( function ( mw, $ ) {
	/**
	 * Module containing presentation logic for the revision pointer lines
	 *
	 * @param {Pointer} pointer
	 * @param {string} name
	 * @constructor
	 */
	var PointerLine = function ( pointer, name ) {
		this.pointer = pointer;
		this.name = name;
	};

	$.extend( PointerLine.prototype, {
		/**
		 * @type {string}
		 */
		name: '',

		/**
		 * @type {Pointer}
		 */
		pointer: null,

		/**
		 * @type {jQuery}
		 */
		$html: null,

		/**
		 * Check if the offset method is available for the diff element
		 *
		 * @return {boolean}
		 */
		offsetNotAvailable: function () {
			return typeof $( '.diff-ntitle' ).offset() === 'undefined';
		},

		/**
		 * Calculate the relative distance in between the given pointer and column
		 *
		 * @param {jQuery} $sourcePointer
		 * @param {jQuery} $targetColumn
		 *
		 * @return {int} distance between the given elements
		 */
		calculateDistance: function ( $sourcePointer, $targetColumn ) {
			return ( $targetColumn.offset().left + $targetColumn.width() / 2 ) -
				( $sourcePointer.offset().left + ( $sourcePointer.width() + 4 ) / 2 );
			// +4 there is a negative left-margin in the pointer that needs to be considered
		},

		/**
		 * Calculate and set line's width and position with the given pointer and column
		 *
		 * @param {jQuery} $sourcePointer
		 * @param {jQuery} $targetColumn
		 */
		setCssProperties: function ( $sourcePointer, $targetColumn ) {
			var distance, widthToSet, leftToSet;

			distance = this.calculateDistance( $sourcePointer, $targetColumn );

			widthToSet = Math.abs( distance );
			leftToSet = ( $targetColumn.offset().left + $targetColumn.width() / 2 ) -
				$( '.mw-revslider-revision-slider' ).offset().left;

			if ( distance < 0 ) {
				// targetColumn is left relative to sourcePointer
				leftToSet += 2; // in that case somehow the border-width of the line-box seems to affect the positioning
			} else {
				// targetColumn is right relative to sourcePointer
				leftToSet -= widthToSet;
			}

			this.$html.css( {
				width: widthToSet + 'px',
				left: leftToSet + 'px'
			} );
		},

		/**
		 * Check if the target column is located right form the source pointer
		 *
		 * @param {jQuery} $sourcePointer
		 * @param {jQuery} $targetColumn
		 *
		 * @return {boolean}
		 */
		targetColumnIsRightFromPointer: function ( $sourcePointer, $targetColumn ) {
			return this.calculateDistance( $sourcePointer, $targetColumn ) > 0;
		},

		/**
		 * Draws the line between pointer and column by setting borders, position and width of the line box
		 *
		 * @return {boolean}
		 */
		drawLine: function () {
			var $upperLineDiv = this.$html.find( '.mw-revslider-pointer-line-upper' ),
				$lowerLineDiv = this.$html.find( '.mw-revslider-pointer-line-lower' ),
				$sourcePointer = this.pointer.getView().getElement(),
				$targetColumn;

			if ( this.offsetNotAvailable() ) {
				// offset is not available in QUnit tests so skip calculation and drawing
				return false;
			}

			if ( this.pointer.getView().isUpperPointer() ) {
				$lowerLineDiv.removeClass( 'mw-revslider-lower-color' ).addClass( 'mw-revslider-upper-color' );
				$upperLineDiv.removeClass( 'mw-revslider-lower-color' ).addClass( 'mw-revslider-upper-color' );
				$targetColumn = $( '.diff-ntitle' );
			} else {
				$lowerLineDiv.removeClass( 'mw-revslider-upper-color' ).addClass( 'mw-revslider-lower-color' );
				$upperLineDiv.removeClass( 'mw-revslider-upper-color' ).addClass( 'mw-revslider-lower-color' );
				$targetColumn = $( '.diff-otitle' );
			}

			this.setCssProperties( $sourcePointer, $targetColumn );

			$upperLineDiv.addClass( 'mw-revslider-bottom-line' );

			if ( this.targetColumnIsRightFromPointer( $sourcePointer, $targetColumn ) ) {
				$upperLineDiv.addClass( 'mw-revslider-left-line' );
				$lowerLineDiv.addClass( 'mw-revslider-right-line' );
			} else {
				$upperLineDiv.addClass( 'mw-revslider-right-line' );
				$lowerLineDiv.addClass( 'mw-revslider-left-line' );
			}

			return true;
		},

		/**
		 * Initializes the DOM element with the line-box for drawing the lines
		 */
		initialize: function () {
			this.$html = $( '<div>' )
				.addClass( 'mw-revslider-pointer-line ' + this.name )
				.append(
					$( '<div>' ).addClass( 'mw-revslider-pointer-line-upper ' + this.name ),
					$( '<div>' ).addClass( 'mw-revslider-pointer-line-lower ' + this.name )
				);
		},

		/**
		 * Adds colored top-borders for the diff columns fitting the line colors between pointers and columns
		 */
		addColoredColumnBorders: function () {
			$( '#mw-diff-otitle1' ).addClass( 'mw-revslider-older-diff-column' );
			$( '#mw-diff-ntitle1' ).addClass( 'mw-revslider-newer-diff-column' );
		},

		/**
		 * Remove colored top-borders for the diff columns fitting the line colors between pointers and columns
		 */
		removeColoredColumnBorders: function () {
			$( '#mw-diff-otitle1' ).removeClass( 'mw-revslider-older-diff-column' );
			$( '#mw-diff-ntitle1' ).removeClass( 'mw-revslider-newer-diff-column' );
		},

		/**
		 * Sets the hooks to draw the column borders
		 */
		setColumnBorderHooks: function () {
			mw.hook( 'wikipage.diff' ).add( this.addColoredColumnBorders );
			mw.hook( 'revslider.expand' ).add( this.addColoredColumnBorders );
			mw.hook( 'revslider.collapse' ).add( this.removeColoredColumnBorders );
		},

		/**
		 * @return {jQuery}
		 */
		render: function () {
			this.initialize();
			this.setColumnBorderHooks();
			return this.getElement();
		},

		/**
		 * @return {jQuery}
		 */
		getElement: function () {
			return this.$html;
		}
	} );

	mw.libs.revisionSlider = mw.libs.revisionSlider || {};
	mw.libs.revisionSlider.PointerLine = PointerLine;
}( mediaWiki, jQuery ) );