pryley / site-reviews

;(function() {

	'use strict';

	var Pagination = function( el ) { // HTMLElement

		this.el = el;

		this.initEvents_();

	};

	Pagination.prototype = {

		config: {

			hideClass: 'glsr-hide',

			linkSelector: '.glsr-navigation a',

			scrollTime: 468,

		},

		/** @return string */

		getElementClass_: function( el ) { // HTMLElement

			return el.className ? '.' + el.className.trim().replace( /\s+/g, '.' ) : '';

		},

		/** @return string */

		getElementId_: function( el ) { // HTMLElement

			return el.id ? '#' + el.id.trim() : '';

		},

		/** @return void|string */

		getSelectorOfElement_: function( el ) { // HTMLElement

			if( !el || el.nodeType !== el.ELEMENT_NODE )return;

			return el.nodeName.toLowerCase() + this.getElementId_( el ) + this.getElementClass_( el );

		},

		/** @return void */

		handleResponse_: function( response, location ) { // string

			var parentSelector = this.getSelectorOfElement_( this.el );

			var html = document.implementation.createHTMLDocument( 'new' );

			html.documentElement.innerHTML = response;

			var newParentEl = parentSelector ? html.querySelectorAll( parentSelector ) : '';

			if( newParentEl.length === 1 ) {

				this.el.innerHTML = newParentEl[0].innerHTML;

				this.scrollToTop_( this.el );

				this.el.classList.remove( this.config.hideClass );

				this.initEvents_();

				window.history.pushState( null, '', location );

				new GLSR.Excerpts( this.el );

				return;

			}

			window.location = location; // @todo test location var

		},

		/** @return void */

		initEvents_: function() {

			var links = this.el.querySelectorAll( this.config.linkSelector );

			for( var i = 0; i < links.length; i++ ) {

				links[i].addEventListener( 'click', this.onClick_.bind( this ));

			}

		},

		/** @return void */

		onClick_: function( ev ) { // MouseEvent

			ev.preventDefault();

			this.el.classList.add( this.config.hideClass );

			GLSR.Ajax.get( this.href, this.handleResponse_.bind( this, ev.target.href ));

		},

		/** @return void */

		scrollToTop_: function( el, offset ) { // HTMLElement, int

			offset = offset || 16; // 1rem

			var fixedElement;

			for( var i = 0; i < GLSR.ajaxpagination.length; i++ ) {

				fixedElement = document.querySelector( GLSR.ajaxpagination[i] );

				if( !fixedElement || window.getComputedStyle( fixedElement ).getPropertyValue( 'position' ) !== 'fixed' )continue;

				offset = offset + fixedElement.clientHeight;

			}

			var clientBounds = el.getBoundingClientRect();

			var offsetTop = clientBounds.top - offset;

			if( offsetTop > 0 )return; // if top is in view, don't scroll!

			this.scrollToTopStep_({

				endY: offsetTop,

				offset: window.pageYOffset,

				startTime: window.performance.now(),

				startY: el.scrollTop,

			});

		},

		/** @return void */

		scrollToTopStep_: function( context ) { // object

			var elapsed = ( window.performance.now() - context.startTime ) / this.config.scrollTime;

			elapsed = elapsed > 1 ? 1 : elapsed;

			var easedValue = 0.5 * ( 1 - Math.cos( Math.PI * elapsed ));

			var currentY = context.startY + ( context.endY - context.startY ) * easedValue;

			window.scroll( 0, context.offset + currentY ); // @todo what is this for again?

			if( currentY !== context.endY ) {

				window.requestAnimationFrame( this.scrollToTopStep_.bind( window, context ));

			}

		},

	};