/**
 * 对爬虫任务列表目录进行监控
 * 发现新任务
 * 删除已完成的任务文件
 * 内存中保存所有任务，及其状态
 * 返回当前任务状态
 * -------------------
 * 注意：任务清单文件名不能重复，如果一个新任务文件名跟已经处理过的任务重名，则不会被处理
 * -------------------
 * task数据结构：{id:'', url: '', status:''}
 */
import common from './common.mjs';
import fs from 'node:fs';
import { readdir, readFile } from 'node:fs/promises';
import path from 'node:path';
import cron from 'node-cron';

class TaskMoniter {

  constructor(task_list_dir) {
    this.check_time_gap = 10;           //检测间隔时间，单位：秒
    this.checking = false;

    this.task_dir = task_list_dir;      //监控目录：任务列表保存目录
    this.tasks = {};                    //内存中的任务列表
    this.taskStatus = {                 //当前任务状态
        total: 0,       //总任务数
        waiting: 0,     //等待执行的任务数
        running: 0,     //正在执行的任务数
        done: 0,        //已完成的任务数
        failed: 0       //执行失败的任务数
    };

    this.statusCode = {
        waiting: 'waiting',
        running: 'running',
        done: 'done',
        failed: 'failed',
    };
  }

  getTaskFilePath(task_id) {
    const dirPath = path.resolve(this.task_dir);
    return `${dirPath}/${task_id}.task`;
  }

  //注意：任务文件名不能重复，已经用过的文件名不能再使用
  //推荐以时间戳为任务文件名，如：1694762776985.task
  getTaskId(filename) {
    return filename.replace('.task', '');
  }

  getStatus() {
    return this.taskStatus;
  }

  getNewTask() {
    let task = null;

    for (const id in this.tasks) {
        if (this.tasks[id].status == this.statusCode.waiting) {
            task = this.tasks[id];
            break;
        }
    }

    return task;
  }

  setTaskRunning(task_id) {
    if (typeof(this.tasks[task_id]) == 'undefined') {
        return false;
    }

    this.tasks[task_id].status = this.statusCode.running;
    this.taskStatus[this.statusCode.running] ++;
    this.taskStatus[this.statusCode.waiting] --;

    return true;
  }

  setTaskDone(task_id) {
    if (typeof(this.tasks[task_id]) == 'undefined') {
        return false;
    }

    this.tasks[task_id].status = this.statusCode.done;
    this.taskStatus[this.statusCode.done] ++;
    this.taskStatus[this.statusCode.running] --;

    const filepath = this.getTaskFilePath(task_id);
    common.removeFile(filepath);        //async delete
    return true;
  }

  setTaskFailed(task_id) {
    if (typeof(this.tasks[task_id]) == 'undefined') {
        return false;
    }

    this.tasks[task_id].status = this.statusCode.failed;
    this.taskStatus[this.statusCode.failed] ++;
    this.taskStatus[this.statusCode.running] --;

    return true;
  }

  async parseTaskFile(filename, filepath) {
    let task = {};

    try {
        task.id = this.getTaskId(filename);
        task.status = this.statusCode.waiting;

        task.url = await readFile(filepath, { encoding: 'utf8' });
        if (task.url) {
            task.url = task.url.replace(/[\r\n]/g, '');
        }
    }catch(error) {
        console.error('Get task file content failed: %s', error);
    }

    return task;
  }

  addTask(task) {
    if (typeof(this.tasks[task.id]) != 'undefined') {
        return false;
    }

    this.tasks[task.id] = task;
    this.taskStatus[task.status] ++;
    this.taskStatus.total ++;

    return true;
  }

  async checkTasks() {
    if (this.checking == true) {
        return;
    }

    try {
        console.log('[%s] TaskMoniter auto check...', common.getTimeString());

        this.checking = true;

        const dirPath = path.resolve(this.task_dir);
        const files = await readdir(dirPath);
        let task = null, task_id = null;
        for (const filename of files) {
            if (filename.indexOf('.task') === -1) {continue;}       //ignore not *.task files

            task_id = this.getTaskId(filename);
            if (typeof(this.tasks[task_id]) != 'undefined') {       //跳过已经存在的任务
                continue;
            }

            task = await this.parseTaskFile(filename, `${dirPath}/${filename}`);
            this.addTask(task);
        }

        this.checking = false;
    }catch(error) {
        this.checking = false;
        console.error('Check tasks failed: %s', error);
    }
  }

  run() {     //开始监控任务目录，把所有任务缓存到内存
    console.log('[%s] TaskMoniter started.', common.getTimeString());

    //auto check new tasks
    const _self = this;
    const task_check_time = this.check_time_gap;
    const task_auto_run = cron.schedule(`*/${task_check_time} * * * * *`, async () =>  {
        await _self.checkTasks();
        console.log('Status', _self.getStatus());
    }, {
        scheduled: false
    });

    task_auto_run.start();
    console.log('[%s] TaskMoniter auto check started.', common.getTimeString());

  }

}

export default TaskMoniter;