onlyurei/knockout-spa

define(function () {
  var serialize = function (value) {
    try {
      return JSON.stringify(value);
    } catch (e) {
      if (window.console) {
        window.console.error(e.message);
      }
    }
  }, deserialize = function (value) {
    try {
      return JSON.parse(value);
    } catch (e) {
      if (window.console) {
        window.console.error(e.message);
      }
    }
  }, /**
   * Returns true if local storage is supported. Wrapped in try..catch to prevent
   * uncaught exception when cookies are disabled in older versions of Firefox.
   */
  isLocalStorageAvailable = (function () {
    try {
      return !!localStorage.getItem;
    } catch (e) {
      return false;
    }
  })(), /**
   * Returns true if session storage is supported. Wrapped in try..catch to prevent
   * uncaught exception when cookies are disabled in older versions of Firefox.
   */
  isSessionStorageAvailable = (function () {
    try {
      return !!sessionStorage.getItem;
    } catch (e) {
      return false;
    }
  })();
  return {
    sessionStorageAvailable: isSessionStorageAvailable,
    localStorageAvailable: isLocalStorageAvailable,
    /**
     * Get a key/value pair from storage
     * @param {String} key Name of the item to be retrieved
     * @param {Boolean=true} permanent If true, uses local storage instead of session storage (optional)
     */
    get: function (key, permanent) {
      if (window.JSON) {
        try {
          var _permanent = (permanent || typeof permanent == 'boolean') ? permanent : true;
          if (_permanent && isLocalStorageAvailable) {
            return deserialize(localStorage.getItem(key));
          } else if (isSessionStorageAvailable) {
            return deserialize(sessionStorage.getItem(key));
          }
        } catch (e) {
          if (window.console) {
            window.console.error(e.message);
          }
          return null;
        }
      } else {
        return null;
      }
    },
    /**
     * Set a key/value pair to storage
     * @param {String} key Name of the item to be set
     * @param {Object} value JSON object representing the data to be stored
     * @param {Boolean=true} permanent If true, uses local storage instead of session storage (optional)
     */
    set: function (key, value, permanent) {
      if (window.JSON) {
        try {
          var _permanent = (permanent || typeof permanent == 'boolean') ? permanent : true;
          if (_permanent && isLocalStorageAvailable) {
            localStorage.setItem(key, serialize(value));
          } else if (isSessionStorageAvailable) {
            sessionStorage.setItem(key, serialize(value));
          }
        } catch (e) {
          if (window.console) {
            window.console.error(e.message);
          }
        }
      }
    },
    /**
     * Removes an item from storage
     * @param {String} key Name of the item to be removed
     * @param {Boolean=true} permanent If true, uses local storage instead of session storage (optional)
     */
    remove: function (key, permanent) {
      var _permanent = (permanent || typeof permanent == 'boolean') ? permanent : true;
      try {
        if (_permanent && isLocalStorageAvailable) {
          localStorage.removeItem(key);
        } else if (isSessionStorageAvailable) {
          sessionStorage.removeItem(key);
        }
      } catch (e) {
        if (window.console) {
          window.console.error(e.message);
        }
      }
    },
    /**
     * Clears items from storage
     * @param {Boolean=true} permanent If true, uses local storage instead of session storage (optional)
     */
    clear: function (permanent) {
      var _permanent = (permanent || typeof permanent == 'boolean') ? permanent : true;
      try {
        if (_permanent && isLocalStorageAvailable) {
          localStorage.clear();
        } else if (isSessionStorageAvailable) {
          sessionStorage.clear();
        }
      } catch (e) {
        if (window.console) {
          window.console.error(e.message);
        }
      }
    },
    /**
     * Add event listener for localStorage change
     * @param {Function} handler handler to be called with the param event, which contains 4 interesting properties: {
     *   key, oldValue, newValue, url, source }
     */
    addEventListener: function (handler) {
      if (window.addEventListener) {
        window.addEventListener('storage', handler, false);
      } else {
        window.attachEvent('onstorage', handler);
      }
    }
  };
});