#include "extension.h"

#include "sourcehook.h"
#include "detours.h"

#include "vphysics_interface.h"
#include "ihandleentity.h"

#include "tier1/strtools.h"


// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"



CollisionHook g_CollisionHook;
SMEXT_LINK( &g_CollisionHook );


SH_DECL_HOOK0( IPhysics, CreateEnvironment, SH_NOATTRIB, 0 , IPhysicsEnvironment * );
SH_DECL_HOOK1_void( IPhysicsEnvironment, SetCollisionSolver, SH_NOATTRIB, 0, IPhysicsCollisionSolver * );
SH_DECL_HOOK4( IPhysicsCollisionSolver, ShouldCollide, SH_NOATTRIB, 0, int, IPhysicsObject *, IPhysicsObject *, void *, void * );


IGameConfig *g_pGameConf = NULL;
CDetour *g_pFilterDetour = NULL;

IPhysics *g_pPhysics = NULL;

IForward *g_pCollisionFwd = NULL;
IForward *g_pPassFwd = NULL;


DETOUR_DECL_STATIC2( PassServerEntityFilterFunc, bool, const IHandleEntity *, pTouch, const IHandleEntity *, pPass )
{
	if ( g_pPassFwd->GetFunctionCount() == 0 )
		return DETOUR_STATIC_CALL( PassServerEntityFilterFunc )( pTouch, pPass );

	if ( pTouch == pPass )
		return DETOUR_STATIC_CALL( PassServerEntityFilterFunc )( pTouch, pPass ); // self checks aren't interesting

	if ( !pTouch || !pPass )
		return DETOUR_STATIC_CALL( PassServerEntityFilterFunc )( pTouch, pPass ); // need two valid entities

	CBaseEntity *pEnt1 = const_cast<CBaseEntity *>( UTIL_EntityFromEntityHandle( pTouch ) );
	CBaseEntity *pEnt2 = const_cast<CBaseEntity *>( UTIL_EntityFromEntityHandle( pPass ) );

	if ( !pEnt1 || !pEnt2 )
		return DETOUR_STATIC_CALL( PassServerEntityFilterFunc )( pTouch, pPass ); // we need both entities

	cell_t ent1 = gamehelpers->EntityToBCompatRef( pEnt1 );
	cell_t ent2 = gamehelpers->EntityToBCompatRef( pEnt2 );

	// todo: do we want to fill result with with the game's result? perhaps the forward path is more performant...
	cell_t result = 0;
	g_pPassFwd->PushCell( ent1 );
	g_pPassFwd->PushCell( ent2 );
	g_pPassFwd->PushCellByRef( &result );

	cell_t retValue = 0;
	g_pPassFwd->Execute( &retValue );

	if ( retValue > Pl_Continue )
	{
		// plugin wants to change the result
		return result == 1;
	}

	// otherwise, game decides
	return DETOUR_STATIC_CALL( PassServerEntityFilterFunc )( pTouch, pPass );
}


bool CollisionHook::SDK_OnLoad( char *error, size_t maxlength, bool late )
{
	sharesys->RegisterLibrary( myself, "collisionhook" );

	char szConfError[ 256 ] = "";
	if ( !gameconfs->LoadGameConfigFile( "collisionhook", &g_pGameConf, szConfError, sizeof( szConfError ) ) )
	{
		V_snprintf( error, maxlength, "Could not read collisionhook gamedata: %s", szConfError );
		return false;
	}

	CDetourManager::Init( g_pSM->GetScriptingEngine(), g_pGameConf );

	g_pFilterDetour = DETOUR_CREATE_STATIC( PassServerEntityFilterFunc, "PassServerEntityFilter" );
	if ( !g_pFilterDetour )
	{
		V_snprintf( error, maxlength, "Unable to hook PassServerEntityFilter!" );
		return false;
	}

	g_pFilterDetour->EnableDetour();

	g_pCollisionFwd = forwards->CreateForward( "CH_ShouldCollide", ET_Hook, 3, NULL, Param_Cell, Param_Cell, Param_CellByRef );
	g_pPassFwd = forwards->CreateForward( "CH_PassFilter", ET_Hook, 3, NULL, Param_Cell, Param_Cell, Param_CellByRef );

