<script module lang="ts">
export interface FlameWrapOptions {
  /** Flame color as [r, g, b] in 0-1 range. */
  color?: [number, number, number];
  /** Overall brightness of the fire (0 to 3). */
  intensity?: number;
  /** Reach of the flames above the top edge in CSS pixels. */
  height?: number;
  /** Reach of the glow on the sides and bottom in CSS pixels. */
  spread?: number;
  /** Corner radius of the burning outline in CSS pixels. Match your content. */
  radius?: number;
  /** Animation speed multiplier for the whole effect. */
  speed?: number;
  /** Flame detail from 0 (broad licks) to 1 (fine licks). */
  scale?: number;
  /** Amplitude of the turbulence waves shaping the flames (0 to 1). */
  turbulence?: number;
  /** Frequency multiplier of the turbulence waves (0.2 to 3). */
  turbulenceScale?: number;
  /** How far from the edges the heat warps the content, in CSS pixels. */
  turbulenceReach?: number;
  /** Brightness of the spark highlights (0 to 3). 0 disables them. */
  sparks?: number;
  /** Size multiplier for individual sparks (0.2 to 3). */
  sparkSize?: number;
  /** How many sparks fly at once (0.3 to 2.5). */
  sparkDensity?: number;
  /** How fast sparks rise and flicker (0.1 to 3). */
  sparkSpeed?: number;
  /** Strength of the molten glow hugging the edges (0 to 3). */
  rim?: number;
  /** How far the flames eat into the content silhouette in CSS pixels. */
  melt?: number;
  /** Heat shimmer displacement of the content near the edges in CSS pixels. */
  distortion?: number;
  /** Amount of smoke drifting off the flames (0 to 2). */
  smoke?: number;
  /** Brightness of the glowing ember line on the burnt edges (0 to 2). */
  ember?: number;
  /** Darkness of the charred band on the content edges (0 to 2). */
  scorch?: number;
}

export interface FlameWrapElements {
  /** Canvas with layoutsubtree that hosts the HTML content. */
  source: HTMLCanvasElement;
  /** The element inside the source canvas that gets captured. */
  content: HTMLElement;
  /** Canvas the WebGL effect renders to. */
  output: HTMLCanvasElement;
}

export interface FlameWrapInstance {
  /** Update effect options live. */
  setOptions: (options: FlameWrapOptions) => void;
  /** Re-read canvas size. Call when the element is resized. */
  resize: () => void;
  /** Stop the loop and release all GPU resources. */
  destroy: () => void;
}

const DEFAULTS: Required<FlameWrapOptions> = {
  color: [0.956, 0.247, 0.369],
  intensity: 0.5,
  height: 170,
  spread: 8,
  radius: 40,
  speed: 0.25,
  scale: 0.75,
  turbulence: 0.5,
  turbulenceScale: 0.5,
  turbulenceReach: 25,
  sparks: 1.5,
  sparkSize: 0.35,
  sparkDensity: 1,
  sparkSpeed: 1,
  rim: 2.5,
  melt: 4.5,
  distortion: 10,
  smoke: 1.5,
  ember: 2,
  scorch: 0,
};

type PaintableCanvas = HTMLCanvasElement & {
  onpaint?: (() => void) | null;
  requestPaint?: () => void;
};

type ElementImageContext = CanvasRenderingContext2D & {
  drawElementImage?: (element: Element, x: number, y: number) => void;
};

const VERT = `#version 300 es
precision highp float;
layout(location = 0) in vec2 aPos;
out vec2 vUv;
void main () {
  vUv = aPos * 0.5 + 0.5;
  gl_Position = vec4(aPos, 0.0, 1.0);
}`;

const FRAG = `#version 300 es
precision highp float;
in vec2 vUv;
out vec4 outColor;
uniform sampler2D uContent;
uniform vec2 uResolution;
uniform float uTime;
uniform vec2 uRectCenter;
uniform vec2 uRectHalf;
uniform float uCorner;
uniform vec3 uColor;
uniform float uIntensity;
uniform float uHeight;
uniform float uSpread;
uniform float uScale;
uniform float uTurbulence;
uniform float uTurbScale;
uniform float uTurbReach;
uniform float uSparks;
uniform float uSparkSize;
uniform float uSparkDensity;
uniform float uSparkSpeed;
uniform float uRim;
uniform float uMelt;
uniform float uDistortion;
uniform float uSmoke;
uniform float uEmber;
uniform float uScorch;
uniform float uHasContent;

