#include "light/light.h"
#include "scene/scene.h"
#include "shader/materialshader.h"
#include <cmath>
#include <iostream>

Vector3d
tangentToWorldSpace(const Vector3d &surfaceNormal, const Vector3d &surfaceTangent, const Vector3d &surfaceBitangent,
                    const Vector3d &textureNormal)
{
    return textureNormal.x * surfaceTangent + textureNormal.y * surfaceBitangent + textureNormal.z * surfaceNormal;
}

MaterialShader::MaterialShader() : opacity(1.0f), normalCoefficient(1.0f), diffuseCoefficient(0.5f), reflectance(0.0f),
                                   specularCoefficient(0.5f), shininessExponent(8)
{}

Color MaterialShader::shade(Scene const &scene, Ray const &ray) const
{
    Color fragmentColor;
    // IMPLEMENT ME

    // (Normal Map) Calculate the new normal vector
    Vector3d surfaceNormal = ray.normal;
    if (this->normalMap != nullptr)
    {
        auto surfaceNormalMapColor = this->normalMap->color(ray.surface, true);
        Vector3d textureNormal = {surfaceNormalMapColor.r, surfaceNormalMapColor.g, surfaceNormalMapColor.b};
        textureNormal = textureNormal * 2.0f - Vector3d{1, 1, 1};
        surfaceNormal = ray.normal * normalCoefficient +
                        (1 - normalCoefficient) *
                        tangentToWorldSpace(ray.normal, ray.tangent, ray.bitangent, textureNormal);
    }

    // (Diffuse-/Specular Map) Accumulate the light over all light sources
    Color surfaceDiffuseColor(0, 0, 0);
    if (this->diffuseMap != nullptr)
    {
        surfaceDiffuseColor = this->diffuseMap->color(ray.surface, true);
    }

    Color surfaceSpecularColor(0, 0, 0);
    if (this->specularMap != nullptr)
    {
        surfaceSpecularColor = this->specularMap->color(ray.surface, true);
    }


    // (Reflection Map) Calculate the reflectance, create a reflection ray
    Vector3d const reflection = ray.direction - 2 * dotProduct(surfaceNormal, ray.direction) * ray.normal;
    float surfaceReflectanceCoefficient = this->reflectance;
    if (this->reflectionMap != nullptr)
    {
        auto surfaceReflectiveMapColor = this->reflectionMap->color(ray.surface, true);
        surfaceReflectanceCoefficient = surfaceReflectiveMapColor.r;
    }
    Ray reflectionRay = ray;
    reflectionRay.origin = ray.origin + (ray.length - REFR_EPS) * ray.direction;
    reflectionRay.direction = normalized(reflection);
    reflectionRay.length = INFINITY;
    reflectionRay.primitive = nullptr;

    // (Alpha Map) Calculate the opacity, create a background ray
    float surfaceAlphaCoefficient(1);
    if (this->alphaMap != nullptr)
    {
        auto surfaceAlphaMapColor = this->alphaMap->color(ray.surface, true);
        surfaceAlphaCoefficient = surfaceAlphaMapColor.r;
    }

    Ray propagatedRay = ray;
    propagatedRay.origin = ray.origin + (ray.length + REFR_EPS) * ray.direction;
    propagatedRay.length = INFINITY;
    propagatedRay.primitive = nullptr;

    // Iterate over light sources
    for (const auto &light: scene.lights())
    {
        Light::Illumination const illum = light->illuminate(scene, ray);

        // Diffuse term (lambertian)
        Color const diffuse = this->diffuseCoefficient * surfaceDiffuseColor *
                              std::max(dotProduct(-illum.direction, ray.normal), 0.0f);
        fragmentColor += diffuse * illum.color;

        // Specular term (phong)
        float const cosine = dotProduct(-illum.direction, reflection);
        if (cosine > 0)
        {
            Color const specular = this->specularCoefficient * surfaceSpecularColor // highlight
                                   * powf(cosine, this->shininessExponent);        // shininess factor
            fragmentColor += specular * illum.color;
        }


    }
    // Reflected ray
    if (surfaceReflectanceCoefficient > 0)
    {
        Color const reflectionColor = scene.traceRay(reflectionRay);
        fragmentColor += surfaceReflectanceCoefficient * reflectionColor * reflectance;
    }

    // Opacity
    if (surfaceAlphaCoefficient < 1)
    {
        Color const background = scene.traceRay(propagatedRay);
        fragmentColor = (1 - surfaceAlphaCoefficient) * background + surfaceAlphaCoefficient * fragmentColor;
    }

    return fragmentColor;
}

bool MaterialShader::isTransparent() const
{ return this->opacity < 1.0f || this->alphaMap; }