/*
**  Copyright (c) 1997-2015 Mark Page
**
**  This software is provided 'as-is', without any express or implied
**  warranty.  In no event will the authors be held liable for any damages
**  arising from the use of this software.
**
**  Permission is granted to anyone to use this software for any purpose,
**  including commercial applications, and to alter it and redistribute it
**  freely, subject to the following restrictions:
**
**  1. The origin of this software must not be misrepresented; you must not
**     claim that you wrote the original software. If you use this software
**     in a product, an acknowledgment in the product documentation would be
**     appreciated but is not required.
**  2. Altered source versions must be plainly marked as such, and must not be
**     misrepresented as being the original software.
**  3. This notice may not be removed or altered from any source distribution.
**
*/

#pragma once

#include <string>

/// \brief UTF8 reader helper functions.
class UTF8Reader
{
public:
	/// Important: text is not copied by this class and must remain valid during its usage.
	UTF8Reader(const std::string::value_type *text, std::string::size_type length);

	/// \brief Returns true if the current position is at the end of the string
	bool is_end();

	/// \brief Get the character at the current position
	unsigned int character();

	/// \brief Returns the length of the current character
	std::string::size_type char_length();

	/// \brief Moves position to the previous character
	void prev();

	/// \brief Moves position to the next character
	void next();

	/// \brief Moves position to the lead byte of the character
	void move_to_leadbyte();

	/// \brief Get the current position of the reader
	std::string::size_type position();

	/// \brief Set the current position of the reader
	void set_position(std::string::size_type position);

	static size_t utf8_length(const std::string& text)
	{
		return utf8_length(text.data(), text.size());
	}

	static size_t utf8_length(const std::string::value_type* text, std::string::size_type length)
	{
		UTF8Reader reader(text, length);
		size_t i = 0; 
		while (!reader.is_end())
		{
			reader.next();
			i++;
		}
		return i;
	}

private:
	std::string::size_type current_position = 0;
	std::string::size_type length = 0;
	const unsigned char *data = nullptr;
};