/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* 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.
 */
/* globals PDFJS, PDFView, PresentationMode */

'use strict';

var PDFHistory = {
  initialized: false,
  initialDestination: null,

  initialize: function pdfHistoryInitialize(fingerprint) {
    if (PDFJS.disableHistory || PDFView.isViewerEmbedded) {
      // The browsing history is only enabled when the viewer is standalone,
      // i.e. not when it is embedded in a web page.
      return;
    }
    this.initialized = true;
    this.reInitialized = false;
    this.allowHashChange = true;
    this.historyUnlocked = true;

    this.previousHash = window.location.hash.substring(1);
    this.currentBookmark = '';
    this.currentPage = 0;
    this.updatePreviousBookmark = false;
    this.previousBookmark = '';
    this.previousPage = 0;
    this.nextHashParam = '';

    this.fingerprint = fingerprint;
    this.currentUid = this.uid = 0;
    this.current = {};

    var state = window.history.state;
    if (this._isStateObjectDefined(state)) {
      // This corresponds to navigating back to the document
      // from another page in the browser history.
      if (state.target.dest) {
        this.initialDestination = state.target.dest;
      } else {
        PDFView.initialBookmark = state.target.hash;
      }
      this.currentUid = state.uid;
      this.uid = state.uid + 1;
      this.current = state.target;
    } else {
      // This corresponds to the loading of a new document.
      if (state && state.fingerprint &&
          this.fingerprint !== state.fingerprint) {
        // Reinitialize the browsing history when a new document
        // is opened in the web viewer.
        this.reInitialized = true;
      }
      this._pushOrReplaceState({ fingerprint: this.fingerprint }, true);
    }

    var self = this;
    window.addEventListener('popstate', function pdfHistoryPopstate(evt) {
      evt.preventDefault();
      evt.stopPropagation();

      if (!self.historyUnlocked) {
        return;
      }
      if (evt.state) {
        // Move back/forward in the history.
        self._goTo(evt.state);
      } else {
        // Handle the user modifying the hash of a loaded document.
        self.previousHash = window.location.hash.substring(1);

        // If the history is empty when the hash changes,
        // update the previous entry in the browser history.
        if (self.uid === 0) {
          var previousParams = (self.previousHash && self.currentBookmark &&
                                self.previousHash !== self.currentBookmark) ?
            { hash: self.currentBookmark, page: self.currentPage } :
            { page: 1 };
          self.historyUnlocked = false;
          self.allowHashChange = false;
          window.history.back();
          self._pushToHistory(previousParams, false, true);
          window.history.forward();
          self.historyUnlocked = true;
        }
        self._pushToHistory({ hash: self.previousHash }, false, true);
        self._updatePreviousBookmark();
      }
    }, false);

    function pdfHistoryBeforeUnload() {
      var previousParams = self._getPreviousParams(null, true);
      if (previousParams) {
        var replacePrevious = (!self.current.dest &&
                               self.current.hash !== self.previousHash);
        self._pushToHistory(previousParams, false, replacePrevious);
        self._updatePreviousBookmark();
      }
      // Remove the event listener when navigating away from the document,
      // since 'beforeunload' prevents Firefox from caching the document.
      window.removeEventListener('beforeunload', pdfHistoryBeforeUnload, false);
    }
    window.addEventListener('beforeunload', pdfHistoryBeforeUnload, false);

    window.addEventListener('pageshow', function pdfHistoryPageShow(evt) {
      // If the entire viewer (including the PDF file) is cached in the browser,
      // we need to reattach the 'beforeunload' event listener since
      // the 'DOMContentLoaded' event is not fired on 'pageshow'.
      window.addEventListener('beforeunload', pdfHistoryBeforeUnload, false);
    }, false);
  },

  _isStateObjectDefined: function pdfHistory_isStateObjectDefined(state) {
    return (state && state.uid >= 0 &&
            state.fingerprint && this.fingerprint === state.fingerprint &&
            state.target && state.target.hash) ? true : false;
  },

  _pushOrReplaceState: function pdfHistory_pushOrReplaceState(stateObj,
                                                              replace) {
    if (replace) {
//#if (GENERIC || CHROME)
      window.history.replaceState(stateObj, '', document.URL);
//#else
//    window.history.replaceState(stateObj, '');
//#endif
    } else {
//#if (GENERIC || CHROME)
      window.history.pushState(stateObj, '', document.URL);
//#else
//    window.history.pushState(stateObj, '');
//#endif
//#if CHROME
//    if (top === window) {
//      chrome.runtime.sendMessage('showPageAction');
//    }
//#endif
    }
  },

  get isHashChangeUnlocked() {
    if (!this.initialized) {
      return true;
    }
    // If the current hash changes when moving back/forward in the history,
    // this will trigger a 'popstate' event *as well* as a 'hashchange' event.
    // Since the hash generally won't correspond to the exact the position
    // stored in the history's state object, triggering the 'hashchange' event
    // can thus corrupt the browser history.
    //
    // When the hash changes during a 'popstate' event, we *only* prevent the
    // first 'hashchange' event and immediately reset allowHashChange.
    // If it is not reset, the user would not be able to change the hash.

    var temp = this.allowHashChange;
    this.allowHashChange = true;
    return temp;
  },

