import * as THREE from 'three';
import type { SceneResourceBag } from '@/scene/resources';
import type { MutableChapterPalette } from './palette';

/** Thin, spatially separated air masses. No screen-sized render targets. */
export function createHorizonAir(resources: SceneResourceBag) {
  const group = new THREE.Group();
  group.name = 'horizon-air-masses';
  const uniforms = {
    uTime: { value: 0 },
    uWarmth: { value: 0 },
    uDawn: { value: 0 },
    uColor: { value: new THREE.Color(0xc5646b) },
  };
  const material = resources.own(
    'material',
    new THREE.ShaderMaterial({
      uniforms,
      vertexShader: `
      varying vec2 vUv;
      void main(){vUv=uv;gl_Position=projectionMatrix*modelViewMatrix*vec4(position,1.0);}
    `,
      fragmentShader: `
      uniform float uTime;
      uniform float uWarmth;
      uniform float uDawn;
      uniform vec3 uColor;
      varying vec2 vUv;
      void main(){
        float wave=sin(vUv.x*12.0+uTime*0.018)*0.055+sin(vUv.x*31.0-uTime*0.026)*0.018;
        float ribbon=exp(-pow((vUv.y-0.45-wave)*5.6,2.0));
        float thin=exp(-pow((vUv.y-0.51-wave)*37.0,2.0));
        float horizontal=pow(max(0.0,sin(vUv.x*3.14159)),2.0);
        float colorWave=0.5+0.5*sin(vUv.x*7.0+uTime*0.035);
        vec3 color=mix(uColor,vec3(0.27,0.045,0.75),colorWave*0.55);
        color=mix(color,vec3(0.05,0.52,0.75),smoothstep(0.54,0.82,vUv.y)*0.3);
        gl_FragColor=vec4(color,(ribbon*0.16+thin*0.032)*horizontal*(0.7+uWarmth*0.3)*(1.0+uDawn));
        #include <tonemapping_fragment>
        #include <colorspace_fragment>
      }
    `,
      transparent: true,
      depthWrite: false,
      depthTest: true,
      blending: THREE.AdditiveBlending,
    }),
  );
  const geometry = resources.own('geometry', new THREE.PlaneGeometry(1450, 95));
  for (let i = 0; i < 3; i++) {
    const mesh = new THREE.Mesh(geometry, material);
    mesh.name = `stratified-air-${i + 1}`;
    mesh.position.set((i - 1) * 85, 15 + i * 11, -500 - i * 70);
    mesh.scale.set(1 - i * 0.12, 1 - i * 0.18, 1);
    group.add(mesh);
  }
  return {
    group,
    /** dawn: END OF SHIFT, the air masses catch first light (gain up to 2x). */
    update(palette: Readonly<MutableChapterPalette>, time: number, dawn = 0) {
      uniforms.uTime.value = time;
      uniforms.uDawn.value = Number.isFinite(dawn) ? Math.min(1, Math.max(0, dawn)) : 0;
      uniforms.uWarmth.value = palette.warmth;
      uniforms.uColor.value.copy(palette.sun);
    },
  };
}