#define S(a, b, t) smoothstep(a, b, t)

vec3 permute (vec3 x) {
  return mod(((x * 34.0) + 1.0) * x, 289.0);
}

float snoise (vec2 v) {
  const vec4 C = vec4(
    0.211324865405187, 0.366025403784439,
    -0.577350269189626, 0.024390243902439
  );
  vec2 i = floor(v + dot(v, C.yy));
  vec2 x0 = v - i + dot(i, C.xx);
  vec2 i1 = (x0.x > x0.y) ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
  vec4 x12 = x0.xyxy + C.xxzz;
  x12.xy -= i1;
  i = mod(i, 289.0);
  vec3 p = permute(
    permute(i.y + vec3(0.0, i1.y, 1.0)) + i.x + vec3(0.0, i1.x, 1.0)
  );
  vec3 m = max(
    0.5 - vec3(dot(x0, x0), dot(x12.xy, x12.xy), dot(x12.zw, x12.zw)),
    0.0
  );
  m = m * m;
  m = m * m;
  vec3 x = 2.0 * fract(p * C.www) - 1.0;
  vec3 h = abs(x) - 0.5;
  vec3 ox = floor(x + 0.5);
  vec3 a0 = x - ox;
  m *= 1.79284291400159 - 0.85373472095314 * (a0 * a0 + h * h);
  vec3 g;
  g.x = a0.x * x0.x + h.x * x0.y;
  g.yz = a0.yz * x12.xz + h.yz * x12.yw;
  return 130.0 * dot(m, g);
}

float fbm (vec2 p) {
  mat2 m = mat2(0.8, -0.6, 0.6, 0.8);
  float v = 0.5 * snoise(p);
  p = m * p * 2.03 + vec2(11.3, 7.1);
  v += 0.27 * snoise(p);
  p = m * p * 1.97 + vec2(3.7, 19.1);
  v += 0.15 * snoise(p);
  p = m * p * 2.01 + vec2(8.3, 2.9);
  v += 0.08 * snoise(p);
  return v * 0.5 + 0.5;
}

float fbm2 (vec2 p) {
  float v = 0.62 * snoise(p);
  v += 0.31 * snoise(mat2(0.8, -0.6, 0.6, 0.8) * p * 2.13 + vec2(5.2, 1.3));
  return v * 0.54 + 0.5;
}

vec2 turbulence (vec2 p) {
  float freq = 12.0 * clamp(uScale, 0.05, 1.0) * clamp(uTurbScale, 0.2, 3.0);
  mat2 rot = mat2(0.6, -0.8, 0.8, 0.6);
  for (float i = 0.0; i < 7.0; i++) {
    float phase = freq * (p * rot).y + 6.0 * uTime + i;
    p += uTurbulence * rot[0] * sin(phase) / freq;
    rot *= mat2(0.6, -0.8, 0.8, 0.6);
    freq *= 1.2;
  }
  return p;
}

vec3 hash3 (vec2 p) {
  vec3 q = vec3(
    dot(p, vec2(127.1, 311.7)),
    dot(p, vec2(269.5, 183.3)),
    dot(p, vec2(419.2, 371.9))
  );
  return fract(sin(q) * 43758.5453);
}

float sdRoundRect (vec2 p, vec2 b, float r) {
  vec2 q = abs(p) - b + r;
  return length(max(q, 0.0)) + min(max(q.x, q.y), 0.0) - r;
}