  _updatePreviousBookmark: function pdfHistory_updatePreviousBookmark() {
    if (this.updatePreviousBookmark &&
        this.currentBookmark && this.currentPage) {
      this.previousBookmark = this.currentBookmark;
      this.previousPage = this.currentPage;
      this.updatePreviousBookmark = false;
    }
  },

  updateCurrentBookmark: function pdfHistoryUpdateCurrentBookmark(bookmark,
                                                                  pageNum) {
    if (this.initialized) {
      this.currentBookmark = bookmark.substring(1);
      this.currentPage = pageNum | 0;
      this._updatePreviousBookmark();
    }
  },

  updateNextHashParam: function pdfHistoryUpdateNextHashParam(param) {
    if (this.initialized) {
      this.nextHashParam = param;
    }
  },

  push: function pdfHistoryPush(params, isInitialBookmark) {
    if (!(this.initialized && this.historyUnlocked)) {
      return;
    }
    if (params.dest && !params.hash) {
      params.hash = (this.current.hash && this.current.dest &&
                     this.current.dest === params.dest) ?
        this.current.hash :
        PDFView.getDestinationHash(params.dest).split('#')[1];
    }
    if (params.page) {
      params.page |= 0;
    }
    if (isInitialBookmark) {
      var target = window.history.state.target;
      if (!target) {
        // Invoked when the user specifies an initial bookmark,
        // thus setting PDFView.initialBookmark, when the document is loaded.
        this._pushToHistory(params, false);
        this.previousHash = window.location.hash.substring(1);
      }
      this.updatePreviousBookmark = this.nextHashParam ? false : true;
      if (target) {
        // If the current document is reloaded,
        // avoid creating duplicate entries in the history.
        this._updatePreviousBookmark();
      }
      return;
    }
    if (this.nextHashParam) {
      if (this.nextHashParam === params.hash) {
        this.nextHashParam = null;
        this.updatePreviousBookmark = true;
        return;
      } else {
        this.nextHashParam = null;
      }
    }

    if (params.hash) {
      if (this.current.hash) {
        if (this.current.hash !== params.hash) {
          this._pushToHistory(params, true);
        } else {
          if (!this.current.page && params.page) {
            this._pushToHistory(params, false, true);
          }
          this.updatePreviousBookmark = true;
        }
      } else {
        this._pushToHistory(params, true);
      }
    } else if (this.current.page && params.page &&
               this.current.page !== params.page) {
      this._pushToHistory(params, true);
    }
  },

  _getPreviousParams: function pdfHistory_getPreviousParams(onlyCheckPage,
                                                            beforeUnload) {
    if (!(this.currentBookmark && this.currentPage)) {
      return null;
    } else if (this.updatePreviousBookmark) {
      this.updatePreviousBookmark = false;
    }
    if (this.uid > 0 && !(this.previousBookmark && this.previousPage)) {
      // Prevent the history from getting stuck in the current state,
      // effectively preventing the user from going back/forward in the history.
      //
      // This happens if the current position in the document didn't change when
      // the history was previously updated. The reasons for this are either:
      // 1. The current zoom value is such that the document does not need to,
      //    or cannot, be scrolled to display the destination.
      // 2. The previous destination is broken, and doesn't actally point to a
      //    position within the document.
      //    (This is either due to a bad PDF generator, or the user making a
      //     mistake when entering a destination in the hash parameters.)
      return null;
    }
    if ((!this.current.dest && !onlyCheckPage) || beforeUnload) {
      if (this.previousBookmark === this.currentBookmark) {
        return null;
      }
    } else if (this.current.page || onlyCheckPage) {
      if (this.previousPage === this.currentPage) {
        return null;
      }
    } else {
      return null;
    }
    var params = { hash: this.currentBookmark, page: this.currentPage };
    if (PresentationMode.active) {
      params.hash = null;
    }
    return params;
  },

  _stateObj: function pdfHistory_stateObj(params) {
    return { fingerprint: this.fingerprint, uid: this.uid, target: params };
  },

  _pushToHistory: function pdfHistory_pushToHistory(params,
                                                    addPrevious, overwrite) {
    if (!this.initialized) {
      return;
    }
    if (!params.hash && params.page) {
      params.hash = ('page=' + params.page);
    }
    if (addPrevious && !overwrite) {
      var previousParams = this._getPreviousParams();
      if (previousParams) {
        var replacePrevious = (!this.current.dest &&
                               this.current.hash !== this.previousHash);
        this._pushToHistory(previousParams, false, replacePrevious);
      }
    }
    this._pushOrReplaceState(this._stateObj(params),
                             (overwrite || this.uid === 0));
    this.currentUid = this.uid++;
    this.current = params;
    this.updatePreviousBookmark = true;
  },

  _goTo: function pdfHistory_goTo(state) {
    if (!(this.initialized && this.historyUnlocked &&
          this._isStateObjectDefined(state))) {
      return;
    }
    if (!this.reInitialized && state.uid < this.currentUid) {
      var previousParams = this._getPreviousParams(true);
      if (previousParams) {
        this._pushToHistory(this.current, false);
        this._pushToHistory(previousParams, false);
        this.currentUid = state.uid;
        window.history.back();
        return;
      }
    }
    this.historyUnlocked = false;

    if (state.target.dest) {
      PDFView.navigateTo(state.target.dest);
    } else {
      PDFView.setHash(state.target.hash);
    }
    this.currentUid = state.uid;
    if (state.uid > this.uid) {
      this.uid = state.uid;
    }
    this.current = state.target;
    this.updatePreviousBookmark = true;

    var currentHash = window.location.hash.substring(1);
    if (this.previousHash !== currentHash) {
      this.allowHashChange = false;
    }
    this.previousHash = currentHash;

    this.historyUnlocked = true;
  },

  back: function pdfHistoryBack() {
    this.go(-1);
  },

  forward: function pdfHistoryForward() {
    this.go(1);
  },

  go: function pdfHistoryGo(direction) {
    if (this.initialized && this.historyUnlocked) {
      var state = window.history.state;
      if (direction === -1 && state && state.uid > 0) {
        window.history.back();
      } else if (direction === 1 && state && state.uid < (this.uid - 1)) {
        window.history.forward();
      }
    }
  }
};