/* global $:off */
'use strict';

/**
 * Adapted from MDN polyfill (CC0)
 * https://developer.mozilla.org/en-US/docs/Web/API/Element/closest
 *
 * @param {HTMLElement} el
 * @param {string} selector
 * @return {HTMLElement|null}
 */
function closest( el, selector ) {
	var matches;

	el = el.nodeType === Node.ELEMENT_NODE ? el : el.parentNode;

	if ( Element.prototype.closest ) {
		return el.closest( selector );
	}

	matches = Element.prototype.matches ||
		Element.prototype.msMatchesSelector ||
		Element.prototype.webkitMatchesSelector;
	do {
		if ( matches.call( el, selector ) ) {
			return el;
		}
		el = el.parentNode;
	} while ( el !== null && el.nodeType === 1 );
	return null;
}

function whitespaceParsoidHack( listItem ) {
	// HACK: Setting data-parsoid removes the whitespace after the list item,
	// which makes nested lists work.
	// This is undocumented behaviour and probably very fragile.
	listItem.setAttribute( 'data-parsoid', '{}' );
}

function isTalkpageListNode( node ) {
	var tag = node.tagName ? node.tagName.toLowerCase() : '';
	return tag === 'dl' || tag === 'ul';
}

/**
 * Given a comment and a reply link, add the reply link to its document's DOM tree, at the end of
 * the comment.
 *
 * @param {Object} comment Comment data returned by parser#groupThreads
 * @param {HTMLElement} linkNode Reply link
 */
function addReplyLink( comment, linkNode ) {
	var target = comment.range.endContainer;

	// Skip to the end of the "paragraph".
	// Actually doing this by paragraph would require us to know how the text is laid out, and
	// would be more difficult and probably slower. Instead skip over anything that isn't a list
	// node, which should have the same effect on discussion pages.
	while ( target.nextSibling && !isTalkpageListNode( target.nextSibling ) ) {
		target = target.nextSibling;
	}

	// Insert the link before trailing whitespace.
	// In the MediaWiki parser output, <ul>/<dl> nodes are preceded by a newline. Normally it isn't
	// visible on the page. But if we insert an inline element (the reply link) after it, it becomes
	// meaningful and gets rendered, which results in additional spacing before some reply links.
	// Split the text node, so that we can insert the link before the trailing whitespace.
	if ( target.nodeType === Node.TEXT_NODE ) {
		target.splitText( target.textContent.match( /\s*$/ ).index );
	}

	target.parentNode.insertBefore( linkNode, target.nextSibling );
}

/**
 * Given a comment, add a list item to its document's DOM tree, inside of which a reply to said
 * comment can be added.
 *
 * The DOM tree is suitably rearranged to ensure correct indentation level of the reply (wrapper
 * nodes are added, and other nodes may be moved around).
 *
 * @param {Object} comment Comment data returned by parser#groupThreads
 * @return {HTMLElement}
 */
function addListItem( comment ) {
	var
		currComment, currLevel, desiredLevel,
		target, parent, listType, itemType, list, item, newNode,
		listTypeMap = {
			li: 'ul',
			dd: 'dl'
		};

	// 1. Start at given comment
	// 2. Skip past all comments with level greater than the given
	//    (or in other words, all replies, and replies to replies, and so on)
	// 3. Add comment with level of the given comment plus 1

	currComment = comment;
	while ( currComment.replies.length ) {
		currComment = currComment.replies[ currComment.replies.length - 1 ];
	}

	desiredLevel = comment.level + 1;
	currLevel = currComment.level;
	target = currComment.range.endContainer;

	// Skip to the end of the "paragraph".
	// Actually doing this by paragraph would require us to know how the text is laid out, and
	// would be more difficult and probably slower. Instead skip over anything that isn't a list
	// node, which should have the same effect on discussion pages.
	while ( target.nextSibling && !isTalkpageListNode( target.nextSibling ) ) {
		target = target.nextSibling;
	}

	// target is a text node or an inline element at the end of a "paragraph" (not necessarily paragraph node).
	// First, we need to find a block-level parent that we can mess with.
	// If we can't find a surrounding list item or paragraph (e.g. maybe we're inside a table cell
	// or something), take the parent node and hope for the best.
	parent = closest( target, 'li, dd, p' ) || target.parentNode;
	while ( target.parentNode !== parent ) {
		target = target.parentNode;
	}
	// parent is a list item or paragraph (hopefully)
	// target is an inline node within it

	if ( currLevel < desiredLevel ) {
		// Insert more lists after the target to increase nesting.

