#version 460 core
#include <flutter/runtime_effect.glsl>

out vec4 fragColor;

uniform vec2 uSize;
uniform vec2 uTilt;
uniform float uPrismatic;
uniform float uSparkle;
uniform float uSpecular;
uniform float uDiffraction;
uniform float uOpacity;

#define TWO_PI 6.28318530718

float hash(vec2 p) {
  vec3 p3 = fract(vec3(p.xyx) * 0.1031);
  p3 += dot(p3, p3.yzx + 33.33);
  return fract((p3.x + p3.y) * p3.z);
}

float noise(vec2 p) {
  vec2 i = floor(p);
  vec2 f = fract(p);
  vec2 u = f * f * (3.0 - 2.0 * f);
  float a = hash(i);
  float b = hash(i + vec2(1.0, 0.0));
  float c = hash(i + vec2(0.0, 1.0));
  float d = hash(i + vec2(1.0, 1.0));
  return mix(mix(a, b, u.x), mix(c, d, u.x), u.y);
}

vec3 hsv2rgb(float h, float s, float v) {
  vec3 k = vec3(1.0, 2.0 / 3.0, 1.0 / 3.0);
  vec3 p = abs(fract(vec3(h) + k) * 6.0 - 3.0);
  return v * mix(vec3(1.0), clamp(p - 1.0, 0.0, 1.0), s);
}

vec3 rainbow(float phase, float saturation, float value) {
  return hsv2rgb(fract(phase), saturation, value);
}

vec2 safeNormalize(vec2 p) {
  return p * inversesqrt(max(dot(p, p), 0.000001));
}

float sparkleStarMask(vec2 p, float points, float innerRatio) {
  float angle = atan(p.y, p.x);
  float radius = dot(p, p);
  float spikes = 0.5 + 0.5 * cos(angle * points);
  float starRadius = mix(0.34 * innerRatio, 0.34, pow(spikes, 1.4));
  return smoothstep(0.0009, -0.0009, radius - (starRadius * starRadius));
}

vec3 styleBase(vec2 uv, vec2 tilt) {
  vec2 p = uv * 2.0 - 1.0;
  vec2 tiltWarp = tilt * 0.18;
  float flowA = noise(uv * 3.5 + tiltWarp + vec2(dot(uv, vec2(0.25, -0.22))));
  float flowB = noise(uv * 7.0 - tiltWarp + vec2(dot(uv, vec2(-0.18, 0.21))));
  vec2 warp = p + 0.25 * vec2(flowA - 0.5, flowB - 0.5);
  float ribbon = sin(dot(warp, vec2(6.5, 2.8)) + flowA * 5.0 + dot(tilt, vec2(2.2, -1.7)));
  float plume = sin(length(warp + vec2(flowB - 0.5, flowA - 0.5)) * 9.0 - tilt.x * 3.0 + dot(uv, vec2(1.5, -1.2)));
  float phase = flowA * 1.8 + ribbon * 0.28 + plume * 0.22;
  vec3 holo = rainbow(phase, 0.72, 1.0);
  float blend = smoothstep(-0.65, 0.95, ribbon + plume * 0.55);
  vec3 silver = vec3(0.62, 0.65, 0.70) * (0.85 + 0.15 * flowB);
  return mix(silver, holo, 0.65 * blend);
}

vec3 sparkleLayer(vec2 aspectUV, vec2 tilt, vec2 tiltDir) {
  vec2 sparkleGrid = aspectUV * 18.0;
  vec2 grid = floor(sparkleGrid);
  vec2 cell = fract(sparkleGrid) - 0.5;
  float sparkleHash = hash(grid);
  vec2 sparkleNormal = safeNormalize(vec2(sparkleHash * 2.0 - 1.0, hash(grid + 19.7) * 2.0 - 1.0));
  float rarity = step(0.83, hash(grid + 0.31));
  float alignment = max(0.0, dot(tiltDir, sparkleNormal));
  float twinkle = 0.45 + 0.55 * sin(dot(cell, vec2(21.0, -17.0)) + dot(tilt, vec2(5.3, -4.1)) + sparkleHash * TWO_PI);
  float shapeMask = sparkleStarMask(cell, 8.0, 0.42);
  float sparkleMask = pow(alignment, 3.2) * twinkle * rarity * shapeMask;
  vec3 sparkleColor = mix(vec3(1.0), rainbow(sparkleHash + dot(tilt, vec2(0.2, -0.15)), 0.55, 1.0), 0.35);
  return sparkleColor * sparkleMask * uSparkle;
}

void main() {
  vec2 frag = FlutterFragCoord().xy;
  vec2 uv = frag / uSize;
  vec2 fromCenter = uv - vec2(0.5);
  float maxDim = max(uSize.x, uSize.y);
  vec2 aspectUV = frag / maxDim;
  float tiltMag = length(uTilt);
  vec2 tiltDir = safeNormalize(uTilt + vec2(0.001));
  float highlightDistance = length(uv - (vec2(0.5) + (uTilt * 0.35)));
  float specularMask = pow(max(0.0, 1.0 - highlightDistance * 2.6), 3.0);

  vec3 base = styleBase(aspectUV, uTilt);
  vec3 sparkle = sparkleLayer(aspectUV, uTilt, tiltDir);
  float baseLuma = dot(base, vec3(0.299, 0.587, 0.114));
  vec3 chromaAdjusted = mix(vec3(baseLuma), base, 0.2 + 0.8 * uPrismatic);

  vec2 normal2d = safeNormalize(fromCenter + vec2(0.001));
  float directional = 0.5 + 0.5 * dot(normal2d, tiltDir);
  float tiltLighting = mix(0.86, 1.20, pow(directional, 1.2));
  chromaAdjusted *= tiltLighting;

  float edgeSpec = pow(1.0 - directional, 2.2);
  vec3 specular = vec3(specularMask) * (0.3 + 0.7 * edgeSpec) * uSpecular * (0.35 + 0.65 * tiltMag);
  float prismaticPhase = dot(aspectUV, vec2(3.6, -2.1)) + dot(uTilt, vec2(0.9, -0.7));
  vec3 prismaticTint = rainbow(prismaticPhase, 0.72, 1.0) * uPrismatic * 1.10 * (0.08 + 0.14 * edgeSpec);
  float microMask = 0.5 + 0.5 * sin(dot(aspectUV, vec2(137.0, 57.0)) + noise(aspectUV * 14.0) * 4.0 + dot(uTilt, vec2(9.0, 4.0)) * 2.0);
  vec3 microShimmer = rainbow(noise(aspectUV * 10.0) + dot(uTilt, vec2(0.4, -0.3)) * 0.3, 0.65, 1.0) * microMask * uDiffraction * 0.18;

  vec3 styleColor = chromaAdjusted + microShimmer + prismaticTint + (specular * 0.22) + sparkle;
  vec3 mappedColor = styleColor / (1.0 + styleColor * 0.3);
  float luma = dot(mappedColor, vec3(0.299, 0.587, 0.114));
  vec3 vibrantColor = mix(vec3(luma), mappedColor, 1.4);
  float foilBrightness = dot(vibrantColor, vec3(0.333));
  float alpha = clamp(foilBrightness * 0.5, 0.0, 0.35) * clamp(uOpacity, 0.0, 1.0);
  vec3 finalColor = clamp(vibrantColor, 0.0, 1.0);
  fragColor = vec4(finalColor * alpha, alpha);
}