[PWA] 18. Clean the photo cache

export default function IndexController(container) {
    this._container = container;
    this._postsView = new PostsView(this._container);
    this._toastsView = new ToastsView(this._container);
    this._lostConnectionToast = null;
    this._dbPromise = openDatabase();
    this._registerServiceWorker();
    this._cleanImageCache();

    var indexController = this;

    setInterval(function () {
        indexController._cleanImageCache();
    }, 1000 * 60 * 5);

    this._showCachedMessages().then(function () {
        indexController._openSocket();
    });
}

IndexController.prototype._cleanImageCache = function () {
    return this._dbPromise.then(function (db) {
        if (!db) return;

        // TODO: open the ‘wittr‘ object store, get all the messages,
        // gather all the photo urls.
        //
        // Open the ‘wittr-content-imgs‘ cache, and delete any entry
        // that you no longer need.
        var photosToKeep = [];
        var tx = db.transaction(‘wittrs‘);
        return tx.objectStore(‘wittrs‘).getAll()
            .then(function(messages){
                messages.forEach(function(message){
                    if(message.photo){
                        photosToKeep.push(message.photo);
                    }
                });

                return caches.open(‘wittr-content-imgs‘);
            })
            .then(function(cache){
                return cache.keys().then(function(requests){
                    requests.forEach(function(request){
                        var url = new URL(request.url);
                        if(!photosToKeep.includes(url.pathname)){
                            cache.delete(request);
                        }
                    })
                })
            });
    });
};