#include "Lighting/LightEvaluation.h"
#include "Algorithm/BSDF.h"
#include "Algorithm/RayIntersection.h"

path_output evaluate_bsdf_directional(directional_light_t light, const light_shading_context_t* context, vec3s throughput, uint32_t sample_index)
{
    path_output output = {0.0f};
    output.state = PS_TERMINATE;
    output.pdf = 1.0f;

    if (light.intensity <= 0.0f)
    {
        return output;
    }

    float angular_radius = glm_rad(light.angular_diameter * 0.5f);

    uint32_t scramble = hash_position(context->position);
    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_angular(light.direction, sample_index, angular_radius, d1, d2, scramble);

    float n_dot_l = glms_vec3_dot(context->normal, wi);
    if (n_dot_l <= 0.0f)
    {
        return output;
    }

    ray_t shadow_ray = ray_create(offset_ray_origin(context->position, context->normal, context->wo), wi, 0.0f, 0.0f);

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

    vec3s light_radiance = glms_vec3_scale(light.color, light.intensity);
    vec3s light_contribute = glms_vec3_scale( throughput, fmaxf(0.0f, n_dot_l)); // we always assume pdf = 1.0f for directional light

    output.direct_lighting = glms_vec3_mul(light_radiance, light_contribute);
    output.wi = wi;
    output.state = PS_SUCCESS;
    return output;
}