import * as THREE from 'three'

/**
 * 创建瀑布流光材质
 * - 结合纹理沿 Y 轴流动 + Fresnel 边缘光
 * - 用于 "di" 部件的边缘流光效果
 */
export function createRimFlowMaterial(): THREE.ShaderMaterial {
  const textureLoader = new THREE.TextureLoader()
  const pubuTex = textureLoader.load('/assets/pubu.jpeg')
  pubuTex.wrapS = THREE.RepeatWrapping
  pubuTex.wrapT = THREE.RepeatWrapping
  pubuTex.repeat.set(1, 3)

  return new THREE.ShaderMaterial({
    uniforms: {
      uTime: { value: 0 },
      uColor: { value: new THREE.Color(0x00ccff) },
      uIntensity: { value: 1.0 },
      uSpeed: { value: 0.08 },
      uTexture: { value: pubuTex },
    },
    vertexShader: `
      varying vec3 vNormal;
      varying vec3 vViewDir;
      varying vec3 vWorldPos;
      varying vec2 vUv;
      void main() {
        vec4 worldPos = modelMatrix * vec4(position, 1.0);
        vWorldPos = worldPos.xyz;
        vNormal = normalize(normalMatrix * normal);
        vViewDir = normalize(cameraPosition - worldPos.xyz);
        vUv = uv;
        gl_Position = projectionMatrix * viewMatrix * worldPos;
      }
    `,
    fragmentShader: `
      uniform vec3 uColor;
      uniform float uTime;
      uniform float uIntensity;
      uniform float uSpeed;
      uniform sampler2D uTexture;

      varying vec3 vNormal;
      varying vec3 vViewDir;
      varying vec2 vUv;
      varying vec3 vWorldPos;

      void main() {
        // Fresnel 边缘检测
        float rim = 1.0 - max(dot(vNormal, vViewDir), 0.0);
        rim = pow(rim, 2.5);

        // UV 沿 Y 轴流动（瀑布下落）
        vec2 flowUv = vUv;
        flowUv.y += uTime * uSpeed;

        // 采样贴图
        vec4 texColor = texture2D(uTexture, flowUv);
        float flow = texColor.r;

        // 不透明，流动区域亮蓝色
        vec3 baseColor = vec3(0.02, 0.05, 0.12);
        vec3 glowColor = uColor;
        vec3 finalColor = mix(baseColor, glowColor, flow * 0.8);

        gl_FragColor = vec4(finalColor, 1.0);
      }
    `,
    transparent: false,
    side: THREE.DoubleSide,
  })
}