pdf.js/web/view_history.js

/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use strict';

var DEFAULT_VIEW_HISTORY_CACHE_SIZE = 20;

/**
 * View History - This is a utility for saving various view parameters for
 *                recently opened files.
 *
 * The way that the view parameters are stored depends on how PDF.js is built,
 * for 'node make <flag>' the following cases exist:
 *  - FIREFOX or MOZCENTRAL - uses sessionStorage.
 *  - GENERIC or CHROME     - uses localStorage, if it is available.
 */
var ViewHistory = (function ViewHistoryClosure() {
  function ViewHistory(fingerprint, cacheSize) {
    this.fingerprint = fingerprint;
    this.cacheSize = cacheSize || DEFAULT_VIEW_HISTORY_CACHE_SIZE;
    this.isInitializedPromiseResolved = false;
    this.initializedPromise =
        this._readFromStorage().then(function (databaseStr) {
      this.isInitializedPromiseResolved = true;

      var database = JSON.parse(databaseStr || '{}');
      if (!('files' in database)) {
        database.files = [];
      }
      if (database.files.length >= this.cacheSize) {
        database.files.shift();
      }
      var index;
      for (var i = 0, length = database.files.length; i < length; i++) {
        var branch = database.files[i];
        if (branch.fingerprint === this.fingerprint) {
          index = i;
          break;
        }
      }
      if (typeof index !== 'number') {
        index = database.files.push({fingerprint: this.fingerprint}) - 1;
      }
      this.file = database.files[index];
      this.database = database;
    }.bind(this));
  }

  ViewHistory.prototype = {
    _writeToStorage: function ViewHistory_writeToStorage() {
      return new Promise(function (resolve) {
        var databaseStr = JSON.stringify(this.database);

//#if FIREFOX || MOZCENTRAL
//      sessionStorage.setItem('pdfjsHistory', databaseStr);
//      resolve();
//#endif

//#if !(FIREFOX || MOZCENTRAL)
        localStorage.setItem('database', databaseStr);
        resolve();
//#endif
      }.bind(this));
    },

    _readFromStorage: function ViewHistory_readFromStorage() {
      return new Promise(function (resolve) {
//#if FIREFOX || MOZCENTRAL
//      resolve(sessionStorage.getItem('pdfjsHistory'));
//#endif

//#if !(FIREFOX || MOZCENTRAL)
        resolve(localStorage.getItem('database'));
//#endif
      });
    },

    set: function ViewHistory_set(name, val) {
      if (!this.isInitializedPromiseResolved) {
        return;
      }
      this.file[name] = val;
      return this._writeToStorage();
    },

    setMultiple: function ViewHistory_setMultiple(properties) {
      if (!this.isInitializedPromiseResolved) {
        return;
      }
      for (var name in properties) {
        this.file[name] = properties[name];
      }
      return this._writeToStorage();
    },

    get: function ViewHistory_get(name, defaultValue) {
      if (!this.isInitializedPromiseResolved) {
        return defaultValue;
      }
      return this.file[name] || defaultValue;
    }
  };

  return ViewHistory;
})();