'use client';
import React, { useEffect, useRef } from 'react';

interface ColorRGB {
  r: number;
  g: number;
  b: number;
}

interface SplashCursorProps {
  SIM_RESOLUTION?: number;
  DYE_RESOLUTION?: number;
  CAPTURE_RESOLUTION?: number;
  DENSITY_DISSIPATION?: number;
  VELOCITY_DISSIPATION?: number;
  PRESSURE?: number;
  PRESSURE_ITERATIONS?: number;
  CURL?: number;
  SPLAT_RADIUS?: number;
  SPLAT_FORCE?: number;
  SHADING?: boolean;
  COLOR_UPDATE_SPEED?: number;
  BACK_COLOR?: ColorRGB;
  TRANSPARENT?: boolean;
}

interface Pointer {
  id: number;
  texcoordX: number;
  texcoordY: number;
  prevTexcoordX: number;
  prevTexcoordY: number;
  deltaX: number;
  deltaY: number;
  down: boolean;
  moved: boolean;
  color: ColorRGB;
}

function pointerPrototype(): Pointer {
  return {
    id: -1,
    texcoordX: 0,
    texcoordY: 0,
    prevTexcoordX: 0,
    prevTexcoordY: 0,
    deltaX: 0,
    deltaY: 0,
    down: false,
    moved: false,
    color: { r: 0, g: 0, b: 0 }
  };
}

export function SplashCursor({
  SIM_RESOLUTION = 128,
  DYE_RESOLUTION = 1440,
  CAPTURE_RESOLUTION = 512,
  DENSITY_DISSIPATION = 3.5,
  VELOCITY_DISSIPATION = 2,
  PRESSURE = 0.1,
  PRESSURE_ITERATIONS = 20,
  CURL = 3,
  SPLAT_RADIUS = 0.2,
  SPLAT_FORCE = 6000,
  SHADING = true,
  COLOR_UPDATE_SPEED = 10,
  BACK_COLOR = { r: 0.5, g: 0, b: 0 },
  TRANSPARENT = true
}: SplashCursorProps) {
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;

    let pointers: Pointer[] = [pointerPrototype()];

    let config = {
      SIM_RESOLUTION: SIM_RESOLUTION!,
      DYE_RESOLUTION: DYE_RESOLUTION!,
      CAPTURE_RESOLUTION: CAPTURE_RESOLUTION!,
      DENSITY_DISSIPATION: DENSITY_DISSIPATION!,
      VELOCITY_DISSIPATION: VELOCITY_DISSIPATION!,
      PRESSURE: PRESSURE!,
      PRESSURE_ITERATIONS: PRESSURE_ITERATIONS!,
      CURL: CURL!,
      SPLAT_RADIUS: SPLAT_RADIUS!,
      SPLAT_FORCE: SPLAT_FORCE!,
      SHADING,
      COLOR_UPDATE_SPEED: COLOR_UPDATE_SPEED!,
      PAUSED: false,
      BACK_COLOR,
      TRANSPARENT
    };

    const { gl, ext } = getWebGLContext(canvas);
    if (!gl || !ext) return;

    if (!ext.supportLinearFiltering) {
      config.DYE_RESOLUTION = 256;
      config.SHADING = false;
    }

    function getWebGLContext(canvas: HTMLCanvasElement) {
      const params = {
        alpha: true,
        depth: false,
        stencil: false,
        antialias: false,
        preserveDrawingBuffer: false
      };

      let gl = canvas.getContext('webgl2', params) as WebGL2RenderingContext | null;

      if (!gl) {
        gl = (canvas.getContext('webgl', params) ||
          canvas.getContext('experimental-webgl', params)) as WebGL2RenderingContext | null;
      }

      if (!gl) {
        throw new Error('Unable to initialize WebGL.');
      }

      const isWebGL2 = 'drawBuffers' in gl;

      let supportLinearFiltering = false;
      let halfFloat = null;

      if (isWebGL2) {
        (gl as WebGL2RenderingContext).getExtension('EXT_color_buffer_float');
        supportLinearFiltering = !!(gl as WebGL2RenderingContext).getExtension('OES_texture_float_linear');
      } else {
        halfFloat = gl.getExtension('OES_texture_half_float');
        supportLinearFiltering = !!gl.getExtension('OES_texture_half_float_linear');
      }

      gl.clearColor(0, 0, 0, 1);

      const halfFloatTexType = isWebGL2
        ? (gl as WebGL2RenderingContext).HALF_FLOAT
        : (halfFloat && (halfFloat as any).HALF_FLOAT_OES) || 0;

      let formatRGBA: any;
      let formatRG: any;
      let formatR: any;