void main () {
  vec2 frag = vUv * uResolution;
  vec2 rel = frag - uRectCenter;
  float unit = max(uHeight, 24.0);
  float corner = min(uCorner, min(uRectHalf.x, uRectHalf.y));
  float spreadPx = max(uSpread, 8.0);
  float t = uTime;
  float detail = clamp(uScale, 0.05, 1.0);

  float d0 = sdRoundRect(rel, uRectHalf, corner);
  float px = rel.x / unit;
  float py = rel.y / unit;

  float yA = max(rel.y - uRectHalf.y, 0.0) / unit;
  float sway = snoise(vec2(px * 1.1, t * 0.5)) * 0.55
    + snoise(vec2(px * 2.4, t * 0.9 + 41.0)) * 0.25;
  float sx = px + yA * sway;
  float env = fbm2(vec2(sx * 1.6 * detail + 3.7, t * 0.55 - yA * 0.4));
  float env2 = fbm2(vec2(sx * 3.6 * detail, t * 0.85 + 17.0 - yA * 0.6));
  float tongue = clamp(
    0.75 * S(0.3, 0.9, env) + 0.5 * S(0.4, 0.95, env2),
    0.0,
    1.0
  );

  float meltPx = max(uMelt, 1.0);
  float biteTop = (3.0 + meltPx * 1.4) * (0.35 + 0.65 * tongue)
    + 2.0 * snoise(vec2(px * 5.0 * detail, t * 1.1 + 5.0));
  float yF = uRectHalf.y - biteTop;
  float frontTop = rel.y - yF;

  float perim = fbm2(rel * (1.9 / unit) * detail + vec2(0.0, t * 0.4) + 31.0);
  float biteSB = 3.0 + meltPx * (0.25 + 0.75 * perim);
  float frontSB = d0 + biteSB;

  float wTop = S(-0.62 * unit, -0.1 * unit, rel.y - uRectHalf.y)
    * S(10.0, -30.0, abs(rel.x) - (uRectHalf.x - corner));
  float front = mix(frontSB, frontTop, wTop);

  float reach = mix(
    spreadPx * 0.9,
    unit * (0.2 + 0.45 * tongue),
    wTop
  );
  float q = front / reach;

  vec2 np = vec2(px * 2.3, py * 1.25 - t * 1.85) * detail;
  np = turbulence(np);
  float n = fbm(np);

  float win = S(-0.08, 0.02, q);
  float root = exp(-abs(q) * 5.0);
  float ridge = 1.0 - abs(2.0 * n - 1.0);
  float flameH = mix(1.0, 0.5 + 0.6 * tongue, wTop);
  float g = max(q, 0.0) / flameH;
  float shred = fbm2(np * 1.9 + 63.0);
  g *= 1.0 + 0.7 * (shred - 0.5) * S(0.2, 0.8, g);
  float dens = n * 0.95 + ridge * 0.45 - 0.18
    + (1.0 - min(g, 1.0)) * 0.3
    - g * (0.9 + 0.25 * n);
  dens = clamp(dens * 2.4, 0.0, 1.0) * win;
  dens *= mix(1.0 - S(0.32, 1.05, q), 1.0 - S(0.9, 1.2, g), wTop);
  float body = dens * dens * (3.0 - 2.0 * dens);
  float emis = clamp(uIntensity, 0.0, 2.0);
  float e = body * (0.55 + 0.75 * root) * (0.45 + 0.55 * n)
    + win * root * (0.1 + 0.4 * n);
  e *= mix(0.45, 1.0, wTop) * max(emis, 0.001);

  vec3 hot = mix(uColor, vec3(1.0), 0.35);
  vec3 deep = mix(uColor, uColor * uColor, 0.5) * 0.9;
  float ramp = 1.0 - exp(-e * 2.4);
  vec3 fireCol = mix(deep, uColor, S(0.0, 0.55, ramp));
  float core = ramp * (0.45 + 0.55 * exp(-g * 2.2)) * (0.5 + 0.5 * n);
  fireCol = mix(fireCol, hot, S(0.7, 1.05, core));
  fireCol *= 0.8 + 0.4 * ramp;
  float fireA = clamp(1.0 - exp(-e * 3.4), 0.0, 1.0);

