/**

 * Handles the addition of the comment form.

 *

 * @since 2.7.0

 * @output wp-includes/js/comment-reply.js

 *

 * @namespace addComment

 *

 * @type {Object}

 */

window.addComment = ( function( window ) {

	// Avoid scope lookups on commonly used variables.

	var document = window.document;

	// Settings.

	var config = {

		commentReplyClass   : 'comment-reply-link',

		commentReplyTitleId : 'reply-title',

		cancelReplyId       : 'cancel-comment-reply-link',

		commentFormId       : 'commentform',

		temporaryFormId     : 'wp-temp-form-div',

		parentIdFieldId     : 'comment_parent',

		postIdFieldId       : 'comment_post_ID'

	};

	// Cross browser MutationObserver.

	var MutationObserver = window.MutationObserver || window.WebKitMutationObserver || window.MozMutationObserver;

	// Check browser cuts the mustard.

	var cutsTheMustard = 'querySelector' in document && 'addEventListener' in window;

	/*

	 * Check browser supports dataset.

	 * !! sets the variable to true if the property exists.

	 */

	var supportsDataset = !! document.documentElement.dataset;

	// For holding the cancel element.

	var cancelElement;

	// For holding the comment form element.

	var commentFormElement;

	// The respond element.

	var respondElement;

	// The mutation observer.

	var observer;

	if ( cutsTheMustard && document.readyState !== 'loading' ) {

		ready();

	} else if ( cutsTheMustard ) {

		window.addEventListener( 'DOMContentLoaded', ready, false );

	}

	/**

	 * Sets up object variables after the DOM is ready.

	 *

	 * @since 5.1.1

	 */

	function ready() {

		// Initialise the events.

		init();

		// Set up a MutationObserver to check for comments loaded late.

		observeChanges();

	}

	/**

	 * Add events to links classed .comment-reply-link.

	 *

	 * Searches the context for reply links and adds the JavaScript events

	 * required to move the comment form. To allow for lazy loading of

	 * comments this method is exposed as window.commentReply.init().

	 *

	 * @since 5.1.0

	 *

	 * @memberOf addComment

	 *

	 * @param {HTMLElement} context The parent DOM element to search for links.

	 */

	function init( context ) {

		if ( ! cutsTheMustard ) {

			return;

		}

		// Get required elements.

		cancelElement = getElementById( config.cancelReplyId );

		commentFormElement = getElementById( config.commentFormId );

		// No cancel element, no replies.

		if ( ! cancelElement ) {

			return;

		}

		cancelElement.addEventListener( 'touchstart', cancelEvent );

		cancelElement.addEventListener( 'click',      cancelEvent );

		// Submit the comment form when the user types [Ctrl] or [Cmd] + [Enter].

		var submitFormHandler = function( e ) {

			if ( ( e.metaKey || e.ctrlKey ) && e.keyCode === 13 ) {

				commentFormElement.removeEventListener( 'keydown', submitFormHandler );

				e.preventDefault();

				// The submit button ID is 'submit' so we can't call commentFormElement.submit(). Click it instead.

				commentFormElement.submit.click();

				return false;

			}

		};

		if ( commentFormElement ) {

			commentFormElement.addEventListener( 'keydown', submitFormHandler );

		}

		var links = replyLinks( context );

		var element;

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

			element = links[i];

			element.addEventListener( 'touchstart', clickEvent );

			element.addEventListener( 'click',      clickEvent );

		}

	}

	/**

	 * Return all links classed .comment-reply-link.

	 *

	 * @since 5.1.0

	 *

	 * @param {HTMLElement} context The parent DOM element to search for links.

	 *

	 * @return {HTMLCollection|NodeList|Array}

	 */

	function replyLinks( context ) {

		var selectorClass = config.commentReplyClass;

		var allReplyLinks;

		// childNodes is a handy check to ensure the context is a HTMLElement.

		if ( ! context || ! context.childNodes ) {

			context = document;

		}

		if ( document.getElementsByClassName ) {

			// Fastest.

			allReplyLinks = context.getElementsByClassName( selectorClass );

		}

		else {

			// Fast.

			allReplyLinks = context.querySelectorAll( '.' + selectorClass );

		}

		return allReplyLinks;

	}

	/**

	 * Cancel event handler.

	 *

	 * @since 5.1.0

	 *

	 * @param {Event} event The calling event.

	 */

	function cancelEvent( event ) {

		var cancelLink = this;

		var temporaryFormId  = config.temporaryFormId;

		var temporaryElement = getElementById( temporaryFormId );

		if ( ! temporaryElement || ! respondElement ) {

			// Conditions for cancel link fail.

			return;

		}

		getElementById( config.parentIdFieldId ).value = '0';

		// Move the respond form back in place of the temporary element.

		var headingText = temporaryElement.textContent;

		temporaryElement.parentNode.replaceChild( respondElement, temporaryElement );

		cancelLink.style.display = 'none';

		var replyHeadingElement  = getElementById( config.commentReplyTitleId );

		var replyHeadingTextNode = replyHeadingElement && replyHeadingElement.firstChild;

		if ( replyHeadingTextNode && replyHeadingTextNode.nodeType === Node.TEXT_NODE && headingText ) {

			replyHeadingTextNode.textContent = headingText;

		}

		event.preventDefault();

	}

	/**

	 * Click event handler.

