/*  Starshatter: The Open Source Project
    Copyright (c) 2021-2024, Starshatter: The Open Source Project Contributors
    Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
    Copyright (c) 1997-2006, Destroyer Studios LLC.

    AUTHOR:       John DiCamillo


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

#include "ShipAI.h"

#include "Asteroid.h"
#include "Clock.h"
#include "Contact.h"
#include "ContentBundle.h"
#include "Debris.h"
#include "Drive.h"
#include "Element.h"
#include "Farcaster.h"
#include "FlightComp.h"
#include "Instruction.h"
#include "NavLight.h"
#include "Player.h"
#include "QuantumDrive.h"
#include "RadioMessage.h"
#include "RadioTraffic.h"
#include "Random.h"
#include "Shield.h"
#include "ShipDesign.h"
#include "Ship.h"
#include "Shot.h"
#include "Sim.h"
#include "StarSystem.h"
#include "TacticalAI.h"
#include "WeaponGroup.h"

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

ShipAI::ShipAI(SimObject* s)
    : SteerAI(s),
      support(0), rumor(0), threat(0), threat_missile(0), drop_time(0),
      too_close(0), navpt(0), patrol(0), engaged_ship_id(0),
      bracket(false), identify(false), hold(false), takeoff(false),
      throttle(0), old_throttle(0), element_index(1), splash_count(0),
      tactical(0), farcaster(0), ai_level(2), last_avoid_time(0),
      last_call_time(0)
{
    ship = (Ship*) self;

    Sim*  sim         = Sim::GetSim();
    Ship* pship       = sim->GetPlayerShip();
    int   player_team = 1;

    if (pship)
    player_team = pship->GetIFF();

    Player* player = Player::GetCurrentPlayer();
    if (player) {
        if (ship && ship->GetIFF() && ship->GetIFF() != player_team) {
            ai_level = player->AILevel();
        }
        else if (player->AILevel() == 0) {
            ai_level = 1;
        }
    }

    // evil alien ships are *always* smart:
    if (ship && ship->GetIFF() > 1 && ship->Design()->auto_roll > 1) {
        ai_level = 2;
    }
}


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

ShipAI::~ShipAI()
{
    delete tactical;
}

void
ShipAI::ClearTactical()
{
    delete tactical;
    tactical = 0;
}

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

Ship*
ShipAI::GetWard() const
{
    return ship->GetWard();
}

void
ShipAI::SetWard(Ship* s)
{
    if (ship == nullptr)
    return;
    if (s == ship->GetWard())
    return;

    if (ship)
        ship->SetWard(s);

    Point form = RandomDirection();
    form.SwapYZ();

    if (fabs(form.x) < 0.5) {
        if (form.x < 0)
        form.x = -0.5;
        else
        form.x = 0.5;
    }

    if (ship && ship->IsStarship()) {
        form *= 30e3;
    }
    else {
        form *= 15e3;
        form.y = 500;
    }

    SetFormationDelta(form);
}

void
ShipAI::SetSupport(Ship* s)
{
    if (support == s)
    return;

    support = s;

    if (support)
    Observe(support);
}

void
ShipAI::SetRumor(Ship* s)
{
    if (!s || rumor == s)
    return;

    rumor = s;

    if (rumor)
    Observe(rumor);
}

void
ShipAI::ClearRumor()
{
    rumor = 0;
}

void
ShipAI::SetThreat(Ship* s)
{
    if (threat == s)
    return;

    threat = s;

    if (threat)
    Observe(threat);
}

void
ShipAI::SetThreatMissile(Shot* s)
{
    if (threat_missile == s)
    return;

    threat_missile = s;

    if (threat_missile)
    Observe(threat_missile);
}

bool
ShipAI::Update(SimObject* obj)
{
    if (obj == support)
    support = 0;

    if (obj == threat)
    threat = 0;

    if (obj == threat_missile)
    threat_missile = 0;