      if (isWebGL2) {
        formatRGBA = getSupportedFormat(gl, (gl as WebGL2RenderingContext).RGBA16F, gl.RGBA, halfFloatTexType);
        formatRG = getSupportedFormat(
          gl,
          (gl as WebGL2RenderingContext).RG16F,
          (gl as WebGL2RenderingContext).RG,
          halfFloatTexType
        );
        formatR = getSupportedFormat(
          gl,
          (gl as WebGL2RenderingContext).R16F,
          (gl as WebGL2RenderingContext).RED,
          halfFloatTexType
        );
      } else {
        formatRGBA = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
      }

      return {
        gl,
        ext: {
          formatRGBA,
          formatRG,
          formatR,
          halfFloatTexType,
          supportLinearFiltering
        }
      };
    }

    function getSupportedFormat(
      gl: WebGLRenderingContext | WebGL2RenderingContext,
      internalFormat: number,
      format: number,
      type: number
    ): { internalFormat: number; format: number } | null {
      if (!supportRenderTextureFormat(gl, internalFormat, format, type)) {
        if ('drawBuffers' in gl) {
          const gl2 = gl as WebGL2RenderingContext;
          switch (internalFormat) {
            case gl2.R16F:
              return getSupportedFormat(gl2, gl2.RG16F, gl2.RG, type);
            case gl2.RG16F:
              return getSupportedFormat(gl2, gl2.RGBA16F, gl2.RGBA, type);
            default:
              return null;
          }
        }
        return null;
      }
      return { internalFormat, format };
    }

    function supportRenderTextureFormat(
      gl: WebGLRenderingContext | WebGL2RenderingContext,
      internalFormat: number,
      format: number,
      type: number
    ) {
      const texture = gl.createTexture();
      if (!texture) return false;

      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
      gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, 4, 4, 0, format, type, null);

      const fbo = gl.createFramebuffer();
      if (!fbo) return false;

      gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
      gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
      const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
      return status === gl.FRAMEBUFFER_COMPLETE;
    }

    function hashCode(s: string) {
      if (!s.length) return 0;
      let hash = 0;
      for (let i = 0; i < s.length; i++) {
        hash = (hash << 5) - hash + s.charCodeAt(i);
        hash |= 0;
      }
      return hash;
    }

    function addKeywords(source: string, keywords: string[] | null) {
      if (!keywords) return source;
      let keywordsString = '';
      for (const keyword of keywords) {
        keywordsString += `#define ${keyword}\n`;
      }
      return keywordsString + source;
    }

    function compileShader(type: number, source: string, keywords: string[] | null = null): WebGLShader | null {
      const shaderSource = addKeywords(source, keywords);
      const shader = gl.createShader(type);
      if (!shader) return null;
      gl.shaderSource(shader, shaderSource);
      gl.compileShader(shader);
      if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        console.trace(gl.getShaderInfoLog(shader));
      }
      return shader;
    }

    function createProgram(vertexShader: WebGLShader | null, fragmentShader: WebGLShader | null): WebGLProgram | null {
      if (!vertexShader || !fragmentShader) return null;
      const program = gl.createProgram();
      if (!program) return null;
      gl.attachShader(program, vertexShader);
      gl.attachShader(program, fragmentShader);
      gl.linkProgram(program);
      if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
        console.trace(gl.getProgramInfoLog(program));
      }
      return program;
    }

    function getUniforms(program: WebGLProgram) {
      let uniforms: Record<string, WebGLUniformLocation | null> = {};
      const uniformCount = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
      for (let i = 0; i < uniformCount; i++) {
        const uniformInfo = gl.getActiveUniform(program, i);
        if (uniformInfo) {
          uniforms[uniformInfo.name] = gl.getUniformLocation(program, uniformInfo.name);
        }
      }
      return uniforms;
    }

    class Program {
      program: WebGLProgram | null;
      uniforms: Record<string, WebGLUniformLocation | null>;

      constructor(vertexShader: WebGLShader | null, fragmentShader: WebGLShader | null) {
        this.program = createProgram(vertexShader, fragmentShader);
        this.uniforms = this.program ? getUniforms(this.program) : {};
      }

      bind() {
        if (this.program) gl.useProgram(this.program);
      }
    }

    class Material {
      vertexShader: WebGLShader | null;
      fragmentShaderSource: string;
      programs: Record<number, WebGLProgram | null>;
      activeProgram: WebGLProgram | null;
      uniforms: Record<string, WebGLUniformLocation | null>;

      constructor(vertexShader: WebGLShader | null, fragmentShaderSource: string) {
        this.vertexShader = vertexShader;
        this.fragmentShaderSource = fragmentShaderSource;
        this.programs = {};
        this.activeProgram = null;
        this.uniforms = {};
      }

      setKeywords(keywords: string[]) {
        let hash = 0;
        for (const kw of keywords) {
          hash += hashCode(kw);
        }
        let program = this.programs[hash];
        if (program == null) {
          const fragmentShader = compileShader(gl.FRAGMENT_SHADER, this.fragmentShaderSource, keywords);
          program = createProgram(this.vertexShader, fragmentShader);
          this.programs[hash] = program;
        }
        if (program === this.activeProgram) return;
        if (program) {
          this.uniforms = getUniforms(program);
        }
        this.activeProgram = program;
      }

