/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/

#pragma once

#include <QDomElement>
#include <QString>
#include "sllconfig.h"

namespace LC::Util
{
	/** @brief Creates a range iterating over direct children named \em tag.
	 *
	 * The returned range is suitable for range-based for loops, in particular. For instance, the
	 * following is correct:
	 * \code{.cpp}
	 	QDomDocument doc;
	 	doc.setContent (R"(
	 				<root>
	 					<child num="1">first text</child>
	 					<child num="2">second text</child>
	 					<child num="3">third text</child>
	 				</root>
	 			)");

	 	for (const auto& elem : MakeDomSiblingsRange (doc.firstChildElement ("root"), "child"))
	 		qDebug () << elem.text () << elem.attribute ("num");
	   \endcode
	 *
	 * Modifying the underlying DOM tree will result in the same effects as modifying it during the
	 * canonical Qt-way of repeatedly calling <code>QDomElement::nextSiblingElement()</code> until
	 * the element becomes null.
	 *
	 * @param parent The parent element whose children should be iterated over.
	 * @param tag The tag name of the child nodes (or an empty string for all children).
	 * @return The range object representing the collection of the child nodes.
	 *
	 * @sa DomDescendants()
	 */
	inline auto DomChildren (const QDomNode& parent, const QString& tag)
	{
		struct Iterator
		{
			using difference_type = ptrdiff_t;
			using value_type = QDomElement;
			using reference = QDomElement&;
			using iterator_category = std::forward_iterator_tag;

			QDomElement Elem_;
			const QString Tag_;

			bool operator== (const Iterator& other) const
			{
				return Elem_ == other.Elem_;
			}

			Iterator& operator++ ()
			{
				Elem_ = Elem_.nextSiblingElement (Tag_);
				return *this;
			}

			QDomElement& operator* ()
			{
				return Elem_;
			}
		};

		struct Range
		{
			const Iterator Begin_;

			auto begin () const { return Begin_; }
			auto end () const { return Iterator {}; }
		};

		auto firstChild = parent.firstChildElement (tag);
		return Range { { firstChild, tag } };
	}

	/** @brief Creates a vector with all descendants of `parent` named `tag`.
	 *
	 * The returned vector is _not_ a live DOM node list, so modifying its elements
	 * does not modify the vector. Thus it is also faster to iterate in case of
	 * modifications.
	 *
	 * @param parent The parent element whose children should be iterated over.
	 * @param tag The name of the tag that the returned descendants should have.
	 * @return The vector with all descendants named `tag`.
	 *
	 * @sa DomChildren()
	 */
	UTIL_SLL_API QVector<QDomElement> DomDescendants (const QDomElement& parent, const QString& tag);
}
