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

out vec4 fragColor;

uniform vec2 uSize;
uniform vec2 uTilt;
uniform float uTime;
uniform float uPrismatic;
uniform float uSparkle;
uniform float uSpecular;
uniform float uDiffraction;
uniform float uStyle;
uniform float uSparkleShapeKind;
uniform float uSparklePrimary;
uniform float uSparkleSecondary;
uniform float uSparkleTertiary;
uniform float uOpacity;

#define TWO_PI 6.28318530718

// Precomputed rotation matrices reduce repeated sin/cos work in tiled layers.
#define ROT_0_78  mat2( 0.71091,  0.70328, -0.70328,  0.71091)
#define ROT_M0_5  mat2( 0.87758, -0.47943,  0.47943,  0.87758)
#define ROT_1_2   mat2( 0.36236,  0.93204, -0.93204,  0.36236)

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);
}

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

float sdRegularPolygon(vec2 p, float sides, float radius) {
  float angle = atan(p.y, p.x);
  float sector = TWO_PI / sides;
  return cos(floor(0.5 + angle / sector) * sector - angle) * length(p) - radius;
}

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));
}

vec2 rotatePoint(vec2 p, float rotation) {
  float c = cos(rotation);
  float s = sin(rotation);
  return vec2(c * p.x - s * p.y, s * p.x + c * p.y);
}

float sparkleRectangleMask(vec2 p, float halfWidth, float halfHeight, float rotation) {
  vec2 q = rotatePoint(p, rotation);
  float body = sdBox(q, vec2(halfWidth, halfHeight));
  float bevel = sdBox(q, vec2(halfWidth * 0.78, halfHeight * 0.78));
  float bodyMask = smoothstep(0.03, -0.03, body);

  float centerLine = 1.0 - smoothstep(0.0, halfHeight * 1.25, abs(q.y));
  float endFade = 1.0 - smoothstep(halfWidth * 0.55, halfWidth * 1.05, abs(q.x));
  float streak = centerLine * endFade;
  float bevelRing = smoothstep(0.025, -0.025, body) - smoothstep(0.025, -0.025, bevel);
  return clamp(bodyMask * (0.58 + 0.42 * streak) + bevelRing * 0.25, 0.0, 1.0);
}

float sparklePolygonMask(vec2 p, float sides, float aspectRatio, float rotation) {
  vec2 q = rotatePoint(p, rotation);
  q.x /= aspectRatio;
  float poly = sdRegularPolygon(q, sides, 0.26);
  return smoothstep(0.03, -0.03, poly);
}

float sparkleShapeMask(vec2 p, vec2 id) {
  float randomRotation = hash(id + 5.1) * TWO_PI;
  if (uSparkleShapeKind < 0.5) {
    return 0.0;
  }
  if (uSparkleShapeKind < 1.5) {
    return sparkleStarMask(p, uSparklePrimary, uSparkleSecondary);
  }
  if (uSparkleShapeKind < 2.5) {
    return sparkleRectangleMask(p, uSparklePrimary, uSparkleSecondary, randomRotation * uSparkleTertiary);
  }
  if (uSparkleShapeKind < 3.5) {
    return sparklePolygonMask(p, uSparklePrimary, uSparkleSecondary, uSparkleTertiary);
  }
  if (uSparkleShapeKind < 4.5) {
    float sides = 5.0 + floor(hash(id + 9.4) * 4.0);
    float aspect = 0.7 + hash(id + 13.1) * 0.7;
    return sparklePolygonMask(p, sides, aspect, randomRotation);
  }
  return sparkleRectangleMask(p, uSparklePrimary, uSparkleSecondary, randomRotation * uSparkleTertiary);
}

vec3 styleHolographicSilver(vec2 uv, vec2 tilt, float time) {
  vec2 p = uv * 2.0 - 1.0;
  float flowA = noise(uv * 3.5 + vec2(time * 0.03, -time * 0.02));
  float flowB = noise(uv * 7.0 + vec2(-time * 0.02, time * 0.03));
  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 + time * 0.2);
  float phase = flowA * 1.8 + ribbon * 0.28 + plume * 0.22 + time * 0.03;
  
  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 styleCrackedIce(vec2 uv, vec2 tilt, float time) {
  float maxZ = -999.0;
  vec2 bestSlope = vec2(0.0);
  float bestHash = 0.0;
  float bestEdge = 1.0;

  vec2 warp = vec2(sin(uv.y * 10.0), cos(uv.x * 10.0)) * 0.05;
  vec2 baseUV = uv + warp;

