// utf_iterators.hpp
// Copyright (c) 2012 Ben Hanson (http://www.benhanson.net/)
// Inspired by http://utfcpp.sourceforge.net/
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file licence_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef LEXERTL_UTF_ITERATORS_HPP
#define LEXERTL_UTF_ITERATORS_HPP

#include <iterator>

namespace lexertl
{
template<typename char_iterator, typename char_type>
class basic_utf8_in_iterator :
    public std::iterator<std::input_iterator_tag, char_type>
{
public:
    basic_utf8_in_iterator () :
        _char (0)
    {
    }

    explicit basic_utf8_in_iterator (const char_iterator& it_) :
        _it (it_),
        _char (0)
    {
        next ();
    }

    char_type operator * () const
    {
        return _char;
    }

    bool operator == (const basic_utf8_in_iterator &rhs_) const
    {
        return _it == rhs_._it;
    }

    bool operator != (const basic_utf8_in_iterator &rhs_) const
    {
        return _it != rhs_._it;
    }

    basic_utf8_in_iterator &operator ++ ()
    {
        next ();
        return *this;
    }

    basic_utf8_in_iterator operator ++ (int)
    {
        basic_utf8_in_iterator temp_ = *this;

        next ();
        return temp_;
    }

private:
    typedef typename std::iterator_traits<char_iterator>::
        difference_type difference_type;
    char_iterator _it;
    char_type _char;

    void next ()
    {
        const char len_ = len (_it);
        char_type ch_ = *_it & 0xff;

        switch (len_)
        {
        case 1:
            break;
        case 2:
            ++_it;
            ch_ = (ch_ << 6 & 0x7ff) | (*_it & 0x3f);
            break;
        case 3:
            ++_it;
            ch_ = (ch_ << 12 & 0xffff) | ((*_it & 0xff) << 6 & 0xfff);
            ++_it;
            ch_ |= *_it & 0x3f;
            break;
        case 4:
            ++_it;
            ch_ = (ch_ << 18 & 0x1fffff) | ((*_it & 0xff) << 12 & 0x3ffff);
            ++_it;
            ch_ |= (*_it & 0xff) << 6 & 0xfff;
            ++_it;
            ch_ |= *_it & 0x3f;
            break;
        }

        ++_it;
        _char = ch_;
    }

    char len (const char_iterator &it_) const
    {
        const unsigned char ch_ = *it_;

        return ch_ < 0x80 ? 1 :
            ch_ >> 5 == 0x06 ? 2 :
            ch_ >> 4 == 0x0e ? 3 :
            ch_ >> 3 == 0x1e ? 4 : 0;
    }
};

template<typename char_iterator>
class basic_utf8_out_iterator :
    public std::iterator<std::input_iterator_tag, char>
{
public:
    basic_utf8_out_iterator () :
        _count (0),
        _index (0)
    {
    }

    explicit basic_utf8_out_iterator (const char_iterator& it_) :
        _it (it_),
        _count (0),
        _index (0)
    {
        next ();
    }

    char operator * () const
    {
        return _bytes[_index];
    }

    bool operator == (const basic_utf8_out_iterator &rhs_) const
    {
        return _it == rhs_._it;
    }

    bool operator != (const basic_utf8_out_iterator &rhs_) const
    {
        return _it != rhs_._it;
    }

    basic_utf8_out_iterator &operator ++ ()
    {
        ++_index;

        if (_index >= _count)
        {
            next ();
        }

        return *this;
    }

    basic_utf8_out_iterator operator ++ (int)
    {
        basic_utf8_out_iterator temp_ = *this;

        ++_index;

        if (_index >= _count)
        {
            next ();
        }

        return temp_;
    }

private:
    char_iterator _it;
    char _bytes[4];
    unsigned char _count;
    unsigned char _index;

    void next ()
    {
        const std::size_t ch_ = *_it;

