/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  https://bulletphysics.org

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.
	
	Elsevier CDROM license agreements grants nonexclusive license to use the software
	for any purpose, commercial or non-commercial as long as the following credit is included
	identifying the original source of the software:

	Parts of the source are "from the book Real-Time Collision Detection by
	Christer Ericson, published by Morgan Kaufmann Publishers,
	(c) 2005 Elsevier Inc."
		
*/

#include "b3VoronoiSimplexSolver.h"

#define VERTA 0
#define VERTB 1
#define VERTC 2
#define VERTD 3

#define B3_CATCH_DEGENERATE_TETRAHEDRON 1
void b3VoronoiSimplexSolver::removeVertex(int index)
{
	b3Assert(m_numVertices > 0);
	m_numVertices--;
	m_simplexVectorW[index] = m_simplexVectorW[m_numVertices];
	m_simplexPointsP[index] = m_simplexPointsP[m_numVertices];
	m_simplexPointsQ[index] = m_simplexPointsQ[m_numVertices];
}

void b3VoronoiSimplexSolver::reduceVertices(const b3UsageBitfield& usedVerts)
{
	if ((numVertices() >= 4) && (!usedVerts.usedVertexD))
		removeVertex(3);

	if ((numVertices() >= 3) && (!usedVerts.usedVertexC))
		removeVertex(2);

	if ((numVertices() >= 2) && (!usedVerts.usedVertexB))
		removeVertex(1);

	if ((numVertices() >= 1) && (!usedVerts.usedVertexA))
		removeVertex(0);
}

//clear the simplex, remove all the vertices
void b3VoronoiSimplexSolver::reset()
{
	m_cachedValidClosest = false;
	m_numVertices = 0;
	m_needsUpdate = true;
	m_lastW = b3MakeVector3(b3Scalar(B3_LARGE_FLOAT), b3Scalar(B3_LARGE_FLOAT), b3Scalar(B3_LARGE_FLOAT));
	m_cachedBC.reset();
}

//add a vertex
void b3VoronoiSimplexSolver::addVertex(const b3Vector3& w, const b3Vector3& p, const b3Vector3& q)
{
	m_lastW = w;
	m_needsUpdate = true;

	m_simplexVectorW[m_numVertices] = w;
	m_simplexPointsP[m_numVertices] = p;
	m_simplexPointsQ[m_numVertices] = q;

	m_numVertices++;
}

bool b3VoronoiSimplexSolver::updateClosestVectorAndPoints()
{
	if (m_needsUpdate)
	{
		m_cachedBC.reset();

		m_needsUpdate = false;

		switch (numVertices())
		{
			case 0:
				m_cachedValidClosest = false;
				break;
			case 1:
			{
				m_cachedP1 = m_simplexPointsP[0];
				m_cachedP2 = m_simplexPointsQ[0];
				m_cachedV = m_cachedP1 - m_cachedP2;  //== m_simplexVectorW[0]
				m_cachedBC.reset();
				m_cachedBC.setBarycentricCoordinates(b3Scalar(1.), b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));
				m_cachedValidClosest = m_cachedBC.isValid();
				break;
			};
			case 2:
			{
				//closest point origin from line segment
				const b3Vector3& from = m_simplexVectorW[0];
				const b3Vector3& to = m_simplexVectorW[1];
				b3Vector3 nearest;

				b3Vector3 p = b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));
				b3Vector3 diff = p - from;
				b3Vector3 v = to - from;
				b3Scalar t = v.dot(diff);

				if (t > 0)
				{
					b3Scalar dotVV = v.dot(v);
					if (t < dotVV)
					{
						t /= dotVV;
						diff -= t * v;
						m_cachedBC.m_usedVertices.usedVertexA = true;
						m_cachedBC.m_usedVertices.usedVertexB = true;
					}
					else
					{
						t = 1;
						diff -= v;
						//reduce to 1 point
						m_cachedBC.m_usedVertices.usedVertexB = true;
					}
				}
				else
				{
					t = 0;
					//reduce to 1 point
					m_cachedBC.m_usedVertices.usedVertexA = true;
				}
				m_cachedBC.setBarycentricCoordinates(1 - t, t);
				nearest = from + t * v;