      bind() {
        if (this.activeProgram) {
          gl.useProgram(this.activeProgram);
        }
      }
    }

    const baseVertexShader = compileShader(
      gl.VERTEX_SHADER,
      `
      precision highp float;
      attribute vec2 aPosition;
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform vec2 texelSize;

      void main () {
        vUv = aPosition * 0.5 + 0.5;
        vL = vUv - vec2(texelSize.x, 0.0);
        vR = vUv + vec2(texelSize.x, 0.0);
        vT = vUv + vec2(0.0, texelSize.y);
        vB = vUv - vec2(0.0, texelSize.y);
        gl_Position = vec4(aPosition, 0.0, 1.0);
      }
    `
    );

    const copyShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      uniform sampler2D uTexture;

      void main () {
          gl_FragColor = texture2D(uTexture, vUv);
      }
    `
    );

    const clearShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      uniform sampler2D uTexture;
      uniform float value;

      void main () {
          gl_FragColor = value * texture2D(uTexture, vUv);
      }
    `
    );

    const displayShaderSource = `
      precision highp float;
      precision highp sampler2D;
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uTexture;
      uniform sampler2D uDithering;
      uniform vec2 ditherScale;
      uniform vec2 texelSize;

      vec3 linearToGamma (vec3 color) {
          color = max(color, vec3(0));
          return max(1.055 * pow(color, vec3(0.416666667)) - 0.055, vec3(0));
      }

      void main () {
          vec3 c = texture2D(uTexture, vUv).rgb;
          #ifdef SHADING
              vec3 lc = texture2D(uTexture, vL).rgb;
              vec3 rc = texture2D(uTexture, vR).rgb;
              vec3 tc = texture2D(uTexture, vT).rgb;
              vec3 bc = texture2D(uTexture, vB).rgb;

              float dx = length(rc) - length(lc);
              float dy = length(tc) - length(bc);

              vec3 n = normalize(vec3(dx, dy, length(texelSize)));
              vec3 l = vec3(0.0, 0.0, 1.0);

              float diffuse = clamp(dot(n, l) + 0.7, 0.7, 1.0);
              c *= diffuse;
          #endif

          float a = max(c.r, max(c.g, c.b));
          gl_FragColor = vec4(c, a);
      }
    `;

    const splatShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision highp float;
      precision highp sampler2D;
      varying vec2 vUv;
      uniform sampler2D uTarget;
      uniform float aspectRatio;
      uniform vec3 color;
      uniform vec2 point;
      uniform float radius;

      void main () {
          vec2 p = vUv - point.xy;
          p.x *= aspectRatio;
          vec3 splat = exp(-dot(p, p) / radius) * color;
          vec3 base = texture2D(uTarget, vUv).xyz;
          gl_FragColor = vec4(base + splat, 1.0);
      }
    `
    );

    const advectionShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision highp float;
      precision highp sampler2D;
      varying vec2 vUv;
      uniform sampler2D uVelocity;
      uniform sampler2D uSource;
      uniform vec2 texelSize;
      uniform vec2 dyeTexelSize;
      uniform float dt;
      uniform float dissipation;

      vec4 bilerp (sampler2D sam, vec2 uv, vec2 tsize) {
          vec2 st = uv / tsize - 0.5;
          vec2 iuv = floor(st);
          vec2 fuv = fract(st);

          vec4 a = texture2D(sam, (iuv + vec2(0.5, 0.5)) * tsize);
          vec4 b = texture2D(sam, (iuv + vec2(1.5, 0.5)) * tsize);
          vec4 c = texture2D(sam, (iuv + vec2(0.5, 1.5)) * tsize);
          vec4 d = texture2D(sam, (iuv + vec2(1.5, 1.5)) * tsize);

          return mix(mix(a, b, fuv.x), mix(c, d, fuv.x), fuv.y);
      }

      void main () {
          #ifdef MANUAL_FILTERING
              vec2 coord = vUv - dt * bilerp(uVelocity, vUv, texelSize).xy * texelSize;
              vec4 result = bilerp(uSource, coord, dyeTexelSize);
          #else
              vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;
              vec4 result = texture2D(uSource, coord);
          #endif
          float decay = 1.0 + dissipation * dt;
          gl_FragColor = result / decay;
      }
    `,
      ext.supportLinearFiltering ? null : ['MANUAL_FILTERING']
    );

    const divergenceShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uVelocity;

      void main () {
          float L = texture2D(uVelocity, vL).x;
          float R = texture2D(uVelocity, vR).x;
          float T = texture2D(uVelocity, vT).y;
          float B = texture2D(uVelocity, vB).y;

