#include "Lighting/SkyLight.h"
#include "Algorithm/BSDF.h"
#include "Algorithm/RayIntersection.h"
#include "Material/Material.h"

vec3s evaluate_bsdf_const_sky(const void* data, const light_shading_context_t* context, vec3s throughput, uint32_t sample_index)
{
    constant_sky_data_t sky_data = *(const constant_sky_data_t*)data;
    vec3s sky_color = glms_vec3_scale(sky_data.color, sky_data.intensity);

    if (context == NULL)
    {
        return glms_vec3_mul(sky_color, throughput);
        // return sky_data.color;
    }

    uint16_t d1 = sobol_get_dimension(context->bounce_depth, PRNG_LIGHT_U);
    uint16_t d2 = sobol_get_dimension(context->bounce_depth, PRNG_LIGHT_V);

    vec3s wi = random_uniform_cdf_direction(context->normal, sample_index, d1, d2);
    float pdf = 1.0f / (4.0f * (float)M_PI);

    ray_t shadow_ray = {
        .origin = BIAS_RAY_ORIGION(context->hit_point, context->normal),
        .direction = wi,
    };

    float closest = FLT_MAX;
    hit_result_t shadow_hit = {1};
    ray_intersect_bvh(shadow_ray, context->bvh_tree->nodes, context->bvh_tree->primitive_indices, context->bvh_tree->triangles, 0, &closest, &shadow_hit);
    if (shadow_hit.hit)
    {
        return glms_vec3_zero();
    }

    shading_context_t shading_context = {
        .normal = context->normal,
        .wi = wi,
        .wo = glms_vec3_negate(context->wo)
    };

    vec3s bsdf = evaluate_material_bsdf(context->material, &shading_context);
    bsdf = glms_vec3_mul(bsdf, sky_color);
    float cos_theta = fmaxf(glms_vec3_dot(wi, context->normal), 0.0f);

    float pdf_bsdf = sample_material_bsdf_pdf(context->material, shading_context.normal, shading_context.wo, shading_context.wi);
    float weight = power_heuristic(pdf, pdf_bsdf);

    vec3s env_contrib = glms_vec3_scale(glms_vec3_mul(throughput, bsdf), cos_theta / pdf);
    return glms_vec3_scale(env_contrib, weight);
}