/wp-admin/js/revisions.js

/* global _wpRevisionsSettings, isRtl */

window.wp = window.wp || {};



(function($) {

	var revisions;



	revisions = wp.revisions = { model: {}, view: {}, controller: {} };



	// Link settings.

	revisions.settings = _.isUndefined( _wpRevisionsSettings ) ? {} : _wpRevisionsSettings;



	// For debugging

	revisions.debug = false;



	revisions.log = function() {

		if ( window.console && revisions.debug ) {

			window.console.log.apply( window.console, arguments );

		}

	};



	// Handy functions to help with positioning

	$.fn.allOffsets = function() {

		var offset = this.offset() || {top: 0, left: 0}, win = $(window);

		return _.extend( offset, {

			right:  win.width()  - offset.left - this.outerWidth(),

			bottom: win.height() - offset.top  - this.outerHeight()

		});

	};



	$.fn.allPositions = function() {

		var position = this.position() || {top: 0, left: 0}, parent = this.parent();

		return _.extend( position, {

			right:  parent.outerWidth()  - position.left - this.outerWidth(),

			bottom: parent.outerHeight() - position.top  - this.outerHeight()

		});

	};



	// wp_localize_script transforms top-level numbers into strings. Undo that.

	if ( revisions.settings.to ) {

		revisions.settings.to = parseInt( revisions.settings.to, 10 );

	}

	if ( revisions.settings.from ) {

		revisions.settings.from = parseInt( revisions.settings.from, 10 );

	}



	// wp_localize_script does not allow for top-level booleans. Fix that.

	if ( revisions.settings.compareTwoMode ) {

		revisions.settings.compareTwoMode = revisions.settings.compareTwoMode === '1';

	}



	/**

	 * ========================================================================

	 * MODELS

	 * ========================================================================

	 */

	revisions.model.Slider = Backbone.Model.extend({

		defaults: {

			value: null,

			values: null,

			min: 0,

			max: 1,

			step: 1,

			range: false,

			compareTwoMode: false

		},



		initialize: function( options ) {

			this.frame = options.frame;

			this.revisions = options.revisions;



			// Listen for changes to the revisions or mode from outside

			this.listenTo( this.frame, 'update:revisions', this.receiveRevisions );

			this.listenTo( this.frame, 'change:compareTwoMode', this.updateMode );



			// Listen for internal changes

			this.listenTo( this, 'change:from', this.handleLocalChanges );

			this.listenTo( this, 'change:to', this.handleLocalChanges );

			this.listenTo( this, 'change:compareTwoMode', this.updateSliderSettings );

			this.listenTo( this, 'update:revisions', this.updateSliderSettings );



			// Listen for changes to the hovered revision

			this.listenTo( this, 'change:hoveredRevision', this.hoverRevision );



			this.set({

				max:   this.revisions.length - 1,

				compareTwoMode: this.frame.get('compareTwoMode'),

				from: this.frame.get('from'),

				to: this.frame.get('to')

			});

			this.updateSliderSettings();

		},



		getSliderValue: function( a, b ) {

			return isRtl ? this.revisions.length - this.revisions.indexOf( this.get(a) ) - 1 : this.revisions.indexOf( this.get(b) );

		},



		updateSliderSettings: function() {

			if ( this.get('compareTwoMode') ) {

				this.set({

					values: [

						this.getSliderValue( 'to', 'from' ),

						this.getSliderValue( 'from', 'to' )

					],

					value: null,

					range: true // ensures handles cannot cross

				});

			} else {

				this.set({

					value: this.getSliderValue( 'to', 'to' ),

					values: null,

					range: false

				});

			}

			this.trigger( 'update:slider' );

		},



		// Called when a revision is hovered

		hoverRevision: function( model, value ) {

			this.trigger( 'hovered:revision', value );

		},



		// Called when `compareTwoMode` changes

		updateMode: function( model, value ) {

			this.set({ compareTwoMode: value });

		},



		// Called when `from` or `to` changes in the local model

		handleLocalChanges: function() {

			this.frame.set({

				from: this.get('from'),

				to: this.get('to')

			});

		},



		// Receives revisions changes from outside the model

		receiveRevisions: function( from, to ) {

			// Bail if nothing changed

			if ( this.get('from') === from && this.get('to') === to ) {

				return;

