                downloadStream.on('downloadProgress', (progress) => {
                    downloadedBytes = progress.transferred;
                    totalBytes = progress.total || 0;

                    this.emit(this.EVENTS.TASK_PROGRESS, {
                        task,
                        downloaded: downloadedBytes,
                        total: totalBytes,
                        percent: totalBytes ? (downloadedBytes / totalBytes * 100) : 0
                    });
                });

                // 管道流到文件
                downloadStream.pipe(fileWriterStream);

                // 处理下载完成
                fileWriterStream.on('finish', () => {
                    console.log(`下载完成: ${fileName}`);
                    resolve();
                });

                // 处理错误
                fileWriterStream.on('error', (error) => {
                    console.log(`文件写入错误: ${fileName}`, error.message);
                    reject(error);
                });

                downloadStream.on('error', (error) => {
                    console.log(`下载错误: ${fileName}`, error.message);

                    // 重试逻辑
                    if (retryCount < this.options.retryCount) {
                        console.log(`准备第 ${retryCount + 1} 次重试: ${fileName}`);
                        setTimeout(() => {
                            this.downloadFile(task, retryCount + 1)
                                .then(resolve)
                                .catch(reject);
                        }, this.options.retryDelay);
                    } else {
                        reject(error);
                    }
                });
            });
        } catch (error) {
            console.log(`下载过程出错: ${fileName}`, error.message);

            // 重试逻辑
            if (retryCount < this.options.retryCount) {
                console.log(`准备第 ${retryCount + 1} 次重试: ${fileName}`);
                await new Promise(resolve => setTimeout(resolve, this.options.retryDelay));
                return this.downloadFile(task, retryCount + 1);
            } else {
                throw error;
            }
        }
    }

    // 处理单个任务
    async processTask(task) {
        const { fileName, filePath } = task;

        // 标记任务开始
        this.activeTasks.set(fileName, task);
        this.emit(this.EVENTS.TASK_START, task);
        console.log(`开始处理任务: ${fileName}`);

        try {
            // 检查文件是否已存在且有效
            const isValid = await this.validateFile(filePath, fileName);

            if (isValid) {
                // 文件已存在且有效，跳过下载
                this.emit(this.EVENTS.TASK_SKIP, task, '文件已存在且有效');
                // console.log(`跳过下载: ${fileName} (文件已存在且有效)`);
                this.completedTasks.push(task);
                return;
            }

            // 文件不存在或无效，开始下载
            console.log(`开始下载: ${fileName}`);
            await this.downloadFile(task);

            // 下载完成后再次验证文件
            const postDownloadValid = await this.validateFile(filePath, fileName);

            if (postDownloadValid) {
                // 文件下载并验证成功
                this.emit(this.EVENTS.TASK_COMPLETE, task);
                console.log(`任务完成: ${fileName}`);
                this.completedTasks.push(task);
            } else {
                // 文件下载后验证失败
                throw new Error('文件下载后验证失败');
            }
        } catch (error) {
            // 任务失败
            this.emit(this.EVENTS.TASK_ERROR, task, error);
            console.log(`任务失败: ${fileName}`, error.message);
            this.failedTasks.push({ task, error });
        } finally {
            // 从活跃任务中移除
            this.activeTasks.delete(fileName);
        }
    }

    // 添加任务到队列
    addTasks(tasks) {
        if (!Array.isArray(tasks)) {
            tasks = [tasks];
        }

        tasks.forEach(task => {
            if (!task.url || !task.fileName || !task.filePath) {
                console.log('任务格式错误，缺少必要字段', task);
                return;
            }

            this.pendingTasks.push(task);
            this.emit(this.EVENTS.TASK_ADDED, task);
            console.log(`任务已添加到队列: ${task.fileName}`);
        });

        // 如果下载器处于运行状态，自动开始处理新任务
        if (this.status === 'downloading') {
            this.processQueue();
        }

        return this.pendingTasks.length;
    }

    // 处理队列中的任务
    processQueue() {
        if (this.status !== 'downloading') {
            return;
        }

        // 将待处理任务添加到队列
        while (this.pendingTasks.length > 0 &&
            this.queue.size < this.options.concurrency * 2) {
            const task = this.pendingTasks.shift();

            this.queue.add(() => this.processTask(task))
                .then(() => {
                    // 检查是否所有任务都已完成
                    if (this.pendingTasks.length === 0 &&
                        this.queue.size === 0 &&
                        this.queue.pending === 0) {
                        this.setStatus('idle');
                        this.emit(this.EVENTS.QUEUE_EMPTY);
                        this.emit(this.EVENTS.ALL_COMPLETE, {
                            completed: this.completedTasks,
                            failed: this.failedTasks
                        });

                        console.log('所有任务处理完成');
                        console.log(`成功: ${this.completedTasks.length}, 失败: ${this.failedTasks.length}`);
                    }
                })
                .catch(error => {
                    console.log('任务处理出错', error.message);
                });
        }
    }

