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   1  /**
   2   * @file Revisions interface functions, Backbone classes and
   3   * the revisions.php document.ready bootstrap.
   4   *
   5   * @output wp-admin/js/revisions.js
   6   */
   7  
   8  /* global isRtl */
   9  
  10  window.wp = window.wp || {};
  11  
  12  (function($) {
  13      var revisions;
  14      /**
  15       * Expose the module in window.wp.revisions.
  16       */
  17      revisions = wp.revisions = { model: {}, view: {}, controller: {} };
  18  
  19      // Link post revisions data served from the back end.
  20      revisions.settings = window._wpRevisionsSettings || {};
  21  
  22      // For debugging.
  23      revisions.debug = false;
  24  
  25      /**
  26       * wp.revisions.log
  27       *
  28       * A debugging utility for revisions. Works only when a
  29       * debug flag is on and the browser supports it.
  30       */
  31      revisions.log = function() {
  32          if ( window.console && revisions.debug ) {
  33              window.console.log.apply( window.console, arguments );
  34          }
  35      };
  36  
  37      // Handy functions to help with positioning.
  38      $.fn.allOffsets = function() {
  39          var offset = this.offset() || {top: 0, left: 0}, win = $(window);
  40          return _.extend( offset, {
  41              right:  win.width()  - offset.left - this.outerWidth(),
  42              bottom: win.height() - offset.top  - this.outerHeight()
  43          });
  44      };
  45  
  46      $.fn.allPositions = function() {
  47          var position = this.position() || {top: 0, left: 0}, parent = this.parent();
  48          return _.extend( position, {
  49              right:  parent.outerWidth()  - position.left - this.outerWidth(),
  50              bottom: parent.outerHeight() - position.top  - this.outerHeight()
  51          });
  52      };
  53  
  54      /**
  55       * ========================================================================
  56       * MODELS
  57       * ========================================================================
  58       */
  59      revisions.model.Slider = Backbone.Model.extend({
  60          defaults: {
  61              value: null,
  62              values: null,
  63              min: 0,
  64              max: 1,
  65              step: 1,
  66              range: false,
  67              compareTwoMode: false
  68          },
  69  
  70          initialize: function( options ) {
  71              this.frame = options.frame;
  72              this.revisions = options.revisions;
  73  
  74              // Listen for changes to the revisions or mode from outside.
  75              this.listenTo( this.frame, 'update:revisions', this.receiveRevisions );
  76              this.listenTo( this.frame, 'change:compareTwoMode', this.updateMode );
  77  
  78              // Listen for internal changes.
  79              this.on( 'change:from', this.handleLocalChanges );
  80              this.on( 'change:to', this.handleLocalChanges );
  81              this.on( 'change:compareTwoMode', this.updateSliderSettings );
  82              this.on( 'update:revisions', this.updateSliderSettings );
  83  
  84              // Listen for changes to the hovered revision.
  85              this.on( 'change:hoveredRevision', this.hoverRevision );
  86  
  87              this.set({
  88                  max:   this.revisions.length - 1,
  89                  compareTwoMode: this.frame.get('compareTwoMode'),
  90                  from: this.frame.get('from'),
  91                  to: this.frame.get('to')
  92              });
  93              this.updateSliderSettings();
  94          },
  95  
  96          getSliderValue: function( a, b ) {
  97              return isRtl ? this.revisions.length - this.revisions.indexOf( this.get(a) ) - 1 : this.revisions.indexOf( this.get(b) );
  98          },
  99  
 100          updateSliderSettings: function() {
 101              if ( this.get('compareTwoMode') ) {
 102                  this.set({
 103                      values: [
 104                          this.getSliderValue( 'to', 'from' ),
 105                          this.getSliderValue( 'from', 'to' )
 106                      ],
 107                      value: null,
 108                      range: true // Ensures handles cannot cross.
 109                  });
 110              } else {
 111                  this.set({
 112                      value: this.getSliderValue( 'to', 'to' ),
 113                      values: null,
 114                      range: false
 115                  });
 116              }
 117              this.trigger( 'update:slider' );
 118          },
 119  
 120          // Called when a revision is hovered.
 121          hoverRevision: function( model, value ) {
 122              this.trigger( 'hovered:revision', value );
 123          },
 124  
 125          // Called when `compareTwoMode` changes.
 126          updateMode: function( model, value ) {
 127              this.set({ compareTwoMode: value });
 128          },
 129  
 130          // Called when `from` or `to` changes in the local model.
 131          handleLocalChanges: function() {
 132              this.frame.set({
 133                  from: this.get('from'),
 134                  to: this.get('to')
 135              });
 136          },
 137  
 138          // Receives revisions changes from outside the model.
 139          receiveRevisions: function( from, to ) {
 140              // Bail if nothing changed.
 141              if ( this.get('from') === from && this.get('to') === to ) {
 142                  return;
 143              }
 144  
 145              this.set({ from: from, to: to }, { silent: true });
 146              this.trigger( 'update:revisions', from, to );
 147          }
 148  
 149      });
 150  
 151      revisions.model.Tooltip = Backbone.Model.extend({
 152          defaults: {
 153              revision: null,
 154              offset: {},
 155              hovering: false, // Whether the mouse is hovering.
 156              scrubbing: false // Whether the mouse is scrubbing.