        _count = len (ch_);
        _index = 0;

        switch (_count)
        {
        case 1:
            _bytes[0] = static_cast<char>(ch_);
            break;
        case 2:
            _bytes[0] = static_cast<char>((ch_ >> 6) | 0xc0);
            _bytes[1] = (ch_ & 0x3f) | 0x80;
            break;
        case 3:
            _bytes[0] = static_cast<char>((ch_ >> 12) | 0xe0);
            _bytes[1] = ((ch_ >> 6) & 0x3f) | 0x80;
            _bytes[2] = (ch_ & 0x3f) | 0x80;
            break;
        case 4:
            _bytes[0] = static_cast<char>((ch_ >> 18) | 0xf0);
            _bytes[1] = ((ch_ >> 12) & 0x3f) | 0x80;
            _bytes[2] = ((ch_ >> 6) & 0x3f) | 0x80;
            _bytes[3] = (ch_ & 0x3f) | 0x80;
            break;
        }

        ++_it;
    }

    char len (const std::size_t ch_) const
    {
        return ch_ < 0x80 ? 1 :
            ch_ < 0x800 ? 2 :
            ch_ < 0x10000 ? 3 :
            4;
    }
};

template<typename char_iterator, typename char_type>
class basic_utf16_in_iterator :
    public std::iterator<std::input_iterator_tag, char_type>
{
public:
    basic_utf16_in_iterator () :
        _char (0)
    {
    }

    explicit basic_utf16_in_iterator (const char_iterator &it_) :
        _it (it_),
        _char (0)
    {
        next ();
    }

    char_type operator * () const
    {
        return _char;
    }

    bool operator == (const basic_utf16_in_iterator &rhs_) const
    {
        return _it == rhs_._it;
    }

    bool operator != (const basic_utf16_in_iterator &rhs_) const
    {
        return _it != rhs_._it;
    }

    basic_utf16_in_iterator &operator ++ ()
    {
        next ();
        return *this;
    }

    basic_utf16_in_iterator operator ++ (int)
    {
        basic_utf16_in_iterator temp_ = *this;

        next ();
        return temp_;
    }

private:
    typedef typename std::iterator_traits<char_iterator>::
        difference_type difference_type;
    char_iterator _it;
    char_type _char;

    void next ()
    {
        char_type ch_ = *_it & 0xffff;

        if (ch_ >= 0xd800 && ch_ <= 0xdbff)
        {
            const char_type surrogate_ = *++_it & 0xffff;

            ch_ = (((ch_ - 0xd800) << 10) | (surrogate_ - 0xdc00)) + 0x10000;
        }

        ++_it;
        _char = ch_;
    }
};

template<typename char_iterator>
class basic_utf16_out_iterator :
    public std::iterator<std::input_iterator_tag, wchar_t>
{
public:
    basic_utf16_out_iterator () :
        _count (0),
        _index (0)
    {
    }

    explicit basic_utf16_out_iterator (const char_iterator& it_) :
        _it (it_),
        _count (0),
        _index (0)
    {
        next ();
    }

    wchar_t operator * () const
    {
        return _chars[_index];
    }

    bool operator == (const basic_utf16_out_iterator &rhs_) const
    {
        return _it == rhs_._it;
    }

    bool operator != (const basic_utf16_out_iterator &rhs_) const
    {
        return _it != rhs_._it;
    }

    basic_utf16_out_iterator &operator ++ ()
    {
        ++_index;

        if (_index >= _count)
        {
            next ();
        }

        return *this;
    }

    basic_utf16_out_iterator operator ++ (int)
    {
        basic_utf16_out_iterator temp_ = *this;

        ++_index;

        if (_index >= _count)
        {
            next ();
        }

        return temp_;
    }

private:
    char_iterator _it;
    wchar_t _chars[2];
    unsigned char _count;
    unsigned char _index;

    void next ()
    {
        const std::size_t ch_ = *_it;

        _count = len (ch_);
        _index = 0;

        switch (_count)
        {
        case 1:
            _chars[0] = static_cast<wchar_t>(ch_);
            break;
        case 2:
            _chars[0] = static_cast<wchar_t>((ch_ >> 10) + 0xdc00u -
                (0x10000 >> 10));
            _chars[1] = static_cast<wchar_t>((ch_ & 0x3ff) + 0xdc00u);
            break;
        }

        ++_it;
    }

    char len (const std::size_t ch_) const
    {
        return ch_ > 0xffff ? 2 : 1;
    }
};
}

#endif