embark-area-51/lib/process/processLauncher.js

const child_process = require('child_process');
const constants = require('../constants');

class ProcessLauncher {
  constructor(options) {
    this.process = child_process.fork(options.modulePath);
    this.logger = options.logger;
    this.normalizeInput = options.normalizeInput;

    this.subscriptions = {};
    this._subscribeToMessages();
  }

  _subscribeToMessages() {
    const self = this;
    this.process.on('message', (msg) => {
      if (msg.result === constants.process.log) {
        return self._handleLog(msg);
      }
      if (msg.event) {
        return this._handleEvent(msg);
      }
      this._checkSubscriptions(msg);
    });
  }

  _handleLog(msg) {
    if (this.logger[msg.type]) {
      return this.logger[msg.type](this.normalizeInput(msg.message));
    }
    this.logger.debug(this.normalizeInput(msg.message));
  }

  _handleEvent(msg) {
    console.log(msg);
  }

  _checkSubscriptions(msg) {
    const messageKeys = Object.keys(msg);
    const subscriptionsKeys = Object.keys(this.subscriptions);
    let subscriptions;
    let messageKey;
    // Find if the message contains a key that we are subscribed to
    messageKeys.some(_messageKey => {
      return subscriptionsKeys.some(subscriptionKey => {
        if (_messageKey === subscriptionKey) {
          subscriptions = this.subscriptions[subscriptionKey];
          messageKey = _messageKey;
          return true;
        }
        return false;
      });
    });

    if (subscriptions) {
      let subscription;
      // Find if we are subscribed to one of the values
      subscriptions.some(sub => {
        if (msg[messageKey] === sub.value) {
          subscription = sub;
          return true;
        }
        return false;
      });

      if (subscription) {
        // We are subscribed to that message, call the callback
        subscription.callback(msg);
      }
    }
  }

  subscribeTo(key, value, callback) {
    if (this.subscriptions[key]) {
      this.subscriptions[key].push(value);
      return;
    }
    this.subscriptions[key] = [{value, callback}];
  }

  unsubscribeTo(key, value) {
    if (!value) {
      this.subscriptions[key] = [];
    }
    if (this.subscriptions[key]) {
      this.subscriptions[key].filter((val, index) => {
        if (val.value === value) {
          this.subscriptions[key] = this.subscriptions[key].splice(index, 1);
        }
      });
    }
  }

  unsubsribeToAll() {
    this.subscriptions = {};
  }

  send() {
    this.process.send(...arguments);
  }

  disconnect() {
    this.process.disconnect();
  }

  kill() {
    this.process.kill(...arguments);
  }
}

module.exports = ProcessLauncher;