 157          },
 158  
 159          initialize: function( options ) {
 160              this.frame = options.frame;
 161              this.revisions = options.revisions;
 162              this.slider = options.slider;
 163  
 164              this.listenTo( this.slider, 'hovered:revision', this.updateRevision );
 165              this.listenTo( this.slider, 'change:hovering', this.setHovering );
 166              this.listenTo( this.slider, 'change:scrubbing', this.setScrubbing );
 167          },
 168  
 169  
 170          updateRevision: function( revision ) {
 171              this.set({ revision: revision });
 172          },
 173  
 174          setHovering: function( model, value ) {
 175              this.set({ hovering: value });
 176          },
 177  
 178          setScrubbing: function( model, value ) {
 179              this.set({ scrubbing: value });
 180          }
 181      });
 182  
 183      revisions.model.Revision = Backbone.Model.extend({});
 184  
 185      /**
 186       * wp.revisions.model.Revisions
 187       *
 188       * A collection of post revisions.
 189       */
 190      revisions.model.Revisions = Backbone.Collection.extend({
 191          model: revisions.model.Revision,
 192  
 193          initialize: function() {
 194              _.bindAll( this, 'next', 'prev' );
 195          },
 196  
 197          next: function( revision ) {
 198              var index = this.indexOf( revision );
 199  
 200              if ( index !== -1 && index !== this.length - 1 ) {
 201                  return this.at( index + 1 );
 202              }
 203          },
 204  
 205          prev: function( revision ) {
 206              var index = this.indexOf( revision );
 207  
 208              if ( index !== -1 && index !== 0 ) {
 209                  return this.at( index - 1 );
 210              }
 211          }
 212      });
 213  
 214      revisions.model.Field = Backbone.Model.extend({});
 215  
 216      revisions.model.Fields = Backbone.Collection.extend({
 217          model: revisions.model.Field
 218      });
 219  
 220      revisions.model.Diff = Backbone.Model.extend({
 221          initialize: function() {
 222              var fields = this.get('fields');
 223              this.unset('fields');
 224  
 225              this.fields = new revisions.model.Fields( fields );
 226          }
 227      });
 228  
 229      revisions.model.Diffs = Backbone.Collection.extend({
 230          initialize: function( models, options ) {
 231              _.bindAll( this, 'getClosestUnloaded' );
 232              this.loadAll = _.once( this._loadAll );
 233              this.revisions = options.revisions;
 234              this.postId = options.postId;
 235              this.requests  = {};
 236          },
 237  
 238          model: revisions.model.Diff,
 239  
 240          ensure: function( id, context ) {
 241              var diff     = this.get( id ),
 242                  request  = this.requests[ id ],
 243                  deferred = $.Deferred(),
 244                  ids      = {},
 245                  from     = id.split(':')[0],
 246                  to       = id.split(':')[1];
 247              ids[id] = true;
 248  
 249              wp.revisions.log( 'ensure', id );
 250  
 251              this.trigger( 'ensure', ids, from, to, deferred.promise() );
 252  
 253              if ( diff ) {
 254                  deferred.resolveWith( context, [ diff ] );
 255              } else {
 256                  this.trigger( 'ensure:load', ids, from, to, deferred.promise() );
 257                  _.each( ids, _.bind( function( id ) {
 258                      // Remove anything that has an ongoing request.
 259                      if ( this.requests[ id ] ) {
 260                          delete ids[ id ];
 261                      }
 262                      // Remove anything we already have.
 263                      if ( this.get( id ) ) {
 264                          delete ids[ id ];
 265                      }
 266                  }, this ) );
 267                  if ( ! request ) {
 268                      // Always include the ID that started this ensure.
 269                      ids[ id ] = true;
 270                      request   = this.load( _.keys( ids ) );
 271                  }
 272  
 273                  request.done( _.bind( function() {
 274                      deferred.resolveWith( context, [ this.get( id ) ] );
 275                  }, this ) ).fail( _.bind( function() {
 276                      deferred.reject();
 277                  }) );
 278              }
 279  
 280              return deferred.promise();
 281          },
 282  
 283          // Returns an array of proximal diffs.
 284          getClosestUnloaded: function( ids, centerId ) {
 285              var self = this;
 286              return _.chain([0].concat( ids )).initial().zip( ids ).sortBy( function( pair ) {
 287                  return Math.abs( centerId - pair[1] );
 288              }).map( function( pair ) {
 289                  return pair.join(':');
 290              }).filter( function( diffId ) {
 291                  return _.isUndefined( self.get( diffId ) ) && ! self.requests[ diffId ];
 292              }).value();
 293          },
 294  
 295          _loadAll: function( allRevisionIds, centerId, num ) {
 296              var self = this, deferred = $.Deferred(),
 297                  diffs = _.first( this.getClosestUnloaded( allRevisionIds, centerId ), num );
 298              if ( _.size( diffs ) > 0 ) {
 299                  this.load( diffs ).done( function() {
 300                      self._loadAll( allRevisionIds, centerId, num ).done( function() {
 301                          deferred.resolve();
 302                      });
 303                  }).fail( function() {
 304                      if ( 1 === num ) { // Already tried 1. This just isn't working. Give up.
 305                          deferred.reject();
 306                      } else { // Request fewer diffs this time.
