//===========================================================================//
// File:	missile.cpp                                                         //
// Project: BattleTech           Brick: Mech weapons                          //
// Contents: Missile -- the guided self-propelled projectile entity          //
//---------------------------------------------------------------------------//
// Copyright (C) 1995, Virtual World Entertainment, Inc.                     //
// All Rights reserved worldwide                                             //
// This unpublished sourcecode is PROPRIETARY and CONFIDENTIAL               //
//===========================================================================//
//
// RECONSTRUCTED against the binary via the BT411 decomp (ctor @004bf5b4,
// MoveAndCollide @004bef78, allocator @004bf8bc) and the surviving
// SEEKER.HPP / MISTHRST.HPP.  See MISSILE.NOTES.md for the staged pieces
// (flight constants pending the missile GameModel record decode; world
// collision + explosion entity are the render/effects wave).
//

#include <bt.hpp>
#pragma hdrstop

#if !defined(MISSILE_HPP)
#	include <missile.hpp>
#endif

#if !defined(SEEKER_HPP)
#	include <seeker.hpp>
#endif

#if !defined(MISTHRST_HPP)
#	include <misthrst.hpp>
#endif

#if !defined(MECH_HPP)
#	include <mech.hpp>
#endif

#if !defined(RANDOM_HPP)
#	include <random.hpp>
#endif

//
// Guidance tuning (binary .rdata @004bf594..@004bf5b0, BT411-decoded).
// STAGED-DEFAULT flight envelope: lifetime / thrust come from the missile
// GameModel record (model +0x44 / +0x48) once that layout is decoded; until
// then the defaults below fly a believable SRM (fast, short-burn).
//
static const Scalar MissileSteerEps		= 1.0e-4f;	// _DAT_004bf598 steering deadband
static const Scalar MissileTurnGain		= 4.0f;		// _DAT_004bf5a4 turn rate gain (1/s)
static const Scalar MissileDriftGain	= 0.1f;		// _DAT_004bf5a8
static const Scalar DefaultLifetime		= 10.0f;	// model +0x44 (staged default)
static const Scalar DefaultFuseRadius	= 20.0f;	// proximity fuse (staged)

Derivation
	Missile::ClassDerivations(
		Projectile::ClassDerivations,
		"Missile"
	);

Missile::SharedData
	Missile::DefaultData(
		Missile::ClassDerivations,
		Mover::MessageHandlers,
		Mover::AttributeIndex,
		1,
		(Entity::MakeHandler)Missile::Make
	);

Missile*
	Missile::Make(MakeMessage *creation_message)
{
	return new Missile(creation_message);
}

//
//#############################################################################
// Construction (binary @004bf5b4).  Chains the Projectile base (Entity
// transform + Mover motion/model stream -- the MakeMessage's resourceID is
// the launcher's explosion/projectile GameModel).  The subsystem roster is
// built in Launch(), which carries the target the binary's spawn descriptor
// delivered to the ctor.
//#############################################################################
//
Missile::Missile(
	MakeMessage	*creation_message,
	SharedData	&shared_data
):
	Projectile(creation_message, shared_data)
{
	Check(creation_message);

	lifetime			= DefaultLifetime;
	ageFraction			= 0.0f;
	age					= 0.0f;
	detonationFlag		= 0;
	flightVelocity		= Vector3D(0.0f, 0.0f, 0.0f);
	fuseRadius			= DefaultFuseRadius;
	launcherEntityID	= EntityID::Null;
	telemetryCountdown	= 0;

	Check_Fpu();
}

Missile::~Missile()
{
	if (getenv("BT_MECH_LOG"))
	{
		DEBUG_STREAM << "[msl] dtor (death row fry)" << endl << flush;
	}
}

Logical
	Missile::TestInstance() const
{
	return IsDerivedFrom(ClassDerivations);
}

//
//#############################################################################
// Launch -- seed the flight (the binary ctor tail + spawn-descriptor
// unpack).  Builds the two-subsystem roster (Seeker @004bec34 with the
// homing target, MissileThruster @004be7c4), aims the initial velocity at
// the target and installs the guided integrator as the per-frame
// Performance.  Tail = SetValidFlag(), like every 1995 entity.
//#############################################################################
//
void
	Missile::Launch(
		Mech	*launcher,
		Entity	*target,
		Damage	&damage,
		Scalar	launch_speed
	)
{
	Check(this);
	Check(launcher);

	launcherEntityID	= launcher->GetEntityID();
	damageData			= damage;

	//
	// The 2-entry subsystem roster (binary this[0x49] = 2).
	//
	subsystemCount	= SubsystemCount;
	subsystemArray	= new Subsystem *[SubsystemCount];
	Register_Pointer(subsystemArray);
	subsystemArray[SeekerSubsystem] =
		new Seeker(this, SeekerSubsystem, NULL, target,
			Point3D(0.0f, 0.0f, 0.0f));
	Register_Object(subsystemArray[SeekerSubsystem]);
	subsystemArray[MissileThrusterSubsystem] =
		new MissileThruster(this, MissileThrusterSubsystem, NULL);
	Register_Object(subsystemArray[MissileThrusterSubsystem]);

	//
	// Initial velocity: straight at the target's current position (the
	// authored MuzzleVelocity up-tilt arc through the MOUNT frame is the
	// muzzle wave -- the seeker converges either way).
	//
	if (target != NULL)
	{
		Vector3D aim;
		aim.Subtract(
			target->localOrigin.linearPosition,
			localOrigin.linearPosition
		);
		Scalar range = aim.Length();
		if (range > 0.01f)
		{
			flightVelocity.x = aim.x / range * launch_speed;
			flightVelocity.y = aim.y / range * launch_speed;
			flightVelocity.z = aim.z / range * launch_speed;
		}
	}

