/***
*
*	Copyright (c) 1996-2002, Valve LLC. All rights reserved.
*	
*	This product contains software technology licensed from Id 
*	Software, Inc. ("Id Technology").  Id Technology (c) 1996 Id Software, Inc. 
*	All Rights Reserved.
*
*   Use, distribution, and modification of this source code and/or resulting
*   object code is restricted to non-commercial enhancements to products from
*   Valve LLC.  All other use, distribution, or modification is prohibited
*   without written permission from Valve LLC.
*
****/
/*

  h_ai.cpp - halflife specific ai code

*/

#include	"extdll.h"
#include	"util.h"
#include	"cbase.h"
#include	"monsters.h"
#include	"game.h"
	
#define		NUM_LATERAL_CHECKS		13  // how many checks are made on each side of a monster looking for lateral cover
#define		NUM_LATERAL_LOS_CHECKS		6  // how many checks are made on each side of a monster looking for lateral cover

//float flRandom = RANDOM_FLOAT( 0, 1 );

DLL_GLOBAL	BOOL	g_fDrawLines = FALSE;

//=========================================================
// 
// AI UTILITY FUNCTIONS
//
// !!!UNDONE - move CBaseMonster functions to monsters.cpp
//=========================================================

//=========================================================
// FBoxVisible - a more accurate ( and slower ) version
// of FVisible. 
//
// !!!UNDONE - make this CBaseMonster?
//=========================================================
BOOL FBoxVisible( entvars_t *pevLooker, entvars_t *pevTarget, Vector &vecTargetOrigin, float flSize )
{
	// don't look through water
	if( ( pevLooker->waterlevel != 3 && pevTarget->waterlevel == 3 )
		|| ( pevLooker->waterlevel == 3 && pevTarget->waterlevel == 0 ) )
		return FALSE;

	TraceResult tr;
	Vector	vecLookerOrigin = pevLooker->origin + pevLooker->view_ofs;//look through the monster's 'eyes'
	for( int i = 0; i < 5; i++ )
	{
		Vector vecTarget = pevTarget->origin;
		vecTarget.x += RANDOM_FLOAT( pevTarget->mins.x + flSize, pevTarget->maxs.x - flSize );
		vecTarget.y += RANDOM_FLOAT( pevTarget->mins.y + flSize, pevTarget->maxs.y - flSize );
		vecTarget.z += RANDOM_FLOAT( pevTarget->mins.z + flSize, pevTarget->maxs.z - flSize );

		UTIL_TraceLine( vecLookerOrigin, vecTarget, ignore_monsters, ignore_glass, ENT( pevLooker )/*pentIgnore*/, &tr );

		if( tr.flFraction == 1.0f )
		{
			vecTargetOrigin = vecTarget;
			return TRUE;// line of sight is valid.
		}
	}
	return FALSE;// Line of sight is not established
}

//
// VecCheckToss - returns the velocity at which an object should be lobbed from vecspot1 to land near vecspot2.
// returns g_vecZero if toss is not feasible.
// 
Vector VecCheckToss( entvars_t *pev, const Vector &vecSpot1, Vector vecSpot2, float flGravityAdj )
{
	TraceResult		tr;
	Vector			vecMidPoint;// halfway point between Spot1 and Spot2
	Vector			vecApex;// highest point 
	Vector			vecScale;
	Vector			vecGrenadeVel;
	Vector			vecTemp;
	float			flGravity = g_psv_gravity->value * flGravityAdj;

	if( vecSpot2.z - vecSpot1.z > 500 )
	{
		// to high, fail
		return g_vecZero;
	}

	UTIL_MakeVectors( pev->angles );

	// toss a little bit to the left or right, not right down on the enemy's bean (head). 
	vecSpot2 = vecSpot2 + gpGlobals->v_right * ( RANDOM_FLOAT( -8, 8 ) + RANDOM_FLOAT( -16, 16 ) );
	vecSpot2 = vecSpot2 + gpGlobals->v_forward * ( RANDOM_FLOAT( -8, 8 ) + RANDOM_FLOAT( -16, 16 ) );

	// calculate the midpoint and apex of the 'triangle'
	// UNDONE: normalize any Z position differences between spot1 and spot2 so that triangle is always RIGHT

	// How much time does it take to get there?

