
#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "Math.hpp"
#include "BodyEnvironment.hpp"
#include "RigidBody.hpp"

#include <cfloat>
#include <simgear/bvh/BVHMaterial.hxx>
#include <FDM/flight.hxx>
#include "Gear.hpp"
namespace yasim {
static const float YASIM_PI = 3.14159265358979323846;
static const float maxGroundBumpAmplitude=0.4;
        //Amplitude can be positive and negative

Gear::Gear()
{
    int i;
    for(i=0; i<3; i++)
        _pos[i] = _cmpr[i] = 0;
    _spring = 1;
    _damp = 0;
    _sfric = 0.8f;
    _dfric = 0.7f;
    _brake = 0;
    _rot = 0;
    _initialLoad = 0;
    _extension = 1;
    _castering = false;
    _frac = 0;
    _ground_frictionFactor = 1;
    _ground_rollingFriction = 0.02;
    _ground_loadCapacity = 1e30;
    _ground_loadResistance = 1e30;
    _ground_isSolid = 1;
    _ground_bumpiness = 0;
    _onWater = 0;
    _onSolid = 1;
    _global_x = 0.0;
    _global_y = 0.0;
    _reduceFrictionByExtension = 0;
    _spring_factor_not_planing = 1;
    _speed_planing = 0;
    _isContactPoint = 0;
    _ignoreWhileSolving = 0;

    for(i=0; i<3; i++)
        _global_ground[i] = _global_vel[i] = 0;
    _global_ground[2] = 1;
    _global_ground[3] = -1e3;
}

void Gear::setGlobalGround(double *global_ground, float* global_vel,
                           double globalX, double globalY,
                           const simgear::BVHMaterial *material)
{
    int i;
    double frictionFactor,rollingFriction,loadCapacity,loadResistance,bumpiness;
    bool isSolid;

    for(i=0; i<4; i++) _global_ground[i] = global_ground[i];
    for(i=0; i<3; i++) _global_vel[i] = global_vel[i];

    if (material) {
        loadCapacity = (*material).get_load_resistance();
        frictionFactor =(*material).get_friction_factor();
        rollingFriction = (*material).get_rolling_friction();
        loadResistance = (*material).get_load_resistance();
        bumpiness = (*material).get_bumpiness();
        isSolid = (*material).get_solid();
    } else {
        // no material, assume solid
        loadCapacity = DBL_MAX;
        frictionFactor = 1.0;
        rollingFriction = 0.02;
        loadResistance = DBL_MAX;
        bumpiness = 0.0;
        isSolid = true;
    }
    _ground_frictionFactor = frictionFactor;
    _ground_rollingFriction = rollingFriction;
    _ground_loadCapacity = loadCapacity;
    _ground_loadResistance = loadResistance;
    _ground_bumpiness = bumpiness;
    _ground_isSolid = isSolid;
    _global_x = globalX;
    _global_y = globalY;

}

void Gear::getGlobalGround(double* global_ground)
{
    for(int i=0; i<4; i++) global_ground[i] = _global_ground[i];
}

void Gear::getForce(float* force, float* contact)
{
    Math::set3(_force, force);
    Math::set3(_contact, contact);
}


float Gear::getBumpAltitude()
{
    if (_ground_bumpiness<0.001) return 0.0;
    double x = _global_x*0.1;
    double y = _global_y*0.1;
    x -= Math::floor(x);
    y -= Math::floor(y);
    x *= 2*YASIM_PI;
    y *= 2*YASIM_PI;
    //now x and y are in the range of 0..2pi
    //we need a function, that is periodically on 2pi and gives some
    //height. This is not very fast, but for a beginning.
    //maybe this should be done by interpolating between some precalculated
    //values
    float h = Math::sin(x)+Math::sin(7*x)+Math::sin(8*x)+Math::sin(13*x);
    h += Math::sin(2*y)+Math::sin(5*y)+Math::sin(9*y*x)+Math::sin(17*y);

    return h*(1/8.)*_ground_bumpiness*maxGroundBumpAmplitude;
}

void Gear::integrate(float dt)
{
    // Slowly spin down wheel
    if (_rollSpeed > 0) {
        // The brake factor of 13.0 * dt was copied from JSBSim's FGLGear.cpp and seems to work reasonably.
        // If more precise control is needed, then we need wheel mass and diameter parameters.
        _rollSpeed -= (13.0 * dt + 1300 * _brake * dt);
        if (_rollSpeed < 0) _rollSpeed = 0;
    }
    return;
}

void Gear::calcForce(RigidBody* body, State *s, float* v, float* rot)
{
    // Init the return values
    int i;
    for(i=0; i<3; i++) _force[i] = _contact[i] = 0;