	SetPerformance(&Missile::MoveAndCollide);
	AlwaysExecute();
	SetValidFlag();

	if (getenv("BT_MECH_LOG"))
	{
		DEBUG_STREAM << "[msl] LAUNCH from " << launcherEntityID
			<< " at (" << localOrigin.linearPosition.x
			<< "," << localOrigin.linearPosition.y
			<< "," << localOrigin.linearPosition.z
			<< ") spd=" << launch_speed
			<< " dmg=" << damageData.damageAmount
			<< "x" << damageData.burstCount << endl << flush;
	}
}

//
//#############################################################################
// MoveAndCollide (binary @004bef78) -- the guided per-frame integrator.
//
//  1. Age; past the lifetime the round fizzles (death row, no damage).
//  2. Re-lead the target (Seeker::FindTarget) + bleed the thruster burn.
//  3. Steer the velocity toward the Seeker's lead point (turn gain 4.0,
//     deadband 1e-4) and integrate the position.
//  4. Proximity fuse: inside fuseRadius of the aim point the round
//     DETONATES -- the cluster damage record lands on the target (random
//     hull zone interim, same as the direct path) and the round retires.
//     World-geometry collision (@0042291c) + the explosion entity
//     (@004be078, ClassID 0x5C) are the render/effects wave.
//#############################################################################
//
void
	Missile::MoveAndCollide(Scalar time_slice)
{
	Check(this);

	age += time_slice;
	ageFraction = (age <= lifetime) ? age / lifetime : 1.0f;
	if (age > lifetime)
	{
		if (getenv("BT_MECH_LOG"))
		{
			DEBUG_STREAM << "[msl] fizzle (lifetime) at ("
				<< localOrigin.linearPosition.x << ","
				<< localOrigin.linearPosition.y << ","
				<< localOrigin.linearPosition.z << ")" << endl << flush;
		}
		CondemnToDeathRow();
		Check_Fpu();
		return;
	}

	Seeker *seeker =
		(Seeker *)subsystemArray[SeekerSubsystem];
	MissileThruster *thruster =
		(MissileThruster *)subsystemArray[MissileThrusterSubsystem];
	Check(seeker);
	Check(thruster);

	//
	// The hosted subsystems are advanced FROM the integrator (the binary
	// folds their work into this pass -- no separate roster tick).
	//
	seeker->FindTarget(time_slice);
	thruster->MissileThrusterSimulation(time_slice);

	//
	// Steering: bend the velocity toward the seeker's lead point at
	// MissileTurnGain per second, holding speed; the thruster adds pace
	// while burning.
	//
	Vector3D toLead;
	toLead.Subtract(seeker->targetPosition, localOrigin.linearPosition);
	Scalar range = toLead.Length();

	Scalar speed = flightVelocity.Length();
	if (thruster->burnTimeRemaining > 0.0f)
	{
		speed += thruster->thrusterAcceleration * time_slice;
	}

	if (range > MissileSteerEps)
	{
		Scalar blend = MissileTurnGain * time_slice;
		if (blend > 1.0f)
		{
			blend = 1.0f;
		}
		Vector3D desired;
		desired.x = toLead.x / range * speed;
		desired.y = toLead.y / range * speed;
		desired.z = toLead.z / range * speed;
		flightVelocity.x += (desired.x - flightVelocity.x) * blend;
		flightVelocity.y += (desired.y - flightVelocity.y) * blend;
		flightVelocity.z += (desired.z - flightVelocity.z) * blend;
	}

	localOrigin.linearPosition.x += flightVelocity.x * time_slice;
	localOrigin.linearPosition.y += flightVelocity.y * time_slice;
	localOrigin.linearPosition.z += flightVelocity.z * time_slice;
	localToWorld = localOrigin;

	//
	// The proximity fuse (the BANKED seeker notes: fuse on the seeker's
	// rangeToTarget).
	//
	seeker->rangeToTarget = range;
	if (range <= fuseRadius && seeker->targetEntity != NULL)
	{
		Entity *victim = seeker->targetEntity;
		int zone = -1;
		if (victim->damageZoneCount > 0)
		{
			zone = Random(victim->damageZoneCount);
		}
		Entity::TakeDamageMessage
			hit(
				Entity::TakeDamageMessageID,
				sizeof(Entity::TakeDamageMessage),
				launcherEntityID,
				zone,
				damageData
			);
		victim->Dispatch(&hit);

		if (getenv("BT_MECH_LOG"))
		{
			DEBUG_STREAM << "[msl] DETONATE on zone " << zone
				<< " amount=" << damageData.damageAmount
				<< " burst=" << damageData.burstCount
				<< " after " << age << "s" << endl << flush;
		}
		CondemnToDeathRow();
		Check_Fpu();
		return;
	}

	if (getenv("BT_MECH_LOG") && --telemetryCountdown <= 0)
	{
		telemetryCountdown = 30;
		DEBUG_STREAM << "[msl] t=" << age
			<< " pos=(" << localOrigin.linearPosition.x
			<< "," << localOrigin.linearPosition.y
			<< "," << localOrigin.linearPosition.z
			<< ") range=" << range
			<< " spd=" << speed << endl << flush;
	}

	Check_Fpu();
}