  // --- LAYER 1 ---
  vec2 p1 = baseUV * 12.0;
  vec2 id1 = floor(p1);
  vec2 f1 = fract(p1) - 0.5;
  vec2 slope1 = vec2(hash(id1 + 1.2), hash(id1 + 1.3)) * 2.0 - 1.0;
  float z1 = dot(f1, slope1) * 3.5;
  if (z1 > maxZ) {
    maxZ = z1; bestSlope = slope1; bestHash = hash(id1 + 1.1); bestEdge = min(0.5 - abs(f1.x), 0.5 - abs(f1.y));
  }

  // --- LAYER 2 (Optimized Rotation) ---
  vec2 p2 = (ROT_0_78 * baseUV) * 15.0; 
  vec2 id2 = floor(p2);
  vec2 f2 = fract(p2) - 0.5;
  vec2 slope2 = vec2(hash(id2 + 2.2), hash(id2 + 2.3)) * 2.0 - 1.0;
  float z2 = 0.8 + dot(f2, slope2) * 3.5; 
  if (z2 > maxZ) {
    maxZ = z2; bestSlope = slope2; bestHash = hash(id2 + 2.1); bestEdge = min(0.5 - abs(f2.x), 0.5 - abs(f2.y));
  }

  // --- LAYER 3 (Optimized Rotation) ---
  vec2 p3 = (ROT_M0_5 * baseUV) * 18.0; 
  vec2 id3 = floor(p3);
  vec2 f3 = fract(p3) - 0.5;
  vec2 slope3 = vec2(hash(id3 + 3.2), hash(id3 + 3.3)) * 2.0 - 1.0;
  float z3 = 1.6 + dot(f3, slope3) * 3.5;
  if (z3 > maxZ) {
    maxZ = z3; bestSlope = slope3; bestHash = hash(id3 + 3.1); bestEdge = min(0.5 - abs(f3.x), 0.5 - abs(f3.y));
  }

  // --- LAYER 4 (Optimized Rotation) ---
  vec2 p4 = (ROT_1_2 * baseUV) * 21.0;
  vec2 id4 = floor(p4);
  vec2 f4 = fract(p4) - 0.5;
  vec2 slope4 = vec2(hash(id4 + 4.2), hash(id4 + 4.3)) * 2.0 - 1.0;
  float z4 = 2.4 + dot(f4, slope4) * 3.5;
  if (z4 > maxZ) {
    maxZ = z4; bestSlope = slope4; bestHash = hash(id4 + 4.1); bestEdge = min(0.5 - abs(f4.x), 0.5 - abs(f4.y));
  }

  // --- VIBRANT COLOR OPTICS ---
  float alignment = dot(tilt, normalize(bestSlope + vec2(0.001)));
  float phase = dot(uv, vec2(0.6, -0.4)) + time * 0.05 + bestHash * 0.6 + alignment * 0.5;
  float saturation = 0.7 + 0.3 * hash(vec2(bestHash, 6.1));
  vec3 baseColor = rainbow(phase, saturation, 1.0);

  float lightCycle = sin(alignment * 4.0 + bestHash * TWO_PI + time * 0.15);
  float ambient = 0.15 + 0.25 * max(0.0, lightCycle);
  vec3 finalColor = baseColor * ambient;
  float flash = pow(max(0.0, lightCycle), 5.0);
  finalColor += mix(baseColor, vec3(1.0, 0.95, 0.85), 0.6) * flash * 0.55;
  finalColor += baseColor * smoothstep(0.05, 0.0, bestEdge) * flash * 0.4;

  return finalColor;
}

vec3 styleSilverMosaic(vec2 uv, vec2 tilt, float time) {
  // Mosaic tile grid.
  vec2 g = uv * 6.0;
  vec2 id = floor(g);
  
  // Center local tile coordinates for radial optics.
  vec2 f = fract(g) - 0.5;

  // Real foil sheets often alternate the grain of the squares to catch light from all angles.
  if (mod(id.x + id.y, 2.0) > 0.5) {
      f = vec2(-f.y, f.x); 
  }

  vec2 radialDir = normalize(f + vec2(0.0001)); 

  vec2 lightDir = normalize(tilt + vec2(0.001));

  // Radial highlight where tile direction aligns with light direction.
  float alignment = abs(dot(radialDir, lightDir));
  
  float highlight = pow(alignment, 12.0); 

  float angleDiff = acos(alignment); 
  