    // Don't bother if gear is retracted
    if(_extension < 1)
    {
        _wow = 0;
        _frac = 0;
        return;
    }

    // Dont bother if we are in the "wrong" ground
    if (!((_onWater&&!_ground_isSolid)||(_onSolid&&_ground_isSolid)))  {
         _wow = 0;
         _frac = 0;
        _compressDist = 0;
        _rollSpeed = 0;
        _casterAngle = 0;
        return;
    }

    // The ground plane transformed to the local frame.
    float ground[4];
    s->planeGlobalToLocal(_global_ground, ground);

    // The velocity of the contact patch transformed to local coordinates.
    float glvel[3];
    s->globalToLocal(_global_vel, glvel);

    // First off, make sure that the gear "tip" is below the ground.
    // If it's not, there's no force.
    float a = ground[3] - Math::dot3(_pos, ground);
    float BumpAltitude=0;
    if (a<maxGroundBumpAmplitude)
    {
        BumpAltitude=getBumpAltitude();
        a+=BumpAltitude;
    }
    _compressDist = -a;
    if(a > 0) {
        _wow = 0;
        _frac = 0;
        _compressDist = 0;
        _casterAngle = 0;
        return;
    }

    // Now a is the distance from the tip to ground, so make b the
    // distance from the base to ground.  We can get the fraction
    // (0-1) of compression from a/(a-b). Note the minus sign -- stuff
    // above ground is negative.
    float tmp[3];
    Math::add3(_cmpr, _pos, tmp);
    float b = ground[3] - Math::dot3(tmp, ground)+BumpAltitude;

    // Calculate the point of ground _contact.
    if(b < 0)
        _frac = 1;
    else
        _frac = a/(a-b);
    for(i=0; i<3; i++)
        _contact[i] = _pos[i] + _frac*_cmpr[i];

    // Turn _cmpr into a unit vector and a magnitude
    float cmpr[3];
    float clen = Math::mag3(_cmpr);
    Math::mul3(1/clen, _cmpr, cmpr);

    // Now get the velocity of the point of contact
    float cv[3];
    body->pointVelocity(_contact, rot, cv);
    Math::add3(cv, v, cv);
    Math::sub3(cv, glvel, cv);

    // Finally, we can start adding up the forces.  First the spring
    // compression.   (note the clamping of _frac to 1):
    _frac = (_frac > 1) ? 1 : _frac;

    // Add the initial load to frac, but with continous transistion around 0
    float frac_with_initial_load;
    if (_frac>0.2 || _initialLoad==0.0)
        frac_with_initial_load = _frac+_initialLoad;
    else
        frac_with_initial_load = (_frac+_initialLoad)
            *_frac*_frac*3*25-_frac*_frac*_frac*2*125;

    float fmag = frac_with_initial_load*clen*_spring;
    if (_speed_planing>0)
    {
        float v = Math::mag3(cv);
        if (v < _speed_planing)
        {
            float frac = v/_speed_planing;
            fmag = fmag*_spring_factor_not_planing*(1-frac)+fmag*frac;
        }
    }
    // Then the damping.  Use the only the velocity into the ground
    // (projection along "ground") projected along the compression
    // axis.  So Vdamp = ground*(ground dot cv) dot cmpr
    Math::mul3(Math::dot3(ground, cv), ground, tmp);
    float dv = Math::dot3(cmpr, tmp);
    float damp = _damp * dv;
    if(damp > fmag) damp = fmag; // can't pull the plane down!
    if(damp < -fmag) damp = -fmag; // sanity

