;(function($) {

  "use strict";

  $.memoize = function(factory, ctx) {
    var cache = {};
    return function(key) {
      if (!(key in cache)) {
        cache[key] = factory.call(ctx, key);
      }
      return cache[key];
    };
  };

  $.indexedDB = function(dbname, store, keyPath) {
    var def = $.Deferred();
    var version;

    (function retry() {

      var request;
      if (typeof version === 'undefined') {
        request = indexedDB.open(dbname);
      } else {
        request = indexedDB.open(dbname, version);
      }

      request.onupgradeneeded = function(ev) {
        var db = ev.target.result;
        if (!db.objectStoreNames.contains(store)) {
          db.createObjectStore(store, {keyPath: keyPath});
        }
      };

      request.onsuccess = function(ev) {
        var db = ev.target.result;
        if (!db.objectStoreNames.contains(store)) {
          version = db.version + 1;
          db.close();
          retry();
        } else {
          def.resolve(db);
        }
      };

      request.onerror = function() {
        throw "help!";
      };
    })();

    return def.promise();
  };

  $.memoizeForever = function(factory, store, keyPath, ctx) {
    var idb = $.indexedDB("indexed", store, keyPath);
    return function(key) {
      var def = $.Deferred();
      idb.done(function(db) {
        db.transaction(store).objectStore(store).get(key).onsuccess = function(ev) {
          if (typeof ev.target.result === 'undefined') {
            $.when(factory.call(ctx, key)).done(function(data) {
              db.transaction(store, 'readwrite').objectStore(store)
                .add(data).onsuccess = function() {
                  def.resolve(data);
                };
            }).fail(def.reject);
          } else {
            def.resolve(ev.target.result);
          }
        };
      });
      return def.promise();
    };
  };

})(jQuery);