/**
 * Provides interface for unit apis.
 */
(function() {
    var restResource = function($resource) {
        return function() {
            arguments[2]["create"] = {
                method: "PUT"
            };
            arguments[2]["update"] = {
                method: "POST"
            };
            var res = $resource.apply(null, arguments);
            res.prototype.$save = function() {
                return this[this.id? "$update":"$create"].apply(this, arguments);
            };
            return res;
        };
    };

    function normalizeFromMass(amountG, food) {
        switch (food.unit_type) {
        case "volume":
            return amountG / food.density;
        case "count":
            throw "Not yet implemented!";
            //return amountG / food.mass_p_unit;
        }
    }

    function normalizeFromVolume(amountMl, food) {
        switch (food.unit_type) {
        case "mass":
            return amountMl * food.density;
        case "count":
            throw "Not yet implemented!";
            //return amountMl * food.density / food.mass_p_unit;
        }
    }

    function normalizeFromCount(amountUnit, food) {
        switch (food.unit_type) {
        case "mass":
            throw "Not yet implemented!";
            //return amountUnit * food.mass_p_unit;
        case "volume":
            throw "Not yet implemented!";
            //return amountUnit * food.mass_p_unit / food.density;
        }
    }
    
    angular.module('Units', ['ngResource'])
    /*
     * Collection of unit apis.
     *  
     * Methods:
     * get: Gets information for a unit by id
     * query: Get a list of all units
     * queryType: Get a list of all units of a type
     * delete: Deletes a unit with an id
     * create: Creates a unit
     * update: Updates a unit
     * normalize: Converts from the given unit amount to the primary unit
     * save: Creates a new unit or updates an existing unit
     */
        .factory('Unit', ['$resource', function($resource) {
            var res = restResource($resource)("unit/:id", {id: "@id"}, {
                "queryType": {
                    method: 'GET',
                    isArray: true,
                    url: "unit/type/:type"
                },
                "primary": {
                    method: 'GET',
                    isArray: true,
                    url: "unit/primary/:type"
                }
            });
            res.prototype.normalize = function(food, amount) {
                var normalizedToType = amount * this.conversion;
                if (food.unit_type == this.type) {
                    return normalizedToType;
                }
                else {
                    switch (this.type) {
                    case "mass":
                        return normalizeFromMass(normalizedToType, food);
                    case "volume":
                        return normalizeFromVolume(normalizedToType, food);
                    case "count":
                        return normalizeFromCount(normalizedToType, food);
                    }
                }
            };
            res.prototype.toGrams = function(food, amount) {
                var normalized = amount * this.conversion;
                switch (this.type) {
                case "mass":
                    return normalized;
                case "volume":
                    return normalized * food.density;
                case "count":
                    throw "Not yet implemented!";
                    //return amountUnit * food.mass_p_unit;
                }
            };
            return res;
        }]);
})();