/*
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.
*/

#include "LinearMath/btScalar.h"
#include "btSimulationIslandManager.h"
#include "BulletCollision/BroadphaseCollision/btDispatcher.h"
#include "BulletCollision/NarrowPhaseCollision/btPersistentManifold.h"
#include "BulletCollision/CollisionDispatch/btCollisionObject.h"
#include "BulletCollision/CollisionDispatch/btCollisionWorld.h"

//#include <stdio.h>
#include "LinearMath/btQuickprof.h"

btSimulationIslandManager::btSimulationIslandManager() : m_splitIslands(true)
{
}

btSimulationIslandManager::~btSimulationIslandManager()
{
}

void btSimulationIslandManager::initUnionFind(int n)
{
	m_unionFind.reset(n);
}

void btSimulationIslandManager::findUnions(btDispatcher* /* dispatcher */, btCollisionWorld* colWorld)
{
	{
		btOverlappingPairCache* pairCachePtr = colWorld->getPairCache();
		const int numOverlappingPairs = pairCachePtr->getNumOverlappingPairs();
		if (numOverlappingPairs)
		{
			btBroadphasePair* pairPtr = pairCachePtr->getOverlappingPairArrayPtr();

			for (int i = 0; i < numOverlappingPairs; i++)
			{
				const btBroadphasePair& collisionPair = pairPtr[i];
				btCollisionObject* colObj0 = (btCollisionObject*)collisionPair.m_pProxy0->m_clientObject;
				btCollisionObject* colObj1 = (btCollisionObject*)collisionPair.m_pProxy1->m_clientObject;

				if (((colObj0) && ((colObj0)->mergesSimulationIslands())) &&
					((colObj1) && ((colObj1)->mergesSimulationIslands())))
				{
					m_unionFind.unite((colObj0)->getIslandTag(),
									  (colObj1)->getIslandTag());
				}
			}
		}
	}
}

#ifdef STATIC_SIMULATION_ISLAND_OPTIMIZATION
void btSimulationIslandManager::updateActivationState(btCollisionWorld* colWorld, btDispatcher* dispatcher)
{
	// put the index into m_controllers into m_tag
	int index = 0;
	{
		int i;
		for (i = 0; i < colWorld->getCollisionObjectArray().size(); i++)
		{
			btCollisionObject* collisionObject = colWorld->getCollisionObjectArray()[i];
			//Adding filtering here
			if (!collisionObject->isStaticOrKinematicObject())
			{
				collisionObject->setIslandTag(index++);
			}
			collisionObject->setCompanionId(-1);
			collisionObject->setHitFraction(btScalar(1.));
		}
	}
	// do the union find

	initUnionFind(index);

	findUnions(dispatcher, colWorld);
}

void btSimulationIslandManager::storeIslandActivationState(btCollisionWorld* colWorld)
{
	// put the islandId ('find' value) into m_tag
	{
		int index = 0;
		int i;
		for (i = 0; i < colWorld->getCollisionObjectArray().size(); i++)
		{
			btCollisionObject* collisionObject = colWorld->getCollisionObjectArray()[i];
			if (!collisionObject->isStaticOrKinematicObject())
			{
				collisionObject->setIslandTag(m_unionFind.find(index));
				//Set the correct object offset in Collision Object Array
				m_unionFind.getElement(index).m_sz = i;
				collisionObject->setCompanionId(-1);
				index++;
			}
			else
			{
				collisionObject->setIslandTag(-1);
				collisionObject->setCompanionId(-2);
			}
		}
	}
}

#else  //STATIC_SIMULATION_ISLAND_OPTIMIZATION
void btSimulationIslandManager::updateActivationState(btCollisionWorld* colWorld, btDispatcher* dispatcher)
{
	initUnionFind(int(colWorld->getCollisionObjectArray().size()));