 307                          self._loadAll( allRevisionIds, centerId, Math.ceil( num / 2 ) ).done( function() {
 308                              deferred.resolve();
 309                          });
 310                      }
 311                  });
 312              } else {
 313                  deferred.resolve();
 314              }
 315              return deferred;
 316          },
 317  
 318          load: function( comparisons ) {
 319              wp.revisions.log( 'load', comparisons );
 320              // Our collection should only ever grow, never shrink, so `remove: false`.
 321              return this.fetch({ data: { compare: comparisons }, remove: false }).done( function() {
 322                  wp.revisions.log( 'load:complete', comparisons );
 323              });
 324          },
 325  
 326          sync: function( method, model, options ) {
 327              if ( 'read' === method ) {
 328                  options = options || {};
 329                  options.context = this;
 330                  options.data = _.extend( options.data || {}, {
 331                      action: 'get-revision-diffs',
 332                      post_id: this.postId
 333                  });
 334  
 335                  var deferred = wp.ajax.send( options ),
 336                      requests = this.requests;
 337  
 338                  // Record that we're requesting each diff.
 339                  if ( options.data.compare ) {
 340                      _.each( options.data.compare, function( id ) {
 341                          requests[ id ] = deferred;
 342                      });
 343                  }
 344  
 345                  // When the request completes, clear the stored request.
 346                  deferred.always( function() {
 347                      if ( options.data.compare ) {
 348                          _.each( options.data.compare, function( id ) {
 349                              delete requests[ id ];
 350                          });
 351                      }
 352                  });
 353  
 354                  return deferred;
 355  
 356              // Otherwise, fall back to `Backbone.sync()`.
 357              } else {
 358                  return Backbone.Model.prototype.sync.apply( this, arguments );
 359              }
 360          }
 361      });
 362  
 363  
 364      /**
 365       * wp.revisions.model.FrameState
 366       *
 367       * The frame state.
 368       *
 369       * @see wp.revisions.view.Frame
 370       *
 371       * @param {object}                    attributes        Model attributes - none are required.
 372       * @param {object}                    options           Options for the model.
 373       * @param {revisions.model.Revisions} options.revisions A collection of revisions.
 374       */
 375      revisions.model.FrameState = Backbone.Model.extend({
 376          defaults: {
 377              loading: false,
 378              error: false,
 379              compareTwoMode: false
 380          },
 381  
 382          initialize: function( attributes, options ) {
 383              var state = this.get( 'initialDiffState' );
 384              _.bindAll( this, 'receiveDiff' );
 385              this._debouncedEnsureDiff = _.debounce( this._ensureDiff, 200 );
 386  
 387              this.revisions = options.revisions;
 388  
 389              this.diffs = new revisions.model.Diffs( [], {
 390                  revisions: this.revisions,
 391                  postId: this.get( 'postId' )
 392              } );
 393  
 394              // Set the initial diffs collection.
 395              this.diffs.set( this.get( 'diffData' ) );
 396  
 397              // Set up internal listeners.
 398              this.listenTo( this, 'change:from', this.changeRevisionHandler );
 399              this.listenTo( this, 'change:to', this.changeRevisionHandler );
 400              this.listenTo( this, 'change:compareTwoMode', this.changeMode );
 401              this.listenTo( this, 'update:revisions', this.updatedRevisions );
 402              this.listenTo( this.diffs, 'ensure:load', this.updateLoadingStatus );
 403              this.listenTo( this, 'update:diff', this.updateLoadingStatus );
 404  
 405              // Set the initial revisions, baseUrl, and mode as provided through attributes.
 406  
 407              this.set( {
 408                  to : this.revisions.get( state.to ),
 409                  from : this.revisions.get( state.from ),
 410                  compareTwoMode : state.compareTwoMode
 411              } );
 412  
 413              // Start the router if browser supports History API.
 414              if ( window.history && window.history.pushState ) {
 415                  this.router = new revisions.Router({ model: this });
 416                  if ( Backbone.History.started ) {
 417                      Backbone.history.stop();
 418                  }
 419                  Backbone.history.start({ pushState: true });
 420              }
 421          },
 422  
 423          updateLoadingStatus: function() {
 424              this.set( 'error', false );
 425              this.set( 'loading', ! this.diff() );
 426          },
 427  
 428          changeMode: function( model, value ) {
 429              var toIndex = this.revisions.indexOf( this.get( 'to' ) );
 430  
 431              // If we were on the first revision before switching to two-handled mode,
 432              // bump the 'to' position over one.
 433              if ( value && 0 === toIndex ) {
 434                  this.set({
 435                      from: this.revisions.at( toIndex ),
 436                      to:   this.revisions.at( toIndex + 1 )
 437                  });
 438              }
 439  
 440              // When switching back to single-handled mode, reset 'from' model to
 441              // one position before the 'to' model.
 442              if ( ! value && 0 !== toIndex ) { // '! value' means switching to single-handled mode.
 443                  this.set({
 444                      from: this.revisions.at( toIndex - 1 ),
 445                      to:   this.revisions.at( toIndex )
 446                  });
 447              }
 448          },
 449  
 450          updatedRevisions: function( from, to ) {
 451              if ( this.get( 'compareTwoMode' ) ) {
 452                  // @todo Compare-two loading strategy.
 453              } else {
 454                  this.diffs.loadAll( this.revisions.pluck('id'), to.id, 40 );
 455              }
 456          },
 457  
 458          // Fetch the currently loaded diff.