          vec2 C = texture2D(uVelocity, vUv).xy;
          if (vL.x < 0.0) { L = -C.x; }
          if (vR.x > 1.0) { R = -C.x; }
          if (vT.y > 1.0) { T = -C.y; }
          if (vB.y < 0.0) { B = -C.y; }

          float div = 0.5 * (R - L + T - B);
          gl_FragColor = vec4(div, 0.0, 0.0, 1.0);
      }
    `
    );

    const curlShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uVelocity;

      void main () {
          float L = texture2D(uVelocity, vL).y;
          float R = texture2D(uVelocity, vR).y;
          float T = texture2D(uVelocity, vT).x;
          float B = texture2D(uVelocity, vB).x;
          float vorticity = R - L - T + B;
          gl_FragColor = vec4(0.5 * vorticity, 0.0, 0.0, 1.0);
      }
    `
    );

    const vorticityShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision highp float;
      precision highp sampler2D;
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uVelocity;
      uniform sampler2D uCurl;
      uniform float curl;
      uniform float dt;

      void main () {
          float L = texture2D(uCurl, vL).x;
          float R = texture2D(uCurl, vR).x;
          float T = texture2D(uCurl, vT).x;
          float B = texture2D(uCurl, vB).x;
          float C = texture2D(uCurl, vUv).x;

          vec2 force = 0.5 * vec2(abs(T) - abs(B), abs(R) - abs(L));
          force /= length(force) + 0.0001;
          force *= curl * C;
          force.y *= -1.0;

          vec2 velocity = texture2D(uVelocity, vUv).xy;
          velocity += force * dt;
          velocity = min(max(velocity, -1000.0), 1000.0);
          gl_FragColor = vec4(velocity, 0.0, 1.0);
      }
    `
    );

    const pressureShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uPressure;
      uniform sampler2D uDivergence;

      void main () {
          float L = texture2D(uPressure, vL).x;
          float R = texture2D(uPressure, vR).x;
          float T = texture2D(uPressure, vT).x;
          float B = texture2D(uPressure, vB).x;
          float C = texture2D(uPressure, vUv).x;
          float divergence = texture2D(uDivergence, vUv).x;
          float pressure = (L + R + B + T - divergence) * 0.25;
          gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);
      }
    `
    );

    const gradientSubtractShader = compileShader(
      gl.FRAGMENT_SHADER,
      `
      precision mediump float;
      precision mediump sampler2D;
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uPressure;
      uniform sampler2D uVelocity;

      void main () {
          float L = texture2D(uPressure, vL).x;
          float R = texture2D(uPressure, vR).x;
          float T = texture2D(uPressure, vT).x;
          float B = texture2D(uPressure, vB).x;
          vec2 velocity = texture2D(uVelocity, vUv).xy;
          velocity.xy -= vec2(R - L, T - B);
          gl_FragColor = vec4(velocity, 0.0, 1.0);
      }
    `
    );

    const blit = (() => {
      const buffer = gl.createBuffer()!;
      gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]), gl.STATIC_DRAW);
      const elemBuffer = gl.createBuffer()!;
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, elemBuffer);
      gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 0, 2, 3]), gl.STATIC_DRAW);
      gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
      gl.enableVertexAttribArray(0);

      return (target: FBO | null, doClear = false) => {
        if (!gl) return;
        if (!target) {
          gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
          gl.bindFramebuffer(gl.FRAMEBUFFER, null);
        } else {
          gl.viewport(0, 0, target.width, target.height);
          gl.bindFramebuffer(gl.FRAMEBUFFER, target.fbo);
        }
        if (doClear) {
          gl.clearColor(0, 0, 0, 1);
          gl.clear(gl.COLOR_BUFFER_BIT);
        }
        gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
      };
    })();

    interface FBO {
      texture: WebGLTexture;
      fbo: WebGLFramebuffer;
      width: number;
      height: number;
      texelSizeX: number;
      texelSizeY: number;
      attach: (id: number) => number;
    }

    interface DoubleFBO {
      width: number;
      height: number;
      texelSizeX: number;
      texelSizeY: number;
      read: FBO;
      write: FBO;
      swap: () => void;
    }

    let dye: DoubleFBO;
    let velocity: DoubleFBO;
    let divergence: FBO;
    let curl: FBO;
    let pressure: DoubleFBO;

    const copyProgram = new Program(baseVertexShader, copyShader);
    const clearProgram = new Program(baseVertexShader, clearShader);
    const splatProgram = new Program(baseVertexShader, splatShader);
    const advectionProgram = new Program(baseVertexShader, advectionShader);
    const divergenceProgram = new Program(baseVertexShader, divergenceShader);
    const curlProgram = new Program(baseVertexShader, curlShader);
    const vorticityProgram = new Program(baseVertexShader, vorticityShader);
    const pressureProgram = new Program(baseVertexShader, pressureShader);
    const gradienSubtractProgram = new Program(baseVertexShader, gradientSubtractShader);
    const displayMaterial = new Material(baseVertexShader, displayShaderSource);

