uow/lib/uow.js

A unit-of-work queue.

var isArray       = require('util').isArray;
var uuid          = require('uuid');
var Queue         = require('./queue.js');
var TaskRequest   = require('./task/request.js');
var TaskWorker    = require('./worker.js');
var MemoryStore   = require('uow-store').MemoryStore;

// @TODO - implement concurrency on the task request.
// @TODO - implement task ready search retry back-off algorithm.

/**
 * A list of queue singletons.
 */
var queues        = {};

/**
 * Create a new queue and store it in the queue list at the given namespace.
 * -------------------------------------------------------------------------
 * @param {Object} options
 * @return {Queue}
 */
function createQueue(options) {
  options         = options || {};

  if(!options.store) {
    options.store = MemoryStore();
  }

  return new Queue(options.store);
}

function getTypes(options) {
  if(!options || !options.types) {
    throw new TypeError('NoTypesSpecified');
  }
  var types   = options.types;

  if(typeof types === 'string') {
    types     = [ types ];
  }
  if(!isArray(types)) {
    throw new TypeError('TypesInvalid');
  }
  if(types.length < 1) {
    throw new TypeError('NoTypesSpecified');
  }

  return types;
}

function createUOWInstance(options) {
  var queue = createQueue(options);

  return {
    /**
     * Unique identifier for this queue.
     * ---------------------------------
     * @var {string}
     */
    id: uuid.v4(),

    /**
     * Initiate a new task request.
     * ----------------------------
     * @param {string} name
     * @return {TaskRequest}
     */
    requestTask:    function(name) {
      return new TaskRequest(name, queue, options.TaskClass);
    },

    /**
     * Register a new task worker.
     * ---------------------------
     * @param {Object} options {
     *    types: {Array.<string>}
     * }
     * @return {Worker}
     */
    registerWorker: function(options) {

      var types = getTypes(options);

      return new TaskWorker(queue, {
        types:  types
      });
    }
  };

}

/**
 * Initialize a unit of work queue.
 * --------------------------------
 * @param {string} name
 * @param {Object} options {
 *    store: {Store}
 * }
 * @return {uow}
 */
function init(name, options) {

  if(!queues.hasOwnProperty(name)) {
    queues[name]  = createUOWInstance(options);
  }

  return queues[name];
}

module.exports = init;