#include <Gosu/Color.hpp>
#include <Gosu/Math.hpp>
#include <cmath>
#include <algorithm>

namespace
{
    struct HSV { double h, s, v; };
    
    HSV color_to_hsv(const Gosu::Color& c)
    {
        double r = c.red() / 255.0;
        double g = c.green() / 255.0;
        double b = c.blue() / 255.0;
        
        double min = std::min(std::min(r, g), b);
        double max = std::max(std::max(r, g), b);
        double delta = max - min;

        if (max == 0) {
            HSV hsv = { 0, 0, 0 };
            return hsv;
        }
        
        HSV hsv;

        // Value.
        hsv.v = max;
        
        // Saturation.
        hsv.s = delta / max;
        
        // Hue.
        if (delta == 0) {
            hsv.h = 0;
        }
        else if (r == max) {
            hsv.h = (g - b) / delta + (g < b ? 6 : 0);
        }
        else if (g == max) {
            hsv.h = (b - r) / delta + 2;
        }
        else {
            hsv.h = (r - g) / delta + 4;
        }
        hsv.h *= 60;
        
        return hsv;
    }
}

Gosu::Color Gosu::Color::from_hsv(double h, double s, double v)
{
    return from_ahsv(255, h, s, v);
}

Gosu::Color Gosu::Color::from_ahsv(Channel alpha, double h, double s, double v)
{
    // Normalize hue so that is always in the [0, 360) range and wraps around.
    h = normalize_angle(h);
    // Clamp s and v for consistency with the Ruby/Gosu ARGB getters/setters.
    s = clamp(s, 0.0, 1.0);
    v = clamp(v, 0.0, 1.0);
    
    int sector = static_cast<int>(h / 60);
    double factorial = h / 60 - sector;
    
    double p = v * (1 - s);
    double q = v * (1 - s * factorial);
    double t = v * (1 - s * (1 - factorial));
    
    switch (sector) {
    case 0:
        return Color(alpha, v * 255, t * 255, p * 255);
    case 1:
        return Color(alpha, q * 255, v * 255, p * 255);
    case 2:
        return Color(alpha, p * 255, v * 255, t * 255);
    case 3:
        return Color(alpha, p * 255, q * 255, v * 255);
    case 4:
        return Color(alpha, t * 255, p * 255, v * 255);
    default: // sector 5
        return Color(alpha, v * 255, p * 255, q * 255);
    }
}

double Gosu::Color::hue() const
{
    return color_to_hsv(*this).h;
}

void Gosu::Color::set_hue(double h)
{
    *this = from_ahsv(alpha(), h, saturation(), value());
}

double Gosu::Color::saturation() const
{
    return color_to_hsv(*this).s;
}

void Gosu::Color::set_saturation(double s)
{
    *this = from_ahsv(alpha(), hue(), s, value());
}

double Gosu::Color::value() const
{
    return color_to_hsv(*this).v;
}

void Gosu::Color::set_value(double v)
{
    *this = from_ahsv(alpha(), hue(), saturation(), v);
}

Gosu::Color Gosu::interpolate(Color a, Color b, double weight)
{
    return Color(clamp<long>(round(interpolate(a.alpha(), b.alpha(), weight)), 0, 255),
                 clamp<long>(round(interpolate(a.red(),   b.red(),   weight)), 0, 255),
                 clamp<long>(round(interpolate(a.green(), b.green(), weight)), 0, 255),
                 clamp<long>(round(interpolate(a.blue(),  b.blue(),  weight)), 0, 255));
}

Gosu::Color Gosu::multiply(Color a, Color b)
{
    return Color(round(a.alpha() * b.alpha() / 255.0),
                 round(a.red()   * b.red()   / 255.0),
                 round(a.green() * b.green() / 255.0),
                 round(a.blue()  * b.blue()  / 255.0));
}

const Gosu::Color Gosu::Color::NONE      (0x00000000);
const Gosu::Color Gosu::Color::BLACK     (0xff000000);
const Gosu::Color Gosu::Color::GRAY      (0xff808080);
const Gosu::Color Gosu::Color::WHITE     (0xffffffff);
const Gosu::Color Gosu::Color::AQUA      (0xff00ffff);
const Gosu::Color Gosu::Color::RED       (0xffff0000);
const Gosu::Color Gosu::Color::GREEN     (0xff00ff00);
const Gosu::Color Gosu::Color::BLUE      (0xff0000ff);
const Gosu::Color Gosu::Color::YELLOW    (0xffffff00);
const Gosu::Color Gosu::Color::FUCHSIA   (0xffff00ff);
const Gosu::Color Gosu::Color::CYAN      (0xff00ffff);