	// get a rough idea of how high it can be thrown
	vecMidPoint = vecSpot1 + ( vecSpot2 - vecSpot1 ) * 0.5;
	UTIL_TraceLine(vecMidPoint, vecMidPoint + Vector( 0, 0, 500 ), ignore_monsters, ENT( pev ), &tr );
	vecMidPoint = tr.vecEndPos;
	// (subtract 15 so the grenade doesn't hit the ceiling)
	vecMidPoint.z -= 15;

	if( vecMidPoint.z < vecSpot1.z || vecMidPoint.z < vecSpot2.z )
	{
		// to not enough space, fail
		return g_vecZero;
	}

	// How high should the grenade travel to reach the apex
	float distance1 = vecMidPoint.z - vecSpot1.z;
	float distance2 = vecMidPoint.z - vecSpot2.z;

	// How long will it take for the grenade to travel this distance
	float time1 = sqrt( distance1 / ( 0.5f * flGravity ) );
	float time2 = sqrt( distance2 / ( 0.5f * flGravity ) );

	if( time1 < 0.1f )
	{
		// too close
		return g_vecZero;
	}

	// how hard to throw sideways to get there in time.
	vecGrenadeVel = ( vecSpot2 - vecSpot1 ) / ( time1 + time2 );
	// how hard upwards to reach the apex at the right time.
	vecGrenadeVel.z = flGravity * time1;

	// find the apex
	vecApex  = vecSpot1 + vecGrenadeVel * time1;
	vecApex.z = vecMidPoint.z;

	UTIL_TraceLine( vecSpot1, vecApex, dont_ignore_monsters, ENT( pev ), &tr );
	if( tr.flFraction != 1.0f )
	{
		// fail!
		return g_vecZero;
	}

	// UNDONE: either ignore monsters or change it to not care if we hit our enemy
	UTIL_TraceLine( vecSpot2, vecApex, ignore_monsters, ENT( pev ), &tr ); 
	if( tr.flFraction != 1.0f )
	{
		// fail!
		return g_vecZero;
	}

	return vecGrenadeVel;
}

//
// VecCheckThrow - returns the velocity vector at which an object should be thrown from vecspot1 to hit vecspot2.
// returns g_vecZero if throw is not feasible.
// 
Vector VecCheckThrow( entvars_t *pev, const Vector &vecSpot1, Vector vecSpot2, float flSpeed, float flGravityAdj )
{
	float	flGravity = g_psv_gravity->value * flGravityAdj;

	Vector vecGrenadeVel = vecSpot2 - vecSpot1;

	// throw at a constant time
	float time = vecGrenadeVel.Length() / flSpeed;
	vecGrenadeVel = vecGrenadeVel * ( 1.0f / time );

	// adjust upward toss to compensate for gravity loss
	vecGrenadeVel.z += flGravity * time * 0.5f;

	Vector vecApex = vecSpot1 + ( vecSpot2 - vecSpot1 ) * 0.5f;
	vecApex.z += 0.5f * flGravity * ( time * 0.5f ) * ( time * 0.5f );

	TraceResult tr;
	UTIL_TraceLine( vecSpot1, vecApex, dont_ignore_monsters, ENT( pev ), &tr );
	if( tr.flFraction != 1.0f )
	{
		// fail!
		return g_vecZero;
	}

	UTIL_TraceLine( vecSpot2, vecApex, ignore_monsters, ENT( pev ), &tr );
	if( tr.flFraction != 1.0f )
	{
		// fail!
		return g_vecZero;
	}

	return vecGrenadeVel;
}