//
// Copyright (c) 2008-2014 the Urho3D project.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#include "Precompiled.h"
#include "CollisionShape.h"
#include "Constraint.h"
#include "Context.h"
#include "DebugRenderer.h"
#include "Log.h"
#include "Model.h"
#include "Mutex.h"
#include "PhysicsEvents.h"
#include "PhysicsUtils.h"
#include "PhysicsWorld.h"
#include "Profiler.h"
#include "Ray.h"
#include "RigidBody.h"
#include "Scene.h"
#include "SceneEvents.h"
#include "Sort.h"

#include <BulletCollision/BroadphaseCollision/btDbvtBroadphase.h>
#include <BulletCollision/CollisionDispatch/btDefaultCollisionConfiguration.h>
#include <BulletCollision/CollisionDispatch/btInternalEdgeUtility.h>
#include <BulletCollision/CollisionShapes/btBoxShape.h>
#include <BulletCollision/CollisionShapes/btSphereShape.h>
#include <BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h>
#include <BulletDynamics/Dynamics/btDiscreteDynamicsWorld.h>

extern ContactAddedCallback gContactAddedCallback;

namespace Urho3D
{

const char* PHYSICS_CATEGORY = "Physics";
extern const char* SUBSYSTEM_CATEGORY;

static const int MAX_SOLVER_ITERATIONS = 256;
static const int DEFAULT_FPS = 60;
static const Vector3 DEFAULT_GRAVITY = Vector3(0.0f, -9.81f, 0.0f);

static bool CompareRaycastResults(const PhysicsRaycastResult& lhs, const PhysicsRaycastResult& rhs)
{
    return lhs.distance_ < rhs.distance_;
}

void InternalPreTickCallback(btDynamicsWorld *world, btScalar timeStep)
{
    static_cast<PhysicsWorld*>(world->getWorldUserInfo())->PreStep(timeStep);
}

void InternalTickCallback(btDynamicsWorld *world, btScalar timeStep)
{
    static_cast<PhysicsWorld*>(world->getWorldUserInfo())->PostStep(timeStep);
}

static bool CustomMaterialCombinerCallback(btManifoldPoint& cp, const btCollisionObjectWrapper* colObj0Wrap, int partId0, int index0, const btCollisionObjectWrapper* colObj1Wrap, int partId1, int index1)
{
    btAdjustInternalEdgeContacts(cp, colObj1Wrap, colObj0Wrap, partId1, index1);

    cp.m_combinedFriction = colObj0Wrap->getCollisionObject()->getFriction() * colObj1Wrap->getCollisionObject()->getFriction();
    cp.m_combinedRestitution = colObj0Wrap->getCollisionObject()->getRestitution() * colObj1Wrap->getCollisionObject()->getRestitution();

    return true;
}

/// Callback for physics world queries.
struct PhysicsQueryCallback : public btCollisionWorld::ContactResultCallback
{
    /// Construct.
    PhysicsQueryCallback(PODVector<RigidBody*>& result, unsigned collisionMask) : result_(result),
        collisionMask_(collisionMask)
    {
    }

    /// Add a contact result.
    virtual btScalar addSingleResult(btManifoldPoint &, const btCollisionObjectWrapper *colObj0Wrap, int, int, const btCollisionObjectWrapper *colObj1Wrap, int, int)
    {
        RigidBody* body = reinterpret_cast<RigidBody*>(colObj0Wrap->getCollisionObject()->getUserPointer());
        if (body && !result_.Contains(body) && (body->GetCollisionLayer() & collisionMask_))
            result_.Push(body);
        body = reinterpret_cast<RigidBody*>(colObj1Wrap->getCollisionObject()->getUserPointer());
        if (body && !result_.Contains(body) && (body->GetCollisionLayer() & collisionMask_))
            result_.Push(body);
        return 0.0f;
    }

    /// Found rigid bodies.
    PODVector<RigidBody*>& result_;
    /// Collision mask for the query.
    unsigned collisionMask_;
};