			}



			this.set({ from: from, to: to }, { silent: true });

			this.trigger( 'update:revisions', from, to );

		}



	});



	revisions.model.Tooltip = Backbone.Model.extend({

		defaults: {

			revision: null,

			offset: {},

			hovering: false, // Whether the mouse is hovering

			scrubbing: false // Whether the mouse is scrubbing

		},



		initialize: function( options ) {

			this.frame = options.frame;

			this.revisions = options.revisions;

			this.slider = options.slider;



			this.listenTo( this.slider, 'hovered:revision', this.updateRevision );

			this.listenTo( this.slider, 'change:hovering', this.setHovering );

			this.listenTo( this.slider, 'change:scrubbing', this.setScrubbing );

		},





		updateRevision: function( revision ) {

			this.set({ revision: revision });

		},



		setHovering: function( model, value ) {

			this.set({ hovering: value });

		},



		setScrubbing: function( model, value ) {

			this.set({ scrubbing: value });

		}

	});



	revisions.model.Revision = Backbone.Model.extend({});



	revisions.model.Revisions = Backbone.Collection.extend({

		model: revisions.model.Revision,



		initialize: function() {

			_.bindAll( this, 'next', 'prev' );

		},



		next: function( revision ) {

			var index = this.indexOf( revision );



			if ( index !== -1 && index !== this.length - 1 ) {

				return this.at( index + 1 );

			}

		},



		prev: function( revision ) {

			var index = this.indexOf( revision );



			if ( index !== -1 && index !== 0 ) {

				return this.at( index - 1 );

			}

		}

	});



	revisions.model.Field = Backbone.Model.extend({});



	revisions.model.Fields = Backbone.Collection.extend({

		model: revisions.model.Field

	});



	revisions.model.Diff = Backbone.Model.extend({

		initialize: function() {

			var fields = this.get('fields');

			this.unset('fields');



			this.fields = new revisions.model.Fields( fields );

		}

	});



	revisions.model.Diffs = Backbone.Collection.extend({

		initialize: function( models, options ) {

			_.bindAll( this, 'getClosestUnloaded' );

			this.loadAll = _.once( this._loadAll );

			this.revisions = options.revisions;

			this.requests  = {};

		},



		model: revisions.model.Diff,



		ensure: function( id, context ) {

			var diff     = this.get( id ),

				request  = this.requests[ id ],

				deferred = $.Deferred(),

				ids      = {},

				from     = id.split(':')[0],

				to       = id.split(':')[1];

			ids[id] = true;



			wp.revisions.log( 'ensure', id );



			this.trigger( 'ensure', ids, from, to, deferred.promise() );



			if ( diff ) {

				deferred.resolveWith( context, [ diff ] );

			} else {

				this.trigger( 'ensure:load', ids, from, to, deferred.promise() );

				_.each( ids, _.bind( function( id ) {

					// Remove anything that has an ongoing request

					if ( this.requests[ id ] ) {

						delete ids[ id ];

					}

					// Remove anything we already have

					if ( this.get( id ) ) {

						delete ids[ id ];

					}

				}, this ) );

				if ( ! request ) {

					// Always include the ID that started this ensure

					ids[ id ] = true;

					request   = this.load( _.keys( ids ) );

				}



				request.done( _.bind( function() {

					deferred.resolveWith( context, [ this.get( id ) ] );

				}, this ) ).fail( _.bind( function() {

					deferred.reject();

				}) );

			}



			return deferred.promise();

		},



		// Returns an array of proximal diffs

		getClosestUnloaded: function( ids, centerId ) {

			var self = this;

			return _.chain([0].concat( ids )).initial().zip( ids ).sortBy( function( pair ) {

				return Math.abs( centerId - pair[1] );

			}).map( function( pair ) {

				return pair.join(':');

			}).filter( function( diffId ) {

				return _.isUndefined( self.get( diffId ) ) && ! self.requests[ diffId ];

			}).value();

		},



		_loadAll: function( allRevisionIds, centerId, num ) {

			var self = this, deferred = $.Deferred(),

				diffs = _.first( this.getClosestUnloaded( allRevisionIds, centerId ), num );

			if ( _.size( diffs ) > 0 ) {

				this.load( diffs ).done( function() {

					self._loadAll( allRevisionIds, centerId, num ).done( function() {

						deferred.resolve();