    // 开始下载
    start() {
        if (this.status === 'downloading') {
            console.log('下载器已经在运行中');
            return;
        }

        this.setStatus('downloading');
        this.queue.start();
        this.processQueue();

        console.log('下载器已启动');
    }

    // 暂停下载
    pause() {
        if (this.status !== 'downloading') {
            console.log('下载器未运行，无法暂停');
            return;
        }

        this.setStatus('paused');
        this.queue.pause();

        console.log('下载器已暂停');
    }

    // 恢复下载
    resume() {
        if (this.status !== 'paused') {
            console.log('下载器未暂停，无法恢复');
            return;
        }

        this.setStatus('downloading');
        this.queue.start();
        this.processQueue();

        console.log('下载器已恢复');
    }

    // 停止下载
    stop() {
        this.setStatus('stopped');
        this.queue.clear();
        this.pendingTasks = [];

        console.log('下载器已停止，所有待处理任务已清除');
    }

    // 获取状态信息
    getStatus() {
        return {
            status: this.status,
            pending: this.pendingTasks.length,
            active: this.activeTasks.size,
            completed: this.completedTasks.length,
            failed: this.failedTasks.length
        };
    }
}

// 使用示例
async function main() {
    // 创建下载器实例
    const downloader = new grb2DownloadManager({
        concurrency: 5, // 减少并发数以避免服务器压力
        retryCount: 3,
        retryDelay: 5000,
        wgrib2Path: 'wgrib2' // 确保系统已安装wgrib2
    });

    // 监听事件
    downloader.on(downloader.EVENTS.STATUS_CHANGE, (status) => {
        console.log('状态变更:', status);
    });

    downloader.on(downloader.EVENTS.TASK_ADDED, (task) => {
        console.log('任务已添加:', task.fileName);
    });

    downloader.on(downloader.EVENTS.TASK_START, (task) => {
        console.log('任务开始:', task.fileName);
    });

    downloader.on(downloader.EVENTS.TASK_PROGRESS, (progress) => {
        console.log(`下载进度: ${progress.task.fileName} - ${progress.percent.toFixed(2)}%`);
    });

    downloader.on(downloader.EVENTS.TASK_COMPLETE, (task) => {
        console.log('任务完成:', task.fileName);
    });

    downloader.on(downloader.EVENTS.TASK_SKIP, (task, reason) => {
        console.log('任务跳过:', task.fileName, '-', reason);
    });

    downloader.on(downloader.EVENTS.TASK_ERROR, (task, error) => {
        console.log('任务错误:', task.fileName, '-', error.message);
    });

    downloader.on(downloader.EVENTS.QUEUE_EMPTY, () => {
        console.log('队列已空');
    });

    downloader.on(downloader.EVENTS.ALL_COMPLETE, (result) => {
        console.log('所有任务完成');
        console.log('成功:', result.completed.length);
        console.log('失败:', result.failed.length);
    });

    // 添加任务
    const tasks = [
        {
            "url": "https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p50.pl?dir=%2Fgfs.20250901%2F18/atmos&file=gfs.t18z.pgrb2full.0p50.f000&all_lev=on&all_var=on&leftlon=0&rightlon=360&toplat=90&bottomlat=-90",
            "filePath": "./model/grb2/gfs.20250901/18/atmos",
            "fileName": "gfs.t18z.pgrb2full.0p50.f000"
        },
        {
            "url": "https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p50.pl?dir=%2Fgfs.20250901%2F18/atmos&file=gfs.t18z.pgrb2full.0p50.f003&all_lev=on&all_var=on&leftlon=0&rightlon=360&toplat=90&bottomlat=-90",
            "filePath": "./model/grb2/gfs.20250901/18/atmos",
            "fileName": "gfs.t18z.pgrb2full.0p50.f003"
        },
        {
            "url": "https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p50.pl?dir=%2Fgfs.20250901%2F18/atmos&file=gfs.t18z.pgrb2full.0p50.f006&all_lev=on&all_var=on&leftlon=0&rightlon=360&toplat=90&bottomlat=-90",
            "filePath": "./model/grb2/gfs.20250901/18/atmos",
            "fileName": "gfs.t18z.pgrb2full.0p50.f006"
        }
    ];

    console.log('添加任务到下载器');
    downloader.addTasks(tasks);

    // 开始下载
    console.log('开始下载任务');
    downloader.start();

    // 模拟中途添加新任务
    setTimeout(() => {
        const newTasks = [
            {
                "url": "https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p50.pl?dir=%2Fgfs.20250901%2F18/atmos&file=gfs.t18z.pgrb2full.0p50.f009&all_lev=on&all_var=on&leftlon=0&rightlon=360&toplat=90&bottomlat=-90",
                "filePath": "./model/grb2/gfs.20250901/18/atmos",
                "fileName": "gfs.t18z.pgrb2full.0p50.f009"
            }
        ];

        console.log('添加新任务到下载器');
        downloader.addTasks(newTasks);
    }, 10000);

    // 监控下载状态
    setInterval(() => {
        const status = downloader.getStatus();
        console.log('当前状态:', status);
    }, 5000);
}

// 运行示例
if (require.main === module) {
    main().catch(console.error);
}

module.exports = { grb2DownloadManager };