    // The actual force applied is only the component perpendicular to
    // the ground.  Side forces come from velocity only.
    _wow = (fmag - damp) * -Math::dot3(cmpr, ground);
    Math::mul3(-_wow, ground, _force);

    // Wheels are funky.  Split the velocity along the ground plane
    // into rolling and skidding components.  Assuming small angles,
    // we generate "forward" and "left" unit vectors (the compression
    // goes "up") for the gear, make a "steer" direction from these,
    // and then project it onto the ground plane.  Project the
    // velocity onto the ground plane too, and extract the "steer"
    // component.  The remainder is the skid velocity.

    float gup[3]; // "up" unit vector from the ground
    Math::set3(ground, gup);
    Math::mul3(-1, gup, gup);

    float xhat[] = {1,0,0};
    float steer[3], skid[3];
    Math::cross3(gup, xhat, skid);  // up cross xhat =~ skid
    Math::unit3(skid, skid);        //               == skid

    Math::cross3(skid, gup, steer); // skid cross up == steer

    if(_rot != 0) {
        // Correct for a rotation
        float srot = Math::sin(_rot);
        float crot = Math::cos(_rot);
        float tx = steer[0];
        float ty = steer[1];
        steer[0] =  crot*tx + srot*ty;
        steer[1] = -srot*tx + crot*ty;

        tx = skid[0];
        ty = skid[1];
        skid[0] =  crot*tx + srot*ty;
        skid[1] = -srot*tx + crot*ty;
    }

    float vsteer = Math::dot3(cv, steer);
    float vskid  = Math::dot3(cv, skid);
    float wgt = Math::dot3(_force, gup); // force into the ground

    if(_castering) {
        _rollSpeed = Math::sqrt(vsteer*vsteer + vskid*vskid);
        // Don't modify caster angle when the wheel isn't moving,
        // or else the angle will animate the "jitter" of a stopped
        // gear.
        if(_rollSpeed > 0.05)
            _casterAngle = Math::atan2(vskid, vsteer);
        return;
    } else {
        _rollSpeed = vsteer;
        _casterAngle = _rot;
    }
    float fsteer,fskid;
    if(_ground_isSolid)
    {
        fsteer = (_brake * _ground_frictionFactor
                    +(1-_brake)*_ground_rollingFriction
                 )*calcFriction(wgt, vsteer);
        fskid  = calcFriction(wgt, vskid)*(_ground_frictionFactor);
    }
    else
    {
        fsteer = calcFrictionFluid(wgt, vsteer)*_ground_frictionFactor;
        fskid  = 10*calcFrictionFluid(wgt, vskid)*_ground_frictionFactor;
        //factor 10: floats have different drag in x and y.
    }
    if(vsteer > 0) fsteer = -fsteer;
    if(vskid > 0) fskid = -fskid;

    //reduce friction if wanted by _reduceFrictionByExtension
    float factor = (1-_frac)*(1-_reduceFrictionByExtension)+_frac*1;
    factor = Math::clamp(factor,0,1);
    fsteer *= factor;
    fskid *= factor;

    // Phoo!  All done.  Add it up and get out of here.
    Math::mul3(fsteer, steer, tmp);
    Math::add3(tmp, _force, _force);

    Math::mul3(fskid, skid, tmp);
    Math::add3(tmp, _force, _force);
}

float Gear::calcFriction(float wgt, float v) //used on solid ground
{
    // How slow is stopped?  10 cm/second?
    const float STOP = 0.1f;
    const float iSTOP = 1.0f/STOP;
    v = Math::abs(v);
    if(v < STOP) return v*iSTOP * wgt * _sfric;
    else         return wgt * _dfric;
}

float Gear::calcFrictionFluid(float wgt, float v) //used on fluid ground
{
    // How slow is stopped?  1 cm/second?
    const float STOP = 0.01f;
    const float iSTOP = 1.0f/STOP;
    v = Math::abs(v);
    if(v < STOP) return v*iSTOP * wgt * _sfric;
    else return wgt * _dfric*v*v*0.01;
    //*0.01: to get _dfric of the same size than _dfric on solid
}
}; // namespace yasim

