#include "scene/SphereSegment.h"

SphereSegment::SphereSegment(void) {}

SphereSegment::SphereSegment(float radius,
    unsigned int longitudeSteps,
    unsigned int lattitudeSteps,
    float longStart,
    float longEnd,
    float latStart,
    float latEnd) {
    Compute(radius, longitudeSteps, lattitudeSteps, longStart, longEnd, latStart, latEnd);
}

SphereSegment::SphereSegment(const SphereSegment& copy, const osg::CopyOp& copyop) :
    osg::Geode(copy, copyop) {}

SphereSegment::~SphereSegment(void) {}

// 0 >= longStart/longEnd <= 180
// 0 >= latStart/latEnd <= 360

void SphereSegment::Compute(float radius,
    unsigned int longitudeSteps,
    unsigned int lattitudeSteps,
    float longStart,
    float longEnd,
    float latStart,
    float latEnd)

{
    removeDrawables(0, getNumDrawables());

    osg::Vec3Array* vertices = new osg::Vec3Array();
    osg::Vec2Array* texcoords = new osg::Vec2Array();

    double x, y, z, t, p, sin_t, cos_t;

    double longInc = (longEnd - longStart) / (double)longitudeSteps;
    double latInc = (latEnd - latStart) / (double)lattitudeSteps;

    double theta = longStart, phi = latStart;

    float uScale = 1.f / longitudeSteps;
    float vScale = 1.f / lattitudeSteps;

    for (unsigned int i = 0; i <= longitudeSteps; ++i) {
        t = osg::DegreesToRadians(theta);
        sin_t = sin(t);
        cos_t = cos(t);

        for (unsigned int j = 0; j <= lattitudeSteps; ++j) {
            p = osg::DegreesToRadians(phi);

            x = radius * sin_t * cos(p);
            y = radius * sin_t * sin(p);
            z = radius * cos_t;

            vertices->push_back(osg::Vec3(x, y, z));
            texcoords->push_back(osg::Vec2(j * vScale, i * uScale));

            phi += latInc;
        }

        theta -= longInc;
        phi = latStart;
    }

    osg::ref_ptr<osg::Geometry> geom = new osg::Geometry();

    for (unsigned int r = 0; r <= longitudeSteps - 1; r += 1) {
        osg::DrawElementsUInt* indices =
            new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLE_STRIP, 0);

        for (unsigned int c = 0; c <= lattitudeSteps; c += 1) {
            indices->push_back(Idx(r, c, lattitudeSteps + 1));
            indices->push_back(Idx(r + 1, c, lattitudeSteps + 1));
        }

        geom->addPrimitiveSet(indices);
    }

    osg::Vec4Array* colors = new osg::Vec4Array();
    colors->push_back(osg::Vec4(1.f, 1.f, 1.f, 1.f));

    geom->setVertexArray(vertices);
    geom->setTexCoordArray(0, texcoords);
    geom->setColorArray(colors);
    geom->setColorBinding(osg::Geometry::BIND_OVERALL);

    addDrawable(geom.get());
}

osg::Vec2 SphereSegment::SphereMap(osg::Vec3& vertex, float radius) {
    float u, v;

    float TWOPI = osg::PI * 2.f;

    v = acos(vertex.y() / radius) / osg::PI;

    if (vertex.z() >= 0.f)
        u = acos(vertex.x() / (radius * sin(osg::PI * v))) / TWOPI;
    else
        u = (osg::PI + acos(vertex.x() / (radius * sin(osg::PI * v)))) / TWOPI;

    return osg::Vec2(u, v);
}