  float halo = exp(-max(front, 0.0) / (spreadPx * 1.2)) * S(0.0, 3.0, front)
    * (0.5 + 0.5 * n) * 0.3 * clamp(uRim, 0.0, 2.0) * mix(1.0, 0.45, wTop);
  vec3 glow = uColor * halo * clamp(uIntensity, 0.0, 2.0);

  if (uSparks > 0.001) {
    float sSpeed = max(uSparkSpeed, 0.05);
    float sCells = 5.0 * clamp(uSparkDensity, 0.3, 2.5);
    float sSize = clamp(uSparkSize, 0.2, 3.0);
    float gate = S(-0.05, 0.1, q) * (1.0 - S(1.3, 2.2, q)) * wTop;
    float spark = 0.0;
    for (float L = 0.0; L < 2.0; L++) {
      float speed = 1.5 * sSpeed * (0.75 + 0.5 * L);
      vec2 ps = vec2(px, py - t * speed);
      ps.x += 0.08 * snoise(vec2(py * 0.9 + L * 5.0, t * 0.5));
      float cells = sCells * (1.0 + 0.6 * L);
      vec2 cl = floor(ps * cells) + L * 19.0;
      vec2 fr = fract(ps * cells);
      vec3 rnd = hash3(cl);
      vec3 rnd2 = hash3(cl + 7.3);
      float on = step(rnd2.x, 0.42);
      float life = fract(rnd.z + t * sSpeed * (0.3 + 0.5 * rnd2.x));
      vec2 ppos = vec2(0.5) + 0.56 * (rnd.xy - 0.5);
      ppos.x += 0.14 * sin(t * (0.7 + rnd.z * 2.8) + rnd.y * 6.2832)
        + 0.1 * snoise(vec2(t * 0.6 + rnd.x * 9.0, cl.y * 0.7))
        + (life - 0.5) * 0.5 * (rnd2.y - 0.5);
      ppos.y += (life - 0.5) * 0.3 * rnd2.y;
      float tw = S(0.02, 0.2, life) * S(1.0, 0.55, life);
      tw *= 0.75 + 0.25 * sin(t * (6.0 + rnd2.z * 9.0) + rnd.x * 6.2832);
      vec2 pd = (fr - ppos) / cells * unit;
      pd.y *= 0.55 + 0.3 * rnd2.z;
      float dp = length(pd);
      float r = (0.004 + 0.014 * rnd.y * rnd.y) * unit * sSize
        * mix(1.15, 0.55, life);
      float bmask = S(0.5, 0.32, max(abs(fr.x - 0.5), abs(fr.y - 0.5)));
      float sbody = exp(-dp * dp / (r * r));
      float sbloom = exp(-dp * dp / (r * r * 6.0)) * 0.3;
      spark += (sbody + sbloom) * tw * tw * on * bmask * (1.0 - 0.35 * L);
    }
    spark *= gate * uSparks;
    fireCol += mix(uColor, vec3(1.0), 0.55) * spark * 1.6;
    fireA = clamp(fireA + spark * 0.85, 0.0, 1.0);
  }

  vec2 edgePx = min(frag, uResolution - frag);
  float fadeW = max(24.0, spreadPx * 0.75);
  float fade = S(0.0, fadeW, edgePx.x) * S(0.0, fadeW, edgePx.y);
  fireA *= fade;
  glow *= fade;
  halo *= fade;

  float wisp = S(0.45, 0.9, fbm2(np * 0.55 + vec2(0.0, 17.0)));
  float smoke = S(1.55, 1.05, g) * S(0.85, 1.15, g)
    * (1.0 - body) * wTop
    * wisp * 0.055 * clamp(uSmoke, 0.0, 2.0) * fade;
  vec3 smokeCol = mix(vec3(0.5), uColor, 0.5);