    function createFBO(w: number, h: number, internalFormat: number, format: number, type: number, param: number): FBO {
      gl.activeTexture(gl.TEXTURE0);
      const texture = gl.createTexture()!;
      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
      gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, w, h, 0, format, type, null);
      const fbo = gl.createFramebuffer()!;
      gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
      gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
      gl.viewport(0, 0, w, h);
      gl.clear(gl.COLOR_BUFFER_BIT);

      const texelSizeX = 1 / w;
      const texelSizeY = 1 / h;

      return {
        texture,
        fbo,
        width: w,
        height: h,
        texelSizeX,
        texelSizeY,
        attach(id: number) {
          gl.activeTexture(gl.TEXTURE0 + id);
          gl.bindTexture(gl.TEXTURE_2D, texture);
          return id;
        }
      };
    }

    function createDoubleFBO(
      w: number,
      h: number,
      internalFormat: number,
      format: number,
      type: number,
      param: number
    ): DoubleFBO {
      const fbo1 = createFBO(w, h, internalFormat, format, type, param);
      const fbo2 = createFBO(w, h, internalFormat, format, type, param);
      return {
        width: w,
        height: h,
        texelSizeX: fbo1.texelSizeX,
        texelSizeY: fbo1.texelSizeY,
        read: fbo1,
        write: fbo2,
        swap() {
          const tmp = this.read;
          this.read = this.write;
          this.write = tmp;
        }
      };
    }

    function resizeFBO(
      target: FBO,
      w: number,
      h: number,
      internalFormat: number,
      format: number,
      type: number,
      param: number
    ) {
      const newFBO = createFBO(w, h, internalFormat, format, type, param);
      copyProgram.bind();
      if (copyProgram.uniforms.uTexture) gl.uniform1i(copyProgram.uniforms.uTexture, target.attach(0));
      blit(newFBO, false);
      return newFBO;
    }

    function resizeDoubleFBO(
      target: DoubleFBO,
      w: number,
      h: number,
      internalFormat: number,
      format: number,
      type: number,
      param: number
    ) {
      if (target.width === w && target.height === h) return target;
      target.read = resizeFBO(target.read, w, h, internalFormat, format, type, param);
      target.write = createFBO(w, h, internalFormat, format, type, param);
      target.width = w;
      target.height = h;
      target.texelSizeX = 1 / w;
      target.texelSizeY = 1 / h;
      return target;
    }

    function initFramebuffers() {
      const simRes = getResolution(config.SIM_RESOLUTION!);
      const dyeRes = getResolution(config.DYE_RESOLUTION!);

      const texType = ext.halfFloatTexType;
      const rgba = ext.formatRGBA;
      const rg = ext.formatRG;
      const r = ext.formatR;
      const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;
      gl.disable(gl.BLEND);

      if (!dye) {
        dye = createDoubleFBO(dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
      } else {
        dye = resizeDoubleFBO(dye, dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
      }

      if (!velocity) {
        velocity = createDoubleFBO(simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
      } else {
        velocity = resizeDoubleFBO(
          velocity,
          simRes.width,
          simRes.height,
          rg.internalFormat,
          rg.format,
          texType,
          filtering
        );
      }

      divergence = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
      curl = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
      pressure = createDoubleFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
    }

    function updateKeywords() {
      const displayKeywords: string[] = [];
      if (config.SHADING) displayKeywords.push('SHADING');
      displayMaterial.setKeywords(displayKeywords);
    }

    function getResolution(resolution: number) {
      const w = gl.drawingBufferWidth;
      const h = gl.drawingBufferHeight;
      const aspectRatio = w / h;
      let aspect = aspectRatio < 1 ? 1 / aspectRatio : aspectRatio;
      const min = Math.round(resolution);
      const max = Math.round(resolution * aspect);
      if (w > h) {
        return { width: max, height: min };
      }
      return { width: min, height: max };
    }

    function scaleByPixelRatio(input: number) {
      const pixelRatio = window.devicePixelRatio || 1;
      return Math.floor(input * pixelRatio);
    }

    updateKeywords();
    initFramebuffers();

    let lastUpdateTime = Date.now();
    let colorUpdateTimer = 0.0;

    function updateFrame() {
      const dt = calcDeltaTime();
      if (resizeCanvas()) initFramebuffers();
      updateColors(dt);
      applyInputs();
      step(dt);
      render(null);
      requestAnimationFrame(updateFrame);
    }

    function calcDeltaTime() {
      const now = Date.now();
      let dt = (now - lastUpdateTime) / 1000;
      dt = Math.min(dt, 0.016666);
      lastUpdateTime = now;
      return dt;
    }