					});

				}).fail( function() {

					if ( 1 === num ) { // Already tried 1. This just isn't working. Give up.

						deferred.reject();

					} else { // Request fewer diffs this time

						self._loadAll( allRevisionIds, centerId, Math.ceil( num / 2 ) ).done( function() {

							deferred.resolve();

						});

					}

				});

			} else {

				deferred.resolve();

			}

			return deferred;

		},



		load: function( comparisons ) {

			wp.revisions.log( 'load', comparisons );

			// Our collection should only ever grow, never shrink, so remove: false

			return this.fetch({ data: { compare: comparisons }, remove: false }).done( function() {

				wp.revisions.log( 'load:complete', comparisons );

			});

		},



		sync: function( method, model, options ) {

			if ( 'read' === method ) {

				options = options || {};

				options.context = this;

				options.data = _.extend( options.data || {}, {

					action: 'get-revision-diffs',

					post_id: revisions.settings.postId

				});



				var deferred = wp.ajax.send( options ),

					requests = this.requests;



				// Record that we're requesting each diff.

				if ( options.data.compare ) {

					_.each( options.data.compare, function( id ) {

						requests[ id ] = deferred;

					});

				}



				// When the request completes, clear the stored request.

				deferred.always( function() {

					if ( options.data.compare ) {

						_.each( options.data.compare, function( id ) {

							delete requests[ id ];

						});

					}

				});



				return deferred;



			// Otherwise, fall back to `Backbone.sync()`.

			} else {

				return Backbone.Model.prototype.sync.apply( this, arguments );

			}

		}

	});





	revisions.model.FrameState = Backbone.Model.extend({

		defaults: {

			loading: false,

			error: false,

			compareTwoMode: false

		},



		initialize: function( attributes, options ) {

			var properties = {};



			_.bindAll( this, 'receiveDiff' );

			this._debouncedEnsureDiff = _.debounce( this._ensureDiff, 200 );



			this.revisions = options.revisions;

			this.diffs = new revisions.model.Diffs( [], { revisions: this.revisions });



			// Set the initial diffs collection provided through the settings

			this.diffs.set( revisions.settings.diffData );



			// Set up internal listeners

			this.listenTo( this, 'change:from', this.changeRevisionHandler );

			this.listenTo( this, 'change:to', this.changeRevisionHandler );

			this.listenTo( this, 'change:compareTwoMode', this.changeMode );

			this.listenTo( this, 'update:revisions', this.updatedRevisions );

			this.listenTo( this.diffs, 'ensure:load', this.updateLoadingStatus );

			this.listenTo( this, 'update:diff', this.updateLoadingStatus );



			// Set the initial revisions, baseUrl, and mode as provided through settings

			properties.to = this.revisions.get( revisions.settings.to );

			properties.from = this.revisions.get( revisions.settings.from );

			properties.compareTwoMode = revisions.settings.compareTwoMode;

			properties.baseUrl = revisions.settings.baseUrl;

			this.set( properties );



			// Start the router if browser supports History API

			if ( window.history && window.history.pushState ) {

				this.router = new revisions.Router({ model: this });

				Backbone.history.start({ pushState: true });

			}

		},



		updateLoadingStatus: function() {

			this.set( 'error', false );

			this.set( 'loading', ! this.diff() );

		},



		changeMode: function( model, value ) {

			var toIndex = this.revisions.indexOf( this.get( 'to' ) );



			// If we were on the first revision before switching to two-handled mode,

			// bump the 'to' position over one

			if ( value && 0 === toIndex ) {

				this.set({

					from: this.revisions.at( toIndex ),

					to:   this.revisions.at( toIndex + 1 )

				});

			}



			// When switching back to single-handled mode, reset 'from' model to

			// one position before the 'to' model

			if ( ! value && 0 !== toIndex ) { // '! value' means switching to single-handled mode

				this.set({

					from: this.revisions.at( toIndex - 1 ),

					to:   this.revisions.at( toIndex )

				});

			}

		},



		updatedRevisions: function( from, to ) {

			if ( this.get( 'compareTwoMode' ) ) {

				// TODO: compare-two loading strategy

			} else {

				this.diffs.loadAll( this.revisions.pluck('id'), to.id, 40 );