				m_cachedP1 = m_simplexPointsP[0] + t * (m_simplexPointsP[1] - m_simplexPointsP[0]);
				m_cachedP2 = m_simplexPointsQ[0] + t * (m_simplexPointsQ[1] - m_simplexPointsQ[0]);
				m_cachedV = m_cachedP1 - m_cachedP2;

				reduceVertices(m_cachedBC.m_usedVertices);

				m_cachedValidClosest = m_cachedBC.isValid();
				break;
			}
			case 3:
			{
				//closest point origin from triangle
				b3Vector3 p = b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));

				const b3Vector3& a = m_simplexVectorW[0];
				const b3Vector3& b = m_simplexVectorW[1];
				const b3Vector3& c = m_simplexVectorW[2];

				closestPtPointTriangle(p, a, b, c, m_cachedBC);
				m_cachedP1 = m_simplexPointsP[0] * m_cachedBC.m_barycentricCoords[0] +
							 m_simplexPointsP[1] * m_cachedBC.m_barycentricCoords[1] +
							 m_simplexPointsP[2] * m_cachedBC.m_barycentricCoords[2];

				m_cachedP2 = m_simplexPointsQ[0] * m_cachedBC.m_barycentricCoords[0] +
							 m_simplexPointsQ[1] * m_cachedBC.m_barycentricCoords[1] +
							 m_simplexPointsQ[2] * m_cachedBC.m_barycentricCoords[2];

				m_cachedV = m_cachedP1 - m_cachedP2;

				reduceVertices(m_cachedBC.m_usedVertices);
				m_cachedValidClosest = m_cachedBC.isValid();

				break;
			}
			case 4:
			{
				b3Vector3 p = b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));

				const b3Vector3& a = m_simplexVectorW[0];
				const b3Vector3& b = m_simplexVectorW[1];
				const b3Vector3& c = m_simplexVectorW[2];
				const b3Vector3& d = m_simplexVectorW[3];

				bool hasSeparation = closestPtPointTetrahedron(p, a, b, c, d, m_cachedBC);

				if (hasSeparation)
				{
					m_cachedP1 = m_simplexPointsP[0] * m_cachedBC.m_barycentricCoords[0] +
								 m_simplexPointsP[1] * m_cachedBC.m_barycentricCoords[1] +
								 m_simplexPointsP[2] * m_cachedBC.m_barycentricCoords[2] +
								 m_simplexPointsP[3] * m_cachedBC.m_barycentricCoords[3];

					m_cachedP2 = m_simplexPointsQ[0] * m_cachedBC.m_barycentricCoords[0] +
								 m_simplexPointsQ[1] * m_cachedBC.m_barycentricCoords[1] +
								 m_simplexPointsQ[2] * m_cachedBC.m_barycentricCoords[2] +
								 m_simplexPointsQ[3] * m_cachedBC.m_barycentricCoords[3];

					m_cachedV = m_cachedP1 - m_cachedP2;
					reduceVertices(m_cachedBC.m_usedVertices);
				}
				else
				{
					//					printf("sub distance got penetration\n");

					if (m_cachedBC.m_degenerate)
					{
						m_cachedValidClosest = false;
					}
					else
					{
						m_cachedValidClosest = true;
						//degenerate case == false, penetration = true + zero
						m_cachedV.setValue(b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));
					}
					break;
				}

				m_cachedValidClosest = m_cachedBC.isValid();

				//closest point origin from tetrahedron
				break;
			}
			default:
			{
				m_cachedValidClosest = false;
			}
		};
	}

	return m_cachedValidClosest;
}

//return/calculate the closest vertex
bool b3VoronoiSimplexSolver::closest(b3Vector3& v)
{
	bool succes = updateClosestVectorAndPoints();
	v = m_cachedV;
	return succes;
}

b3Scalar b3VoronoiSimplexSolver::maxVertex()
{
	int i, numverts = numVertices();
	b3Scalar maxV = b3Scalar(0.);
	for (i = 0; i < numverts; i++)
	{
		b3Scalar curLen2 = m_simplexVectorW[i].length2();
		if (maxV < curLen2)
			maxV = curLen2;
	}
	return maxV;
}

