/* global define */

/**
* Utility module containing useful static classes.
*
* @module Utils
*/

/**
* A set of useful functions for manipulating dictionaries.
*
* ####Imports RAMP Modules:
* {{#crossLink "Util"}}{{/crossLink}}  
*
* @class Dictionary
* @static
* @uses dojo/_base/array
* @uses dojo/_base/lang
*/
define(["dojo/_base/lang"],
    function () {
        "use strict";

        return {
            /**
            * Iterates over the key-value pair in the given dictionary (in arbitrary order) and
            * calls the given function on each key-value pair.
            *
            * @method forEachEntry
            * @static
            * @param {Object} dict a dictionary object
            * @param {Function} fcn a function that takes the following parameters:
            *  - the `key`
            *  - the `value`
            *  - `obj` (an optional parameter) that contains two fields, exit and returnVal. If exit is set to true,
            * forEachEntry terminates right away (without iterating over the rest of the dictionary). The
            * return value of forEackKeyValuePair is returnVal (which by default is undefined).</param>
            * @param {Function} [sortFcn] true if the dictionary keys are to be sorted before iterating
            * @param {Object} [scope] The scope called with the given fcn
            */
            forEachEntry: function (dict, fcn, sortFcn, scope) {
                if (scope) {
                    fcn = fcn.call(scope);
                }

                var keys = Object.keys(dict);

                if (sortFcn) {
                    keys.sort(sortFcn);
                }

                keys.forEach(function (key) {
                    fcn(key, dict[key]);
                });
            },

            /**
            * Iterates over the key-value pair in the given dictionary and
            * returns the index of the first element to cause the given fcn to return
            * true.
            *
            * @method find
            * @static
            * @param {Object} dict a dictionary object
            * @param {Function} fcn a function that takes the following parameters:
            * - the `key`
            * - the `value`
            * and returns true if the given key or value satisfy some condition
            * @param {Function} [compareFcn] a comparator function (takes two arguments and returns an integer) used to sort the keys
            */
            find: function (dict, fcn, compareFcn) {
                var keys = [];

                for (var key in dict) {
                    if (dict.hasOwnProperty(key)) {
                        keys.push(key);
                    }
                }

                if (compareFcn) {
                    keys.sort(compareFcn);
                }

                var index = -1;
                keys.forEach(function (key, i) {
                    if (index === -1 && fcn(key, dict[key])) {
                        index = i;
                    }
                });

                return index;
            },

            filter: function (dict, predicate) {
                var filteredDict = {};
                this.forEachEntry(dict, function (key, value) {
                    if (predicate(key, value)) {
                        filteredDict[key] = value;
                    }
                });
                return filteredDict;
            },

            /**
            * Returns the number of keys in the given dictionary.
            *
            * @method length
            * @param {Object} dict a dictionary
            * @return {Integer} the number of keys in the dictionary
            * @static
            */
            length: function (dict) {
                return Object.keys(dict).length;
            },

            /**
            * Returns true if the given dictionary is empty (i.e. has no keys)
            *
            * @method isEmpty
            * @static
            * @param {Object} dict a dictionary
            * @return {Boolean} true if the dictionary is empty, false otherwise
            */
            isEmpty: function (dict) {
                return this.length(dict) === 0;
            },

            /**
           * Returns a shallow copy of the given dictionary.
           *
           * @static
           * @method clone
           * @param {Object} dict a dictionary
           * @return {Object} a shallow copy of the given dictionary
           */
            clone: function (dict) {
                var copy = {};
                this.forEachEntry(dict, function (key, value) {
                    copy[key] = value;
                });
                return copy;
            },

            /**
            * Converts the given array into a dictionary, where the values of the dictionary are values in
            * the array, and the keys are the return value of the given function.
            *
            * @static
            * @method arrayToMap
            * @param {Object} arr an array
            * @param {Function} fcn a function that takes one argument and returns a key for the given argument
            * @return {Object} a dictionary
            */
            arrayToMap: function (arr, fcn) {
                var dict = {};
                arr.forEach(function (element) {
                    dict[fcn(arr)] = element;
                });
                return dict;
            },

            /**
            * Convert the given array into a dictionary, where the keys of the dictionary are the elements in the
            * first array and the values of the dictionary are elements in the second array. The size of the two arrays
            * must match.
            *
            * @static
            * @method zip
            * @param {Object} arr1 the key array
            * @param {Object} arr2 the value array
            * @return {Object} a dictionary
            */
            zip: function (arr1, arr2) {
                if (arr1.length !== arr2.length) {
                    throw "Array lengths differ";
                }

                var dict = {};
                arr1.forEach(function (element, i) {
                    dict[element] = arr2[i];
                });
                return dict;
            }
        };
    });