#ifndef TCG_IMAGE_ITERATOR_H
#define TCG_IMAGE_ITERATOR_H
 
// tcg includes
#include "tcg_ptr.h"
#include "tcg_image_ops.h"
#include "tcg_point.h"
 
// STD includes
#include <iterator>
 
namespace tcg
{
 
//*********************************************************************************************************
//    Image Iterator  class
//*********************************************************************************************************
 
/*!
  The image_iterator class models an iterator accessing pixels of an image along its rows.
*/
 
template <typename It>
class image_iterator : public iterator_traits<It>::inheritable_iterator_type
{
	typedef typename iterator_traits<It>::inheritable_iterator_type iter;
 
public:
	typedef typename iter::iterator_category iterator_category;
	typedef typename iter::value_type value_type;
	typedef typename iter::difference_type difference_type;
	typedef typename iter::pointer pointer;
	typedef typename iter::reference reference;
 
public:
	image_iterator() {}
 
	template <typename Img>
	image_iterator(const Img &img, int x, int y)
		: iter(image_traits<Img>::pixel(img, x, y)), m_base(image_traits<Img>::pixel(img, 0, 0)), m_lx(image_traits<Img>::width(img)), m_ly(image_traits<Img>::height(img)), m_wrap(image_traits<Img>::wrap(img)), m_skew(m_wrap - lx) {}
 
	int x() const { return (iter::operator-(m_base)) % m_wrap; }
	int y() const { return (iter::operator-(m_base)) / m_wrap; }
 
	image_iterator &operator++()
	{
		iter::operator++();
		if (x() >= m_lx)
			iter::operator+=(m_skew);
		return *this;
	}
	image_iterator operator++(int)
	{
		image_iterator it(*this);
		operator++();
		return it;
	}
 
	image_iterator &operator--()
	{
		iter::operator--();
		if (x() < 0)
			iter::operator-=(m_skew);
		return *this;
	}
	image_iterator operator--(int)
	{
		image_iterator it(*this);
		operator--();
		return it;
	}
 
	image_iterator &operator+=(difference_type d)
	{
		int yCount = (x() + d) / m_lx;
		iter::operator+=((d - yCount * m_lx) + yCount * m_wrap);
		return *this;
	}
	image_iterator operator+(difference_type d) const
	{
		image_iterator it(*this);
		it += d;
		return it;
	}
 
	image_iterator operator-(difference_type d) const { return operator+(-d); }
	image_iterator &operator-=(difference_type d) { return operator+=(-d); }
 
	difference_type operator-(const image_iterator &other) const
	{
		return (x() - other.x()) + m_lx * (y() - other.y());
	}
 
	reference operator[](difference_type d) const
	{
		const image_iterator &it = operator+(d);
		return *it;
	}
 
protected:
	iter m_base;
	int m_lx, m_ly, m_wrap, m_skew;
};
 
//*********************************************************************************************************
//    image_edge_iterator class
//*********************************************************************************************************
 
enum _iei_adherence_policy { LEFT_ADHERENCE,
							 RIGHT_ADHERENCE };
 
/*!
  The image_edge_iterator class models a forward iterator following the contour of
  an image area of uniform color.
*/
 
template <typename It, _iei_adherence_policy _adherence = RIGHT_ADHERENCE>
class image_edge_iterator
{
	typedef typename iterator_traits<It>::inheritable_iterator_type iter;
 
public:
	typedef std::forward_iterator_tag iterator_category;
	typedef typename iter::value_type value_type;
	typedef typename iter::difference_type difference_type;
	typedef typename iter::pointer pointer;
	typedef typename iter::reference reference;
 
public:
	enum { adherence = _adherence };
 
	enum Direction { STRAIGHT = 0x0,
					 LEFT = 0x1,
					 RIGHT = 0x2,
					 AMBIGUOUS = 0x4,
					 UNKNOWN = 0x8,
					 AMBIGUOUS_LEFT = LEFT | AMBIGUOUS,
					 AMBIGUOUS_RIGHT = RIGHT | AMBIGUOUS };
 