  if (uHasContent < 0.5) {
    float sA = clamp(smoke, 0.0, 1.0);
    float a = clamp(fireA + sA * (1.0 - fireA), 0.0, 1.0);
    outColor = vec4(
      fireCol * fireA + glow + smokeCol * sA * (1.0 - fireA),
      clamp(a + halo * 0.6, 0.0, 1.0)
    );
    return;
  }

  vec2 cUv = (rel + uRectHalf) / (2.0 * uRectHalf);
  float inRect = step(abs(cUv.x - 0.5), 0.5) * step(abs(cUv.y - 0.5), 0.5);

  float heatBand = exp(-abs(front) / max(uTurbReach, 4.0));
  vec2 wob = vec2(
    snoise(np * 1.7 + 9.0),
    snoise(np * 1.7 + 27.0)
  );
  vec2 disp = wob * min(uDistortion, 32.0) * heatBand;
  vec2 cUvD = clamp(cUv + disp / (2.0 * uRectHalf), vec2(0.002), vec2(0.998));
  vec4 content = texture(uContent, vec2(cUvD.x, 1.0 - cUvD.y));

  float burn = clamp(uIntensity, 0.0, 1.0);
  float depth = max(-front, 0.0);
  float charPatch = 0.5 + 0.5 * fbm2(rel * (2.6 / unit) * detail + 57.0);
  float charW = mix(4.0, 6.0 + meltPx * 1.6, wTop) * charPatch;
  float charT = (1.0 - S(charW, charW * 2.4, depth));
  content.rgb = mix(
    content.rgb,
    content.rgb * vec3(0.22, 0.19, 0.17),
    clamp(charT * 0.85 * burn * clamp(uScorch, 0.0, 2.0), 0.0, 1.0)
  );

  float emberW = mix(2.5, 5.5, wTop);
  float emberN = 0.3 + 0.7 * fbm2(np * 2.2 + 73.0);
  float emberK = clamp(uEmber, 0.0, 2.0);
  float ember = exp(-depth / emberW) * emberN * emberK;
  float whiteHot = exp(-depth / (emberW * 0.4)) * emberN * emberN * emberK;
  content.rgb = mix(content.rgb, uColor * 1.2, clamp(ember, 0.0, 1.0) * burn);
  content.rgb = mix(
    content.rgb,
    mix(uColor, vec3(1.0), 0.3) * 1.2,
    clamp(whiteHot, 0.0, 1.0) * burn
  );

  float dn = fbm2(rel * (3.2 / unit) * detail + vec2(0.0, t * 0.5) + 91.0);
  float dw = mix(2.0, 5.0, wTop);
  float dissolve = S(-dw, dw, front + (dn - 0.5) * dw * 2.5);
  float cA = content.a * (1.0 - dissolve) * inRect;
  float smk = smoke * (1.0 - cA);
  float baseA = min(cA + smk, 1.0);
  vec3 base = content.rgb * cA + smokeCol * smk;
  vec3 col = fireCol * fireA + base * (1.0 - fireA) + glow;
  float alpha = clamp(fireA + baseA * (1.0 - fireA) + halo * 0.5, 0.0, 1.0);
  outColor = vec4(col, alpha);
}`;

export function supportsHtmlInCanvas(): boolean {
  if (typeof document === "undefined") return false;
  const probe = document.createElement("canvas") as PaintableCanvas;
  const ctx = probe.getContext("2d") as ElementImageContext | null;
  return Boolean(
    ctx &&
    typeof ctx.drawElementImage === "function" &&
    typeof probe.requestPaint === "function",
  );
}

export function createFlameWrap(
  elements: FlameWrapElements,
  options: FlameWrapOptions = {},
): FlameWrapInstance | null {
  const config = { ...DEFAULTS, ...options };
  const { source, content, output } = elements;

  const gl = output.getContext("webgl2", {
    alpha: true,
    depth: false,
    stencil: false,
    antialias: false,
    premultipliedAlpha: true,
  });
  if (!gl || gl.isContextLost()) return null;

