/**
  @file GLight.cpp

  @maintainer Morgan McGuire, http://graphics.cs.williams.edu

  @created 2003-11-12
  @edited  2009-11-16
*/
#include "GLight.hpp"
#include "Sphere.hpp"
#include "CoordinateFrame.hpp"
#include "stringutils.hpp"

namespace G3D
{

GLight::GLight()
    : position(0, 0, 0, 0)
    , rightDirection(0, 0, 0)
    , spotDirection(0, 0, -1)
    , spotCutoff(180)
    , spotSquare(false)
    , color(Color3::white())
    , enabled(false)
    , specular(true)
    , diffuse(true)
{

    attenuation[0] = 1.0;
    attenuation[1] = 0.0;
    attenuation[2] = 0.0;
}


GLight GLight::directional(const Vector3& toLight, const Color3& color, bool s, bool d)
{
    GLight L;
    L.position = Vector4(toLight.direction(), 0);
    L.color = color;
    L.specular = s;
    L.diffuse = d;
    return L;
}


GLight GLight::point(const Vector3& pos, const Color3& color, float constAtt, float linAtt, float quadAtt, bool s, bool d)
{
    GLight L;
    L.position = Vector4(pos, 1);
    L.color = color;
    L.attenuation[0] = constAtt;
    L.attenuation[1] = linAtt;
    L.attenuation[2] = quadAtt;
    L.specular = s;
    L.diffuse = d;
    return L;
}


GLight GLight::spot(const Vector3& pos, const Vector3& pointDirection, float cutOffAngleDegrees, const Color3& color, float constAtt, float linAtt,
    float quadAtt, bool s, bool d)
{
    GLight L;
    L.position = Vector4(pos, 1.0f);
    L.spotDirection = pointDirection.direction();
    debugAssert(cutOffAngleDegrees <= 90);
    L.spotCutoff = cutOffAngleDegrees;
    L.color = color;
    L.attenuation[0] = constAtt;
    L.attenuation[1] = linAtt;
    L.attenuation[2] = quadAtt;
    L.specular = s;
    L.diffuse = d;
    return L;
}


bool GLight::operator==(const GLight& other) const
{
    return (position == other.position) && (rightDirection == other.rightDirection) && (spotDirection == other.spotDirection) &&
           (spotCutoff == other.spotCutoff) && (spotSquare == other.spotSquare) && (attenuation[0] == other.attenuation[0]) &&
           (attenuation[1] == other.attenuation[1]) && (attenuation[2] == other.attenuation[2]) && (color == other.color) &&
           (enabled == other.enabled) && (specular == other.specular) && (diffuse == other.diffuse);
}


bool GLight::operator!=(const GLight& other) const
{
    return !(*this == other);
}


Sphere GLight::effectSphere(float cutoff) const
{
    if (position.w == 0)
    {
        // Directional light
        return Sphere(Vector3::zero(), finf());
    }
    else
    {
        // Avoid divide by zero
        cutoff = max(cutoff, 0.00001f);
        float maxIntensity = max(color.r, max(color.g, color.b));

        float radius = finf();

        if (attenuation[2] != 0)
        {

            // Solve I / attenuation.dot(1, r, r^2) < cutoff for r
            //
            //  a[0] + a[1] r + a[2] r^2 > I/cutoff
            //

            float a = attenuation[2];
            float b = attenuation[1];
            float c = attenuation[0] - maxIntensity / cutoff;

            float discrim = square(b) - 4 * a * c;

            if (discrim >= 0)
            {
                discrim = sqrt(discrim);

                float r1 = (-b + discrim) / (2 * a);
                float r2 = (-b - discrim) / (2 * a);

                if (r1 < 0)
                {
                    if (r2 > 0)
                    {
                        radius = r2;
                    }
                }
                else if (r2 > 0)
                {
                    radius = min(r1, r2);
                }
                else
                {
                    radius = r1;
                }
            }
        }
        else if (attenuation[1] != 0)
        {

            // Solve I / attenuation.dot(1, r) < cutoff for r
            //
            // r * a[1] + a[0] = I / cutoff
            // r = (I / cutoff - a[0]) / a[1]

            float radius = (maxIntensity / cutoff - attenuation[0]) / attenuation[1];
            radius = max(radius, 0.0f);
        }

        return Sphere(position.xyz(), radius);
    }
}


CoordinateFrame GLight::frame() const
{
    CoordinateFrame f;
    if (rightDirection == Vector3::zero())
    {
        // No specified right direction; choose one automatically
        if (position.w == 0)
        {
            // Directional light
            f.lookAt(-position.xyz());
        }
        else
        {
            // Spot light
            f.lookAt(spotDirection);
        }
    }
    else
    {
        const Vector3& Z = -spotDirection.direction();
        Vector3 X = rightDirection.direction();

        // Ensure the vectors are not too close together
        while (abs(X.dot(Z)) > 0.9f)
        {
            X = Vector3::random();
        }

        // Ensure perpendicular
        X -= Z * Z.dot(X);
        const Vector3& Y = Z.cross(X);

        f.rotation.setColumn(Vector3::X_AXIS, X);
        f.rotation.setColumn(Vector3::Y_AXIS, Y);
        f.rotation.setColumn(Vector3::Z_AXIS, Z);
    }
    f.translation = position.xyz();

    return f;
}


} // namespace G3D