	// put the index into m_controllers into m_tag
	{
		int index = 0;
		int i;
		for (i = 0; i < colWorld->getCollisionObjectArray().size(); i++)
		{
			btCollisionObject* collisionObject = colWorld->getCollisionObjectArray()[i];
			collisionObject->setIslandTag(index);
			collisionObject->setCompanionId(-1);
			collisionObject->setHitFraction(btScalar(1.));
			index++;
		}
	}
	// do the union find

	findUnions(dispatcher, colWorld);
}

void btSimulationIslandManager::storeIslandActivationState(btCollisionWorld* colWorld)
{
	// put the islandId ('find' value) into m_tag
	{
		int index = 0;
		int i;
		for (i = 0; i < colWorld->getCollisionObjectArray().size(); i++)
		{
			btCollisionObject* collisionObject = colWorld->getCollisionObjectArray()[i];
			if (!collisionObject->isStaticOrKinematicObject())
			{
				collisionObject->setIslandTag(m_unionFind.find(index));
				collisionObject->setCompanionId(-1);
			}
			else
			{
				collisionObject->setIslandTag(-1);
				collisionObject->setCompanionId(-2);
			}
			index++;
		}
	}
}

#endif  //STATIC_SIMULATION_ISLAND_OPTIMIZATION

inline int getIslandId(const btPersistentManifold* lhs)
{
	int islandId;
	const btCollisionObject* rcolObj0 = static_cast<const btCollisionObject*>(lhs->getBody0());
	const btCollisionObject* rcolObj1 = static_cast<const btCollisionObject*>(lhs->getBody1());
	islandId = rcolObj0->getIslandTag() >= 0 ? rcolObj0->getIslandTag() : rcolObj1->getIslandTag();
	return islandId;
}

/// function object that routes calls to operator<
class btPersistentManifoldSortPredicate
{
public:
	SIMD_FORCE_INLINE bool operator()(const btPersistentManifold* lhs, const btPersistentManifold* rhs) const
	{
		return getIslandId(lhs) < getIslandId(rhs);
	}
};

class btPersistentManifoldSortPredicateDeterministic
{
public:
	SIMD_FORCE_INLINE bool operator()(const btPersistentManifold* lhs, const btPersistentManifold* rhs) const
	{
		return (
			(getIslandId(lhs) < getIslandId(rhs)) || ((getIslandId(lhs) == getIslandId(rhs)) && lhs->getBody0()->getBroadphaseHandle()->m_uniqueId < rhs->getBody0()->getBroadphaseHandle()->m_uniqueId) || ((getIslandId(lhs) == getIslandId(rhs)) && (lhs->getBody0()->getBroadphaseHandle()->m_uniqueId == rhs->getBody0()->getBroadphaseHandle()->m_uniqueId) && (lhs->getBody1()->getBroadphaseHandle()->m_uniqueId < rhs->getBody1()->getBroadphaseHandle()->m_uniqueId)));
	}
};

void btSimulationIslandManager::buildIslands(btDispatcher* dispatcher, btCollisionWorld* collisionWorld)
{
	BT_PROFILE("islandUnionFindAndQuickSort");

	btCollisionObjectArray& collisionObjects = collisionWorld->getCollisionObjectArray();

	m_islandmanifold.resize(0);

	//we are going to sort the unionfind array, and store the element id in the size
	//afterwards, we clean unionfind, to make sure no-one uses it anymore

	getUnionFind().sortIslands();
	int numElem = getUnionFind().getNumElements();

	int endIslandIndex = 1;
	int startIslandIndex;

	//update the sleeping state for bodies, if all are sleeping
	for (startIslandIndex = 0; startIslandIndex < numElem; startIslandIndex = endIslandIndex)
	{
		int islandId = getUnionFind().getElement(startIslandIndex).m_id;
		for (endIslandIndex = startIslandIndex + 1; (endIslandIndex < numElem) && (getUnionFind().getElement(endIslandIndex).m_id == islandId); endIslandIndex++)
		{
		}