  const sourceCtx = source.getContext("2d") as ElementImageContext | null;
  const paintable = source as PaintableCanvas;
  const htmlInCanvas = Boolean(
    sourceCtx &&
    typeof sourceCtx.drawElementImage === "function" &&
    typeof paintable.requestPaint === "function",
  );

  let contentDirty = false;
  let wake = () => {};

  if (htmlInCanvas) {
    paintable.onpaint = () => {
      try {
        sourceCtx!.reset();
        sourceCtx!.drawElementImage!(content, 0, 0);
        contentDirty = true;
        wake();
      } catch {}
    };
  }

  function compile(type: number, text: string): WebGLShader {
    const shader = gl!.createShader(type)!;
    gl!.shaderSource(shader, text);
    gl!.compileShader(shader);
    if (!gl!.getShaderParameter(shader, gl!.COMPILE_STATUS)) {
      console.error("FlameWrap shader error:", gl!.getShaderInfoLog(shader));
    }
    return shader;
  }

  const vertexShader = compile(gl.VERTEX_SHADER, VERT);
  const fragmentShader = compile(gl.FRAGMENT_SHADER, FRAG);
  const program = gl.createProgram()!;
  gl.attachShader(program, vertexShader);
  gl.attachShader(program, fragmentShader);
  gl.linkProgram(program);

  const uniforms: Record<string, WebGLUniformLocation> = {};
  const count = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
  for (let i = 0; i < count; i++) {
    const info = gl.getActiveUniform(program, i)!;
    uniforms[info.name] = gl.getUniformLocation(program, info.name)!;
  }

  const quad = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, quad);
  gl.bufferData(
    gl.ARRAY_BUFFER,
    new Float32Array([-1, -1, 1, -1, -1, 1, 1, 1]),
    gl.STATIC_DRAW,
  );
  gl.enableVertexAttribArray(0);
  gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);

  const contentTexture = gl.createTexture()!;
  gl.bindTexture(gl.TEXTURE_2D, contentTexture);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
  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,
    gl.RGBA,
    1,
    1,
    0,
    gl.RGBA,
    gl.UNSIGNED_BYTE,
    new Uint8Array([0, 0, 0, 0]),
  );

  const rect = { cx: 0, cy: 0, hx: 1, hy: 1 };
  let dpr = 1;

  function syncCanvasSize() {
    dpr = Math.min(window.devicePixelRatio || 1, 2);
    const width = Math.max(1, Math.round(output.clientWidth * dpr));
    const height = Math.max(1, Math.round(output.clientHeight * dpr));
    if (output.width !== width || output.height !== height) {
      output.width = width;
      output.height = height;
    }
    const box = htmlInCanvas ? source : content;
    const outRect = output.getBoundingClientRect();
    const boxRect = box.getBoundingClientRect();
    if (outRect.width > 0 && boxRect.width > 0) {
      rect.cx = (boxRect.left + boxRect.right) / 2 - outRect.left;
      rect.cy = outRect.bottom - (boxRect.top + boxRect.bottom) / 2;
      rect.hx = boxRect.width / 2;
      rect.hy = boxRect.height / 2;
    }
    if (htmlInCanvas) {
      const cssWidth = Math.max(1, Math.round(source.clientWidth));
      const cssHeight = Math.max(1, Math.round(source.clientHeight));
      if (
        source.width !== cssWidth * dpr ||
        source.height !== cssHeight * dpr
      ) {
        source.width = cssWidth * dpr;
        source.height = cssHeight * dpr;
      }
      paintable.requestPaint!();
    }
  }

  syncCanvasSize();

  function uploadContent() {
    if (!htmlInCanvas || !contentDirty) return;
    contentDirty = false;
    gl!.bindTexture(gl!.TEXTURE_2D, contentTexture);
    gl!.texImage2D(
      gl!.TEXTURE_2D,
      0,
      gl!.RGBA,
      gl!.RGBA,
      gl!.UNSIGNED_BYTE,
      source,
    );
    sourceCtx!.clearRect(0, 0, source.width, source.height);
  }

