(function () {
    'use strict';

    // The base Data Context service provides functionality to interact with remote RESTful endpoints / local cache 
    var serviceId = 'appDataContext';
    angular.module('app').factory(serviceId, ['$http', '$q', 'DSCacheFactory', appDataContext]);

    function appDataContext($http, $q, DSCacheFactory) {

        var service = {};

        /** 
         * Process a GET request, returning the response if successful
         * 
         * Uses a cache to retrieve and store the data if the 
         * cacheName and cacheItemName are set
         * 
         * When refresh is true, the cached data is ignored
         */
        service.get = function (url, cache, cacheItem, refresh) {

            return (cache && cacheItem && !refresh)
                ? getFromCache(url, cache, cacheItem)
                : request(url, 'get');
        };

        /**
         * Process a POST request, returning the response if successful
         */
        service.post = function (url, data) {

            return request(url, 'post', data);
        }

        /**
         * Process a PUT request, returning the response if successful
         */
        service.put = function (url, data) {

            return request(url, 'put', data);
        }

        /**
         * Process a POST request, returning the response if successful
         */
        service.delete = function (url) {

            return request(url, 'delete');
        }

        /**
         * Update a Cache with new data
         */
        service.updateCache = function (cache, cacheItem, data) {

            if (cache = DSCacheFactory.get(cache)) {
                cache.put(cacheItem, data)
            }
        }

        /**
         * Clear any provided caches
         */
        service.clearCaches = function (caches) {

            if (!Array.isArray(caches)) {
                caches = [caches];
            }

            for (var i = 0; i < caches.length; i++) {
                var cache = DSCacheFactory.get(caches[i]);

                if (cache) {
                    cache.removeAll()
                };
            }
        }

        /**
         * Remove an item from the provided cache
         */
        service.removeCacheItem = function (cache, cacheItem) {

            var cache = DSCacheFactory.get(cache);

            if (cache) {
                cache.removeItem(cacheItem);
            }
        }

        /**
         * Make a request with a given type and data
         * 
         * Returns the http promise object
         */
        function request(url, type, data) {

            if (!url) {
            }

            return $http({
                method: type,
                url: url,
                data: data
            }).then(handleSuccess, handleError);
        }

        /**
         * Get an item from a given cache
        */
        function getFromCache(url, cacheName, cacheItem) {

            var cachedValue;
            var cache = DSCacheFactory.get(cacheName) || createCache(cacheName);
            
            return ((cachedValue = cache.get(cacheItem))
                ? Promise.resolve(cachedValue)
                : request(url, 'get').then(function (data) {
                    cache.put(cacheItem, data);
                    return data;
                })
            );
        }

        /**
         * Create and return a new cache
        */
        function createCache(name) {

            var cache = DSCacheFactory(name, { storageMode: 'localStorage' });

            cache.setOptions({
                maxAge: 300000,
                deleteOnExpire: 'aggressive'
            });

            return cache;
        }

        /**
         * Return a success response
        */
        function handleSuccess(response) {
            return response.data;
        }

        /**
         * Returns the error response message from the API, or
         * a default error if the API did not provide a response
         */
        function handleError(response) {
            if (response.status === 404) {
                return $q.reject("Not found.", response.status);
            }

            if (!angular.isObject(response.data) || !response.data.message) {
                return $q.reject("An unknown error occurred.", response.status);
            }

            return $q.reject(response.data.message);
        }

        return service;
    }
})();