    function resizeCanvas() {
      const width = scaleByPixelRatio(canvas!.clientWidth);
      const height = scaleByPixelRatio(canvas!.clientHeight);
      if (canvas!.width !== width || canvas!.height !== height) {
        canvas!.width = width;
        canvas!.height = height;
        return true;
      }
      return false;
    }

    function updateColors(dt: number) {
      colorUpdateTimer += dt * config.COLOR_UPDATE_SPEED;
      if (colorUpdateTimer >= 1) {
        colorUpdateTimer = wrap(colorUpdateTimer, 0, 1);
        pointers.forEach(p => {
          p.color = generateColor();
        });
      }
    }

    function applyInputs() {
      for (const p of pointers) {
        if (p.moved) {
          p.moved = false;
          splatPointer(p);
        }
      }
    }

    function step(dt: number) {
      gl.disable(gl.BLEND);

      curlProgram.bind();
      if (curlProgram.uniforms.texelSize) {
        gl.uniform2f(curlProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (curlProgram.uniforms.uVelocity) {
        gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read.attach(0));
      }
      blit(curl);

      vorticityProgram.bind();
      if (vorticityProgram.uniforms.texelSize) {
        gl.uniform2f(vorticityProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (vorticityProgram.uniforms.uVelocity) {
        gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read.attach(0));
      }
      if (vorticityProgram.uniforms.uCurl) {
        gl.uniform1i(vorticityProgram.uniforms.uCurl, curl.attach(1));
      }
      if (vorticityProgram.uniforms.curl) {
        gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
      }
      if (vorticityProgram.uniforms.dt) {
        gl.uniform1f(vorticityProgram.uniforms.dt, dt);
      }
      blit(velocity.write);
      velocity.swap();

      divergenceProgram.bind();
      if (divergenceProgram.uniforms.texelSize) {
        gl.uniform2f(divergenceProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (divergenceProgram.uniforms.uVelocity) {
        gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read.attach(0));
      }
      blit(divergence);

      clearProgram.bind();
      if (clearProgram.uniforms.uTexture) {
        gl.uniform1i(clearProgram.uniforms.uTexture, pressure.read.attach(0));
      }
      if (clearProgram.uniforms.value) {
        gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE);
      }
      blit(pressure.write);
      pressure.swap();

      pressureProgram.bind();
      if (pressureProgram.uniforms.texelSize) {
        gl.uniform2f(pressureProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (pressureProgram.uniforms.uDivergence) {
        gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence.attach(0));
      }
      for (let i = 0; i < config.PRESSURE_ITERATIONS; i++) {
        if (pressureProgram.uniforms.uPressure) {
          gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.read.attach(1));
        }
        blit(pressure.write);
        pressure.swap();
      }

      gradienSubtractProgram.bind();
      if (gradienSubtractProgram.uniforms.texelSize) {
        gl.uniform2f(gradienSubtractProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (gradienSubtractProgram.uniforms.uPressure) {
        gl.uniform1i(gradienSubtractProgram.uniforms.uPressure, pressure.read.attach(0));
      }
      if (gradienSubtractProgram.uniforms.uVelocity) {
        gl.uniform1i(gradienSubtractProgram.uniforms.uVelocity, velocity.read.attach(1));
      }
      blit(velocity.write);
      velocity.swap();

      advectionProgram.bind();
      if (advectionProgram.uniforms.texelSize) {
        gl.uniform2f(advectionProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      if (!ext.supportLinearFiltering && advectionProgram.uniforms.dyeTexelSize) {
        gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, velocity.texelSizeX, velocity.texelSizeY);
      }
      const velocityId = velocity.read.attach(0);
      if (advectionProgram.uniforms.uVelocity) {
        gl.uniform1i(advectionProgram.uniforms.uVelocity, velocityId);
      }
      if (advectionProgram.uniforms.uSource) {
        gl.uniform1i(advectionProgram.uniforms.uSource, velocityId);
      }
      if (advectionProgram.uniforms.dt) {
        gl.uniform1f(advectionProgram.uniforms.dt, dt);
      }
      if (advectionProgram.uniforms.dissipation) {
        gl.uniform1f(advectionProgram.uniforms.dissipation, config.VELOCITY_DISSIPATION);
      }
      blit(velocity.write);
      velocity.swap();

      if (!ext.supportLinearFiltering && advectionProgram.uniforms.dyeTexelSize) {
        gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, dye.texelSizeX, dye.texelSizeY);
      }
      if (advectionProgram.uniforms.uVelocity) {
        gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read.attach(0));
      }
      if (advectionProgram.uniforms.uSource) {
        gl.uniform1i(advectionProgram.uniforms.uSource, dye.read.attach(1));
      }
      if (advectionProgram.uniforms.dissipation) {
        gl.uniform1f(advectionProgram.uniforms.dissipation, config.DENSITY_DISSIPATION);
      }
      blit(dye.write);
      dye.swap();
    }

