truss/comm/index.js

const {createDebugAction} = require('./debug');
const {pack, unpack} = require('./packer');
const {Dispatcher} = require('./dispatcher');

const debug = require('debug')('truss:comm');

export function createDispatcher(...args) {

  if (0 === args.length) {
    return new Dispatcher();
  }

  if ('function' !== typeof args[0]) {
    const value = args[0]
    args[0] = () => value
  }

  if (1 === args.length) {
    return new Dispatcher(args[0]);
  }

  if ('function' !== typeof args[1]) {
    const value = args[1]
    args[1] = () => value
  }

  if (2 === args.length) {
    return new Dispatcher(args[0], args[1]);
  }
};

export function invokeHook(hook, ...args) {
  return sendActionToService({
    type: 'truss/invoke', payload: {hook, args},
  }, 'gateway');
};

export function invokeHookFlat(hook, ...args) {
  return sendActionToService({
    type: 'truss/invoke-flat', payload: {hook, args},
  }, 'gateway');
};

export function invokeHookSerial(hook, rhs, ...args) {
  return servicesImplementingHook(hook).then((services) => {
    return services.reduce((promise, service) => {
      return promise.then((rhs) => {
        return invokeServiceHook(service, hook, rhs, ...args);
      });
    }, Promise.resolve(rhs));
  });
};

export function invokeServiceHook(service, hook, ...args) {
  return sendActionToService({
    type: 'truss/hook', payload: {hook, args},
  }, service);
};

export function sendActionToService(action, service) {

  const client = require('./socket.ipc').client(service);
  client.setEncoding('utf8');

  client.on('ready', writeClientPacket);

  let response = '';
  client.on('data', (chunk) => {
    response += chunk;
  });

  return new Promise((resolve, reject) => {
    client.on('error', (error) => {
      // try try again...
      if (-1 !== ['ECONNREFUSED', 'ENOTFOUND'].indexOf(error.code)) {
        debug(`Can't connect to ${service}, retrying in 1 second...`);
        return resolve(tryAgain());
      }
      reject(error);
    });
    client.on('end', () => {
      try {
        resolve(response ? unpack(response) : undefined);
      }
      catch (error) {
        reject(error);
      }
    });
  });

  function tryAgain() {
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve(sendActionToService(action, service));
      }, 1000);
    });
  }

  function writeClientPacket() {
    const debugAction = createDebugAction(debug, action);
    if (debugAction) {
      debug(`sendActionToService(${
        JSON.stringify(debugAction, null, '  ')
      }, '${service}')`);
    }
    client.write(pack(action));
  }
}

export function servicesImplementingHook(hook) {
  return sendActionToService({
    type: 'truss/hook-services', payload: {hook},
  }, 'gateway');
};