 459          diff: function() {
 460              return this.diffs.get( this._diffId );
 461          },
 462  
 463          /*
 464           * So long as `from` and `to` are changed at the same time, the diff
 465           * will only be updated once. This is because Backbone updates all of
 466           * the changed attributes in `set`, and then fires the `change` events.
 467           */
 468          updateDiff: function( options ) {
 469              var from, to, diffId, diff;
 470  
 471              options = options || {};
 472              from = this.get('from');
 473              to = this.get('to');
 474              diffId = ( from ? from.id : 0 ) + ':' + to.id;
 475  
 476              // Check if we're actually changing the diff id.
 477              if ( this._diffId === diffId ) {
 478                  return $.Deferred().reject().promise();
 479              }
 480  
 481              this._diffId = diffId;
 482              this.trigger( 'update:revisions', from, to );
 483  
 484              diff = this.diffs.get( diffId );
 485  
 486              // If we already have the diff, then immediately trigger the update.
 487              if ( diff ) {
 488                  this.receiveDiff( diff );
 489                  return $.Deferred().resolve().promise();
 490              // Otherwise, fetch the diff.
 491              } else {
 492                  if ( options.immediate ) {
 493                      return this._ensureDiff();
 494                  } else {
 495                      this._debouncedEnsureDiff();
 496                      return $.Deferred().reject().promise();
 497                  }
 498              }
 499          },
 500  
 501          // A simple wrapper around `updateDiff` to prevent the change event's
 502          // parameters from being passed through.
 503          changeRevisionHandler: function() {
 504              this.updateDiff();
 505          },
 506  
 507          receiveDiff: function( diff ) {
 508              // Did we actually get a diff?
 509              if ( _.isUndefined( diff ) || _.isUndefined( diff.id ) ) {
 510                  this.set({
 511                      loading: false,
 512                      error: true
 513                  });
 514              } else if ( this._diffId === diff.id ) { // Make sure the current diff didn't change.
 515                  this.trigger( 'update:diff', diff );
 516              }
 517          },
 518  
 519          _ensureDiff: function() {
 520              return this.diffs.ensure( this._diffId, this ).always( this.receiveDiff );
 521          }
 522      });
 523  
 524  
 525      /**
 526       * ========================================================================
 527       * VIEWS
 528       * ========================================================================
 529       */
 530  
 531      /**
 532       * wp.revisions.view.Frame
 533       *
 534       * Top level frame that orchestrates the revisions experience.
 535       *
 536       * @param {object}                     options       The options hash for the view.
 537       * @param {revisions.model.FrameState} options.model The frame state model.
 538       */
 539      revisions.view.Frame = wp.Backbone.View.extend({
 540          className: 'revisions',
 541          template: wp.template('revisions-frame'),
 542  
 543          initialize: function() {
 544              this.listenTo( this.model, 'update:diff', this.renderDiff );
 545              this.listenTo( this.model, 'change:compareTwoMode', this.updateCompareTwoMode );
 546              this.listenTo( this.model, 'change:loading', this.updateLoadingStatus );
 547              this.listenTo( this.model, 'change:error', this.updateErrorStatus );
 548  
 549              this.views.set( '.revisions-control-frame', new revisions.view.Controls({
 550                  model: this.model
 551              }) );
 552          },
 553  
 554          render: function() {
 555              wp.Backbone.View.prototype.render.apply( this, arguments );
 556  
 557              $('html').css( 'overflow-y', 'scroll' );
 558              $('#wpbody-content .wrap').append( this.el );
 559              this.updateCompareTwoMode();
 560              this.renderDiff( this.model.diff() );
 561              this.views.ready();
 562  
 563              return this;
 564          },
 565  
 566          renderDiff: function( diff ) {
 567              this.views.set( '.revisions-diff-frame', new revisions.view.Diff({
 568                  model: diff
 569              }) );
 570          },
 571  
 572          updateLoadingStatus: function() {
 573              this.$el.toggleClass( 'loading', this.model.get('loading') );
 574          },
 575  
 576          updateErrorStatus: function() {
 577              this.$el.toggleClass( 'diff-error', this.model.get('error') );
 578          },
 579  
 580          updateCompareTwoMode: function() {
 581              this.$el.toggleClass( 'comparing-two-revisions', this.model.get('compareTwoMode') );
 582          }
 583      });
 584  
 585      /**
 586       * wp.revisions.view.Controls
 587       *
 588       * The controls view.
 589       *
 590       * Contains the revision slider, previous/next buttons, the meta info and the compare checkbox.
 591       */
 592      revisions.view.Controls = wp.Backbone.View.extend({
 593          className: 'revisions-controls',
 594  
 595          initialize: function() {
 596              _.bindAll( this, 'setWidth' );
 597  
 598              // Add the button view.
 599              this.views.add( new revisions.view.Buttons({
 600                  model: this.model
 601              }) );
 602  
 603              // Add the checkbox view.
 604              this.views.add( new revisions.view.Checkbox({
 605                  model: this.model
 606              }) );
 607  
 608              // Prep the slider model.
 609              var slider = new revisions.model.Slider({
 610                  frame: this.model,
 611                  revisions: this.model.revisions
 612              }),
 613  
 614              // Prep the tooltip model.
 615              tooltip = new revisions.model.Tooltip({
 616                  frame: this.model,
 617                  revisions: this.model.revisions,
 618                  slider: slider
 619              });
 620  
 621              // Add the tooltip view.