    if (obj == rumor)
    rumor = 0;

    return SteerAI::Update(obj);
}

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

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

Point
ShipAI::GetPatrol() const
{
    return patrol_loc;
}

void
ShipAI::SetPatrol(const Point& p)
{
    patrol = 1;
    patrol_loc = p;
}

void
ShipAI::ClearPatrol()
{
    patrol = 0;
}

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

void
ShipAI::ExecFrame(double secs)
{
    seconds = secs;

    if (drop_time > 0) drop_time -= seconds;
    if (!ship) return;

    ship->SetDirectorInfo(" ");

    // check to make sure current navpt is still valid:
    if (navpt)
    navpt = ship->GetNextNavPoint();

    if (ship->GetFlightPhase() == Ship::TAKEOFF || ship->GetFlightPhase() == Ship::LAUNCH)
    takeoff = true;

    if (takeoff) {
        FindObjective();
        Navigator();

        if (ship->MissionClock() > 10000)
        takeoff = false;

        return;
    }

    // initial assessment:
    if (ship->MissionClock() < 5000)
    return;

    element_index = ship->GetElementIndex();

    NavlightControl();
    CheckTarget();

    if (tactical)
    tactical->ExecFrame(seconds);

    if (target && target != ship->GetTarget()) {
        ship->LockTarget(target);

        // if able to lock target, and target is a ship (not a shot)...
        if (target == ship->GetTarget() && target->Type() == SimObject::SIM_SHIP) {

            // if this isn't the same ship we last called out:
            if (target->Identity() != engaged_ship_id && Clock::GetInstance()->GameTime() - last_call_time > 10000) {
                // call engaging:
                RadioMessage* msg = new RadioMessage(ship->GetElement(), ship, RadioMessage::CALL_ENGAGING);
                msg->AddTarget(target);
                RadioTraffic::Transmit(msg);
                last_call_time = Clock::GetInstance()->GameTime();

                engaged_ship_id = target->Identity();
            }
        }
    }

    else if (!target) {
        target = ship->GetTarget();

        if (engaged_ship_id && !target) {
            engaged_ship_id = 0;

            /***
        *** XXX
        *** Not the right place to make this decision.
        ***
        *** There is a brief wait between killing a target and
        *** selecting a new one, so this message is sent after
        *** every kill.
        ***
        *** Need to track when the entire element has been
        *** put down.

        if (element_index == 1) {
            RadioMessage* msg = new RadioMessage(ship->GetElement(), ship, RadioMessage::RESUME_MISSION);
            RadioTraffic::Transmit(msg);
        }

        ***
        ***/
        }
    }

    FindObjective();
    Navigator();
}

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

Point
ShipAI::ClosingVelocity()
{
    if (ship && target) {
        if (ship->GetPrimaryDesign()) {
            WeaponDesign* guns  = ship->GetPrimaryDesign();
            Point         delta = target->Location() - ship->Location();

            // fighters need to aim the ship so that the guns will hit the target
            if (guns->firing_cone < 10*DEGREES && guns->max_range <= delta.length()) {
                Point aim_vec = ship->Heading();
                aim_vec.Normalize();

                Point shot_vel = ship->Velocity() + aim_vec * guns->speed;
                return shot_vel - target->Velocity();
            }

            // ships with turreted weapons just need to worry about actual closing speed
            else {
                return ship->Velocity() - target->Velocity();
            }
        }

        else {
            return ship->Velocity();
        }
    }

    return Point(1,0,0);
}

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

void
ShipAI::FindObjective()
{
    distance = 0;

    int   order = ship->GetRadioOrders()->Action();

    if (order == RadioMessage::QUANTUM_TO ||
            order == RadioMessage::FARCAST_TO) {

