#include "cloudshader.h"
#include "common/noise/cloudnoise.h"
#include "common/noise/perlinnoise.h"


Color CloudShader::shade(const Scene &scene, const Ray &ray) const
{
    Vector3d hitPoint = ray.origin + ray.direction * ray.length; // Potentially add epsilon

    // Collect getNoise through the cloud
    float cloudLength = 0.0f;   // Length of cloud in ray direction

    // Get background color behind cloud and information about the clouds length
    Ray cloudRay = ray;
    cloudRay.origin = ray.origin + (ray.length + REFR_EPS) * ray.direction;
    cloudRay.length = INFINITY;
    cloudRay.primitive = nullptr;

    // Get out of cloud primitive first
    if (ray.primitive->intersect(cloudRay))
    {
        // Get length
        cloudLength = cloudRay.length;

        // Prepare ray for background color
        cloudRay.setRemainingBounces(cloudRay.getRemainingBounces() + 1);
        cloudRay.origin = cloudRay.origin + (cloudRay.length + REFR_EPS) * cloudRay.direction;
        cloudRay.length = INFINITY;
        cloudRay.primitive = nullptr;
    }
    Color background = scene.traceRay(cloudRay);

    if (cloudLength == 0.0f) return background; // No cloud or at edge

    // Calculate step length
    int noiseSamples = settings.densitySamples;
    float stepLength = cloudLength / noiseSamples;

    // Step through cloud
    float transmittance = 1.0f;
    for (int i = 0; i < noiseSamples; ++i)
    {
        // Get sample point
        Vector3d samplePoint = hitPoint + i * stepLength * ray.direction;

        // Get data at point
        float sampleDensity = getCloudDensity(samplePoint) * stepLength;

        transmittance *= exp(-sampleDensity * stepLength * settings.densityAbsorption);
    }

    // Add some ambient and diffuse lighting
//    cloud += scene.ambientLight() * material.ambient();
//    for (const auto &light: scene.lights())
//    {
//        Light::Illumination illumination = light->illuminate(scene, ray);
//        if (illumination.distance == 0.0f) continue; // Skip ambient light
//        float diffuse = dotProduct(normal, illumination.direction);
//        cloud += material.cloud() * illumination.cloud * diffuse;
//    }

    return background * transmittance + (1.0f - transmittance) * settings.cloudColor;
}

bool CloudShader::isTransparent() const
{
    return true;
}

CloudShader::CloudShader(const CloudSettings &settings) : settings(settings),
                                                          cloudNoise(CloudNoise(NOISE_SIZE))
{
    cloudNoise.invert = true;
}

float CloudShader::getCloudDensity(Vector3d point) const
{
    point /= settings.scale;

    float density = cloudNoise.getNoise(point);

    // Treshold
    density = std::max(0.0f, density - settings.densityTreshold) * settings.densityIntensity;

    return density;
}