 622              this.views.add( new revisions.view.Tooltip({
 623                  model: tooltip
 624              }) );
 625  
 626              // Add the tickmarks view.
 627              this.views.add( new revisions.view.Tickmarks({
 628                  model: tooltip
 629              }) );
 630  
 631              // Add the slider view.
 632              this.views.add( new revisions.view.Slider({
 633                  model: slider
 634              }) );
 635  
 636              // Add the Metabox view.
 637              this.views.add( new revisions.view.Metabox({
 638                  model: this.model
 639              }) );
 640          },
 641  
 642          ready: function() {
 643              this.top = this.$el.offset().top;
 644              this.window = $(window);
 645              this.window.on( 'scroll.wp.revisions', {controls: this}, function(e) {
 646                  var controls  = e.data.controls,
 647                      container = controls.$el.parent(),
 648                      scrolled  = controls.window.scrollTop(),
 649                      frame     = controls.views.parent;
 650  
 651                  if ( scrolled >= controls.top ) {
 652                      if ( ! frame.$el.hasClass('pinned') ) {
 653                          controls.setWidth();
 654                          container.css('height', container.height() + 'px' );
 655                          controls.window.on('resize.wp.revisions.pinning click.wp.revisions.pinning', {controls: controls}, function(e) {
 656                              e.data.controls.setWidth();
 657                          });
 658                      }
 659                      frame.$el.addClass('pinned');
 660                  } else if ( frame.$el.hasClass('pinned') ) {
 661                      controls.window.off('.wp.revisions.pinning');
 662                      controls.$el.css('width', 'auto');
 663                      frame.$el.removeClass('pinned');
 664                      container.css('height', 'auto');
 665                      controls.top = controls.$el.offset().top;
 666                  } else {
 667                      controls.top = controls.$el.offset().top;
 668                  }
 669              });
 670          },
 671  
 672          setWidth: function() {
 673              this.$el.css('width', this.$el.parent().width() + 'px');
 674          }
 675      });
 676  
 677      // The tickmarks view.
 678      revisions.view.Tickmarks = wp.Backbone.View.extend({
 679          className: 'revisions-tickmarks',
 680          direction: isRtl ? 'right' : 'left',
 681  
 682          initialize: function() {
 683              this.listenTo( this.model, 'change:revision', this.reportTickPosition );
 684          },
 685  
 686          reportTickPosition: function( model, revision ) {
 687              var offset, thisOffset, parentOffset, tick, index = this.model.revisions.indexOf( revision );
 688              thisOffset = this.$el.allOffsets();
 689              parentOffset = this.$el.parent().allOffsets();
 690              if ( index === this.model.revisions.length - 1 ) {
 691                  // Last one.
 692                  offset = {
 693                      rightPlusWidth: thisOffset.left - parentOffset.left + 1,
 694                      leftPlusWidth: thisOffset.right - parentOffset.right + 1
 695                  };
 696              } else {
 697                  // Normal tick.
 698                  tick = this.$('div:nth-of-type(' + (index + 1) + ')');
 699                  offset = tick.allPositions();
 700                  _.extend( offset, {
 701                      left: offset.left + thisOffset.left - parentOffset.left,
 702                      right: offset.right + thisOffset.right - parentOffset.right
 703                  });
 704                  _.extend( offset, {
 705                      leftPlusWidth: offset.left + tick.outerWidth(),
 706                      rightPlusWidth: offset.right + tick.outerWidth()
 707                  });
 708              }
 709              this.model.set({ offset: offset });
 710          },
 711  
 712          ready: function() {
 713              var tickCount, tickWidth;
 714              tickCount = this.model.revisions.length - 1;
 715              tickWidth = 1 / tickCount;
 716              this.$el.css('width', ( this.model.revisions.length * 50 ) + 'px');
 717  
 718              _(tickCount).times( function( index ){
 719                  this.$el.append( '<div style="' + this.direction + ': ' + ( 100 * tickWidth * index ) + '%"></div>' );
 720              }, this );
 721          }
 722      });
 723  
 724      // The metabox view.
 725      revisions.view.Metabox = wp.Backbone.View.extend({
 726          className: 'revisions-meta',
 727  
 728          initialize: function() {
 729              // Add the 'from' view.
 730              this.views.add( new revisions.view.MetaFrom({
 731                  model: this.model,
 732                  className: 'diff-meta diff-meta-from'
 733              }) );
 734  
 735              // Add the 'to' view.
 736              this.views.add( new revisions.view.MetaTo({
 737                  model: this.model
 738              }) );
 739          }
 740      });
 741  
 742      // The revision meta view (to be extended).
 743      revisions.view.Meta = wp.Backbone.View.extend({
 744          template: wp.template('revisions-meta'),
 745  
 746          events: {
 747              'click .restore-revision': 'restoreRevision'
 748          },
 749  
 750          initialize: function() {
 751              this.listenTo( this.model, 'update:revisions', this.render );
 752          },
 753  
 754          prepare: function() {
 755              return _.extend( this.model.toJSON()[this.type] || {}, {
 756                  type: this.type
 757              });
 758          },
 759  
 760          restoreRevision: function() {
 761              document.location = this.model.get('to').attributes.restoreUrl;
 762          }
 763      });
 764  
 765      // The revision meta 'from' view.
 766      revisions.view.MetaFrom = revisions.view.Meta.extend({
 767          className: 'diff-meta diff-meta-from',
 768          type: 'from'
 769      });
 770  
 771      // The revision meta 'to' view.