PhysicsWorld::PhysicsWorld(Context* context) :
    Component(context),
    collisionConfiguration_(0),
    collisionDispatcher_(0),
    broadphase_(0),
    solver_(0),
    world_(0),
    fps_(DEFAULT_FPS),
    timeAcc_(0.0f),
    maxNetworkAngularVelocity_(DEFAULT_MAX_NETWORK_ANGULAR_VELOCITY),
    interpolation_(true),
    internalEdge_(true),
    applyingTransforms_(false),
    debugRenderer_(0),
    debugMode_(btIDebugDraw::DBG_DrawWireframe | btIDebugDraw::DBG_DrawConstraints | btIDebugDraw::DBG_DrawConstraintLimits)
{
    gContactAddedCallback = CustomMaterialCombinerCallback;

    collisionConfiguration_ = new btDefaultCollisionConfiguration();
    collisionDispatcher_ = new btCollisionDispatcher(collisionConfiguration_);
    broadphase_ = new btDbvtBroadphase();
    solver_ = new btSequentialImpulseConstraintSolver();
    world_ = new btDiscreteDynamicsWorld(collisionDispatcher_, broadphase_, solver_, collisionConfiguration_);

    world_->setGravity(ToBtVector3(DEFAULT_GRAVITY));
    world_->getDispatchInfo().m_useContinuous = true;
    world_->getSolverInfo().m_splitImpulse = false; // Disable by default for performance
    world_->setDebugDrawer(this);
    world_->setInternalTickCallback(InternalPreTickCallback, static_cast<void*>(this), true);
    world_->setInternalTickCallback(InternalTickCallback, static_cast<void*>(this), false);
}

PhysicsWorld::~PhysicsWorld()
{
    if (scene_)
    {
        // Force all remaining constraints, rigid bodies and collision shapes to release themselves
        for (PODVector<Constraint*>::Iterator i = constraints_.Begin(); i != constraints_.End(); ++i)
            (*i)->ReleaseConstraint();

        for (PODVector<RigidBody*>::Iterator i = rigidBodies_.Begin(); i != rigidBodies_.End(); ++i)
            (*i)->ReleaseBody();

        for (PODVector<CollisionShape*>::Iterator i = collisionShapes_.Begin(); i != collisionShapes_.End(); ++i)
            (*i)->ReleaseShape();
    }

    delete world_;
    world_ = 0;

    delete solver_;
    solver_ = 0;

    delete broadphase_;
    broadphase_ = 0;

    delete collisionDispatcher_;
    collisionDispatcher_ = 0;

    delete collisionConfiguration_;
    collisionConfiguration_ = 0;
}

void PhysicsWorld::RegisterObject(Context* context)
{
    context->RegisterFactory<PhysicsWorld>(SUBSYSTEM_CATEGORY);

    ACCESSOR_ATTRIBUTE(PhysicsWorld, VAR_VECTOR3, "Gravity", GetGravity, SetGravity, Vector3, DEFAULT_GRAVITY, AM_DEFAULT);
    ATTRIBUTE(PhysicsWorld, VAR_INT, "Physics FPS", fps_, DEFAULT_FPS, AM_DEFAULT);
    ACCESSOR_ATTRIBUTE(PhysicsWorld, VAR_INT, "Solver Iterations", GetNumIterations, SetNumIterations, int, 10, AM_DEFAULT);
    ATTRIBUTE(PhysicsWorld, VAR_FLOAT, "Net Max Angular Vel.", maxNetworkAngularVelocity_, DEFAULT_MAX_NETWORK_ANGULAR_VELOCITY, AM_DEFAULT);
    ATTRIBUTE(PhysicsWorld, VAR_BOOL, "Interpolation", interpolation_, true, AM_FILE);
    ATTRIBUTE(PhysicsWorld, VAR_BOOL, "Internal Edge Utility", internalEdge_, true, AM_DEFAULT);
    ACCESSOR_ATTRIBUTE(PhysicsWorld, VAR_BOOL, "Split Impulse", GetSplitImpulse, SetSplitImpulse, bool, false, AM_DEFAULT);
}

