Add complex example: logger, task, scheduler

Author: tshemsedinov

JavaScript/4-scheduler.js

@@ -0,0 +1,150 @@
+'use strict';
+
+const { EventEmitter } = require('events');
+
+class Logger {
+  static color(level) {
+    return Logger.COLORS[level] || Logger.COLORS.info;
+  }
+  log(level, s) {
+    const date = new Date().toISOString();
+    const color = Logger.color(level);
+    console.log(color + date + '\t' + s + '\x1b[0m');
+  }
+  warn(s) {
+    this.log('warn', s);
+  }
+  error(s) {
+    this.log('error', s);
+  }
+  info(s) {
+    this.log('info', s);
+  }
+}
+
+Logger.COLORS = {
+  warn: '\x1b[1;33m',
+  error: '\x1b[0;31m',
+  info: '\x1b[1;37m',
+};
+
+class Task extends EventEmitter {
+  constructor(name, time, exec) {
+    super();
+    this.name = name;
+    if (typeof time === 'number') {
+      this.time = Date.now() + time;
+      this.set = setInterval;
+      this.clear = clearInterval;
+    } else {
+      this.time = new Date(time).getTime();
+      this.set = setTimeout;
+      this.clear = clearTimeout;
+    }
+    this.exec = exec;
+    this.running = false;
+    this.count = 0;
+    this.timer = null;
+  }
+  get active() {
+    return !!this.timer;
+  }
+  start() {
+    this.stop();
+    if (this.running) return false;
+    const time = this.time - Date.now();
+    if (time < 0) return false;
+    this.timer = this.set(() => {
+      this.run();
+    }, time);
+    return true;
+  }
+  stop() {
+    if (!this.active || this.running) return false;
+    this.clear(this.timer);
+    this.timer = null;
+    return true;
+  }
+  run() {
+    if (!this.active || this.running) return false;
+    this.running = true;
+    this.emit('begin');
+    this.exec((err, res) => {
+      if (err) this.emit('error', err);
+      this.emit('end', res);
+      this.count++;
+      this.running = false;
+    });
+    return true;
+  }
+}
+
+class Scheduler extends EventEmitter {
+  constructor() {
+    super();
+    this.tasks = new Map();
+    this.logger = new Logger();
+  }
+  task(name, time, exec) {
+    this.stop(name);
+    const task = new Task(name, time, exec);
+    this.tasks.set(name, task);
+    task.on('error', err => {
+      this.logger.error(task.name + '\t' + err.message);
+      this.emit('error', err);
+    });
+    task.on('begin', () => {
+      this.logger.info(task.name + '\tbegin');
+    });
+    task.on('end', res => {
+      this.logger.warn(task.name + '\tend\t' + res);
+    });
+    task.start();
+    return task;
+  }
+  stop(name) {
+    const task = this.tasks.get(name);
+    if (task) {
+      task.stop();
+      this.tasks.delete(name);
+    }
+  }
+  stopAll() {
+    for (const name of this.tasks.keys()) {
+      this.stop(name);
+    }
+  }
+}
+
+// Usage
+
+const scheduler = new Scheduler();
+
+scheduler.on('error', err => {
+  console.log(err.stack);
+  //process.exit(1);
+});
+
+scheduler.task('name1', '2019-03-12T14:30Z', done => {
+  setTimeout(() => {
+    done(null, 'task successed');
+  }, 1000);
+});
+
+scheduler.task('name2', '2019-03-12T14:31Z', done => {
+  setTimeout(() => {
+    done(new Error('task failed'));
+  }, 1100);
+});
+
+scheduler.task('name3', 500, done => {
+  setTimeout(() => {
+    done(null, 'task successed');
+  }, 1200);
+});
+
+scheduler.task('name4', 800, done => {
+  setTimeout(() => {
+    done(new Error('task failed'));
+  }, 2000);
+});