			}

		},



		// Fetch the currently loaded diff.

		diff: function() {

			return this.diffs.get( this._diffId );

		},



		// So long as `from` and `to` are changed at the same time, the diff

		// will only be updated once. This is because Backbone updates all of

		// the changed attributes in `set`, and then fires the `change` events.

		updateDiff: function( options ) {

			var from, to, diffId, diff;



			options = options || {};

			from = this.get('from');

			to = this.get('to');

			diffId = ( from ? from.id : 0 ) + ':' + to.id;



			// Check if we're actually changing the diff id.

			if ( this._diffId === diffId ) {

				return $.Deferred().reject().promise();

			}



			this._diffId = diffId;

			this.trigger( 'update:revisions', from, to );



			diff = this.diffs.get( diffId );



			// If we already have the diff, then immediately trigger the update.

			if ( diff ) {

				this.receiveDiff( diff );

				return $.Deferred().resolve().promise();

			// Otherwise, fetch the diff.

			} else {

				if ( options.immediate ) {

					return this._ensureDiff();

				} else {

					this._debouncedEnsureDiff();

					return $.Deferred().reject().promise();

				}

			}

		},



		// A simple wrapper around `updateDiff` to prevent the change event's

		// parameters from being passed through.

		changeRevisionHandler: function() {

			this.updateDiff();

		},



		receiveDiff: function( diff ) {

			// Did we actually get a diff?

			if ( _.isUndefined( diff ) || _.isUndefined( diff.id ) ) {

				this.set({

					loading: false,

					error: true

				});

			} else if ( this._diffId === diff.id ) { // Make sure the current diff didn't change

				this.trigger( 'update:diff', diff );

			}

		},



		_ensureDiff: function() {

			return this.diffs.ensure( this._diffId, this ).always( this.receiveDiff );

		}

	});





	/**

	 * ========================================================================

	 * VIEWS

	 * ========================================================================

	 */



	// The frame view. This contains the entire page.

	revisions.view.Frame = wp.Backbone.View.extend({

		className: 'revisions',

		template: wp.template('revisions-frame'),



		initialize: function() {

			this.listenTo( this.model, 'update:diff', this.renderDiff );

			this.listenTo( this.model, 'change:compareTwoMode', this.updateCompareTwoMode );

			this.listenTo( this.model, 'change:loading', this.updateLoadingStatus );

			this.listenTo( this.model, 'change:error', this.updateErrorStatus );



			this.views.set( '.revisions-control-frame', new revisions.view.Controls({

				model: this.model

			}) );

		},



		render: function() {

			wp.Backbone.View.prototype.render.apply( this, arguments );



			$('html').css( 'overflow-y', 'scroll' );

			$('#wpbody-content .wrap').append( this.el );

			this.updateCompareTwoMode();

			this.renderDiff( this.model.diff() );

			this.views.ready();



			return this;

		},



		renderDiff: function( diff ) {

			this.views.set( '.revisions-diff-frame', new revisions.view.Diff({

				model: diff

			}) );

		},



		updateLoadingStatus: function() {

			this.$el.toggleClass( 'loading', this.model.get('loading') );

		},



		updateErrorStatus: function() {

			this.$el.toggleClass( 'diff-error', this.model.get('error') );

		},



		updateCompareTwoMode: function() {

			this.$el.toggleClass( 'comparing-two-revisions', this.model.get('compareTwoMode') );

		}

	});



	// The control view.

	// This contains the revision slider, previous/next buttons, the meta info and the compare checkbox.

	revisions.view.Controls = wp.Backbone.View.extend({

		className: 'revisions-controls',



		initialize: function() {

			_.bindAll( this, 'setWidth' );



			// Add the button view

			this.views.add( new revisions.view.Buttons({

				model: this.model

			}) );



			// Add the checkbox view

			this.views.add( new revisions.view.Checkbox({

				model: this.model

			}) );



			// Prep the slider model

			var slider = new revisions.model.Slider({

				frame: this.model,

				revisions: this.model.revisions

			}),



			// Prep the tooltip model

			tooltip = new revisions.model.Tooltip({

				frame: this.model,

				revisions: this.model.revisions,

				slider: slider

			});



			// Add the tooltip view

			this.views.add( new revisions.view.Tooltip({

				model: tooltip

			}) );