 772      revisions.view.MetaTo = revisions.view.Meta.extend({
 773          className: 'diff-meta diff-meta-to',
 774          type: 'to'
 775      });
 776  
 777      // The checkbox view.
 778      revisions.view.Checkbox = wp.Backbone.View.extend({
 779          className: 'revisions-checkbox',
 780          template: wp.template('revisions-checkbox'),
 781  
 782          events: {
 783              'click .compare-two-revisions': 'compareTwoToggle'
 784          },
 785  
 786          initialize: function() {
 787              this.listenTo( this.model, 'change:compareTwoMode', this.updateCompareTwoMode );
 788          },
 789  
 790          ready: function() {
 791              if ( this.model.revisions.length < 3 ) {
 792                  $('.revision-toggle-compare-mode').hide();
 793              }
 794          },
 795  
 796          updateCompareTwoMode: function() {
 797              this.$('.compare-two-revisions').prop( 'checked', this.model.get('compareTwoMode') );
 798          },
 799  
 800          // Toggle the compare two mode feature when the compare two checkbox is checked.
 801          compareTwoToggle: function() {
 802              // Activate compare two mode?
 803              this.model.set({ compareTwoMode: $('.compare-two-revisions').prop('checked') });
 804          }
 805      });
 806  
 807      // The tooltip view.
 808      // Encapsulates the tooltip.
 809      revisions.view.Tooltip = wp.Backbone.View.extend({
 810          className: 'revisions-tooltip',
 811          template: wp.template('revisions-meta'),
 812  
 813          initialize: function() {
 814              this.listenTo( this.model, 'change:offset', this.render );
 815              this.listenTo( this.model, 'change:hovering', this.toggleVisibility );
 816              this.listenTo( this.model, 'change:scrubbing', this.toggleVisibility );
 817          },
 818  
 819          prepare: function() {
 820              if ( _.isNull( this.model.get('revision') ) ) {
 821                  return;
 822              } else {
 823                  return _.extend( { type: 'tooltip' }, {
 824                      attributes: this.model.get('revision').toJSON()
 825                  });
 826              }
 827          },
 828  
 829          render: function() {
 830              var otherDirection,
 831                  direction,
 832                  directionVal,
 833                  flipped,
 834                  css      = {},
 835                  position = this.model.revisions.indexOf( this.model.get('revision') ) + 1;
 836  
 837              flipped = ( position / this.model.revisions.length ) > 0.5;
 838              if ( isRtl ) {
 839                  direction = flipped ? 'left' : 'right';
 840                  directionVal = flipped ? 'leftPlusWidth' : direction;
 841              } else {
 842                  direction = flipped ? 'right' : 'left';
 843                  directionVal = flipped ? 'rightPlusWidth' : direction;
 844              }
 845              otherDirection = 'right' === direction ? 'left': 'right';
 846              wp.Backbone.View.prototype.render.apply( this, arguments );
 847              css[direction] = this.model.get('offset')[directionVal] + 'px';
 848              css[otherDirection] = '';
 849              this.$el.toggleClass( 'flipped', flipped ).css( css );
 850          },
 851  
 852          visible: function() {
 853              return this.model.get( 'scrubbing' ) || this.model.get( 'hovering' );
 854          },
 855  
 856          toggleVisibility: function() {
 857              if ( this.visible() ) {
 858                  this.$el.stop().show().fadeTo( 100 - this.el.style.opacity * 100, 1 );
 859              } else {
 860                  this.$el.stop().fadeTo( this.el.style.opacity * 300, 0, function(){ $(this).hide(); } );
 861              }
 862              return;
 863          }
 864      });
 865  
 866      // The buttons view.
 867      // Encapsulates all of the configuration for the previous/next buttons.
 868      revisions.view.Buttons = wp.Backbone.View.extend({
 869          className: 'revisions-buttons',
 870          template: wp.template('revisions-buttons'),
 871  
 872          events: {
 873              'click .revisions-next .button': 'nextRevision',
 874              'click .revisions-previous .button': 'previousRevision'
 875          },
 876  
 877          initialize: function() {
 878              this.listenTo( this.model, 'update:revisions', this.disabledButtonCheck );
 879          },
 880  
 881          ready: function() {
 882              this.disabledButtonCheck();
 883          },
 884  
 885          // Go to a specific model index.
 886          gotoModel: function( toIndex ) {
 887              var attributes = {
 888                  to: this.model.revisions.at( toIndex )
 889              };
 890              // If we're at the first revision, unset 'from'.
 891              if ( toIndex ) {
 892                  attributes.from = this.model.revisions.at( toIndex - 1 );
 893              } else {
 894                  this.model.unset('from', { silent: true });
 895              }
 896  
 897              this.model.set( attributes );
 898          },
 899  
 900          // Go to the 'next' revision.
 901          nextRevision: function() {
 902              var toIndex = this.model.revisions.indexOf( this.model.get('to') ) + 1;
 903              this.gotoModel( toIndex );
 904          },
 905  
 906          // Go to the 'previous' revision.
 907          previousRevision: function() {
 908              var toIndex = this.model.revisions.indexOf( this.model.get('to') ) - 1;
 909              this.gotoModel( toIndex );
 910          },
 911  
 912          // Check to see if the Previous or Next buttons need to be disabled or enabled.
