#ifndef _PHYSICS_POLYGON_
#define _PHYSICS_POLYGON_

#include "body.h"

#include <vector>

namespace wgd { class Vector2D; };

class Polygon : public Body
{
	public:
	Polygon (const wgd::InstanceID &);
	
	void update();
	void draw();
	
	float getArea () const { checkVertexCache(); return area; }
	float getMomentOfInertia () const { checkVertexCache(); return momentOfInertia * getDensity(); }
	
	float getMinX ()
	{
		checkCache();
		return vertices[xMin].x;
	}

	float getMaxX ()
	{
		checkCache();
		return vertices[xMax].x;
	}

	float getMinY ()
	{
		checkCache();
		return vertices[yMin].y;
	}

	float getMaxY ()
	{
		checkCache();
		return vertices[yMax].y;
	}
	
	bool contains (const wgd::Vector2D& p);
	
	void addVertex (float x, float y);
	
	int getVertexCount () const { return count; }
	
	wgd::Vector2D getVertex (int i) const
	{
		checkCache();
		
		i %= getVertexCount();
		
		return vertices[i];
	}
	
	wgd::Vector2D getNormal (int i) const
	{
		checkCache();
		
		wgd::Vector2D side = getVertex(i+1) - getVertex(i);
		
		wgd::Vector2D axis = wgd::Vector2D(-side.y, side.x);
		
		axis = axis.normalise();
		
		return axis;
	}
	
	wgd::Vector2D getExtremePoint (const wgd::Vector2D& direction, int& index) const;
	
	INSTANCE(Body, Polygon, "polygon");
	
	DOSTE_BEGINEVENTS_INHERIT(Body);
	DOSTE_EVENT(102, positionChanged);
	DOSTE_EVENT(103, positionChanged);
	DOSTE_EVENT(104, positionChanged);
	DOSTE_EVENT(100, vertexAdded);
	DOSTE_EVENT(101, vertexChanged);
	DOSTE_ENDEVENTS;
	
	private:
	void vertexAdded (WGD_HANDLER);
	void vertexChanged (WGD_HANDLER);
	void positionChanged (WGD_HANDLER);
	void remakeCOM ();
	
	bool m_verticesChanged;
	bool m_moved_polygon;
	
	void checkCache () const { if (m_moved_polygon) { const_cast<Polygon*>(this)->generateCache(); } }
	
	void checkVertexCache () const { if (m_verticesChanged) { const_cast<Polygon*>(this)->remakeCOM(); } }
	
	void generateCache ();
	std::vector<wgd::Vector2D> vertices;
	
	int xMin;
	int xMax;
	int yMin;
	int yMax;
	
	int count;
	
	float area;
	float momentOfInertia;
};

#endif