			// Add the tickmarks view

			this.views.add( new revisions.view.Tickmarks({

				model: tooltip

			}) );



			// Add the slider view

			this.views.add( new revisions.view.Slider({

				model: slider

			}) );



			// Add the Metabox view

			this.views.add( new revisions.view.Metabox({

				model: this.model

			}) );

		},



		ready: function() {

			this.top = this.$el.offset().top;

			this.window = $(window);

			this.window.on( 'scroll.wp.revisions', {controls: this}, function(e) {

				var controls  = e.data.controls,

					container = controls.$el.parent(),

					scrolled  = controls.window.scrollTop(),

					frame     = controls.views.parent;



				if ( scrolled >= controls.top ) {

					if ( ! frame.$el.hasClass('pinned') ) {

						controls.setWidth();

						container.css('height', container.height() + 'px' );

						controls.window.on('resize.wp.revisions.pinning click.wp.revisions.pinning', {controls: controls}, function(e) {

							e.data.controls.setWidth();

						});

					}

					frame.$el.addClass('pinned');

				} else if ( frame.$el.hasClass('pinned') ) {

					controls.window.off('.wp.revisions.pinning');

					controls.$el.css('width', 'auto');

					frame.$el.removeClass('pinned');

					container.css('height', 'auto');

					controls.top = controls.$el.offset().top;

				} else {

					controls.top = controls.$el.offset().top;

				}

			});

		},



		setWidth: function() {

			this.$el.css('width', this.$el.parent().width() + 'px');

		}

	});



	// The tickmarks view

	revisions.view.Tickmarks = wp.Backbone.View.extend({

		className: 'revisions-tickmarks',

		direction: isRtl ? 'right' : 'left',



		initialize: function() {

			this.listenTo( this.model, 'change:revision', this.reportTickPosition );

		},



		reportTickPosition: function( model, revision ) {

			var offset, thisOffset, parentOffset, tick, index = this.model.revisions.indexOf( revision );

			thisOffset = this.$el.allOffsets();

			parentOffset = this.$el.parent().allOffsets();

			if ( index === this.model.revisions.length - 1 ) {

				// Last one

				offset = {

					rightPlusWidth: thisOffset.left - parentOffset.left + 1,

					leftPlusWidth: thisOffset.right - parentOffset.right + 1

				};

			} else {

				// Normal tick

				tick = this.$('div:nth-of-type(' + (index + 1) + ')');

				offset = tick.allPositions();

				_.extend( offset, {

					left: offset.left + thisOffset.left - parentOffset.left,

					right: offset.right + thisOffset.right - parentOffset.right

				});

				_.extend( offset, {

					leftPlusWidth: offset.left + tick.outerWidth(),

					rightPlusWidth: offset.right + tick.outerWidth()

				});

			}

			this.model.set({ offset: offset });

		},



		ready: function() {

			var tickCount, tickWidth;

			tickCount = this.model.revisions.length - 1;

			tickWidth = 1 / tickCount;

			this.$el.css('width', ( this.model.revisions.length * 50 ) + 'px');



			_(tickCount).times( function( index ){

				this.$el.append( '<div style="' + this.direction + ': ' + ( 100 * tickWidth * index ) + '%"></div>' );

			}, this );

		}

	});



	// The metabox view

	revisions.view.Metabox = wp.Backbone.View.extend({

		className: 'revisions-meta',



		initialize: function() {

			// Add the 'from' view

			this.views.add( new revisions.view.MetaFrom({

				model: this.model,

				className: 'diff-meta diff-meta-from'

			}) );



			// Add the 'to' view

			this.views.add( new revisions.view.MetaTo({

				model: this.model

			}) );

		}

	});



	// The revision meta view (to be extended)

	revisions.view.Meta = wp.Backbone.View.extend({

		template: wp.template('revisions-meta'),



		events: {

			'click .restore-revision': 'restoreRevision'

		},



		initialize: function() {

			this.listenTo( this.model, 'update:revisions', this.render );

		},



		prepare: function() {

			return _.extend( this.model.toJSON()[this.type] || {}, {

				type: this.type

			});

		},



		restoreRevision: function() {

			document.location = this.model.get('to').attributes.restoreUrl;

		}

	});