bool PhysicsWorld::isVisible(const btVector3& aabbMin, const btVector3& aabbMax)
{
    if (debugRenderer_)
        return debugRenderer_->IsInside(BoundingBox(ToVector3(aabbMin), ToVector3(aabbMax)));
    else
        return false;
}

void PhysicsWorld::drawLine(const btVector3& from, const btVector3& to, const btVector3& color)
{
    if (debugRenderer_)
        debugRenderer_->AddLine(ToVector3(from), ToVector3(to), Color(color.x(), color.y(), color.z()), debugDepthTest_);
}

void PhysicsWorld::DrawDebugGeometry(DebugRenderer* debug, bool depthTest)
{
    if (debug)
    {
        PROFILE(PhysicsDrawDebug);

        debugRenderer_ = debug;
        debugDepthTest_ = depthTest;
        world_->debugDrawWorld();
        debugRenderer_ = 0;
    }
}

void PhysicsWorld::reportErrorWarning(const char* warningString)
{
    LOGWARNING("Physics: " + String(warningString));
}

void PhysicsWorld::Update(float timeStep)
{
    PROFILE(UpdatePhysics);

    float internalTimeStep = 1.0f / fps_;
    delayedWorldTransforms_.Clear();

    if (interpolation_)
    {
        int maxSubSteps = (int)(timeStep * fps_) + 1;
        world_->stepSimulation(timeStep, maxSubSteps, internalTimeStep);
    }
    else
    {
        timeAcc_ += timeStep;
        while (timeAcc_ >= internalTimeStep)
        {
            world_->stepSimulation(internalTimeStep, 0, internalTimeStep);
            timeAcc_ -= internalTimeStep;
        }
    }

    // Apply delayed (parented) world transforms now
    while (!delayedWorldTransforms_.Empty())
    {
        for (HashMap<RigidBody*, DelayedWorldTransform>::Iterator i = delayedWorldTransforms_.Begin();
            i != delayedWorldTransforms_.End(); ++i)
        {
            const DelayedWorldTransform& transform = i->second_;

            // If parent's transform has already been assigned, can proceed
            if (!delayedWorldTransforms_.Contains(transform.parentRigidBody_))
            {
                transform.rigidBody_->ApplyWorldTransform(transform.worldPosition_, transform.worldRotation_);
                delayedWorldTransforms_.Erase(i);
            }
        }
    }
}

void PhysicsWorld::UpdateCollisions()
{
    world_->performDiscreteCollisionDetection();
}

void PhysicsWorld::SetFps(int fps)
{
    fps_ = Clamp(fps, 1, 1000);
    
    MarkNetworkUpdate();
}

void PhysicsWorld::SetGravity(Vector3 gravity)
{
    world_->setGravity(ToBtVector3(gravity));
    
    MarkNetworkUpdate();
}

void PhysicsWorld::SetNumIterations(int num)
{
    num = Clamp(num, 1, MAX_SOLVER_ITERATIONS);
    world_->getSolverInfo().m_numIterations = num;
    
    MarkNetworkUpdate();
}

void PhysicsWorld::SetInterpolation(bool enable)
{
    interpolation_ = enable;
}

void PhysicsWorld::SetInternalEdge(bool enable)
{
    internalEdge_ = enable;
    
    MarkNetworkUpdate();
}

void PhysicsWorld::SetSplitImpulse(bool enable)
{
    world_->getSolverInfo().m_splitImpulse = enable;
    
    MarkNetworkUpdate();
}

void PhysicsWorld::SetMaxNetworkAngularVelocity(float velocity)
{
    maxNetworkAngularVelocity_ = Clamp(velocity, 1.0f, 32767.0f);
    
    MarkNetworkUpdate();
}

void PhysicsWorld::Raycast(PODVector<PhysicsRaycastResult>& result, const Ray& ray, float maxDistance, unsigned collisionMask)
{
    PROFILE(PhysicsRaycast);

    btCollisionWorld::AllHitsRayResultCallback rayCallback(ToBtVector3(ray.origin_), ToBtVector3(ray.origin_ +
        maxDistance * ray.direction_));
    rayCallback.m_collisionFilterGroup = (short)0xffff;
    rayCallback.m_collisionFilterMask = collisionMask;

    world_->rayTest(rayCallback.m_rayFromWorld, rayCallback.m_rayToWorld, rayCallback);

    for (int i = 0; i < rayCallback.m_collisionObjects.size(); ++i)
    {
        PhysicsRaycastResult newResult;
        newResult.body_ = static_cast<RigidBody*>(rayCallback.m_collisionObjects[i]->getUserPointer());
        newResult.position_ = ToVector3(rayCallback.m_hitPointWorld[i]);
        newResult.normal_ = ToVector3(rayCallback.m_hitNormalWorld[i]);
        newResult.distance_ = (newResult.position_ - ray.origin_).Length();
        result.Push(newResult);
    }

    Sort(result.Begin(), result.End(), CompareRaycastResults);
}

void PhysicsWorld::RaycastSingle(PhysicsRaycastResult& result, const Ray& ray, float maxDistance, unsigned collisionMask)
{
    PROFILE(PhysicsRaycastSingle);

    btCollisionWorld::ClosestRayResultCallback rayCallback(ToBtVector3(ray.origin_), ToBtVector3(ray.origin_ +
        maxDistance * ray.direction_));
    rayCallback.m_collisionFilterGroup = (short)0xffff;
    rayCallback.m_collisionFilterMask = collisionMask;

    world_->rayTest(rayCallback.m_rayFromWorld, rayCallback.m_rayToWorld, rayCallback);

    if (rayCallback.hasHit())
    {
        result.position_ = ToVector3(rayCallback.m_hitPointWorld);
        result.normal_ = ToVector3(rayCallback.m_hitNormalWorld);
        result.distance_ = (result.position_ - ray.origin_).Length();
        result.body_ = static_cast<RigidBody*>(rayCallback.m_collisionObject->getUserPointer());
    }
    else
    {
        result.position_ = Vector3::ZERO;
        result.normal_ = Vector3::ZERO;
        result.distance_ = M_INFINITY;
        result.body_ = 0;
    }
}

void PhysicsWorld::SphereCast(PhysicsRaycastResult& result, const Ray& ray, float radius, float maxDistance, unsigned collisionMask)
{
    PROFILE(PhysicsSphereCast);

    btSphereShape shape(radius);

    btCollisionWorld::ClosestConvexResultCallback convexCallback(ToBtVector3(ray.origin_), ToBtVector3(ray.origin_ +
        maxDistance * ray.direction_));
    convexCallback.m_collisionFilterGroup = (short)0xffff;
    convexCallback.m_collisionFilterMask = collisionMask;

    world_->convexSweepTest(&shape, btTransform(btQuaternion::getIdentity(), convexCallback.m_convexFromWorld),
        btTransform(btQuaternion::getIdentity(), convexCallback.m_convexToWorld), convexCallback);

    if (convexCallback.hasHit())
    {
        result.body_ = static_cast<RigidBody*>(convexCallback.m_hitCollisionObject->getUserPointer());
        result.position_ = ToVector3(convexCallback.m_hitPointWorld);
        result.normal_ = ToVector3(convexCallback.m_hitNormalWorld);
        result.distance_ = (result.position_ - ray.origin_).Length();
    }
    else
    {
        result.body_ = 0;
        result.position_ = Vector3::ZERO;
        result.normal_ = Vector3::ZERO;
        result.distance_ = M_INFINITY;
    }
}

void PhysicsWorld::RemoveCachedGeometry(Model* model)
{
    for (HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator i = triMeshCache_.Begin();
        i != triMeshCache_.End();)
    {
        HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator current = i++;
        if (current->first_.first_ == model)
            triMeshCache_.Erase(current);
    }
    for (HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator i = convexCache_.Begin();
        i != convexCache_.End();)
    {
        HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator current = i++;
        if (current->first_.first_ == model)
            convexCache_.Erase(current);
    }
}

void PhysicsWorld::GetRigidBodies(PODVector<RigidBody*>& result, const Sphere& sphere, unsigned collisionMask)
{
    PROFILE(PhysicsSphereQuery);

    result.Clear();

    btSphereShape sphereShape(sphere.radius_);
    btRigidBody* tempRigidBody = new btRigidBody(1.0f, 0, &sphereShape);
    tempRigidBody->setWorldTransform(btTransform(btQuaternion::getIdentity(), ToBtVector3(sphere.center_)));
    // Need to activate the temporary rigid body to get reliable results from static, sleeping objects
    tempRigidBody->activate();
    world_->addRigidBody(tempRigidBody);

    PhysicsQueryCallback callback(result, collisionMask);
    world_->contactTest(tempRigidBody, callback);

    world_->removeRigidBody(tempRigidBody);
    delete tempRigidBody;
}

void PhysicsWorld::GetRigidBodies(PODVector<RigidBody*>& result, const BoundingBox& box, unsigned collisionMask)
{
    PROFILE(PhysicsBoxQuery);

    result.Clear();

    btBoxShape boxShape(ToBtVector3(box.HalfSize()));
    btRigidBody* tempRigidBody = new btRigidBody(1.0f, 0, &boxShape);
    tempRigidBody->setWorldTransform(btTransform(btQuaternion::getIdentity(), ToBtVector3(box.Center())));
    tempRigidBody->activate();
    world_->addRigidBody(tempRigidBody);

    PhysicsQueryCallback callback(result, collisionMask);
    world_->contactTest(tempRigidBody, callback);

    world_->removeRigidBody(tempRigidBody);
    delete tempRigidBody;
}

void PhysicsWorld::GetRigidBodies(PODVector<RigidBody*>& result, const RigidBody* body)
{
    PROFILE(GetCollidingBodies);

    result.Clear();

    for (HashMap<Pair<WeakPtr<RigidBody>, WeakPtr<RigidBody> >, btPersistentManifold*>::Iterator i = currentCollisions_.Begin();
        i != currentCollisions_.End(); ++i)
    {
        if (i->first_.first_ == body)
            result.Push(i->first_.second_);
        else if (i->first_.second_ == body)
            result.Push(i->first_.first_);
    }
}

Vector3 PhysicsWorld::GetGravity() const
{
    return ToVector3(world_->getGravity());
}

int PhysicsWorld::GetNumIterations() const
{
    return world_->getSolverInfo().m_numIterations;
}

bool PhysicsWorld::GetSplitImpulse() const
{
    return world_->getSolverInfo().m_splitImpulse != 0;
}

void PhysicsWorld::AddRigidBody(RigidBody* body)
{
    rigidBodies_.Push(body);
}

void PhysicsWorld::RemoveRigidBody(RigidBody* body)
{
    rigidBodies_.Remove(body);
}

void PhysicsWorld::AddCollisionShape(CollisionShape* shape)
{
    collisionShapes_.Push(shape);
}

void PhysicsWorld::RemoveCollisionShape(CollisionShape* shape)
{
    collisionShapes_.Remove(shape);
}

void PhysicsWorld::AddConstraint(Constraint* constraint)
{
    constraints_.Push(constraint);
}

void PhysicsWorld::RemoveConstraint(Constraint* constraint)
{
    constraints_.Remove(constraint);
}

void PhysicsWorld::AddDelayedWorldTransform(const DelayedWorldTransform& transform)
{
    delayedWorldTransforms_[transform.rigidBody_] = transform;
}

void PhysicsWorld::DrawDebugGeometry(bool depthTest)
{
    DebugRenderer* debug = GetComponent<DebugRenderer>();
    DrawDebugGeometry(debug, depthTest);
}

void PhysicsWorld::SetDebugRenderer(DebugRenderer* debug)
{
    debugRenderer_ = debug;
}

void PhysicsWorld::SetDebugDepthTest(bool enable)
{
    debugDepthTest_ = enable;
}

void PhysicsWorld::CleanupGeometryCache()
{
    // Remove cached shapes whose only reference is the cache itself
    for (HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator i = triMeshCache_.Begin();
        i != triMeshCache_.End();)
    {
        HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator current = i++;
        if (current->second_.Refs() == 1)
            triMeshCache_.Erase(current);
    }
    for (HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator i = convexCache_.Begin();
        i != convexCache_.End();)
    {
        HashMap<Pair<Model*, unsigned>, SharedPtr<CollisionGeometryData> >::Iterator current = i++;
        if (current->second_.Refs() == 1)
            convexCache_.Erase(current);
    }
}

void PhysicsWorld::OnNodeSet(Node* node)
{
    // Subscribe to the scene subsystem update, which will trigger the physics simulation step
    if (node)
    {
        scene_ = GetScene();
        SubscribeToEvent(node, E_SCENESUBSYSTEMUPDATE, HANDLER(PhysicsWorld, HandleSceneSubsystemUpdate));
    }
}

void PhysicsWorld::HandleSceneSubsystemUpdate(StringHash eventType, VariantMap& eventData)
{
    using namespace SceneSubsystemUpdate;

    Update(eventData[P_TIMESTEP].GetFloat());
}

void PhysicsWorld::PreStep(float timeStep)
{
    // Send pre-step event
    using namespace PhysicsPreStep;

    VariantMap& eventData = GetEventDataMap();
    eventData[P_WORLD] = this;
    eventData[P_TIMESTEP] = timeStep;
    SendEvent(E_PHYSICSPRESTEP, eventData);

    // Start profiling block for the actual simulation step
#ifdef URHO3D_PROFILING
    Profiler* profiler = GetSubsystem<Profiler>();
    if (profiler)
        profiler->BeginBlock("StepSimulation");
#endif
}

void PhysicsWorld::PostStep(float timeStep)
{
#ifdef URHO3D_PROFILING
    Profiler* profiler = GetSubsystem<Profiler>();
    if (profiler)
        profiler->EndBlock();
#endif

    SendCollisionEvents();

    // Send post-step event
    using namespace PhysicsPreStep;

    VariantMap& eventData = GetEventDataMap();
    eventData[P_WORLD] = this;
    eventData[P_TIMESTEP] = timeStep;
    SendEvent(E_PHYSICSPOSTSTEP, eventData);
}

void PhysicsWorld::SendCollisionEvents()
{
    PROFILE(SendCollisionEvents);

    currentCollisions_.Clear();
    physicsCollisionData_.Clear();
    nodeCollisionData_.Clear();
    
    int numManifolds = collisionDispatcher_->getNumManifolds();

    if (numManifolds)
    {
        physicsCollisionData_[PhysicsCollision::P_WORLD] = this;

        for (int i = 0; i < numManifolds; ++i)
        {
            btPersistentManifold* contactManifold = collisionDispatcher_->getManifoldByIndexInternal(i);
            int numContacts = contactManifold->getNumContacts();
            // First check that there are actual contacts, as the manifold exists also when objects are close but not touching
            if (!numContacts)
                continue;

            const btCollisionObject* objectA = contactManifold->getBody0();
            const btCollisionObject* objectB = contactManifold->getBody1();

            RigidBody* bodyA = static_cast<RigidBody*>(objectA->getUserPointer());
            RigidBody* bodyB = static_cast<RigidBody*>(objectB->getUserPointer());
            // If it's not a rigidbody, maybe a ghost object
            if (!bodyA || !bodyB)
                continue;

            // Skip collision event signaling if both objects are static, or if collision event mode does not match
            if (bodyA->GetMass() == 0.0f && bodyB->GetMass() == 0.0f)
                continue;
            if (bodyA->GetCollisionEventMode() == COLLISION_NEVER || bodyB->GetCollisionEventMode() == COLLISION_NEVER)
                continue;
            if (bodyA->GetCollisionEventMode() == COLLISION_ACTIVE && bodyB->GetCollisionEventMode() == COLLISION_ACTIVE &&
                !bodyA->IsActive() && !bodyB->IsActive())
                continue;

            WeakPtr<RigidBody> bodyWeakA(bodyA);
            WeakPtr<RigidBody> bodyWeakB(bodyB);

            Pair<WeakPtr<RigidBody>, WeakPtr<RigidBody> > bodyPair;
            if (bodyA < bodyB)
                bodyPair = MakePair(bodyWeakA, bodyWeakB);
            else
                bodyPair = MakePair(bodyWeakB, bodyWeakA);

            // First only store the collision pair as weak pointers and the manifold pointer, so user code can safely destroy
            // objects during collision event handling
            currentCollisions_[bodyPair] = contactManifold;
        }

        for (HashMap<Pair<WeakPtr<RigidBody>, WeakPtr<RigidBody> >, btPersistentManifold*>::Iterator i = currentCollisions_.Begin();
            i != currentCollisions_.End(); ++i)
        {
            RigidBody* bodyA = i->first_.first_;
            RigidBody* bodyB = i->first_.second_;
            if (!bodyA || !bodyB)
                continue;

            btPersistentManifold* contactManifold = i->second_;
            int numContacts = contactManifold->getNumContacts();

            Node* nodeA = bodyA->GetNode();
            Node* nodeB = bodyB->GetNode();
            WeakPtr<Node> nodeWeakA(nodeA);
            WeakPtr<Node> nodeWeakB(nodeB);

            bool trigger = bodyA->IsTrigger() || bodyB->IsTrigger();
            bool newCollision = !previousCollisions_.Contains(i->first_);

            physicsCollisionData_[PhysicsCollision::P_NODEA] = nodeA;
            physicsCollisionData_[PhysicsCollision::P_NODEB] = nodeB;
            physicsCollisionData_[PhysicsCollision::P_BODYA] = bodyA;
            physicsCollisionData_[PhysicsCollision::P_BODYB] = bodyB;
            physicsCollisionData_[PhysicsCollision::P_TRIGGER] = trigger;

            contacts_.Clear();

            for (int j = 0; j < numContacts; ++j)
            {
                btManifoldPoint& point = contactManifold->getContactPoint(j);
                contacts_.WriteVector3(ToVector3(point.m_positionWorldOnB));
                contacts_.WriteVector3(ToVector3(point.m_normalWorldOnB));
                contacts_.WriteFloat(point.m_distance1);
                contacts_.WriteFloat(point.m_appliedImpulse);
            }

            physicsCollisionData_[PhysicsCollision::P_CONTACTS] = contacts_.GetBuffer();

            // Send separate collision start event if collision is new
            if (newCollision)
            {
                SendEvent(E_PHYSICSCOLLISIONSTART, physicsCollisionData_);
                // Skip rest of processing if either of the nodes or bodies is removed as a response to the event
                if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                    continue;
            }

            // Then send the ongoing collision event
            SendEvent(E_PHYSICSCOLLISION, physicsCollisionData_);
            if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                continue;

            nodeCollisionData_[NodeCollision::P_BODY] = bodyA;
            nodeCollisionData_[NodeCollision::P_OTHERNODE] = nodeB;
            nodeCollisionData_[NodeCollision::P_OTHERBODY] = bodyB;
            nodeCollisionData_[NodeCollision::P_TRIGGER] = trigger;
            nodeCollisionData_[NodeCollision::P_CONTACTS] = contacts_.GetBuffer();

            if (newCollision)
            {
                nodeA->SendEvent(E_NODECOLLISIONSTART, nodeCollisionData_);
                if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                    continue;
            }

            nodeA->SendEvent(E_NODECOLLISION, nodeCollisionData_);
            if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                continue;

            contacts_.Clear();
            for (int j = 0; j < numContacts; ++j)
            {
                btManifoldPoint& point = contactManifold->getContactPoint(j);
                contacts_.WriteVector3(ToVector3(point.m_positionWorldOnB));
                contacts_.WriteVector3(-ToVector3(point.m_normalWorldOnB));
                contacts_.WriteFloat(point.m_distance1);
                contacts_.WriteFloat(point.m_appliedImpulse);
            }

            nodeCollisionData_[NodeCollision::P_BODY] = bodyB;
            nodeCollisionData_[NodeCollision::P_OTHERNODE] = nodeA;
            nodeCollisionData_[NodeCollision::P_OTHERBODY] = bodyA;
            nodeCollisionData_[NodeCollision::P_CONTACTS] = contacts_.GetBuffer();

            if (newCollision)
            {
                nodeB->SendEvent(E_NODECOLLISIONSTART, nodeCollisionData_);
                if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                    continue;
            }

            nodeB->SendEvent(E_NODECOLLISION, nodeCollisionData_);
        }
    }

    // Send collision end events as applicable
    {
        physicsCollisionData_[PhysicsCollisionEnd::P_WORLD] = this;

        for (HashMap<Pair<WeakPtr<RigidBody>, WeakPtr<RigidBody> >, btPersistentManifold*>::Iterator i = previousCollisions_.Begin(); i != previousCollisions_.End(); ++i)
        {
            if (!currentCollisions_.Contains(i->first_))
            {
                RigidBody* bodyA = i->first_.first_;
                RigidBody* bodyB = i->first_.second_;
                if (!bodyA || !bodyB)
                    continue;

                bool trigger = bodyA->IsTrigger() || bodyB->IsTrigger();

                // Skip collision event signaling if both objects are static, or if collision event mode does not match
                if (bodyA->GetMass() == 0.0f && bodyB->GetMass() == 0.0f)
                    continue;
                if (bodyA->GetCollisionEventMode() == COLLISION_NEVER || bodyB->GetCollisionEventMode() == COLLISION_NEVER)
                    continue;
                if (bodyA->GetCollisionEventMode() == COLLISION_ACTIVE && bodyB->GetCollisionEventMode() == COLLISION_ACTIVE &&
                    !bodyA->IsActive() && !bodyB->IsActive())
                    continue;

                Node* nodeA = bodyA->GetNode();
                Node* nodeB = bodyB->GetNode();
                WeakPtr<Node> nodeWeakA(nodeA);
                WeakPtr<Node> nodeWeakB(nodeB);

                physicsCollisionData_[PhysicsCollisionEnd::P_BODYA] = bodyA;
                physicsCollisionData_[PhysicsCollisionEnd::P_BODYB] = bodyB;
                physicsCollisionData_[PhysicsCollisionEnd::P_NODEA] = nodeA;
                physicsCollisionData_[PhysicsCollisionEnd::P_NODEB] = nodeB;
                physicsCollisionData_[PhysicsCollisionEnd::P_TRIGGER] = trigger;

                SendEvent(E_PHYSICSCOLLISIONEND, physicsCollisionData_);
                // Skip rest of processing if either of the nodes or bodies is removed as a response to the event
                if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                    continue;

                nodeCollisionData_[NodeCollisionEnd::P_BODY] = bodyA;
                nodeCollisionData_[NodeCollisionEnd::P_OTHERNODE] = nodeB;
                nodeCollisionData_[NodeCollisionEnd::P_OTHERBODY] = bodyB;
                nodeCollisionData_[NodeCollisionEnd::P_TRIGGER] = trigger;

                nodeA->SendEvent(E_NODECOLLISIONEND, nodeCollisionData_);
                if (!nodeWeakA || !nodeWeakB || !i->first_.first_ || !i->first_.second_)
                    continue;

                nodeCollisionData_[NodeCollisionEnd::P_BODY] = bodyB;
                nodeCollisionData_[NodeCollisionEnd::P_OTHERNODE] = nodeA;
                nodeCollisionData_[NodeCollisionEnd::P_OTHERBODY] = bodyA;

                nodeB->SendEvent(E_NODECOLLISIONEND, nodeCollisionData_);
            }
        }
    }

    previousCollisions_ = currentCollisions_;
}

void RegisterPhysicsLibrary(Context* context)
{
    CollisionShape::RegisterObject(context);
    RigidBody::RegisterObject(context);
    Constraint::RegisterObject(context);
    PhysicsWorld::RegisterObject(context);
}

}