		//int numSleeping = 0;

		bool allSleeping = true;

		int idx;
		for (idx = startIslandIndex; idx < endIslandIndex; idx++)
		{
			int i = getUnionFind().getElement(idx).m_sz;

			btCollisionObject* colObj0 = collisionObjects[i];
			if ((colObj0->getIslandTag() != islandId) && (colObj0->getIslandTag() != -1))
			{
				//				printf("error in island management\n");
			}

            btAssert((colObj0->getIslandTag() == islandId) || (colObj0->getIslandTag() == -1));
			if (colObj0->getIslandTag() == islandId)
			{
				if (colObj0->getActivationState() == ACTIVE_TAG ||
					colObj0->getActivationState() == DISABLE_DEACTIVATION)
				{
					allSleeping = false;
					break;
				}
			}
		}

		if (allSleeping)
		{
			int idx;
			for (idx = startIslandIndex; idx < endIslandIndex; idx++)
			{
				int i = getUnionFind().getElement(idx).m_sz;
				btCollisionObject* colObj0 = collisionObjects[i];
				if ((colObj0->getIslandTag() != islandId) && (colObj0->getIslandTag() != -1))
				{
					//					printf("error in island management\n");
				}

                btAssert((colObj0->getIslandTag() == islandId) || (colObj0->getIslandTag() == -1));

				if (colObj0->getIslandTag() == islandId)
				{
					colObj0->setActivationState(ISLAND_SLEEPING);
				}
			}
		}
		else
		{
			int idx;
			for (idx = startIslandIndex; idx < endIslandIndex; idx++)
			{
				int i = getUnionFind().getElement(idx).m_sz;

				btCollisionObject* colObj0 = collisionObjects[i];
				if ((colObj0->getIslandTag() != islandId) && (colObj0->getIslandTag() != -1))
				{
					//					printf("error in island management\n");
				}

                 btAssert((colObj0->getIslandTag() == islandId) || (colObj0->getIslandTag() == -1));


				if (colObj0->getIslandTag() == islandId)
				{
					if (colObj0->getActivationState() == ISLAND_SLEEPING)
					{
						colObj0->setActivationState(WANTS_DEACTIVATION);
						colObj0->setDeactivationTime(0.f);
					}
				}
			}
		}
	}

	int i;
	int maxNumManifolds = dispatcher->getNumManifolds();

	//#define SPLIT_ISLANDS 1
	//#ifdef SPLIT_ISLANDS

	//#endif //SPLIT_ISLANDS

	for (i = 0; i < maxNumManifolds; i++)
	{
		btPersistentManifold* manifold = dispatcher->getManifoldByIndexInternal(i);
		if (collisionWorld->getDispatchInfo().m_deterministicOverlappingPairs)
		{
			if (manifold->getNumContacts() == 0)
				continue;
		}

		const btCollisionObject* colObj0 = static_cast<const btCollisionObject*>(manifold->getBody0());
		const btCollisionObject* colObj1 = static_cast<const btCollisionObject*>(manifold->getBody1());

		///@todo: check sleeping conditions!
		if (((colObj0) && colObj0->getActivationState() != ISLAND_SLEEPING) ||
			((colObj1) && colObj1->getActivationState() != ISLAND_SLEEPING))
		{
			//kinematic objects don't merge islands, but wake up all connected objects
			if (colObj0->isKinematicObject() && colObj0->getActivationState() != ISLAND_SLEEPING)
			{
				if (colObj0->hasContactResponse())
					colObj1->activate();
			}
			if (colObj1->isKinematicObject() && colObj1->getActivationState() != ISLAND_SLEEPING)
			{
				if (colObj1->hasContactResponse())
					colObj0->activate();
			}
			if (m_splitIslands)
			{
				//filtering for response
				if (dispatcher->needsResponse(colObj0, colObj1))
					m_islandmanifold.push_back(manifold);
			}
		}
	}
}