	// The revision meta 'from' view

	revisions.view.MetaFrom = revisions.view.Meta.extend({

		className: 'diff-meta diff-meta-from',

		type: 'from'

	});



	// The revision meta 'to' view

	revisions.view.MetaTo = revisions.view.Meta.extend({

		className: 'diff-meta diff-meta-to',

		type: 'to'

	});



	// The checkbox view.

	revisions.view.Checkbox = wp.Backbone.View.extend({

		className: 'revisions-checkbox',

		template: wp.template('revisions-checkbox'),



		events: {

			'click .compare-two-revisions': 'compareTwoToggle'

		},



		initialize: function() {

			this.listenTo( this.model, 'change:compareTwoMode', this.updateCompareTwoMode );

		},



		ready: function() {

			if ( this.model.revisions.length < 3 ) {

				$('.revision-toggle-compare-mode').hide();

			}

		},



		updateCompareTwoMode: function() {

			this.$('.compare-two-revisions').prop( 'checked', this.model.get('compareTwoMode') );

		},



		// Toggle the compare two mode feature when the compare two checkbox is checked.

		compareTwoToggle: function() {

			// Activate compare two mode?

			this.model.set({ compareTwoMode: $('.compare-two-revisions').prop('checked') });

		}

	});



	// The tooltip view.

	// Encapsulates the tooltip.

	revisions.view.Tooltip = wp.Backbone.View.extend({

		className: 'revisions-tooltip',

		template: wp.template('revisions-meta'),



		initialize: function() {

			this.listenTo( this.model, 'change:offset', this.render );

			this.listenTo( this.model, 'change:hovering', this.toggleVisibility );

			this.listenTo( this.model, 'change:scrubbing', this.toggleVisibility );

		},



		prepare: function() {

			if ( _.isNull( this.model.get('revision') ) ) {

				return;

			} else {

				return _.extend( { type: 'tooltip' }, {

					attributes: this.model.get('revision').toJSON()

				});

			}

		},



		render: function() {

			var otherDirection,

				direction,

				directionVal,

				flipped,

				css      = {},

				position = this.model.revisions.indexOf( this.model.get('revision') ) + 1;



			flipped = ( position / this.model.revisions.length ) > 0.5;

			if ( isRtl ) {

				direction = flipped ? 'left' : 'right';

				directionVal = flipped ? 'leftPlusWidth' : direction;

			} else {

				direction = flipped ? 'right' : 'left';

				directionVal = flipped ? 'rightPlusWidth' : direction;

			}

			otherDirection = 'right' === direction ? 'left': 'right';

			wp.Backbone.View.prototype.render.apply( this, arguments );

			css[direction] = this.model.get('offset')[directionVal] + 'px';

			css[otherDirection] = '';

			this.$el.toggleClass( 'flipped', flipped ).css( css );

		},



		visible: function() {

			return this.model.get( 'scrubbing' ) || this.model.get( 'hovering' );

		},



		toggleVisibility: function() {

			if ( this.visible() ) {

				this.$el.stop().show().fadeTo( 100 - this.el.style.opacity * 100, 1 );

			} else {

				this.$el.stop().fadeTo( this.el.style.opacity * 300, 0, function(){ $(this).hide(); } );

			}

			return;

		}

	});



	// The buttons view.

	// Encapsulates all of the configuration for the previous/next buttons.

	revisions.view.Buttons = wp.Backbone.View.extend({

		className: 'revisions-buttons',

		template: wp.template('revisions-buttons'),



		events: {

			'click .revisions-next .button': 'nextRevision',

			'click .revisions-previous .button': 'previousRevision'

		},



		initialize: function() {

			this.listenTo( this.model, 'update:revisions', this.disabledButtonCheck );

		},



		ready: function() {

			this.disabledButtonCheck();

		},



		// Go to a specific model index

		gotoModel: function( toIndex ) {

			var attributes = {

				to: this.model.revisions.at( toIndex )

			};

			// If we're at the first revision, unset 'from'.

			if ( toIndex ) {

				attributes.from = this.model.revisions.at( toIndex - 1 );

			} else {

				this.model.unset('from', { silent: true });

			}



			this.model.set( attributes );

		},



		// Go to the 'next' revision

		nextRevision: function() {

			var toIndex = this.model.revisions.indexOf( this.model.get('to') ) + 1;

			this.gotoModel( toIndex );