//return the current simplex
int b3VoronoiSimplexSolver::getSimplex(b3Vector3* pBuf, b3Vector3* qBuf, b3Vector3* yBuf) const
{
	int i;
	for (i = 0; i < numVertices(); i++)
	{
		yBuf[i] = m_simplexVectorW[i];
		pBuf[i] = m_simplexPointsP[i];
		qBuf[i] = m_simplexPointsQ[i];
	}
	return numVertices();
}

bool b3VoronoiSimplexSolver::inSimplex(const b3Vector3& w)
{
	bool found = false;
	int i, numverts = numVertices();
	//b3Scalar maxV = b3Scalar(0.);

	//w is in the current (reduced) simplex
	for (i = 0; i < numverts; i++)
	{
#ifdef BT_USE_EQUAL_VERTEX_THRESHOLD
		if (m_simplexVectorW[i].distance2(w) <= m_equalVertexThreshold)
#else
		if (m_simplexVectorW[i] == w)
#endif
			found = true;
	}

	//check in case lastW is already removed
	if (w == m_lastW)
		return true;

	return found;
}

void b3VoronoiSimplexSolver::backup_closest(b3Vector3& v)
{
	v = m_cachedV;
}

bool b3VoronoiSimplexSolver::emptySimplex() const
{
	return (numVertices() == 0);
}

void b3VoronoiSimplexSolver::compute_points(b3Vector3& p1, b3Vector3& p2)
{
	updateClosestVectorAndPoints();
	p1 = m_cachedP1;
	p2 = m_cachedP2;
}

bool b3VoronoiSimplexSolver::closestPtPointTriangle(const b3Vector3& p, const b3Vector3& a, const b3Vector3& b, const b3Vector3& c, b3SubSimplexClosestResult& result)
{
	result.m_usedVertices.reset();

	// Check if P in vertex region outside A
	b3Vector3 ab = b - a;
	b3Vector3 ac = c - a;
	b3Vector3 ap = p - a;
	b3Scalar d1 = ab.dot(ap);
	b3Scalar d2 = ac.dot(ap);
	if (d1 <= b3Scalar(0.0) && d2 <= b3Scalar(0.0))
	{
		result.m_closestPointOnSimplex = a;
		result.m_usedVertices.usedVertexA = true;
		result.setBarycentricCoordinates(1, 0, 0);
		return true;  // a; // barycentric coordinates (1,0,0)
	}

	// Check if P in vertex region outside B
	b3Vector3 bp = p - b;
	b3Scalar d3 = ab.dot(bp);
	b3Scalar d4 = ac.dot(bp);
	if (d3 >= b3Scalar(0.0) && d4 <= d3)
	{
		result.m_closestPointOnSimplex = b;
		result.m_usedVertices.usedVertexB = true;
		result.setBarycentricCoordinates(0, 1, 0);

		return true;  // b; // barycentric coordinates (0,1,0)
	}
	// Check if P in edge region of AB, if so return projection of P onto AB
	b3Scalar vc = d1 * d4 - d3 * d2;
	if (vc <= b3Scalar(0.0) && d1 >= b3Scalar(0.0) && d3 <= b3Scalar(0.0))
	{
		b3Scalar v = d1 / (d1 - d3);
		result.m_closestPointOnSimplex = a + v * ab;
		result.m_usedVertices.usedVertexA = true;
		result.m_usedVertices.usedVertexB = true;
		result.setBarycentricCoordinates(1 - v, v, 0);
		return true;
		//return a + v * ab; // barycentric coordinates (1-v,v,0)
	}

	// Check if P in vertex region outside C
	b3Vector3 cp = p - c;
	b3Scalar d5 = ab.dot(cp);
	b3Scalar d6 = ac.dot(cp);
	if (d6 >= b3Scalar(0.0) && d5 <= d6)
	{
		result.m_closestPointOnSimplex = c;
		result.m_usedVertices.usedVertexC = true;
		result.setBarycentricCoordinates(0, 0, 1);
		return true;  //c; // barycentric coordinates (0,0,1)
	}

	// Check if P in edge region of AC, if so return projection of P onto AC
	b3Scalar vb = d5 * d2 - d1 * d6;
	if (vb <= b3Scalar(0.0) && d2 >= b3Scalar(0.0) && d6 <= b3Scalar(0.0))
	{
		b3Scalar w = d2 / (d2 - d6);
		result.m_closestPointOnSimplex = a + w * ac;
		result.m_usedVertices.usedVertexA = true;
		result.m_usedVertices.usedVertexC = true;
		result.setBarycentricCoordinates(1 - w, 0, w);
		return true;
		//return a + w * ac; // barycentric coordinates (1-w,0,w)
	}

