/* 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.
 */

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 'gulp <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 (typeof PDFJSDev !== 'undefined' &&
            PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
          sessionStorage.setItem('pdfjs.history', databaseStr);
        } else {
          localStorage.setItem('pdfjs.history', databaseStr);
        }
        resolve();
      }.bind(this));
    },

    _readFromStorage: function ViewHistory_readFromStorage() {
      return new Promise(function (resolve) {
        if (typeof PDFJSDev !== 'undefined' &&
            PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
          resolve(sessionStorage.getItem('pdfjs.history'));
        } else {
          var value = localStorage.getItem('pdfjs.history');

          // TODO: Remove this key-name conversion after a suitable time-frame.
          // Note that we only remove the old 'database' entry if it looks like
          // it was created by PDF.js. to avoid removing someone else's data.
          if (!value) {
            var databaseStr = localStorage.getItem('database');
            if (databaseStr) {
              try {
                var database = JSON.parse(databaseStr);
                if (typeof database.files[0].fingerprint === 'string') {
                  localStorage.setItem('pdfjs.history', databaseStr);
                  localStorage.removeItem('database');
                  value = databaseStr;
                }
              } catch (ex) { }
            }
          }

          resolve(value);
        }
      });
    },

    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;
})();

export {
  ViewHistory,
};