#include "depth_shader.h"
#include "constants.h"
#include "img.h"
#include "shader.h"
#include "utils.h"

VertexData depth_shader_vertex(void *shader, const VertexData *vert, u8 index, const Model *model) {
  DepthShader *shdr = (DepthShader *)shader;

  V4f vh = V3_to_V4(vert->position);
  vh.y   = 0.0 - vh.y;
  vh     = mat4x4_mul_vec4(shdr->final, vh);
  shdr->vertices[index].position = project_vec4(vh);

  return shdr->vertices[index];
}

FragmentResult depth_shader_fragment(void *shader, const V3f *barycentric, const Colour *colour,
                                     const Model *model) {
  DepthShader *shdr = (DepthShader *)shader;

  M3x3f pos_mat = {.rows = {shdr->vertices[0].position, shdr->vertices[1].position, shdr->vertices[2].position}};
  pos_mat       = mat3x3_transpose(pos_mat);

  V3f    position = mat3x3_mul_vec3(pos_mat, (*barycentric));
  f32    channel  = clamp(position.z + DEPTH_MAX, 0.0f, DEPTH_MAX);
  Colour output   = {.r = (u8)(channel), .g = (u8)(channel), .b = (u8)(channel), .a = 255};

  return (FragmentResult){.colour = output};
}