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/*  Project Starshatter 4.5
	Destroyer Studios LLC
	Copyright © 1997-2004. All Rights Reserved.

	SUBSYSTEM:    Stars.exe
	FILE:         SeekerAI.cpp
	AUTHOR:       John DiCamillo


	OVERVIEW
	========
	Seeker Missile (low-level) Artificial Intelligence class
*/

#include "MemDebug.h"
#include "SeekerAI.h"
#include "Ship.h"
#include "Shot.h"
#include "System.h"
#include "WeaponDesign.h"

#include "Game.h"

// +----------------------------------------------------------------------+

SeekerAI::SeekerAI(SimObject* s)
: SteerAI(s), shot((Shot*) s), orig_target(0),
pursuit(1), delay(0), overshot(false)
{
	ai_type = SEEKER;

	seek_gain = 25;
	seek_damp = 0.55;
}


// +--------------------------------------------------------------------+

SeekerAI::~SeekerAI()
{
	if (shot) {
		if (shot->Owner())
		((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), 0);
	}
}

// +--------------------------------------------------------------------+

void
SeekerAI::ExecFrame(double seconds)
{
	// setup:
	FindObjective();

	// adaptive behavior:
	Navigator();
}

// +--------------------------------------------------------------------+

void
SeekerAI::Navigator()
{
	if (delay > 0) {
		delay -= Game::FrameTime();
	}
	else {
		Steer s = SeekTarget();
		self->ApplyYaw((float) s.yaw);
		self->ApplyPitch((float) s.pitch);
	}
}

void
SeekerAI::SetTarget(SimObject* targ, System* sub)
{
	if (!orig_target && targ && targ->Type() == SimObject::SIM_SHIP) {
		orig_target = (Ship*) targ;
		Observe(orig_target);
	}

	SteerAI::SetTarget(targ, sub);

	if (!target) {
		shot->SetEta(0);

		if (shot->Owner())
		((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), 0);
	}
}

void
SeekerAI::FindObjective()
{
	if (!shot || !target) return;

	if (target->Life() == 0) {
		if (target != orig_target)
		SetTarget(orig_target,0);
		else
		SetTarget(0,0);

		return;
	}

	Point tloc = target->Location();
	tloc = Transform(tloc);

	// seeker head limit of 45 degrees:
	if (tloc.z < 0 || tloc.z < fabs(tloc.x) || tloc.z < fabs(tloc.y)) {
		overshot = true;
		SetTarget(0,0);
		return;
	}

	// distance from self to target:
	distance = Point(target->Location() - self->Location()).length();

	// are we being spoofed?
	CheckDecoys(distance);

	Point cv = ClosingVelocity();

	// time to reach target:
	double time    = distance / cv.length();
	double predict = time;
	if (predict > 15)
	predict = 15;

	// pure pursuit:
	if (pursuit == 1 || time < 0.1) {
		obj_w = target->Location();
	}

	// lead pursuit:
	else {
		// where the target will be when we reach it:
		Point run_vec = target->Velocity();
		obj_w   = target->Location() + (run_vec * predict);
	}

	// subsystem offset:
	if (subtarget) {
		Point offset = target->Location() - subtarget->MountLocation();
		obj_w -= offset;
	}
	else if (target->Type() == SimObject::SIM_SHIP) {
		Ship* tgt_ship = (Ship*) target;

		if (tgt_ship->IsGroundUnit())
		obj_w += Point(0,150,0);
	}


	distance = Point(obj_w - self->Location()).length();
	time     = distance / cv.length();

	// where we will be when the target gets there:
	if (predict > 0.1 && predict < 15) {
		Point self_dest = self->Location() + cv * predict;
		Point err = obj_w - self_dest;

		obj_w += err;
	}

	// transform into camera coords:
	objective = Transform(obj_w);
	objective.Normalize();

	shot->SetEta((int) time);

	if (shot->Owner())
	((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), (int) time);
}

// +--------------------------------------------------------------------+

void
SeekerAI::CheckDecoys(double target_distance)
{
	// if the assigned target has the burner lit,
	// ignore the decoys:
	if (orig_target && orig_target->Augmenter()) {
		SetTarget(orig_target);
		return;
	}

	if (target && 
			target == orig_target && 
			orig_target->GetActiveDecoys().size()) {

		ListIter<Shot> decoy = orig_target->GetActiveDecoys();

		while (++decoy) {
			double decoy_distance = Point(decoy->Location() - self->Location()).length();

			if (decoy_distance < target_distance) {
				if (rand() < 1600) {
					SetTarget(decoy.value(), 0);
					return;
				}
			}
		}
	}
}

// +--------------------------------------------------------------------+

bool
SeekerAI::Overshot()
{
	return overshot;
}

// +--------------------------------------------------------------------+

Steer
SeekerAI::AvoidCollision()
{
	return Steer();
}

// +--------------------------------------------------------------------+

Steer
SeekerAI::SeekTarget()
{
	if (!self || !target || Overshot())
	return Steer();

	return Seek(objective);
}

// +--------------------------------------------------------------------+

bool
SeekerAI::Update(SimObject* obj)
{
	if (obj == target) {
		if (obj->Type() == SimObject::SIM_SHOT && orig_target != 0)
		target = orig_target;
	}

	if (obj == orig_target)
	orig_target = 0;

	return SteerAI::Update(obj);
}

const char*
SeekerAI::GetObserverName() const
{
	static char name[64];
	sprintf_s(name, "SeekerAI(%s)", self->Name());
	return name;
}