lib/mapreduce/utils.js

'use strict';

exports.Promise = require('../deps/promise');
exports.inherits = require('inherits');
exports.extend = require('pouchdb-extend');
var argsarray = require('argsarray');

exports.promisedCallback = function (promise, callback) {
  if (callback) {
    promise.then(function (res) {
      process.nextTick(function () {
        callback(null, res);
      });
    }, function (reason) {
      process.nextTick(function () {
        callback(reason);
      });
    });
  }
  return promise;
};

exports.callbackify = function (fun) {
  return argsarray(function (args) {
    var cb = args.pop();
    var promise = fun.apply(this, args);
    if (typeof cb === 'function') {
      exports.promisedCallback(promise, cb);
    }
    return promise;
  });
};

// Promise finally util similar to Q.finally
exports.fin = function (promise, finalPromiseFactory) {
  return promise.then(function (res) {
    return finalPromiseFactory().then(function () {
      return res;
    });
  }, function (reason) {
    return finalPromiseFactory().then(function () {
      throw reason;
    });
  });
};

exports.sequentialize = function (queue, promiseFactory) {
  return function () {
    var args = arguments;
    var that = this;
    return queue.add(function () {
      return promiseFactory.apply(that, args);
    });
  };
};

exports.flatten = function (arrs) {
  var res = [];
  for (var i = 0, len = arrs.length; i < len; i++) {
    res = res.concat(arrs[i]);
  }
  return res;
};

// uniq an array of strings, order not guaranteed
// similar to underscore/lodash _.uniq
exports.uniq = function (arr) {
  var map = {};

  for (var i = 0, len = arr.length; i < len; i++) {
    map['$' + arr[i]] = true;
  }

  var keys = Object.keys(map);
  var output = new Array(keys.length);

  for (i = 0, len = keys.length; i < len; i++) {
    output[i] = keys[i].substring(1);
  }
  return output;
};

exports.MD5 = require('./md5');