        FindObjectiveQuantum();
        objective = Transform(obj_w);
        return;
    }

    bool  form  = (order == RadioMessage::WEP_HOLD)    ||
    (order == RadioMessage::FORM_UP)     ||
    (order == RadioMessage::MOVE_PATROL) ||
    (order == RadioMessage::RTB)         ||
    (order == RadioMessage::DOCK_WITH)   ||
    (!order && !target)                  ||
    (farcaster);

    Ship* ward  = ship->GetWard();

    // if not the element leader, stay in formation:
    if (form && element_index > 1) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.formation"));

        if (navpt && navpt->Action() == Instruction::LAUNCH) {
            FindObjectiveNavPoint();
        }
        else {
            navpt = 0;
            FindObjectiveFormation();
        }

        // transform into camera coords:
        objective = Transform(obj_w);
        return;
    }

    // under orders?
    bool directed = false;
    if (tactical)
    directed = (tactical->RulesOfEngagement() == TacticalAI::DIRECTED);

    // threat processing:
    if (threat && !directed) {
        double d_threat = Point(threat->Location() - ship->Location()).length();

        // seek support:
        if (support) {
            double d_support = Point(support->Location() - ship->Location()).length();
            if (d_support > 35e3) {
                ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.regroup"));
                FindObjectiveTarget(support);
                objective = Transform(obj_w);
                return;
            }
        }

        // run away:
        else if (threat != target) {
            ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.retreat"));
            obj_w = ship->Location() + Point(ship->Location() - threat->Location()) * 100;
            objective = Transform(obj_w);
            return;
        }
    }

    // normal processing:
    if (target) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.seek-target"));
        FindObjectiveTarget(target);
        objective = AimTransform(obj_w);
    }

    else if (patrol) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.patrol"));
        FindObjectivePatrol();
        objective = Transform(obj_w);
    }

    else if (ward) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.seek-ward"));
        FindObjectiveFormation();
        objective = Transform(obj_w);
    }

    else if (navpt && form) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.seek-navpt"));
        FindObjectiveNavPoint();
        objective = Transform(obj_w);
    }

    else if (rumor) {
        ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.search"));
        FindObjectiveTarget(rumor);
        objective = Transform(obj_w);
    }

    else {
        obj_w     = Point();
        objective = Point();
    }
}

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

void
ShipAI::FindObjectiveTarget(SimObject* tgt)
{
    if (!tgt) {
        obj_w = Point();
        return;
    }

    navpt = 0; // this tells fire control that we are chasing a target,
    // instead of a navpoint!

    Point  cv   = ClosingVelocity();
    double cvl  = cv.length();
    double time = 0;

    if (cvl > 50) {
        // distance from self to target:
        distance = Point(tgt->Location() - self->Location()).length();

        // time to reach target:
        time = distance / cvl;

        // where the target will be when we reach it:
        if (time < 15) {
            Point run_vec = tgt->Velocity();
            obj_w   = tgt->Location() + (run_vec * time);


            if (time < 10)
            obj_w += (tgt->Acceleration() * 0.33 * time * time);
        }
        else {
            obj_w = tgt->Location();
        }
    }

    else {
        obj_w = tgt->Location();
    }

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

    if (cvl > 50) {
        time = distance / cvl;

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

            obj_w += err;
        }
    }

    Point approach = obj_w - self->Location();
    distance = approach.length();

    if (bracket && distance > 25e3) {
        Point offset = approach.cross(Point(0,1,0));
        offset.Normalize();
        offset *= 15e3;

        Ship* s = (Ship*) self;
        if (s->GetElementIndex() & 1)
        obj_w -= offset;
        else
        obj_w += offset;
    }
}

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

void
ShipAI::FindObjectivePatrol()
{
    navpt = 0;

    Point npt = patrol_loc;
    obj_w = npt;

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

    if (distance < 1000) {
        ship->ClearRadioOrders();
        ClearPatrol();
    }
}