	 *

	 * @since 5.1.0

	 *

	 * @param {Event} event The calling event.

	 */

	function clickEvent( event ) {

		var replyNode = getElementById( config.commentReplyTitleId );

		var defaultReplyHeading = replyNode && replyNode.firstChild.textContent;

		var replyLink = this,

			parentId  = getDataAttribute( replyLink, 'commentid' ),

			respondId = getDataAttribute( replyLink, 'respondelement' ),

			postId    = getDataAttribute( replyLink, 'postid' ),

			replyTo   = getDataAttribute( replyLink, 'replyto' ) || defaultReplyHeading,

			follow;

		if ( ! commId || ! parentId || ! respondId || ! postId ) {

			/*

			 * Theme or plugin defines own link via custom `wp_list_comments()` callback

			 * and calls `moveForm()` either directly or via a custom event hook.

			 */

			return;

		}

		/*

		 * Third party comments systems can hook into this function via the global scope,

		 * therefore the click event needs to reference the global scope.

		 */

		follow = window.addComment.moveForm( commId, parentId, respondId, postId, replyTo );

		if ( false === follow ) {

			event.preventDefault();

		}

	}

	/**

	 * Creates a mutation observer to check for newly inserted comments.

	 *

	 * @since 5.1.0

	 */

	function observeChanges() {

		if ( ! MutationObserver ) {

			return;

		}

		var observerOptions = {

			childList: true,

			subtree: true

		};

		observer = new MutationObserver( handleChanges );

		observer.observe( document.body, observerOptions );

	}

	/**

	 * Handles DOM changes, calling init() if any new nodes are added.

	 *

	 * @since 5.1.0

	 *

	 * @param {Array} mutationRecords Array of MutationRecord objects.

	 */

	function handleChanges( mutationRecords ) {

		var i = mutationRecords.length;

		while ( i-- ) {

			// Call init() once if any record in this set adds nodes.

			if ( mutationRecords[ i ].addedNodes.length ) {

				init();

				return;

			}

		}

	}

	/**

	 * Backward compatible getter of data-* attribute.

	 *

	 * Uses element.dataset if it exists, otherwise uses getAttribute.

	 *

	 * @since 5.1.0

	 *

	 * @param {HTMLElement} Element DOM element with the attribute.

	 * @param {string}      Attribute the attribute to get.

	 *

	 * @return {string}

	 */

	function getDataAttribute( element, attribute ) {

		if ( supportsDataset ) {

			return element.dataset[attribute];

		}

		else {

			return element.getAttribute( 'data-' + attribute );

		}

	}

	/**

	 * Get element by ID.

	 *

	 * Local alias for document.getElementById.

	 *

	 * @since 5.1.0

	 *

	 * @param {HTMLElement} The requested element.

	 */

	function getElementById( elementId ) {

		return document.getElementById( elementId );

	}

	/**

	 * Moves the reply form from its current position to the reply location.

	 *

	 * @since 2.7.0

	 *

	 * @memberOf addComment

	 *

	 * @param {string} addBelowId HTML ID of element the form follows.

	 * @param {string} commentId  Database ID of comment being replied to.

	 * @param {string} respondId  HTML ID of 'respond' element.

	 * @param {string} postId     Database ID of the post.

	 * @param {string} replyTo    Form heading content.

	 */

	function moveForm( addBelowId, commentId, respondId, postId, replyTo ) {

		// Get elements based on their IDs.

		var addBelowElement = getElementById( addBelowId );

		respondElement  = getElementById( respondId );

		// Get the hidden fields.

		var parentIdField   = getElementById( config.parentIdFieldId );

		var postIdField     = getElementById( config.postIdFieldId );

		var element, cssHidden, style;

		var replyHeading         = getElementById( config.commentReplyTitleId );

		var replyHeadingTextNode = replyHeading && replyHeading.firstChild;

		if ( ! addBelowElement || ! respondElement || ! parentIdField ) {

			// Missing key elements, fail.

			return;

		}

		if ( 'undefined' === typeof replyTo ) {

			replyTo = replyHeadingTextNode && replyHeadingTextNode.textContent;

		}

		addPlaceHolder( respondElement );

		// Set the value of the post.

		if ( postId && postIdField ) {

			postIdField.value = postId;

		}

		parentIdField.value = commentId;

		cancelElement.style.display = '';

		addBelowElement.parentNode.insertBefore( respondElement, addBelowElement.nextSibling );

		if ( replyHeadingTextNode && replyHeadingTextNode.nodeType === Node.TEXT_NODE ) {

			replyHeadingTextNode.textContent = replyTo;

		}

		/*

		 * This is for backward compatibility with third party commenting systems

		 * hooking into the event using older techniques.

		 */

		cancelElement.onclick = function() {

			return false;

		};

		// Focus on the first field in the comment form.

		try {

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

				element = commentFormElement.elements[i];

				cssHidden = false;

				// Get elements computed style.