    function render(target: FBO | null) {
      gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
      gl.enable(gl.BLEND);
      drawDisplay(target);
    }

    function drawDisplay(target: FBO | null) {
      const width = target ? target.width : gl.drawingBufferWidth;
      const height = target ? target.height : gl.drawingBufferHeight;
      displayMaterial.bind();
      if (config.SHADING && displayMaterial.uniforms.texelSize) {
        gl.uniform2f(displayMaterial.uniforms.texelSize, 1 / width, 1 / height);
      }
      if (displayMaterial.uniforms.uTexture) {
        gl.uniform1i(displayMaterial.uniforms.uTexture, dye.read.attach(0));
      }
      blit(target, false);
    }

    function splatPointer(pointer: Pointer) {
      const dx = pointer.deltaX * config.SPLAT_FORCE;
      const dy = pointer.deltaY * config.SPLAT_FORCE;
      splat(pointer.texcoordX, pointer.texcoordY, dx, dy, pointer.color);
    }

    function clickSplat(pointer: Pointer) {
      const color = generateColor();
      color.r *= 10;
      color.g *= 10;
      color.b *= 10;
      const dx = 10 * (Math.random() - 0.5);
      const dy = 30 * (Math.random() - 0.5);
      splat(pointer.texcoordX, pointer.texcoordY, dx, dy, color);
    }

    function splat(x: number, y: number, dx: number, dy: number, color: ColorRGB) {
      splatProgram.bind();
      if (splatProgram.uniforms.uTarget) {
        gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read.attach(0));
      }
      if (splatProgram.uniforms.aspectRatio) {
        gl.uniform1f(splatProgram.uniforms.aspectRatio, canvas!.width / canvas!.height);
      }
      if (splatProgram.uniforms.point) {
        gl.uniform2f(splatProgram.uniforms.point, x, y);
      }
      if (splatProgram.uniforms.color) {
        gl.uniform3f(splatProgram.uniforms.color, dx, dy, 0);
      }
      if (splatProgram.uniforms.radius) {
        gl.uniform1f(splatProgram.uniforms.radius, correctRadius(config.SPLAT_RADIUS / 100)!);
      }
      blit(velocity.write);
      velocity.swap();

      if (splatProgram.uniforms.uTarget) {
        gl.uniform1i(splatProgram.uniforms.uTarget, dye.read.attach(0));
      }
      if (splatProgram.uniforms.color) {
        gl.uniform3f(splatProgram.uniforms.color, color.r, color.g, color.b);
      }
      blit(dye.write);
      dye.swap();
    }

    function correctRadius(radius: number) {
      const aspectRatio = canvas!.width / canvas!.height;
      if (aspectRatio > 1) radius *= aspectRatio;
      return radius;
    }

    function updatePointerDownData(pointer: Pointer, id: number, posX: number, posY: number) {
      pointer.id = id;
      pointer.down = true;
      pointer.moved = false;
      pointer.texcoordX = posX / canvas!.width;
      pointer.texcoordY = 1 - posY / canvas!.height;
      pointer.prevTexcoordX = pointer.texcoordX;
      pointer.prevTexcoordY = pointer.texcoordY;
      pointer.deltaX = 0;
      pointer.deltaY = 0;
      pointer.color = generateColor();
    }

    function updatePointerMoveData(pointer: Pointer, posX: number, posY: number, color: ColorRGB) {
      pointer.prevTexcoordX = pointer.texcoordX;
      pointer.prevTexcoordY = pointer.texcoordY;
      pointer.texcoordX = posX / canvas!.width;
      pointer.texcoordY = 1 - posY / canvas!.height;
      pointer.deltaX = correctDeltaX(pointer.texcoordX - pointer.prevTexcoordX)!;
      pointer.deltaY = correctDeltaY(pointer.texcoordY - pointer.prevTexcoordY)!;
      pointer.moved = Math.abs(pointer.deltaX) > 0 || Math.abs(pointer.deltaY) > 0;
      pointer.color = color;
    }

    function updatePointerUpData(pointer: Pointer) {
      pointer.down = false;
    }

    function correctDeltaX(delta: number) {
      const aspectRatio = canvas!.width / canvas!.height;
      if (aspectRatio < 1) delta *= aspectRatio;
      return delta;
    }

    function correctDeltaY(delta: number) {
      const aspectRatio = canvas!.width / canvas!.height;
      if (aspectRatio > 1) delta /= aspectRatio;
      return delta;
    }

    function generateColor(): ColorRGB {
      const c = HSVtoRGB(Math.random(), 1.0, 1.0);
      c.r *= 0.15;
      c.g *= 0.15;
      c.b *= 0.15;
      return c;
    }

