'use strict';

var a = require('./a');
var once = require('./once');
var concurrent = require('./concurrent');
var CONCURRENTLY = require('./CONCURRENTLY');
var SERIAL = require('./SERIAL');

module.exports = function _map (cap, then, attached) {
  function api (collection, concurrency, iterator, done) {
    var args = arguments;
    if (args.length === 2) { iterator = concurrency; concurrency = CONCURRENTLY; }
    if (args.length === 3 && typeof concurrency !== 'number') { done = iterator; iterator = concurrency; concurrency = CONCURRENTLY; }
    var keys = Object.keys(collection);
    var tasks = a(collection) ? [] : {};
    keys.forEach(function insert (key) {
      tasks[key] = function iterate (cb) {
        if (iterator.length === 3) {
          iterator(collection[key], key, cb);
        } else {
          iterator(collection[key], cb);
        }
      };
    });
    concurrent(tasks, cap || concurrency, then ? then(collection, once(done)) : done);
  }
  if (!attached) { api.series = _map(SERIAL, then, true); }
  return api;
};