/**
 * 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;
var replyLinkToParent    = replyHeadingTextNode && replyHeadingTextNode.nextSibling;

if ( replyHeadingTextNode && replyHeadingTextNode.nodeType === Node.TEXT_NODE && headingText ) {
if ( replyLinkToParent && 'A' === replyLinkToParent.nodeName && replyLinkToParent.id !== config.cancelReplyId ) {
replyLinkToParent.style.display = '';
}

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,
commId    = getDataAttribute( replyLink, 'belowelement' ),
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;
var replyLinkToParent    = replyHeadingTextNode && replyHeadingTextNode.nextSibling;

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 ) {
if ( replyLinkToParent && 'A' === replyLinkToParent.nodeName && replyLinkToParent.id !== config.cancelReplyId ) {
replyLinkToParent.style.display = 'none';
}

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.
if ( 'getComputedStyle' in window ) {
// Modern browsers.
style = window.getComputedStyle( element );
} else if ( document.documentElement.currentStyle ) {
// IE 8.
style = element.currentStyle;
}

/*
* For display none, do the same thing jQuery does. For visibility,
* check the element computed style since browsers are already doing
* the job for us. In fact, the visibility computed style is the actual
* computed value and already takes into account the element ancestors.
*/
if ( ( element.offsetWidth <= 0 && element.offsetHeight <= 0 ) || style.visibility === 'hidden' ) {
cssHidden = true;
}

// Skip form elements that are hidden or disabled.
if ( 'hidden' === element.type || element.disabled || cssHidden ) {
continue;
}

element.focus();
// Stop after the first focusable element.
break;
}
}
catch(e) {

}

/*
* false is returned for backward compatibility with third party commenting systems
* hooking into this function.
*/
return false;
}

/**
* Add placeholder element.
*
* Places a place holder element above the #respond element for
* the form to be returned to if needs be.
*
* @since 2.7.0
*
* @param {HTMLelement} respondElement the #respond element holding comment form.
*/
function addPlaceHolder( respondElement ) {
var temporaryFormId  = config.temporaryFormId;
var temporaryElement = getElementById( temporaryFormId );
var replyElement = getElementById( config.commentReplyTitleId );
var initialHeadingText = replyElement ? replyElement.firstChild.textContent : '';

if ( temporaryElement ) {
// The element already exists, no need to recreate.
return;
}

temporaryElement = document.createElement( 'div' );
temporaryElement.id = temporaryFormId;
temporaryElement.style.display = 'none';
temporaryElement.textContent = initialHeadingText;
respondElement.parentNode.insertBefore( temporaryElement, respondElement );
}

return {
init: init,
moveForm: moveForm
};
})( window );