public:
	image_edge_iterator() {}
 
	template <typename Img>
	image_edge_iterator(const Img &img, int x, int y, int dirX, int dirY);
 
	const Point &pos() const { return m_pos; }
	const Point &dir() const { return m_dir; }
 
	const value_type &leftColor() const { return m_leftColor; }
	const value_type &rightColor() const { return m_rightColor; }
 
	const value_type &color() const { return color(policy<_adherence>()); }
	const value_type &oppositeColor() const { return oppositeColor(policy<_adherence>()); }
	const value_type &elbowColor() const { return m_elbowColor; }
 
	iter leftPixel() const { return m_leftPix; }
	iter rightPixel() const { return m_rightPix; }
 
	iter pixel() const { return pixel(policy<_adherence>()); }
	iter oppositePixel() const { return oppositePixel(policy<_adherence>()); }
 
	Direction turn() const { return Direction(m_turn); }
 
public:
	// Iterator functions
 
	bool operator==(const image_edge_iterator &it) const { return (m_pos == it.m_pos) && (m_dir == it.m_dir); }
	bool operator!=(const image_edge_iterator &it) const { return !operator==(it); }
 
	image_edge_iterator &operator++()
	{
		advance(policy<_adherence>());
		return *this;
	}
	image_edge_iterator operator++(int)
	{
		image_edge_iterator temp(*this);
		operator++();
		return temp;
	}
 
private:
	void pixels(iter pixLeft, iter pixRight);
	void colors(value_type &leftColor, value_type &rightColor);
 
	void turnLeft()
	{
		int temp = m_dir.x;
		m_dir.x = -m_dir.y;
		m_dir.y = temp;
		m_turn = LEFT;
	}
	void turnRight()
	{
		int temp = m_dir.x;
		m_dir.x = m_dir.y;
		m_dir.y = -temp;
		m_turn = RIGHT;
	}
 
	void turn(const value_type &newLeftColor, const value_type &newRightColor)
	{
		turn(newLeftColor, newRightColor, policy<_adherence>());
	}
	void turnAmbiguous(const value_type &newLeftColor, const value_type &newRightColor);
 
private:
	template <_iei_adherence_policy>
	struct policy {
	};
 
	const value_type &color(policy<LEFT_ADHERENCE>) const { return m_leftColor; }
	const value_type &color(policy<RIGHT_ADHERENCE>) const { return m_rightColor; }
 
	const value_type &oppositeColor(policy<LEFT_ADHERENCE>) const { return m_rightColor; }
	const value_type &oppositeColor(policy<RIGHT_ADHERENCE>) const { return m_leftColor; }
 
	iter pixel(policy<LEFT_ADHERENCE>) const { return m_leftPix; }
	iter pixel(policy<RIGHT_ADHERENCE>) const { return m_rightPix; }
 
	iter oppositePixel(policy<LEFT_ADHERENCE>) const { return m_rightPix; }
	iter oppositePixel(policy<RIGHT_ADHERENCE>) const { return m_leftPix; }
 
	void turn(const value_type &newLeftColor, const value_type &newRightColor, policy<LEFT_ADHERENCE>);
	void turn(const value_type &newLeftColor, const value_type &newRightColor, policy<RIGHT_ADHERENCE>);
 
	void advance(policy<LEFT_ADHERENCE>);
	void advance(policy<RIGHT_ADHERENCE>);
 
private:
	int m_lx_1, m_ly_1, m_wrap;
 
	Point m_pos, m_dir;
 
	value_type m_leftColor, m_rightColor, m_outsideColor, m_elbowColor;
	iter m_pix, m_leftPix, m_rightPix;
 
	int m_turn;
};
 
} // namespace tcg
 
#endif // TCG_IMAGE_ITERATOR_H
 
//=====================================================================================
 
#ifdef INCLUDE_HPP
#include "hpp/image_iterator.hpp"
#endif // INCLUDE_HPP