	return true;
}

void CollisionHook::SDK_OnUnload()
{
	forwards->ReleaseForward( g_pCollisionFwd );
	forwards->ReleaseForward( g_pPassFwd );

	gameconfs->CloseGameConfigFile( g_pGameConf );

	if ( g_pFilterDetour )
	{
		g_pFilterDetour->Destroy();
		g_pFilterDetour = NULL;
	}
}

bool CollisionHook::SDK_OnMetamodLoad( ISmmAPI *ismm, char *error, size_t maxlen, bool late )
{
	GET_V_IFACE_CURRENT( GetPhysicsFactory, g_pPhysics, IPhysics, VPHYSICS_INTERFACE_VERSION );

	SH_ADD_HOOK( IPhysics, CreateEnvironment, g_pPhysics, SH_MEMBER( this, &CollisionHook::CreateEnvironment ), false );

	return true;
}

bool CollisionHook::SDK_OnMetamodUnload(char *error, size_t maxlength)
{
	SH_REMOVE_HOOK( IPhysics, CreateEnvironment, g_pPhysics, SH_MEMBER( this, &CollisionHook::CreateEnvironment ), false );

	g_pPhysics = NULL;

	return true;
}


IPhysicsEnvironment *CollisionHook::CreateEnvironment()
{
	// in order to hook IPhysicsCollisionSolver::ShouldCollide, we need to know when a solver is installed
	// in order to hook any installed solvers, we need to hook any created physics environments

	IPhysicsEnvironment *pEnvironment = SH_CALL( g_pPhysics, &IPhysics::CreateEnvironment )();

	Assert( pEnvironment );
	if ( !pEnvironment )
		RETURN_META_VALUE( MRES_SUPERCEDE, pEnvironment ); // just in case

	// hook so we know when a solver is installed
	SH_ADD_HOOK( IPhysicsEnvironment, SetCollisionSolver, pEnvironment, SH_MEMBER( this, &CollisionHook::SetCollisionSolver ), false );

	RETURN_META_VALUE( MRES_SUPERCEDE, pEnvironment );
}

void CollisionHook::SetCollisionSolver( IPhysicsCollisionSolver *pSolver )
{
	Assert( pSolver );
	if ( !pSolver )
		RETURN_META( MRES_IGNORED ); // this shouldn't happen, but knowing valve...

	// the game is installing a solver, hook the func we want
	SH_ADD_HOOK( IPhysicsCollisionSolver, ShouldCollide, pSolver, SH_MEMBER( this, &CollisionHook::VPhysics_ShouldCollide ), false );

	RETURN_META( MRES_IGNORED );
}

int CollisionHook::VPhysics_ShouldCollide( IPhysicsObject *pObj1, IPhysicsObject *pObj2, void *pGameData1, void *pGameData2 )
{
	if ( g_pCollisionFwd->GetFunctionCount() == 0 )
		RETURN_META_VALUE( MRES_IGNORED, 1 ); // no plugins are interested, let the game decide

	if ( pObj1 == pObj2 )
		RETURN_META_VALUE( MRES_IGNORED, 1 ); // self collisions aren't interesting

	CBaseEntity *pEnt1 = reinterpret_cast<CBaseEntity *>( pGameData1 );
	CBaseEntity *pEnt2 = reinterpret_cast<CBaseEntity *>( pGameData2 );

	if ( !pEnt1 || !pEnt2 )
		RETURN_META_VALUE( MRES_IGNORED, 1 ); // we need two entities

	cell_t ent1 = gamehelpers->EntityToBCompatRef( pEnt1 );
	cell_t ent2 = gamehelpers->EntityToBCompatRef( pEnt2 );

	// todo: do we want to fill result with with the game's result? perhaps the forward path is more performant...
	cell_t result = 0;
	g_pCollisionFwd->PushCell( ent1 );
	g_pCollisionFwd->PushCell( ent2 );
	g_pCollisionFwd->PushCellByRef( &result );

	cell_t retValue = 0;
	g_pCollisionFwd->Execute( &retValue );

	if ( retValue > Pl_Continue )
	{
		// plugin wants to change the result
		RETURN_META_VALUE( MRES_SUPERCEDE, result == 1 );
	}

	// otherwise, game decides
	RETURN_META_VALUE( MRES_IGNORED, 0 );
}