///@todo: this is random access, it can be walked 'cache friendly'!
void btSimulationIslandManager::buildAndProcessIslands(btDispatcher* dispatcher, btCollisionWorld* collisionWorld, IslandCallback* callback)
{
	buildIslands(dispatcher, collisionWorld);
    processIslands(dispatcher, collisionWorld, callback);
}

void btSimulationIslandManager::processIslands(btDispatcher* dispatcher, btCollisionWorld* collisionWorld, IslandCallback* callback)
{
    btCollisionObjectArray& collisionObjects = collisionWorld->getCollisionObjectArray();
	int endIslandIndex = 1;
	int startIslandIndex;
	int numElem = getUnionFind().getNumElements();

	BT_PROFILE("processIslands");

	if (!m_splitIslands)
	{
		btPersistentManifold** manifold = dispatcher->getInternalManifoldPointer();
		int maxNumManifolds = dispatcher->getNumManifolds();
		callback->processIsland(&collisionObjects[0], collisionObjects.size(), manifold, maxNumManifolds, -1);
	}
	else
	{
		// Sort manifolds, based on islands
		// Sort the vector using predicate and std::sort
		//std::sort(islandmanifold.begin(), islandmanifold.end(), btPersistentManifoldSortPredicate);

		int numManifolds = int(m_islandmanifold.size());

		//tried a radix sort, but quicksort/heapsort seems still faster
		//@todo rewrite island management
		//btPersistentManifoldSortPredicateDeterministic sorts contact manifolds based on islandid,
		//but also based on object0 unique id and object1 unique id
		if (collisionWorld->getDispatchInfo().m_deterministicOverlappingPairs)
		{
			m_islandmanifold.quickSort(btPersistentManifoldSortPredicateDeterministic());
		}
		else
		{
			m_islandmanifold.quickSort(btPersistentManifoldSortPredicate());
		}

		//m_islandmanifold.heapSort(btPersistentManifoldSortPredicate());

		//now process all active islands (sets of manifolds for now)

		int startManifoldIndex = 0;
		int endManifoldIndex = 1;

		//int islandId;

		//	printf("Start Islands\n");

		//traverse the simulation islands, and call the solver, unless all objects are sleeping/deactivated
		for (startIslandIndex = 0; startIslandIndex < numElem; startIslandIndex = endIslandIndex)
		{
			int islandId = getUnionFind().getElement(startIslandIndex).m_id;

			bool islandSleeping = true;

			for (endIslandIndex = startIslandIndex; (endIslandIndex < numElem) && (getUnionFind().getElement(endIslandIndex).m_id == islandId); endIslandIndex++)
			{
				int i = getUnionFind().getElement(endIslandIndex).m_sz;
				btCollisionObject* colObj0 = collisionObjects[i];
				m_islandBodies.push_back(colObj0);
				if (colObj0->isActive())
					islandSleeping = false;
			}

			//find the accompanying contact manifold for this islandId
			int numIslandManifolds = 0;
			btPersistentManifold** startManifold = 0;

			if (startManifoldIndex < numManifolds)
			{
				int curIslandId = getIslandId(m_islandmanifold[startManifoldIndex]);
				if (curIslandId == islandId)
				{
					startManifold = &m_islandmanifold[startManifoldIndex];

					for (endManifoldIndex = startManifoldIndex + 1; (endManifoldIndex < numManifolds) && (islandId == getIslandId(m_islandmanifold[endManifoldIndex])); endManifoldIndex++)
					{
					}
					/// Process the actual simulation, only if not sleeping/deactivated
					numIslandManifolds = endManifoldIndex - startManifoldIndex;
				}
			}

			if (!islandSleeping)
			{
				callback->processIsland(&m_islandBodies[0], m_islandBodies.size(), startManifold, numIslandManifolds, islandId);
				//			printf("Island callback of size:%d bodies, %d manifolds\n",islandBodies.size(),numIslandManifolds);
			}

			if (numIslandManifolds)
			{
				startManifoldIndex = endManifoldIndex;
			}

			m_islandBodies.resize(0);
		}
	}  // else if(!splitIslands)
}