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

void
ShipAI::FindObjectiveNavPoint()
{
    SimRegion*     self_rgn = ship->GetRegion();
    SimRegion*     nav_rgn  = navpt->Region();
    QuantumDrive*  qdrive   = ship->GetQuantumDrive();

    if (!self_rgn)
    return;

    if (!nav_rgn) {
        nav_rgn = self_rgn;
        navpt->SetRegion(nav_rgn);
    }

    bool use_farcaster      = self_rgn != nav_rgn &&
    (navpt->Farcast() ||
    !qdrive ||
    !qdrive->IsPowerOn() ||
    qdrive->Status() < System::DEGRADED
    );

    if (use_farcaster) {
        FindObjectiveFarcaster(self_rgn, nav_rgn);
    }

    else {
        if (farcaster) {
            if (farcaster->GetShip()->GetRegion() != self_rgn)
            farcaster = farcaster->GetDest()->GetFarcaster();

            obj_w = farcaster->EndPoint();
        }

        else {
            // transform from starsystem to world coordinates:
            Point npt = navpt->Region()->Location() + navpt->Location();

            SimRegion* active_region = ship->GetRegion();

            if (active_region)
            npt -= active_region->Location();

            npt = npt.OtherHand();

            obj_w = npt;
        }

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

        if (farcaster && distance < 1000)
        farcaster = 0;

        if (distance <  1000 || (navpt->Action() == Instruction::LAUNCH && distance > 25000))
        ship->SetNavptStatus(navpt, Instruction::COMPLETE);
    }
}

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

void
ShipAI::FindObjectiveQuantum()
{
    Instruction*   orders   = ship->GetRadioOrders();
    SimRegion*     self_rgn = ship->GetRegion();
    SimRegion*     nav_rgn  = orders->Region();
    QuantumDrive*  qdrive   = ship->GetQuantumDrive();

    if (!self_rgn || !nav_rgn)
    return;

    bool use_farcaster      = self_rgn != nav_rgn &&
    (orders->Farcast() ||
    !qdrive ||
    !qdrive->IsPowerOn() ||
    qdrive->Status() < System::DEGRADED
    );

    if (use_farcaster) {
        FindObjectiveFarcaster(self_rgn, nav_rgn);
    }

    else {
        if (farcaster) {
            if (farcaster->GetShip()->GetRegion() != self_rgn)
            farcaster = farcaster->GetDest()->GetFarcaster();

            obj_w = farcaster->EndPoint();
        }

        else {
            // transform from starsystem to world coordinates:
            Point npt = orders->Region()->Location() + orders->Location();

            SimRegion* active_region = ship->GetRegion();

            if (active_region)
            npt -= active_region->Location();

            npt = npt.OtherHand();

            obj_w = npt;

            if (qdrive && qdrive->ActiveState() == QuantumDrive::ACTIVE_READY) {
                qdrive->SetDestination(nav_rgn, orders->Location());
                qdrive->Engage();
                return;
            }
        }

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

        if (farcaster) {
            if (distance < 1000) {
                farcaster = 0;
                ship->ClearRadioOrders();
            }
        }
        else if (self_rgn == nav_rgn) {
            ship->ClearRadioOrders();
        }
    }
}

void
ShipAI::FindObjectiveFarcaster(SimRegion* src_rgn, SimRegion* dst_rgn)
{
    if (!farcaster) {
        ListIter<Ship> s = src_rgn->Ships();
        while (++s && !farcaster) {
            if (s->GetFarcaster()) {
                const Ship* dest = s->GetFarcaster()->GetDest();
                if (dest && dest->GetRegion() == dst_rgn) {
                    farcaster = s->GetFarcaster();
                }
            }
        }
    }

    if (farcaster) {
        Point apt   = farcaster->ApproachPoint(0);
        Point npt   = farcaster->StartPoint();
        double r1   = (ship->Location() - npt).length();

        if (r1 > 50e3) {
            obj_w     = apt;
            distance  = r1;
        }

        else {
            double r2 = (ship->Location() - apt).length();
            double r3 = (npt - apt).length();

            if (r1+r2 < 1.2*r3) {
                obj_w     = npt;
                distance  = r1;
            }
            else {
                obj_w     = apt;
                distance  = r2;
            }
        }

        objective = Transform(obj_w);
    }
}

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

void
ShipAI::SetFormationDelta(const Point& point)
{
    formation_delta = point;
}

void
ShipAI::FindObjectiveFormation()
{
    const double prediction = 5;