    function HSVtoRGB(h: number, s: number, v: number): ColorRGB {
      let r = 0,
        g = 0,
        b = 0;
      const i = Math.floor(h * 6);
      const f = h * 6 - i;
      const p = v * (1 - s);
      const q = v * (1 - f * s);
      const t = v * (1 - (1 - f) * s);

      switch (i % 6) {
        case 0:
          r = v;
          g = t;
          b = p;
          break;
        case 1:
          r = q;
          g = v;
          b = p;
          break;
        case 2:
          r = p;
          g = v;
          b = t;
          break;
        case 3:
          r = p;
          g = q;
          b = v;
          break;
        case 4:
          r = t;
          g = p;
          b = v;
          break;
        case 5:
          r = v;
          g = p;
          b = q;
          break;
      }
      return { r, g, b };
    }

    function wrap(value: number, min: number, max: number) {
      const range = max - min;
      if (range === 0) return min;
      return ((value - min) % range) + min;
    }

    function getCanvasOffset() {
      const rect = canvas!.getBoundingClientRect();
      return { left: rect.left, top: rect.top };
    }

    window.addEventListener('mousedown', e => {
      const pointer = pointers[0];
      const offset = getCanvasOffset();
      const posX = scaleByPixelRatio(e.clientX - offset.left);
      const posY = scaleByPixelRatio(e.clientY - offset.top);
      updatePointerDownData(pointer, -1, posX, posY);
      clickSplat(pointer);
    });

    function handleFirstMouseMove(e: MouseEvent) {
      const pointer = pointers[0];
      const offset = getCanvasOffset();
      const posX = scaleByPixelRatio(e.clientX - offset.left);
      const posY = scaleByPixelRatio(e.clientY - offset.top);
      const color = generateColor();
      updateFrame();
      updatePointerMoveData(pointer, posX, posY, color);
      document.body.removeEventListener('mousemove', handleFirstMouseMove);
    }
    document.body.addEventListener('mousemove', handleFirstMouseMove);

    window.addEventListener('mousemove', e => {
      const pointer = pointers[0];
      const offset = getCanvasOffset();
      const posX = scaleByPixelRatio(e.clientX - offset.left);
      const posY = scaleByPixelRatio(e.clientY - offset.top);
      const color = pointer.color;
      updatePointerMoveData(pointer, posX, posY, color);
    });

    function handleFirstTouchStart(e: TouchEvent) {
      const touches = e.targetTouches;
      const pointer = pointers[0];
      const offset = getCanvasOffset();
      for (let i = 0; i < touches.length; i++) {
        const posX = scaleByPixelRatio(touches[i].clientX - offset.left);
        const posY = scaleByPixelRatio(touches[i].clientY - offset.top);
        updateFrame();
        updatePointerDownData(pointer, touches[i].identifier, posX, posY);
      }
      document.body.removeEventListener('touchstart', handleFirstTouchStart);
    }
    document.body.addEventListener('touchstart', handleFirstTouchStart);

    window.addEventListener(
      'touchstart',
      e => {
        const touches = e.targetTouches;
        const pointer = pointers[0];
        const offset = getCanvasOffset();
        for (let i = 0; i < touches.length; i++) {
          const posX = scaleByPixelRatio(touches[i].clientX - offset.left);
          const posY = scaleByPixelRatio(touches[i].clientY - offset.top);
          updatePointerDownData(pointer, touches[i].identifier, posX, posY);
        }
      },
      false
    );

    window.addEventListener(
      'touchmove',
      e => {
        const touches = e.targetTouches;
        const pointer = pointers[0];
        const offset = getCanvasOffset();
        for (let i = 0; i < touches.length; i++) {
          const posX = scaleByPixelRatio(touches[i].clientX - offset.left);
          const posY = scaleByPixelRatio(touches[i].clientY - offset.top);
          updatePointerMoveData(pointer, posX, posY, pointer.color);
        }
      },
      false
    );

    window.addEventListener('touchend', e => {
      const touches = e.changedTouches;
      const pointer = pointers[0];
      for (let i = 0; i < touches.length; i++) {
        updatePointerUpData(pointer);
      }
    });
  }, [
    SIM_RESOLUTION,
    DYE_RESOLUTION,
    CAPTURE_RESOLUTION,
    DENSITY_DISSIPATION,
    VELOCITY_DISSIPATION,
    PRESSURE,
    PRESSURE_ITERATIONS,
    CURL,
    SPLAT_RADIUS,
    SPLAT_FORCE,
    SHADING,
    COLOR_UPDATE_SPEED,
    BACK_COLOR,
    TRANSPARENT
  ]);

  return (
    <div className="fixed top-0 left-0 z-50 pointer-events-none w-full h-full">
      <canvas ref={canvasRef} id="fluid" className="w-screen h-screen block"></canvas>
    </div>
  );
}
Splash Cursor

Installation