	// Check if P in edge region of BC, if so return projection of P onto BC
	b3Scalar va = d3 * d6 - d5 * d4;
	if (va <= b3Scalar(0.0) && (d4 - d3) >= b3Scalar(0.0) && (d5 - d6) >= b3Scalar(0.0))
	{
		b3Scalar w = (d4 - d3) / ((d4 - d3) + (d5 - d6));

		result.m_closestPointOnSimplex = b + w * (c - b);
		result.m_usedVertices.usedVertexB = true;
		result.m_usedVertices.usedVertexC = true;
		result.setBarycentricCoordinates(0, 1 - w, w);
		return true;
		// return b + w * (c - b); // barycentric coordinates (0,1-w,w)
	}

	// P inside face region. Compute Q through its barycentric coordinates (u,v,w)
	b3Scalar denom = b3Scalar(1.0) / (va + vb + vc);
	b3Scalar v = vb * denom;
	b3Scalar w = vc * denom;

	result.m_closestPointOnSimplex = a + ab * v + ac * w;
	result.m_usedVertices.usedVertexA = true;
	result.m_usedVertices.usedVertexB = true;
	result.m_usedVertices.usedVertexC = true;
	result.setBarycentricCoordinates(1 - v - w, v, w);

	return true;
	//	return a + ab * v + ac * w; // = u*a + v*b + w*c, u = va * denom = b3Scalar(1.0) - v - w
}

/// Test if point p and d lie on opposite sides of plane through abc
int b3VoronoiSimplexSolver::pointOutsideOfPlane(const b3Vector3& p, const b3Vector3& a, const b3Vector3& b, const b3Vector3& c, const b3Vector3& d)
{
	b3Vector3 normal = (b - a).cross(c - a);

	b3Scalar signp = (p - a).dot(normal);  // [AP AB AC]
	b3Scalar signd = (d - a).dot(normal);  // [AD AB AC]

#ifdef B3_CATCH_DEGENERATE_TETRAHEDRON
#ifdef BT_USE_DOUBLE_PRECISION
	if (signd * signd < (b3Scalar(1e-8) * b3Scalar(1e-8)))
	{
		return -1;
	}
#else
	if (signd * signd < (b3Scalar(1e-4) * b3Scalar(1e-4)))
	{
		//		printf("affine dependent/degenerate\n");//
		return -1;
	}
#endif

#endif
	// Points on opposite sides if expression signs are opposite
	return signp * signd < b3Scalar(0.);
}

bool b3VoronoiSimplexSolver::closestPtPointTetrahedron(const b3Vector3& p, const b3Vector3& a, const b3Vector3& b, const b3Vector3& c, const b3Vector3& d, b3SubSimplexClosestResult& finalResult)
{
	b3SubSimplexClosestResult tempResult;

	// Start out assuming point inside all halfspaces, so closest to itself
	finalResult.m_closestPointOnSimplex = p;
	finalResult.m_usedVertices.reset();
	finalResult.m_usedVertices.usedVertexA = true;
	finalResult.m_usedVertices.usedVertexB = true;
	finalResult.m_usedVertices.usedVertexC = true;
	finalResult.m_usedVertices.usedVertexD = true;

	int pointOutsideABC = pointOutsideOfPlane(p, a, b, c, d);
	int pointOutsideACD = pointOutsideOfPlane(p, a, c, d, b);
	int pointOutsideADB = pointOutsideOfPlane(p, a, d, b, c);
	int pointOutsideBDC = pointOutsideOfPlane(p, b, d, c, a);

	if (pointOutsideABC < 0 || pointOutsideACD < 0 || pointOutsideADB < 0 || pointOutsideBDC < 0)
	{
		finalResult.m_degenerate = true;
		return false;
	}

	if (!pointOutsideABC && !pointOutsideACD && !pointOutsideADB && !pointOutsideBDC)
	{
		return false;
	}

	b3Scalar bestSqDist = FLT_MAX;
	// If point outside face abc then compute closest point on abc
	if (pointOutsideABC)
	{
		closestPtPointTriangle(p, a, b, c, tempResult);
		b3Vector3 q = tempResult.m_closestPointOnSimplex;