    // find the base position:
    Element* elem = ship->GetElement();
    Ship*    lead = elem->GetShip(1);
    Ship*    ward = ship->GetWard();

    if (!lead || lead == ship) {
        lead = ward;

        distance = (lead->Location() - self->Location()).length();
        if (distance < 30e3 && lead->Velocity().length() < 50) {
            obj_w = self->Location() + lead->Heading() * 1e6;
            distance = -1;
            return;
        }
    }

    obj_w       = lead->Location() + lead->Velocity() * prediction;
    Matrix m;   m.Rotate(0, 0, lead->CompassHeading() - PI);
    Point  fd   = formation_delta * m;
    obj_w       += fd;

    // try to avoid smacking into the ground...
    if (ship->IsAirborne()) {
        if (ship->AltitudeAGL() < 3000 || lead->AltitudeAGL() < 3000) {
            obj_w.y += 500;
        }
    }

    Point dst_w = self->Location() + self->Velocity() * prediction;
    Point dlt_w = obj_w - dst_w;

    distance    = dlt_w.length();

    // get slot z distance:
    dlt_w       += ship->Location();
    slot_dist   = Transform(dlt_w).z;

    Director* lead_dir = lead->GetDirector();
    if (lead_dir && (lead_dir->Type() == FIGHTER || lead_dir->Type() == STARSHIP)) {
        ShipAI* lead_ai = (ShipAI*) lead_dir;
        farcaster = lead_ai->GetFarcaster();
    }
    else {
        Instruction* navpt = elem->GetNextNavPoint();
        if (!navpt) {
            farcaster = 0;
            return;
        }

        SimRegion*     self_rgn = ship->GetRegion();
        SimRegion*     nav_rgn  = navpt->Region();
        QuantumDrive*  qdrive   = ship->GetQuantumDrive();

        if (self_rgn && !nav_rgn) {
            nav_rgn = self_rgn;
            navpt->SetRegion(nav_rgn);
        }

        bool use_farcaster      = self_rgn != nav_rgn &&
        (navpt->Farcast() ||
        !qdrive ||
        !qdrive->IsPowerOn() ||
        qdrive->Status() < System::DEGRADED
        );

        if (use_farcaster) {
            ListIter<Ship> s = self_rgn->Ships();
            while (++s && !farcaster) {
                if (s->GetFarcaster()) {
                    const Ship* dest = s->GetFarcaster()->GetDest();
                    if (dest && dest->GetRegion() == nav_rgn) {
                        farcaster = s->GetFarcaster();
                    }
                }
            }
        }
        else if (farcaster) {
            if (farcaster->GetShip()->GetRegion() != self_rgn)
            farcaster = farcaster->GetDest()->GetFarcaster();

            obj_w = farcaster->EndPoint();
            distance = Point(obj_w - ship->Location()).length();

            if (distance < 1000)
            farcaster = 0;
        }
    }
}

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

void
ShipAI::Splash(const Ship* targ)
{
    if (splash_count > 6)
    splash_count = 4;

    // call splash:
    RadioTraffic::SendQuickMessage(ship, RadioMessage::SPLASH_1 + splash_count);
    splash_count++;
}

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

void
ShipAI::SetTarget(SimObject* targ, System* sub)
{
    if (targ != target) {
        bracket = false;
    }

