pi-rfid-jukebox/jukebox/child-process.js

"use strict";

// TODO: These should really be their own individual classes. Are
// there enough commonalities to warrant a base class?

const spawn = require('child_process').spawn;
const EventEmitter = require('events').EventEmitter;

module.exports.ChildProcessEmitter = class ChildProcessEmitter extends EventEmitter {
  constructor(command, logger) {
    super();

    this.logger = logger;
    this.stderrFilters = [];

    var cmd = command[0],
        args = command.slice(1);

    this.childProcess = spawn(cmd, args);

    this.childProcess.on('error', function(err) {
      this.logger.error("process error", { class: this.constructor.name, name: name, err: String(err).trim() });
    });

    this.childProcess.on('close', function(code, signal) {
      this.logger.debug("process closed", { class: this.constructor.name, name: name, code: code, signal: signal });
    });

    this.childProcess.stdout.on('data', (data) => {
      var lines = data.toString().split(/\n/g);
      lines.map(line => line.trim())
        .filter(line => line.length)
        .map(line => this.emit('message', line));
    });

    this.childProcess.stderr.on('data', (data) => {
      var line = data.toString().trim();
      var filtered = this.stderrFilters.reduce((filter, filtered) => {
        return filtered || filter(line);
      }, false);
      if (filtered) {
        return;
      }
      this.logger.error('process stderr', { class: this.constructor.name, stderr: line});
    });
  }

  kill() {
    this.logger.debug("killing child process");
    this.childProcess.kill();
  }

  send(message) {
    this.childProcess.stdin.write(message);
  }
}

// vim:set ts=2 sw=2 et: