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 /*
 * Copyright (c) 2006-2009 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 <Box2D/Dynamics/b2ContactManager.h>
 #include <Box2D/Dynamics/b2Body.h>
 #include <Box2D/Dynamics/b2Fixture.h>
 #include <Box2D/Dynamics/b2WorldCallbacks.h>
 #include <Box2D/Dynamics/Contacts/b2Contact.h>
 
 b2ContactFilter b2_defaultFilter;
 b2ContactListener b2_defaultListener;
 
 b2ContactManager::b2ContactManager()
 {
     m_contactList = NULL;
     m_contactCount = 0;
     m_contactFilter = &b2_defaultFilter;
     m_contactListener = &b2_defaultListener;
     m_allocator = NULL;
 }
 
 void b2ContactManager::Destroy(b2Contact* c)
 {
     b2Fixture* fixtureA = c->GetFixtureA();
     b2Fixture* fixtureB = c->GetFixtureB();
     b2Body* bodyA = fixtureA->GetBody();
     b2Body* bodyB = fixtureB->GetBody();
 
     if (m_contactListener && c->IsTouching())
     {
         m_contactListener->EndContact(c);
     }
 
     // Remove from the world.
     if (c->m_prev)
     {
         c->m_prev->m_next = c->m_next;
     }
 
     if (c->m_next)
     {
         c->m_next->m_prev = c->m_prev;
     }
 
     if (c == m_contactList)
     {
         m_contactList = c->m_next;
     }
 
     // Remove from body 1
     if (c->m_nodeA.prev)
     {
         c->m_nodeA.prev->next = c->m_nodeA.next;
     }
 
     if (c->m_nodeA.next)
     {
         c->m_nodeA.next->prev = c->m_nodeA.prev;
     }
 
     if (&c->m_nodeA == bodyA->m_contactList)
     {
         bodyA->m_contactList = c->m_nodeA.next;
     }
 
     // Remove from body 2
     if (c->m_nodeB.prev)
     {
         c->m_nodeB.prev->next = c->m_nodeB.next;
     }
 
     if (c->m_nodeB.next)
     {
         c->m_nodeB.next->prev = c->m_nodeB.prev;
     }
 
     if (&c->m_nodeB == bodyB->m_contactList)
     {
         bodyB->m_contactList = c->m_nodeB.next;
     }
 
     // Call the factory.
     b2Contact::Destroy(c, m_allocator);
     --m_contactCount;
 }
 
 // This is the top level collision call for the time step. Here
 // all the narrow phase collision is processed for the world
 // contact list.
 void b2ContactManager::Collide()
 {
     // Update awake contacts.
     b2Contact* c = m_contactList;
     while (c)
     {
         b2Fixture* fixtureA = c->GetFixtureA();
         b2Fixture* fixtureB = c->GetFixtureB();
         int32 indexA = c->GetChildIndexA();
         int32 indexB = c->GetChildIndexB();
         b2Body* bodyA = fixtureA->GetBody();
         b2Body* bodyB = fixtureB->GetBody();
 
         if (bodyA->IsAwake() == false && bodyB->IsAwake() == false)
         {
             c = c->GetNext();
             continue;
         }
 
         // Is this contact flagged for filtering?
         if (c->m_flags & b2Contact::e_filterFlag)
         {
             // Should these bodies collide?
             if (bodyB->ShouldCollide(bodyA) == false)
             {
                 b2Contact* cNuke = c;
                 c = cNuke->GetNext();
                 Destroy(cNuke);
                 continue;
             }
 
             // Check user filtering.
             if (m_contactFilter && m_contactFilter->ShouldCollide(fixtureA, fixtureB) == false)
             {
                 b2Contact* cNuke = c;
                 c = cNuke->GetNext();
                 Destroy(cNuke);
                 continue;
             }
 
             // Clear the filtering flag.
             c->m_flags &= ~b2Contact::e_filterFlag;
         }
 
         int32 proxyIdA = fixtureA->m_proxies[indexA].proxyId;
         int32 proxyIdB = fixtureB->m_proxies[indexB].proxyId;
         bool overlap = m_broadPhase.TestOverlap(proxyIdA, proxyIdB);
 
         // Here we destroy contacts that cease to overlap in the broad-phase.
         if (overlap == false)
         {
             b2Contact* cNuke = c;
             c = cNuke->GetNext();
             Destroy(cNuke);
             continue;
         }
 
         // The contact persists.
         c->Update(m_contactListener);
         c = c->GetNext();
     }
 }
 
 void b2ContactManager::FindNewContacts()
 {
     m_broadPhase.UpdatePairs(this);
 }
 
 void b2ContactManager::AddPair(void* proxyUserDataA, void* proxyUserDataB)
 {
     b2FixtureProxy* proxyA = (b2FixtureProxy*)proxyUserDataA;
     b2FixtureProxy* proxyB = (b2FixtureProxy*)proxyUserDataB;
 
     b2Fixture* fixtureA = proxyA->fixture;
     b2Fixture* fixtureB = proxyB->fixture;
 
     int32 indexA = proxyA->childIndex;
     int32 indexB = proxyB->childIndex;
 
     b2Body* bodyA = fixtureA->GetBody();
     b2Body* bodyB = fixtureB->GetBody();
 
     // Are the fixtures on the same body?
     if (bodyA == bodyB)
     {
         return;
     }
 
     // Does a contact already exist?
     b2ContactEdge* edge = bodyB->GetContactList();
     while (edge)
     {
         if (edge->other == bodyA)
         {
             b2Fixture* fA = edge->contact->GetFixtureA();
             b2Fixture* fB = edge->contact->GetFixtureB();
             int32 iA = edge->contact->GetChildIndexA();
             int32 iB = edge->contact->GetChildIndexB();
 
             if (fA == fixtureA && fB == fixtureB && iA == indexA && iB == indexB)
             {
                 // A contact already exists.
                 return;
             }
 
             if (fA == fixtureB && fB == fixtureA && iA == indexB && iB == indexA)
             {
                 // A contact already exists.
                 return;
             }
         }
 
         edge = edge->next;
     }
 
     // Does a joint override collision? Is at least one body dynamic?
     if (bodyB->ShouldCollide(bodyA) == false)
     {
         return;
     }
 
     // Check user filtering.
     if (m_contactFilter && m_contactFilter->ShouldCollide(fixtureA, fixtureB) == false)
     {
         return;
     }
 
     // Call the factory.
     b2Contact* c = b2Contact::Create(fixtureA, indexA, fixtureB, indexB, m_allocator);
 
     // Contact creation may swap fixtures.
     fixtureA = c->GetFixtureA();
     fixtureB = c->GetFixtureB();
     indexA = c->GetChildIndexA();
     indexB = c->GetChildIndexB();
     bodyA = fixtureA->GetBody();
     bodyB = fixtureB->GetBody();
 
     // Insert into the world.
     c->m_prev = NULL;
     c->m_next = m_contactList;
     if (m_contactList != NULL)
     {
         m_contactList->m_prev = c;
     }
     m_contactList = c;
 
     // Connect to island graph.
 
     // Connect to body A
     c->m_nodeA.contact = c;
     c->m_nodeA.other = bodyB;
 
     c->m_nodeA.prev = NULL;
     c->m_nodeA.next = bodyA->m_contactList;
     if (bodyA->m_contactList != NULL)
     {
         bodyA->m_contactList->prev = &c->m_nodeA;
     }
     bodyA->m_contactList = &c->m_nodeA;
 
     // Connect to body B
     c->m_nodeB.contact = c;
     c->m_nodeB.other = bodyA;
 
     c->m_nodeB.prev = NULL;
     c->m_nodeB.next = bodyB->m_contactList;
     if (bodyB->m_contactList != NULL)
     {
         bodyB->m_contactList->prev = &c->m_nodeB;
     }
     bodyB->m_contactList = &c->m_nodeB;
 
     ++m_contactCount;
 }