// luma.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

export const lightingShader = /* glsl */ `\

uniform float lighting_uAmbient;
uniform float lighting_uDiffuse;
uniform float lighting_uShininess;
uniform vec3  lighting_uSpecularColor;

vec3 lighting_getLightColor(vec3 surfaceColor, vec3 light_direction, vec3 view_direction, vec3 normal_worldspace, vec3 color) {
    vec3 halfway_direction = normalize(light_direction + view_direction);
    float lambertian = dot(light_direction, normal_worldspace);
    float specular = 0.0;
    if (lambertian > 0.0) {
      float specular_angle = max(dot(normal_worldspace, halfway_direction), 0.0);
      specular = pow(specular_angle, lighting_uShininess);
    }
    lambertian = max(lambertian, 0.0);
    return (lambertian * lighting_uDiffuse * surfaceColor + specular * lighting_uSpecularColor) * color;
}

vec3 lighting_getLightColor(vec3 surfaceColor, vec3 cameraPosition, vec3 position_worldspace, vec3 normal_worldspace) {
  vec3 lightColor = surfaceColor;

  if (lighting_uEnabled) {
    vec3 view_direction = normalize(cameraPosition - position_worldspace);
    lightColor = lighting_uAmbient * surfaceColor * lighting_uAmbientLight.color;

    for (int i = 0; i < MAX_LIGHTS; i++) {
      if (i >= lighting_uPointLightCount) {
        break;
      }
      PointLight pointLight = lighting_uPointLight[i];
      vec3 light_position_worldspace = pointLight.position;
      vec3 light_direction = normalize(light_position_worldspace - position_worldspace);
      lightColor += lighting_getLightColor(surfaceColor, light_direction, view_direction, normal_worldspace, pointLight.color);
    }

    for (int i = 0; i < MAX_LIGHTS; i++) {
      if (i >= lighting_uDirectionalLightCount) {
        break;
      }
      DirectionalLight directionalLight = lighting_uDirectionalLight[i];
      lightColor += lighting_getLightColor(surfaceColor, -directionalLight.direction, view_direction, normal_worldspace, directionalLight.color);
    }
  }
  return lightColor;
}

vec3 lighting_getSpecularLightColor(vec3 cameraPosition, vec3 position_worldspace, vec3 normal_worldspace) {
  vec3 lightColor = vec3(0, 0, 0);
  vec3 surfaceColor = vec3(0, 0, 0);

  if (lighting_uEnabled) {
    vec3 view_direction = normalize(cameraPosition - position_worldspace);

    for (int i = 0; i < MAX_LIGHTS; i++) {
      if (i >= lighting_uPointLightCount) {
        break;
      }
      PointLight pointLight = lighting_uPointLight[i];
      vec3 light_position_worldspace = pointLight.position;
      vec3 light_direction = normalize(light_position_worldspace - position_worldspace);
      lightColor += lighting_getLightColor(surfaceColor, light_direction, view_direction, normal_worldspace, pointLight.color);
    }

    for (int i = 0; i < MAX_LIGHTS; i++) {
      if (i >= lighting_uDirectionalLightCount) {
        break;
      }
      DirectionalLight directionalLight = lighting_uDirectionalLight[i];
      lightColor += lighting_getLightColor(surfaceColor, -directionalLight.direction, view_direction, normal_worldspace, directionalLight.color);
    }
  }
  return lightColor;
}
`;