    SteerAI::SetTarget(targ, sub);
}

void
ShipAI::DropTarget(double dtime)
{
    SetTarget(0);
    drop_time = dtime;    // seconds until we can re-acquire

    ship->DropTarget();
}

void
ShipAI::SetBracket(bool b)
{
    bracket = b;
    identify = false;
}

void
ShipAI::SetIdentify(bool i)
{
    identify = i;
    bracket = false;
}

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

void
ShipAI::Navigator()
{
    accumulator.Clear();
    magnitude = 0;

    hold = false;
    if ((ship->GetElement() && ship->GetElement()->GetHoldTime() > 0) ||
            (navpt && navpt->Status() == Instruction::COMPLETE && navpt->HoldTime() > 0))
    hold = true;

    ship->SetFLCSMode(Ship::FLCS_HELM);

    if (target)
    ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.seek-target"));
    else if (rumor)
    ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.seek-rumor"));
    else
    ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.none"));

    Accumulate(AvoidCollision());
    Accumulate(AvoidTerrain());

    if (!hold)
    Accumulate(SeekTarget());

    HelmControl();
    ThrottleControl();
    FireControl();
    AdjustDefenses();
}

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

void
ShipAI::HelmControl()
{
    double trans_x = 0;
    double trans_y = 0;
    double trans_z = 0;

    ship->SetHelmHeading(accumulator.yaw);

    if (fabs(accumulator.pitch) < 5*DEGREES || fabs(accumulator.pitch) > 45*DEGREES) {
        trans_z = objective.y;
        ship->SetHelmPitch(0);
    }

    else {
        ship->SetHelmPitch(accumulator.pitch);
    }

    ship->SetTransX(trans_x);
    ship->SetTransY(trans_y);
    ship->SetTransZ(trans_z);

    ship->ExecFLCSFrame();
}

/*****************************************
**
**  NOTE:
**  No one is really using this method.
**  It is overridden by both StarshipAI
**  and FighterAI.
**
*****************************************/

void
ShipAI::ThrottleControl()
{
    if (navpt && !threat && !target) {     // lead only, get speed from navpt
        double speed = navpt->Speed();

        if (speed > 0)
        throttle = speed / ship->VelocityLimit() * 100;
        else
        throttle = 50;
    }

    else if (patrol && !threat && !target) { // lead only, get speed from navpt
        double speed = 200;

        if (distance > 5000)
        speed = 500;

        if (ship->Velocity().length() > speed)
        throttle = 0;
        else
        throttle = 50;
    }

    else {
        if (threat || target || element_index < 2) { // element lead
            throttle = 100;

            if (!threat && !target)
            throttle = 50;

            if (accumulator.brake > 0) {
                throttle *= (1 - accumulator.brake);
            }
        }

        else {                                       // wingman
            Ship*  lead = ship->GetElement()->GetShip(1);
            double lv = lead->Velocity().length();
            double sv = ship->Velocity().length();
            double dv = lv-sv;
            double dt = 0;

            if (dv > 0)       dt = dv * 1e-2 * seconds;
            else if (dv < 0)  dt = dv * 1e-2 * seconds;

            throttle = old_throttle + dt;
        }
    }

    old_throttle = throttle;
    ship->SetThrottle((int) throttle);
}

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

void
ShipAI::NavlightControl()
{
    Ship* leader  = ship->GetLeader();

    if (leader && leader != ship) {
        bool navlight_enabled = false;

        if (leader->NavLights().size() > 0)
        navlight_enabled = leader->NavLights().at(0)->IsEnabled();

        for (int i = 0; i < ship->NavLights().size(); i++) {
            if (navlight_enabled)
            ship->NavLights().at(i)->Enable();
            else
            ship->NavLights().at(i)->Disable();
        }
    }
}