  let time = 0;

  function render() {
    uploadContent();
    gl!.useProgram(program);
    gl!.activeTexture(gl!.TEXTURE0);
    gl!.bindTexture(gl!.TEXTURE_2D, contentTexture);
    gl!.uniform1i(uniforms.uContent, 0);
    gl!.uniform2f(uniforms.uResolution, output.width, output.height);
    gl!.uniform1f(uniforms.uTime, time);
    gl!.uniform2f(uniforms.uRectCenter, rect.cx * dpr, rect.cy * dpr);
    gl!.uniform2f(
      uniforms.uRectHalf,
      Math.max(rect.hx * dpr, 1),
      Math.max(rect.hy * dpr, 1),
    );
    gl!.uniform1f(uniforms.uCorner, Math.max(config.radius, 0) * dpr);
    gl!.uniform3f(
      uniforms.uColor,
      config.color[0],
      config.color[1],
      config.color[2],
    );
    gl!.uniform1f(uniforms.uIntensity, Math.max(config.intensity, 0));
    gl!.uniform1f(uniforms.uHeight, Math.max(config.height, 24) * dpr);
    gl!.uniform1f(uniforms.uSpread, Math.max(config.spread, 8) * dpr);
    gl!.uniform1f(uniforms.uScale, Math.max(config.scale, 0.05));
    gl!.uniform1f(uniforms.uTurbulence, Math.max(config.turbulence, 0));
    gl!.uniform1f(uniforms.uTurbScale, Math.max(config.turbulenceScale, 0.2));
    gl!.uniform1f(
      uniforms.uTurbReach,
      Math.max(config.turbulenceReach, 4) * dpr,
    );
    gl!.uniform1f(uniforms.uSparks, Math.max(config.sparks, 0));
    gl!.uniform1f(uniforms.uSparkSize, Math.max(config.sparkSize, 0.2));
    gl!.uniform1f(uniforms.uSparkDensity, Math.max(config.sparkDensity, 0.3));
    gl!.uniform1f(uniforms.uSparkSpeed, Math.max(config.sparkSpeed, 0.05));
    gl!.uniform1f(uniforms.uRim, Math.max(config.rim, 0));
    gl!.uniform1f(uniforms.uMelt, Math.max(config.melt, 0) * dpr);
    gl!.uniform1f(uniforms.uDistortion, Math.max(config.distortion, 0) * dpr);
    gl!.uniform1f(uniforms.uSmoke, Math.max(config.smoke, 0));
    gl!.uniform1f(uniforms.uEmber, Math.max(config.ember, 0));
    gl!.uniform1f(uniforms.uScorch, Math.max(config.scorch, 0));
    gl!.uniform1f(uniforms.uHasContent, htmlInCanvas ? 1 : 0);
    gl!.bindFramebuffer(gl!.FRAMEBUFFER, null);
    gl!.viewport(0, 0, output.width, output.height);
    gl!.drawArrays(gl!.TRIANGLE_STRIP, 0, 4);
  }

  let raf = 0;
  let lastTime = performance.now();
  let destroyed = false;
  let running = false;
  let visible = true;

  const motionQuery = window.matchMedia("(prefers-reduced-motion: reduce)");
  let reducedMotion = motionQuery.matches;

  function frame(now: number) {
    if (destroyed) return;
    if (!visible) {
      running = false;
      return;
    }
    const delta = Math.min((now - lastTime) / 1000, 1 / 30);
    lastTime = now;
    if (!reducedMotion) time += delta * config.speed;
    render();
    if (reducedMotion && !contentDirty) {
      running = false;
      return;
    }
    raf = requestAnimationFrame(frame);
  }

  function start() {
    if (destroyed || running || !visible) return;
    running = true;
    lastTime = performance.now();
    raf = requestAnimationFrame(frame);
  }

  wake = start;
  start();

  function onMotionChange() {
    reducedMotion = motionQuery.matches;
    start();
  }
  motionQuery.addEventListener("change", onMotionChange);