 913          disabledButtonCheck: function() {
 914              var maxVal   = this.model.revisions.length - 1,
 915                  minVal   = 0,
 916                  next     = $('.revisions-next .button'),
 917                  previous = $('.revisions-previous .button'),
 918                  val      = this.model.revisions.indexOf( this.model.get('to') );
 919  
 920              // Disable "Next" button if you're on the last node.
 921              next.prop( 'disabled', ( maxVal === val ) );
 922  
 923              // Disable "Previous" button if you're on the first node.
 924              previous.prop( 'disabled', ( minVal === val ) );
 925          }
 926      });
 927  
 928  
 929      // The slider view.
 930      revisions.view.Slider = wp.Backbone.View.extend({
 931          className: 'wp-slider',
 932          direction: isRtl ? 'right' : 'left',
 933  
 934          events: {
 935              'mousemove' : 'mouseMove'
 936          },
 937  
 938          initialize: function() {
 939              _.bindAll( this, 'start', 'slide', 'stop', 'mouseMove', 'mouseEnter', 'mouseLeave' );
 940              this.listenTo( this.model, 'update:slider', this.applySliderSettings );
 941          },
 942  
 943          ready: function() {
 944              this.$el.css('width', ( this.model.revisions.length * 50 ) + 'px');
 945              this.$el.slider( _.extend( this.model.toJSON(), {
 946                  start: this.start,
 947                  slide: this.slide,
 948                  stop:  this.stop
 949              }) );
 950  
 951              this.$el.hoverIntent({
 952                  over: this.mouseEnter,
 953                  out: this.mouseLeave,
 954                  timeout: 800
 955              });
 956  
 957              this.applySliderSettings();
 958          },
 959  
 960          mouseMove: function( e ) {
 961              var zoneCount         = this.model.revisions.length - 1,       // One fewer zone than models.
 962                  sliderFrom        = this.$el.allOffsets()[this.direction], // "From" edge of slider.
 963                  sliderWidth       = this.$el.width(),                      // Width of slider.
 964                  tickWidth         = sliderWidth / zoneCount,               // Calculated width of zone.
 965                  actualX           = ( isRtl ? $(window).width() - e.pageX : e.pageX ) - sliderFrom, // Flipped for RTL - sliderFrom.
 966                  currentModelIndex = Math.floor( ( actualX  + ( tickWidth / 2 )  ) / tickWidth );    // Calculate the model index.
 967  
 968              // Ensure sane value for currentModelIndex.
 969              if ( currentModelIndex < 0 ) {
 970                  currentModelIndex = 0;
 971              } else if ( currentModelIndex >= this.model.revisions.length ) {
 972                  currentModelIndex = this.model.revisions.length - 1;
 973              }
 974  
 975              // Update the tooltip mode.
 976              this.model.set({ hoveredRevision: this.model.revisions.at( currentModelIndex ) });
 977          },
 978  
 979          mouseLeave: function() {
 980              this.model.set({ hovering: false });
 981          },
 982  
 983          mouseEnter: function() {
 984              this.model.set({ hovering: true });
 985          },
 986  
 987          applySliderSettings: function() {
 988              this.$el.slider( _.pick( this.model.toJSON(), 'value', 'values', 'range' ) );
 989              var handles = this.$('a.ui-slider-handle');
 990  
 991              if ( this.model.get('compareTwoMode') ) {
 992                  // In RTL mode the 'left handle' is the second in the slider, 'right' is first.
 993                  handles.first()
 994                      .toggleClass( 'to-handle', !! isRtl )
 995                      .toggleClass( 'from-handle', ! isRtl );
 996                  handles.last()
 997                      .toggleClass( 'from-handle', !! isRtl )
 998                      .toggleClass( 'to-handle', ! isRtl );
 999              } else {
1000                  handles.removeClass('from-handle to-handle');
1001              }
1002          },
1003  
1004          start: function( event, ui ) {
1005              this.model.set({ scrubbing: true });
1006  
1007              // Track the mouse position to enable smooth dragging,
1008              // overrides default jQuery UI step behavior.
1009              $( window ).on( 'mousemove.wp.revisions', { view: this }, function( e ) {
1010                  var handles,
1011                      view              = e.data.view,
1012                      leftDragBoundary  = view.$el.offset().left,
1013                      sliderOffset      = leftDragBoundary,
1014                      sliderRightEdge   = leftDragBoundary + view.$el.width(),
1015                      rightDragBoundary = sliderRightEdge,
1016                      leftDragReset     = '0',
1017                      rightDragReset    = '100%',
1018                      handle            = $( ui.handle );
1019  
1020                  // In two handle mode, ensure handles can't be dragged past each other.
1021                  // Adjust left/right boundaries and reset points.
1022                  if ( view.model.get('compareTwoMode') ) {
1023                      handles = handle.parent().find('.ui-slider-handle');
1024                      if ( handle.is( handles.first() ) ) {
1025                          // We're the left handle.
1026                          rightDragBoundary = handles.last().offset().left;
1027                          rightDragReset    = rightDragBoundary - sliderOffset;
1028                      } else {
1029                          // We're the right handle.
1030                          leftDragBoundary = handles.first().offset().left + handles.first().width();
1031                          leftDragReset    = leftDragBoundary - sliderOffset;
1032                      }
1033                  }
1034  
1035                  // Follow mouse movements, as long as handle remains inside slider.
