/*
* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
*
* 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.
*/

#include "b2CircleContact.h"
#include "../b2Body.h"
#include "../b2WorldCallbacks.h"
#include "../../Common/b2BlockAllocator.h"

#include <new>
#include <cstring>

b2Contact* b2CircleContact::Create(b2Shape* shape1, b2Shape* shape2, b2BlockAllocator* allocator)
{
	void* mem = allocator->Allocate(sizeof(b2CircleContact));
	return new (mem) b2CircleContact(shape1, shape2);
}

void b2CircleContact::Destroy(b2Contact* contact, b2BlockAllocator* allocator)
{
	((b2CircleContact*)contact)->~b2CircleContact();
	allocator->Free(contact, sizeof(b2CircleContact));
}

b2CircleContact::b2CircleContact(b2Shape* s1, b2Shape* s2)
: b2Contact(s1, s2)
{
	b2Assert(m_shape1->GetType() == e_circleShape);
	b2Assert(m_shape2->GetType() == e_circleShape);
	m_manifold.pointCount = 0;
	m_manifold.points[0].normalImpulse = 0.0f;
	m_manifold.points[0].tangentImpulse = 0.0f;
}

void b2CircleContact::Evaluate(b2ContactListener* listener)
{
	b2Body* b1 = m_shape1->GetBody();
	b2Body* b2 = m_shape2->GetBody();

	b2Manifold m0;
	memcpy(&m0, &m_manifold, sizeof(b2Manifold));

	b2CollideCircles(&m_manifold, (b2CircleShape*)m_shape1, b1->GetXForm(), (b2CircleShape*)m_shape2, b2->GetXForm());

	b2ContactPoint cp;
	cp.shape1 = m_shape1;
	cp.shape2 = m_shape2;
	cp.friction = b2MixFriction(m_shape1->GetFriction(), m_shape2->GetFriction());
	cp.restitution = b2MixRestitution(m_shape1->GetRestitution(), m_shape2->GetRestitution());

	if (m_manifold.pointCount > 0)
	{
		m_manifoldCount = 1;
		b2ManifoldPoint* mp = m_manifold.points + 0;

		if (m0.pointCount == 0)
		{
			mp->normalImpulse = 0.0f;
			mp->tangentImpulse = 0.0f;

			if (listener)
			{
				cp.position = b1->GetWorldPoint(mp->localPoint1);
				b2Vec2 v1 = b1->GetLinearVelocityFromLocalPoint(mp->localPoint1);
				b2Vec2 v2 = b2->GetLinearVelocityFromLocalPoint(mp->localPoint2);
				cp.velocity = v2 - v1;
				cp.normal = m_manifold.normal;
				cp.separation = mp->separation;
				cp.id = mp->id;
				listener->Add(&cp);
			}
		}
		else
		{
			b2ManifoldPoint* mp0 = m0.points + 0;
			mp->normalImpulse = mp0->normalImpulse;
			mp->tangentImpulse = mp0->tangentImpulse;

			if (listener)
			{
				cp.position = b1->GetWorldPoint(mp->localPoint1);
				b2Vec2 v1 = b1->GetLinearVelocityFromLocalPoint(mp->localPoint1);
				b2Vec2 v2 = b2->GetLinearVelocityFromLocalPoint(mp->localPoint2);
				cp.velocity = v2 - v1;
				cp.normal = m_manifold.normal;
				cp.separation = mp->separation;
				cp.id = mp->id;
				listener->Persist(&cp);
			}
		}
	}
	else
	{
		m_manifoldCount = 0;
		if (m0.pointCount > 0 && listener)
		{
			b2ManifoldPoint* mp0 = m0.points + 0;
			cp.position = b1->GetWorldPoint(mp0->localPoint1);
			b2Vec2 v1 = b1->GetLinearVelocityFromLocalPoint(mp0->localPoint1);
			b2Vec2 v2 = b2->GetLinearVelocityFromLocalPoint(mp0->localPoint2);
			cp.velocity = v2 - v1;
			cp.normal = m0.normal;
			cp.separation = mp0->separation;
			cp.id = mp0->id;
			listener->Remove(&cp);
		}
	}
}
