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

export const lightingUniformsWGSL = /* wgsl */ `\
// #if (defined(SHADER_TYPE_FRAGMENT) && defined(LIGHTING_FRAGMENT)) || (defined(SHADER_TYPE_VERTEX) && defined(LIGHTING_VERTEX))
const MAX_LIGHTS: i32 = 5;

struct AmbientLight {
  color: vec3<f32>,
};

struct PointLight {
  color: vec3<f32>,
  position: vec3<f32>,
  attenuation: vec3<f32>, // 2nd order x:Constant-y:Linear-z:Exponential
};

struct SpotLight {
  color: vec3<f32>,
  position: vec3<f32>,
  direction: vec3<f32>,
  attenuation: vec3<f32>,
  coneCos: vec2<f32>,
};

struct DirectionalLight {
  color: vec3<f32>,
  direction: vec3<f32>,
};

struct UniformLight {
  color: vec3<f32>,
  position: vec3<f32>,
  direction: vec3<f32>,
  attenuation: vec3<f32>,
  coneCos: vec2<f32>,
};

struct lightingUniforms {
  enabled: i32,
  directionalLightCount: i32,
  pointLightCount: i32,
  spotLightCount: i32,
  ambientColor: vec3<f32>,
  lights: array<UniformLight, 5>,
};

@group(2) @binding(auto) var<uniform> lighting : lightingUniforms;

fn lighting_getPointLight(index: i32) -> PointLight {
  let light = lighting.lights[index];
  return PointLight(light.color, light.position, light.attenuation);
}

fn lighting_getSpotLight(index: i32) -> SpotLight {
  let light = lighting.lights[lighting.pointLightCount + index];
  return SpotLight(light.color, light.position, light.direction, light.attenuation, light.coneCos);
}

fn lighting_getDirectionalLight(index: i32) -> DirectionalLight {
  let light = lighting.lights[lighting.pointLightCount + lighting.spotLightCount + index];
  return DirectionalLight(light.color, light.direction);
}

fn getPointLightAttenuation(pointLight: PointLight, distance: f32) -> f32 {
  return pointLight.attenuation.x
       + pointLight.attenuation.y * distance
       + pointLight.attenuation.z * distance * distance;
}

fn getSpotLightAttenuation(spotLight: SpotLight, positionWorldspace: vec3<f32>) -> f32 {
  let lightDirection = normalize(positionWorldspace - spotLight.position);
  let coneFactor = smoothstep(
    spotLight.coneCos.y,
    spotLight.coneCos.x,
    dot(normalize(spotLight.direction), lightDirection)
  );
  let distanceAttenuation = getPointLightAttenuation(
    PointLight(spotLight.color, spotLight.position, spotLight.attenuation),
    distance(spotLight.position, positionWorldspace)
  );
  return distanceAttenuation / max(coneFactor, 0.0001);
}
`;