1036                  if ( e.pageX < leftDragBoundary ) {
1037                      handle.css( 'left', leftDragReset ); // Mouse to left of slider.
1038                  } else if ( e.pageX > rightDragBoundary ) {
1039                      handle.css( 'left', rightDragReset ); // Mouse to right of slider.
1040                  } else {
1041                      handle.css( 'left', e.pageX - sliderOffset ); // Mouse in slider.
1042                  }
1043              } );
1044          },
1045  
1046          getPosition: function( position ) {
1047              return isRtl ? this.model.revisions.length - position - 1: position;
1048          },
1049  
1050          // Responds to slide events.
1051          slide: function( event, ui ) {
1052              var attributes, movedRevision;
1053              // Compare two revisions mode.
1054              if ( this.model.get('compareTwoMode') ) {
1055                  // Prevent sliders from occupying same spot.
1056                  if ( ui.values[1] === ui.values[0] ) {
1057                      return false;
1058                  }
1059                  if ( isRtl ) {
1060                      ui.values.reverse();
1061                  }
1062                  attributes = {
1063                      from: this.model.revisions.at( this.getPosition( ui.values[0] ) ),
1064                      to: this.model.revisions.at( this.getPosition( ui.values[1] ) )
1065                  };
1066              } else {
1067                  attributes = {
1068                      to: this.model.revisions.at( this.getPosition( ui.value ) )
1069                  };
1070                  // If we're at the first revision, unset 'from'.
1071                  if ( this.getPosition( ui.value ) > 0 ) {
1072                      attributes.from = this.model.revisions.at( this.getPosition( ui.value ) - 1 );
1073                  } else {
1074                      attributes.from = undefined;
1075                  }
1076              }
1077              movedRevision = this.model.revisions.at( this.getPosition( ui.value ) );
1078  
1079              // If we are scrubbing, a scrub to a revision is considered a hover.
1080              if ( this.model.get('scrubbing') ) {
1081                  attributes.hoveredRevision = movedRevision;
1082              }
1083  
1084              this.model.set( attributes );
1085          },
1086  
1087          stop: function() {
1088              $( window ).off('mousemove.wp.revisions');
1089              this.model.updateSliderSettings(); // To snap us back to a tick mark.
1090              this.model.set({ scrubbing: false });
1091          }
1092      });
1093  
1094      // The diff view.
1095      // This is the view for the current active diff.
1096      revisions.view.Diff = wp.Backbone.View.extend({
1097          className: 'revisions-diff',
1098          template:  wp.template('revisions-diff'),
1099  
1100          // Generate the options to be passed to the template.
1101          prepare: function() {
1102              return _.extend({ fields: this.model.fields.toJSON() }, this.options );
1103          }
1104      });
1105  
1106      // The revisions router.
1107      // Maintains the URL routes so browser URL matches state.
1108      revisions.Router = Backbone.Router.extend({
1109          initialize: function( options ) {
1110              this.model = options.model;
1111  
1112              // Maintain state and history when navigating.
1113              this.listenTo( this.model, 'update:diff', _.debounce( this.updateUrl, 250 ) );
1114              this.listenTo( this.model, 'change:compareTwoMode', this.updateUrl );
1115          },
1116  
1117          baseUrl: function( url ) {
1118              return this.model.get('baseUrl') + url;
1119          },
1120  
1121          updateUrl: function() {
1122              var from = this.model.has('from') ? this.model.get('from').id : 0,
1123                  to   = this.model.get('to').id;
1124              if ( this.model.get('compareTwoMode' ) ) {
1125                  this.navigate( this.baseUrl( '?from=' + from + '&to=' + to ), { replace: true } );
1126              } else {
1127                  this.navigate( this.baseUrl( '?revision=' + to ), { replace: true } );
1128              }
1129          },
1130  
1131          handleRoute: function( a, b ) {
1132              var compareTwo = _.isUndefined( b );
1133  
1134              if ( ! compareTwo ) {
1135                  b = this.model.revisions.get( a );
1136                  a = this.model.revisions.prev( b );
1137                  b = b ? b.id : 0;
1138                  a = a ? a.id : 0;
1139              }
1140          }
1141      });
1142  
1143      /**
1144       * Initialize the revisions UI for revision.php.
1145       */
1146      revisions.init = function() {
1147          var state;
1148  
1149          // Bail if the current page is not revision.php.
1150          if ( ! window.adminpage || 'revision-php' !== window.adminpage ) {
1151              return;
1152          }
1153  
1154          state = new revisions.model.FrameState({
1155              initialDiffState: {
1156                  // wp_localize_script doesn't stringifies ints, so cast them.
1157                  to: parseInt( revisions.settings.to, 10 ),
1158                  from: parseInt( revisions.settings.from, 10 ),
1159                  // wp_localize_script does not allow for top-level booleans so do a comparator here.
1160                  compareTwoMode: ( revisions.settings.compareTwoMode === '1' )
1161              },
1162              diffData: revisions.settings.diffData,
1163              baseUrl: revisions.settings.baseUrl,
1164              postId: parseInt( revisions.settings.postId, 10 )
1165          }, {
1166              revisions: new revisions.model.Revisions( revisions.settings.revisionData )
1167          });
1168  
1169          revisions.view.frame = new revisions.view.Frame({
1170              model: state
1171          }).render();
1172      };
1173  
1174      $( revisions.init );
1175  }(jQuery));