		},



		// Go to the 'previous' revision

		previousRevision: function() {

			var toIndex = this.model.revisions.indexOf( this.model.get('to') ) - 1;

			this.gotoModel( toIndex );

		},



		// Check to see if the Previous or Next buttons need to be disabled or enabled.

		disabledButtonCheck: function() {

			var maxVal   = this.model.revisions.length - 1,

				minVal   = 0,

				next     = $('.revisions-next .button'),

				previous = $('.revisions-previous .button'),

				val      = this.model.revisions.indexOf( this.model.get('to') );



			// Disable "Next" button if you're on the last node.

			next.prop( 'disabled', ( maxVal === val ) );



			// Disable "Previous" button if you're on the first node.

			previous.prop( 'disabled', ( minVal === val ) );

		}

	});





	// The slider view.

	revisions.view.Slider = wp.Backbone.View.extend({

		className: 'wp-slider',

		direction: isRtl ? 'right' : 'left',



		events: {

			'mousemove' : 'mouseMove'

		},



		initialize: function() {

			_.bindAll( this, 'start', 'slide', 'stop', 'mouseMove', 'mouseEnter', 'mouseLeave' );

			this.listenTo( this.model, 'update:slider', this.applySliderSettings );

		},



		ready: function() {

			this.$el.css('width', ( this.model.revisions.length * 50 ) + 'px');

			this.$el.slider( _.extend( this.model.toJSON(), {

				start: this.start,

				slide: this.slide,

				stop:  this.stop

			}) );



			this.$el.hoverIntent({

				over: this.mouseEnter,

				out: this.mouseLeave,

				timeout: 800

			});



			this.applySliderSettings();

		},



		mouseMove: function( e ) {

			var zoneCount         = this.model.revisions.length - 1, // One fewer zone than models

				sliderFrom        = this.$el.allOffsets()[this.direction], // "From" edge of slider

				sliderWidth       = this.$el.width(), // Width of slider

				tickWidth         = sliderWidth / zoneCount, // Calculated width of zone

				actualX           = ( isRtl ? $(window).width() - e.pageX : e.pageX ) - sliderFrom, // Flipped for RTL - sliderFrom;

				currentModelIndex = Math.floor( ( actualX  + ( tickWidth / 2 )  ) / tickWidth ); // Calculate the model index



			// Ensure sane value for currentModelIndex.

			if ( currentModelIndex < 0 ) {

				currentModelIndex = 0;

			} else if ( currentModelIndex >= this.model.revisions.length ) {

				currentModelIndex = this.model.revisions.length - 1;

			}



			// Update the tooltip mode

			this.model.set({ hoveredRevision: this.model.revisions.at( currentModelIndex ) });

		},



		mouseLeave: function() {

			this.model.set({ hovering: false });

		},



		mouseEnter: function() {

			this.model.set({ hovering: true });

		},



		applySliderSettings: function() {

			this.$el.slider( _.pick( this.model.toJSON(), 'value', 'values', 'range' ) );

			var handles = this.$('a.ui-slider-handle');



			if ( this.model.get('compareTwoMode') ) {

				// in RTL mode the 'left handle' is the second in the slider, 'right' is first

				handles.first()

					.toggleClass( 'to-handle', !! isRtl )

					.toggleClass( 'from-handle', ! isRtl );

				handles.last()

					.toggleClass( 'from-handle', !! isRtl )

					.toggleClass( 'to-handle', ! isRtl );

			} else {

				handles.removeClass('from-handle to-handle');

			}

		},



		start: function( event, ui ) {

			this.model.set({ scrubbing: true });



			// Track the mouse position to enable smooth dragging,

			// overrides default jQuery UI step behavior.

			$( window ).on( 'mousemove.wp.revisions', { view: this }, function( e ) {

				var handles,

					view              = e.data.view,

					leftDragBoundary  = view.$el.offset().left,

					sliderOffset      = leftDragBoundary,

					sliderRightEdge   = leftDragBoundary + view.$el.width(),

					rightDragBoundary = sliderRightEdge,

					leftDragReset     = '0',

					rightDragReset    = '100%',

					handle            = $( ui.handle );



				// In two handle mode, ensure handles can't be dragged past each other.