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

Steer
ShipAI::AvoidTerrain()
{
    Steer avoid;
    return avoid;
}

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

Steer
ShipAI::AvoidCollision()
{
    Steer avoid;

    if (!ship || !ship->GetRegion() || !ship->GetRegion()->IsActive())
    return avoid;

    if (other && (other->Life() == 0 || other->Integrity() < 1)) {
        other = 0;
        last_avoid_time = 0; // check for a new obstacle immediately
    }

    if (!other && Clock::GetInstance()->GameTime() - last_avoid_time < 500)
    return avoid;

    brake = 0;

    // don't get closer than this:
    double avoid_dist = 5 * self->Radius();

    if      (avoid_dist <  1e3) avoid_dist =  1e3;
    else if (avoid_dist > 12e3) avoid_dist = 12e3;

    // find the soonest potential collision,
    // ignore any that occur after this:
    double avoid_time = 15;

    if (ship->Design()->avoid_time > 0)
    avoid_time = ship->Design()->avoid_time;
    else if (ship->IsStarship())
    avoid_time *= 1.5;

    Point  bearing = self->Velocity();
    bearing.Normalize();

    bool              found          = false;
    int               num_contacts   = ship->NumContacts();
    ListIter<Contact> contact        = ship->ContactList();

    // check current obstacle first:
    if (other) {
        found = AvoidTestSingleObject(other, bearing, avoid_dist, avoid_time, avoid);
    }

    if (!found) {
        // avoid ships:
        while (++contact && !found) {
            Ship* c_ship = contact->GetShip();

            if (c_ship && c_ship != ship && c_ship->IsStarship()) {
                found = AvoidTestSingleObject(c_ship, bearing, avoid_dist, avoid_time, avoid);
            }
        }

        // also avoid large pieces of debris:
        if (!found) {
            ListIter<Debris> iter = ship->GetRegion()->Rocks();
            while (++iter && !found) {
                Debris* debris = iter.value();

                if (debris->Mass() > ship->Mass())
                found = AvoidTestSingleObject(debris, bearing, avoid_dist, avoid_time, avoid);
            }
        }

        // and asteroids:
        if (!found) {
            // give asteroids a wider berth -
            avoid_dist *= 8;

            ListIter<Asteroid> iter = ship->GetRegion()->Roids();
            while (++iter && !found) {
                Asteroid* roid = iter.value();
                found = AvoidTestSingleObject(roid, bearing, avoid_dist, avoid_time, avoid);
            }

            if (!found)
            avoid_dist /= 8;
        }

        // if found, steer to avoid:
        if (other) {
            avoid = Avoid(obstacle, (float) (ship->Radius() + other->Radius() + avoid_dist * 0.9));
            avoid.brake = brake;

            ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.avoid-collision"));
        }
    }

    last_avoid_time = Clock::GetInstance()->GameTime();
    return avoid;
}

bool
ShipAI::AvoidTestSingleObject(SimObject*     obj,
const Point&   bearing,
double         avoid_dist,
double&        avoid_time,
Steer&         avoid)
{
    if (too_close == obj->Identity()) {
        double dist = (ship->Location() - obj->Location()).length();
        double closure = (ship->Velocity() - obj->Velocity()) * bearing;

        if (closure > 1 && dist < avoid_dist) {
            avoid = AvoidCloseObject(obj);
            return true;
        }
        else {
            too_close = 0;
        }
    }

    // will we get close?
    double time = ClosestApproachTime(ship->Location(), ship->Velocity(),
    obj->Location(),  obj->Velocity());

    // already past the obstacle:
    if (time <= 0) {
        if (other == obj) other = 0;
        return false;
    }

    // how quickly could we collide?
    Point  current_relation = ship->Location() - obj->Location();
    double current_distance = current_relation.length() - ship->Radius() - obj->Radius();

    // are we really far away?
    if (current_distance > 25e3) {
        if (other == obj) other = 0;
        return false;
    }