		b3Scalar sqDist = (q - p).dot(q - p);
		// Update best closest point if (squared) distance is less than current best
		if (sqDist < bestSqDist)
		{
			bestSqDist = sqDist;
			finalResult.m_closestPointOnSimplex = q;
			//convert result bitmask!
			finalResult.m_usedVertices.reset();
			finalResult.m_usedVertices.usedVertexA = tempResult.m_usedVertices.usedVertexA;
			finalResult.m_usedVertices.usedVertexB = tempResult.m_usedVertices.usedVertexB;
			finalResult.m_usedVertices.usedVertexC = tempResult.m_usedVertices.usedVertexC;
			finalResult.setBarycentricCoordinates(
				tempResult.m_barycentricCoords[VERTA],
				tempResult.m_barycentricCoords[VERTB],
				tempResult.m_barycentricCoords[VERTC],
				0);
		}
	}

	// Repeat test for face acd
	if (pointOutsideACD)
	{
		closestPtPointTriangle(p, a, c, d, tempResult);
		b3Vector3 q = tempResult.m_closestPointOnSimplex;
		//convert result bitmask!

		b3Scalar sqDist = (q - p).dot(q - p);
		if (sqDist < bestSqDist)
		{
			bestSqDist = sqDist;
			finalResult.m_closestPointOnSimplex = q;
			finalResult.m_usedVertices.reset();
			finalResult.m_usedVertices.usedVertexA = tempResult.m_usedVertices.usedVertexA;

			finalResult.m_usedVertices.usedVertexC = tempResult.m_usedVertices.usedVertexB;
			finalResult.m_usedVertices.usedVertexD = tempResult.m_usedVertices.usedVertexC;
			finalResult.setBarycentricCoordinates(
				tempResult.m_barycentricCoords[VERTA],
				0,
				tempResult.m_barycentricCoords[VERTB],
				tempResult.m_barycentricCoords[VERTC]);
		}
	}
	// Repeat test for face adb

	if (pointOutsideADB)
	{
		closestPtPointTriangle(p, a, d, b, tempResult);
		b3Vector3 q = tempResult.m_closestPointOnSimplex;
		//convert result bitmask!

		b3Scalar sqDist = (q - p).dot(q - p);
		if (sqDist < bestSqDist)
		{
			bestSqDist = sqDist;
			finalResult.m_closestPointOnSimplex = q;
			finalResult.m_usedVertices.reset();
			finalResult.m_usedVertices.usedVertexA = tempResult.m_usedVertices.usedVertexA;
			finalResult.m_usedVertices.usedVertexB = tempResult.m_usedVertices.usedVertexC;

			finalResult.m_usedVertices.usedVertexD = tempResult.m_usedVertices.usedVertexB;
			finalResult.setBarycentricCoordinates(
				tempResult.m_barycentricCoords[VERTA],
				tempResult.m_barycentricCoords[VERTC],
				0,
				tempResult.m_barycentricCoords[VERTB]);
		}
	}
	// Repeat test for face bdc

	if (pointOutsideBDC)
	{
		closestPtPointTriangle(p, b, d, c, tempResult);
		b3Vector3 q = tempResult.m_closestPointOnSimplex;
		//convert result bitmask!
		b3Scalar sqDist = (q - p).dot(q - p);
		if (sqDist < bestSqDist)
		{
			bestSqDist = sqDist;
			finalResult.m_closestPointOnSimplex = q;
			finalResult.m_usedVertices.reset();
			//
			finalResult.m_usedVertices.usedVertexB = tempResult.m_usedVertices.usedVertexA;
			finalResult.m_usedVertices.usedVertexC = tempResult.m_usedVertices.usedVertexC;
			finalResult.m_usedVertices.usedVertexD = tempResult.m_usedVertices.usedVertexB;

			finalResult.setBarycentricCoordinates(
				0,
				tempResult.m_barycentricCoords[VERTA],
				tempResult.m_barycentricCoords[VERTC],
				tempResult.m_barycentricCoords[VERTB]);
		}
	}

	//help! we ended up full !

	if (finalResult.m_usedVertices.usedVertexA &&
		finalResult.m_usedVertices.usedVertexB &&
		finalResult.m_usedVertices.usedVertexC &&
		finalResult.m_usedVertices.usedVertexD)
	{
		return true;
	}

	return true;
}