  const observer = new ResizeObserver(() => {
    syncCanvasSize();
    start();
  });
  observer.observe(output);
  observer.observe(content);

  const intersection = new IntersectionObserver((entries) => {
    visible = entries[entries.length - 1]?.isIntersecting ?? true;
    if (visible) start();
  });
  intersection.observe(output);

  return {
    setOptions(next) {
      let changed = false;
      for (const [key, value] of Object.entries(next)) {
        const prev = config[key as keyof typeof config];
        if (Array.isArray(value) && Array.isArray(prev)) {
          if (
            value.length !== prev.length ||
            value.some((item, i) => item !== prev[i])
          ) {
            changed = true;
            break;
          }
        } else if (prev !== value) {
          changed = true;
          break;
        }
      }
      Object.assign(config, next);
      if (!changed) return;
      syncCanvasSize();
      start();
    },
    resize() {
      syncCanvasSize();
      start();
    },
    destroy() {
      destroyed = true;
      cancelAnimationFrame(raf);
      observer.disconnect();
      intersection.disconnect();
      motionQuery.removeEventListener("change", onMotionChange);
      gl!.deleteTexture(contentTexture);
      gl!.deleteProgram(program);
      gl!.deleteShader(vertexShader);
      gl!.deleteShader(fragmentShader);
      gl!.deleteBuffer(quad);
      if (htmlInCanvas) paintable.onpaint = null;
    },
  };
}

  declare module "svelte/elements" {
    interface HTMLCanvasAttributes {
      layoutsubtree?: string;
    }
  }
</script>

<script lang="ts">
  import { onMount, tick } from "svelte";

  interface Props extends FlameWrapOptions {
    class?: string;
    children?: import("svelte").Snippet;
  }

  let { class: className = "", children, ...options }: Props = $props();

  let sourceEl = $state<HTMLCanvasElement>()!;
  let contentEl = $state<HTMLDivElement>()!;
  let outputEl = $state<HTMLCanvasElement>()!;
  let native = $state(false);
  let instance: FlameWrapInstance | null = null;

  const reach = $derived(Math.round(Math.max(options.height ?? 170, 24) * 1.5) + 40);
  const glow = $derived(Math.round(Math.max(options.spread ?? 8, 8) * 3) + 16);

  onMount(() => {
    native = supportsHtmlInCanvas();
    let disposed = false;
    (async () => {
      await tick();
      if (disposed) return;
      if (!sourceEl || !contentEl || !outputEl) return;
      instance = createFlameWrap(
        { source: sourceEl, content: contentEl, output: outputEl },
        options,
      );
      if (native && !instance) {
        native = false;
        await tick();
        if (disposed) return;
        if (!sourceEl || !contentEl || !outputEl) return;
        instance = createFlameWrap(
          { source: sourceEl, content: contentEl, output: outputEl },
          options,
        );
      }
    })();
    return () => {
      disposed = true;
      instance?.destroy();
      instance = null;
    };
  });

  $effect(() => {
    instance?.setOptions({ ...options });
  });
</script>

<div class={className} style="position: relative;">
  <canvas
    bind:this={sourceEl}
    layoutsubtree="true"
    style={native
      ? "position: absolute; inset: 0; width: 100%; height: 100%;"
      : "display: none;"}
  >
    {#if native}
      <div
        bind:this={contentEl}
        style="position: relative; width: 100%; height: 100%; overflow: auto;"
      >
        {@render children?.()}
      </div>
    {/if}
  </canvas>
  {#if !native}
    <div
      bind:this={contentEl}
      style="position: relative; width: 100%; height: 100%; overflow: auto;"
    >
      {@render children?.()}
    </div>
  {/if}
  <canvas
    bind:this={outputEl}
    aria-hidden="true"
    style="position: absolute; top: {-reach}px; right: {-glow}px; bottom: {-glow}px; left: {-glow}px; width: calc(100% + {glow *
      2}px); height: calc(100% + {reach + glow}px); pointer-events: none;"
  ></canvas>
</div>