				// Adjust left/right boundaries and reset points.

				if ( view.model.get('compareTwoMode') ) {

					handles = handle.parent().find('.ui-slider-handle');

					if ( handle.is( handles.first() ) ) { // We're the left handle

						rightDragBoundary = handles.last().offset().left;

						rightDragReset    = rightDragBoundary - sliderOffset;

					} else { // We're the right handle

						leftDragBoundary = handles.first().offset().left + handles.first().width();

						leftDragReset    = leftDragBoundary - sliderOffset;

					}

				}



				// Follow mouse movements, as long as handle remains inside slider.

				if ( e.pageX < leftDragBoundary ) {

					handle.css( 'left', leftDragReset ); // Mouse to left of slider.

				} else if ( e.pageX > rightDragBoundary ) {

					handle.css( 'left', rightDragReset ); // Mouse to right of slider.

				} else {

					handle.css( 'left', e.pageX - sliderOffset ); // Mouse in slider.

				}

			} );

		},



		getPosition: function( position ) {

			return isRtl ? this.model.revisions.length - position - 1: position;

		},



		// Responds to slide events

		slide: function( event, ui ) {

			var attributes, movedRevision;

			// Compare two revisions mode

			if ( this.model.get('compareTwoMode') ) {

				// Prevent sliders from occupying same spot

				if ( ui.values[1] === ui.values[0] ) {

					return false;

				}

				if ( isRtl ) {

					ui.values.reverse();

				}

				attributes = {

					from: this.model.revisions.at( this.getPosition( ui.values[0] ) ),

					to: this.model.revisions.at( this.getPosition( ui.values[1] ) )

				};

			} else {

				attributes = {

					to: this.model.revisions.at( this.getPosition( ui.value ) )

				};

				// If we're at the first revision, unset 'from'.

				if ( this.getPosition( ui.value ) > 0 ) {

					attributes.from = this.model.revisions.at( this.getPosition( ui.value ) - 1 );

				} else {

					attributes.from = undefined;

				}

			}

			movedRevision = this.model.revisions.at( this.getPosition( ui.value ) );



			// If we are scrubbing, a scrub to a revision is considered a hover

			if ( this.model.get('scrubbing') ) {

				attributes.hoveredRevision = movedRevision;

			}



			this.model.set( attributes );

		},



		stop: function() {

			$( window ).off('mousemove.wp.revisions');

			this.model.updateSliderSettings(); // To snap us back to a tick mark

			this.model.set({ scrubbing: false });

		}

	});



	// The diff view.

	// This is the view for the current active diff.

	revisions.view.Diff = wp.Backbone.View.extend({

		className: 'revisions-diff',

		template:  wp.template('revisions-diff'),



		// Generate the options to be passed to the template.

		prepare: function() {

			return _.extend({ fields: this.model.fields.toJSON() }, this.options );

		}

	});



	// The revisions router.

	// Maintains the URL routes so browser URL matches state.

	revisions.Router = Backbone.Router.extend({

		initialize: function( options ) {

			this.model = options.model;



			// Maintain state and history when navigating

			this.listenTo( this.model, 'update:diff', _.debounce( this.updateUrl, 250 ) );

			this.listenTo( this.model, 'change:compareTwoMode', this.updateUrl );

		},



		baseUrl: function( url ) {

			return this.model.get('baseUrl') + url;

		},



		updateUrl: function() {

			var from = this.model.has('from') ? this.model.get('from').id : 0,

				to   = this.model.get('to').id;

			if ( this.model.get('compareTwoMode' ) ) {

				this.navigate( this.baseUrl( '?from=' + from + '&to=' + to ), { replace: true } );

			} else {

				this.navigate( this.baseUrl( '?revision=' + to ), { replace: true } );

			}

		},



		handleRoute: function( a, b ) {

			var compareTwo = _.isUndefined( b );



			if ( ! compareTwo ) {

				b = this.model.revisions.get( a );

				a = this.model.revisions.prev( b );

				b = b ? b.id : 0;

				a = a ? a.id : 0;

			}

		}

	});



	// Initialize the revisions UI.

	revisions.init = function() {

		revisions.view.frame = new revisions.view.Frame({

			model: new revisions.model.FrameState({}, {

				revisions: new revisions.model.Revisions( revisions.settings.revisionData )

			})

		}).render();

	};



	$( revisions.init );

}(jQuery));