import { MathUtils, Vector3 } from 'three';
import { Sky } from 'three/addons/objects/Sky.js';
import { SCENE } from '../constants/scene.ts';
import { NIGHT_SKY } from '../constants/nightSky.ts';
import { cloudShader, skyCloudFragment } from './clouds.ts';

export function createSky() {
  const mesh = new Sky();
  const fragment = mesh.material.fragmentShader;
  const start = fragment.indexOf('// Clouds');
  const end = fragment.indexOf('gl_FragColor = vec4( texColor, 1.0 );', start);
  if (start < 0 || end < 0) throw new Error('Sky cloud shader integration needs updating');
  const nightBackground = `texColor += vec3(${NIGHT_SKY.backgroundRadiance.map(value => value.toFixed(3)).join(', ')})
    * (1.0 - smoothstep(-0.07, 0.05, vSunDirection.y));`;
  mesh.material.fragmentShader = cloudShader + fragment.slice(0, start) + nightBackground + skyCloudFragment + fragment.slice(end);
  mesh.scale.setScalar(SCENE.skyRadius);
  const uniforms = mesh.material.uniforms;
  uniforms.turbidity.value = 2.5;
  uniforms.rayleigh.value = 2;
  uniforms.mieCoefficient.value = SCENE.mieCoefficient;
  uniforms.mieDirectionalG.value = SCENE.mieDirectionalG;
  uniforms.showSunDisc.value = 0;
  uniforms.cloudCoverage.value = 0;
  return {
    mesh,
    update(direction: Vector3, altitude: number, cloudCover = 0) {
      uniforms.sunPosition.value.copy(direction).multiplyScalar(SCENE.skyRadius);
      uniforms.rayleigh.value = MathUtils.lerp(2.5, 1.7, MathUtils.smoothstep(altitude, -6, 30));
      uniforms.cloudCoverage.value = cloudCover;
    },
  };
}