		// If we can't insert a list directly inside this element, insert after it.
		// TODO Improve this check
		if ( parent.tagName.toLowerCase() === 'p' ) {
			parent = parent.parentNode;
			target = target.parentNode;
		}

		// Decide on tag names for lists and items
		itemType = parent.tagName.toLowerCase();
		itemType = listTypeMap[ itemType ] ? itemType : 'dd';
		listType = listTypeMap[ itemType ];

		// Insert required number of wrappers
		while ( currLevel < desiredLevel ) {
			list = target.ownerDocument.createElement( listType );
			list.discussionToolsModified = 'new';
			item = target.ownerDocument.createElement( itemType );
			item.discussionToolsModified = 'new';
			whitespaceParsoidHack( item );

			parent.insertBefore( list, target.nextSibling );
			list.appendChild( item );

			target = item;
			parent = list;
			currLevel++;
		}
	} else if ( currLevel >= desiredLevel ) {
		// Split the ancestor nodes after the target to decrease nesting.

		do {
			// If target is the last child of its parent, no need to split it
			if ( target.nextSibling ) {
				// Create new identical node after the parent
				newNode = parent.cloneNode( false );
				parent.discussionToolsModified = 'split';
				parent.parentNode.insertBefore( newNode, parent.nextSibling );

				// Move nodes following target to the new node
				while ( target.nextSibling ) {
					newNode.appendChild( target.nextSibling );
				}
			}

			target = parent;
			parent = parent.parentNode;

			// Decrease nesting level if we escaped outside of a list
			if ( listTypeMap[ target.tagName.toLowerCase() ] ) {
				currLevel--;
			}
		} while ( currLevel >= desiredLevel );

		// parent is now a list, target is a list item
		item = target.ownerDocument.createElement( target.tagName );
		item.discussionToolsModified = 'new';
		whitespaceParsoidHack( item );
		parent.insertBefore( item, target.nextSibling );
	}

	return item;
}

/**
 * Undo the effects of #addListItem, also removing or merging any affected parent nodes.
 *
 * @param {HTMLElement} node
 */
function removeListItem( node ) {
	var nextNode;

	while ( node && node.discussionToolsModified ) {
		if ( node.discussionToolsModified === 'new' ) {
			nextNode = node.previousSibling || node.parentNode;

			// Remove this node
			delete node.discussionToolsModified;
			node.parentNode.removeChild( node );

		} else if ( node.discussionToolsModified === 'split' ) {
			// Children might be split too, if so, descend into them afterwards
			if ( node.lastChild && node.lastChild.discussionToolsModified === 'split' ) {
				node.discussionToolsModified = 'done';
				nextNode = node.lastChild;
			} else {
				delete node.discussionToolsModified;
				nextNode = node.parentNode;
			}
			// Merge the following sibling node back into this one
			while ( node.nextSibling.firstChild ) {
				node.appendChild( node.nextSibling.firstChild );
			}
			node.parentNode.removeChild( node.nextSibling );

		} else {
			nextNode = node.parentNode;
		}

		node = nextNode;
	}
}

/**
 * Add another list item after the given one.
 *
 * @param {HTMLElement} previousItem
 * @return {HTMLElement}
 */
function addSiblingListItem( previousItem ) {
	var listItem = previousItem.ownerDocument.createElement( previousItem.nodeName.toLowerCase() );
	whitespaceParsoidHack( listItem );
	previousItem.parentNode.insertBefore( listItem, previousItem.nextSibling );
	return listItem;
}

function createWikitextNode( wt ) {
	var span = document.createElement( 'span' );

	span.setAttribute( 'typeof', 'mw:Transclusion' );
	span.setAttribute( 'data-mw', JSON.stringify( { parts: [ wt ] } ) );

	return span;
}

module.exports = {
	closest: closest,
	addReplyLink: addReplyLink,
	addListItem: addListItem,
	removeListItem: removeListItem,
	addSiblingListItem: addSiblingListItem,
	createWikitextNode: createWikitextNode
};