#include <random>
#include "toneshader.h"


ToneShader::ToneShader(std::shared_ptr<Light> light, const Color &highlightColor, const Color &midtoneColor, const Color &shadowColor,
                       float edgeFade)
        : light(light),
          highlightColor(highlightColor),
          midtoneColor(midtoneColor),
          shadowColor(shadowColor),
          edgeFade(edgeFade)
{

}

Color ToneShader::shade(const Scene &scene, const Ray &ray) const
{
    float brightness;

    // Look at light
    Light::Illumination illum;
    illum = light->illuminate(scene, ray);

    if (illum.color.r < 0.01f)
        // Light does not reach the surface
        brightness = 0;
    else
        // Look at angle of light
        brightness = dotProduct(illum.direction,
                                -ray.normal);  // 0 if light is behind surface, 1 if light is in front of surface

    // Get the tone color base on the brightness
    float const HIGHLIGHT_THRESHOLD = 0.95f;
    float const MIDTONE_HIGHLIGHT_THRESHOLD = HIGHLIGHT_THRESHOLD - 0.2f * edgeFade;
    float const SHADOW_MIDTONE_THRESHOLD = 0.01f;
    float const MIDTONE_THRESHOLD = SHADOW_MIDTONE_THRESHOLD + 0.4f * edgeFade;

    // Used for transitions
    std::random_device dev;
    std::uniform_real_distribution<float> randomDistribution(0, 1);

    Color tone;
    if (brightness > HIGHLIGHT_THRESHOLD)
    {
        tone = highlightColor;
    } else if (brightness > MIDTONE_HIGHLIGHT_THRESHOLD)
    {
        float transition =
                (brightness - MIDTONE_HIGHLIGHT_THRESHOLD) / (HIGHLIGHT_THRESHOLD - MIDTONE_HIGHLIGHT_THRESHOLD);
        tone = highlightColor * transition + midtoneColor * (1 - transition);
    } else if (brightness > MIDTONE_THRESHOLD)
    {
        tone = midtoneColor;
    } else if (brightness > SHADOW_MIDTONE_THRESHOLD)
    {
        float transition = (brightness - SHADOW_MIDTONE_THRESHOLD) / (MIDTONE_THRESHOLD - SHADOW_MIDTONE_THRESHOLD);
        tone = midtoneColor * transition + shadowColor * (1 - transition);
    } else
    {
        tone = shadowColor;
    }

    return tone;
}