    // is the obstacle a farcaster?
    if (obj->Type() == SimObject::SIM_SHIP) {
        Ship* c_ship = (Ship*) obj;

        if (c_ship->GetFarcaster()) {
            // are we on a safe vector?
            Point dir = ship->Velocity();
            dir.Normalize();

            double angle_off = fabs(acos(dir * obj->Cam().vpn()));

            if (angle_off > 90*DEGREES)
            angle_off = 180*DEGREES - angle_off;

            if (angle_off < 35*DEGREES) {
                // will we pass through the center?
                Point  d   = ship->Location() + dir * (current_distance + ship->Radius() + obj->Radius());
                double err = (obj->Location() - d).length();

                if (err < 0.667 * obj->Radius()) {
                    return false;
                }
            }
        }
    }

    // rate of closure:
    double closing_velocity = (ship->Velocity() - obj->Velocity()) * bearing;

    // are we too close already?
    if (current_distance < (avoid_dist * 0.35)) {
        if (closing_velocity > 1 || current_distance < ship->Radius()) {
            avoid = AvoidCloseObject(obj);
            return true;
        }
    }

    // too far away to worry about:
    double separation = (avoid_dist + obj->Radius());
    if ((current_distance-separation) / closing_velocity > avoid_time) {
        if (other == obj) other = 0;
        return false;
    }

    // where will we be?
    Point selfpt = ship->Location()   + ship->Velocity()   * time;
    Point testpt = obj->Location() + obj->Velocity() * time;

    // how close will we get?
    double dist = (selfpt - testpt).length()
    - ship->Radius()
    - obj->Radius();

    // that's too close:
    if (dist < avoid_dist) {
        if (dist < avoid_dist * 0.25 && time < avoid_time * 0.5) {
            avoid = AvoidCloseObject(obj);
            return true;
        }

        obstacle = Transform(testpt);

        if (obstacle.z > 0) {
            other      = obj;
            avoid_time = time;
            brake      = 0.5;

            Observe(other);
        }
    }

    // hysteresis:
    else if (other == obj && dist > avoid_dist * 1.25) {
        other = 0;
    }

    return false;
}

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

Steer
ShipAI::AvoidCloseObject(SimObject* obj)
{
    too_close  = obj->Identity();
    obstacle   = Transform(obj->Location());
    other      = obj;

    Observe(other);

    Steer avoid = Flee(obstacle);
    avoid.brake = 0.3;

    ship->SetDirectorInfo(ContentBundle::GetInstance()->GetText("ai.avoid-collision"));
    return avoid;
}

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

Steer
ShipAI::SeekTarget()
{
    Ship* ward  = ship->GetWard();

    if (!target && !ward && !navpt && !patrol) {
        if (element_index > 1) {
            // wingmen keep in formation:
            return Seek(objective);
        }

        if (farcaster) {
            return Seek(objective);
        }

        if (rumor) {
            return Seek(objective);
        }

        return Steer();
    }

    if (patrol) {
        Steer result = Seek(objective);

        if (distance <  2000) {
            result.brake = 1;
        }

        return result;
    }

    if (target && too_close == target->Identity()) {
        drop_time = 4;
        return Avoid(objective, 0.0f);
    }
    else if (drop_time > 0) {
        return Steer();
    }

    return Seek(objective);
}

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

Steer
ShipAI::EvadeThreat()
{
    return Steer();
}

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

void
ShipAI::FireControl()
{
}

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

void
ShipAI::AdjustDefenses()
{
    Shield* shield = ship->GetShield();

    if (shield) {
        double  desire = 50;

        if (threat_missile || threat)
        desire = 100;

        shield->SetPowerLevel(desire);
    }
}

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

void
ShipAI::CheckTarget()
{
    if (target) {
        if (target->Life() == 0)
        target = 0;

        else if (target->Type() == SimObject::SIM_SHIP) {
            Ship* tgt_ship = (Ship*) target;

            if (tgt_ship->GetIFF() == ship->GetIFF() && !tgt_ship->IsRogue())
            target = 0;
        }
    }
}