  // 2D cross product sign decides which side of the highlight receives hue shift.
  float side = sign(radialDir.x * lightDir.y - radialDir.y * lightDir.x);
  
  float basePhase = length(tilt) * 2.5 + time * 0.1;
  
  float phase = basePhase + side * angleDiff * 1.8;
  vec3 holoColor = rainbow(phase, 0.85, 1.0);

  // White specular core appears when alignment is nearly perfect.
  vec3 core = vec3(1.0) * smoothstep(0.98, 1.0, alignment);

  vec3 foilBase = vec3(0.25, 0.27, 0.30);

  vec3 finalColor = foilBase + (holoColor * highlight * 1.5) + (core * 0.8);

  // Tile borders and edge darkening add perceived depth.
  float edgeX = 0.5 - abs(f.x);
  float edgeY = 0.5 - abs(f.y);
  
  float border = smoothstep(0.0, 0.015, min(edgeX, edgeY));

  float dist = length(f);
  finalColor *= mix(0.7, 1.0, 1.0 - smoothstep(0.0, 0.5, dist) * 0.3);

  return clamp(finalColor * border, 0.0, 1.0);
}

vec3 styleSuperGoldVinyl(vec2 uv, vec2 tilt, float time) {
  vec2 g = uv * 60.0;
  vec2 staggered = vec2(g.x + 0.5 * mod(floor(g.y), 2.0), g.y);
  vec2 f = fract(staggered) - 0.5;
  
  // Distance-squared masks avoid square roots and preserve circular dots.
  float d2 = dot(f, f); 
  float dotMask = smoothstep(0.1764, 0.01, d2);
  float emboss = smoothstep(0.2025, 0.0324, d2);
  
  float sheen = 0.5 + 0.5 * sin(dot(uv, vec2(18.0, -6.0)) + noise(uv * 6.0) * 2.5 + dot(tilt, vec2(2.4, 1.8)) * 2.0 + time * 0.2);
  vec3 gold = vec3(0.84, 0.70, 0.24);
  vec3 warm = vec3(1.0, 0.88, 0.42);
  vec3 shadow = vec3(0.18, 0.14, 0.05);
  
  return gold * (0.75 + 0.25 * sheen) + warm * dotMask * 0.28 + shadow * emboss * 0.08;
}

void main() {
  // UVs in [0, 1] for global lighting and center-based effects.
  vec2 uv = FlutterFragCoord().xy / uSize;
  vec2 center = vec2(0.5, 0.5);
  vec2 fromCenter = uv - center;

  // Aspect-corrected UVs keep grids and sparkles physically proportional.
  float maxDim = max(uSize.x, uSize.y);
  vec2 aspectUV = FlutterFragCoord().xy / maxDim;

  float tiltMag = length(uTilt);
  float safeTiltMag = max(tiltMag, 0.001);
  vec2 tiltDir = uTilt / safeTiltMag;

  // Highlight uses stretched UVs so glare spans the full widget area.
  float highlightDistance = length(uv - (center + (uTilt * 0.35)));
  float specularMask = pow(max(0.0, 1.0 - highlightDistance * 2.6), 3.2);
  vec3 specular = vec3(specularMask) * uSpecular * (0.4 + 0.6 * tiltMag);

  bool isCrackedIce = uStyle >= 0.5 && uStyle < 1.5;
  float sparkleGridScale = isCrackedIce ? 7.0 : 18.0;
  
  // Sparkle grid uses aspect-corrected coordinates to avoid stretching.
  vec2 sparkleGrid = aspectUV * sparkleGridScale;
  vec2 grid = floor(sparkleGrid);
  
  float rarityThreshold = isCrackedIce ? 0.965 : 0.83;
  float rarity = step(rarityThreshold, hash(grid + 0.31));
  
  vec3 sparkle = vec3(0.0);
  if (rarity > 0.0) {
    vec2 cell = fract(sparkleGrid) - 0.5;
    float sparkleHash = hash(grid);
    vec2 sparkleNormal = normalize(vec2(sparkleHash * 2.0 - 1.0, hash(grid + 19.7) * 2.0 - 1.0));
    float alignment = max(0.0, dot(tiltDir, sparkleNormal));
    
    if (alignment > 0.0) {
      float twinkle = 0.5 + 0.5 * sin(uTime * 5.5 + sparkleHash * TWO_PI);
      float shapeMask = 0.0;
      
      if (isCrackedIce) {
        float sides = 5.0 + floor(hash(grid + 9.4) * 4.0);
        float aspect = 0.75 + hash(grid + 13.1) * 0.55;
        shapeMask = sparklePolygonMask(cell, sides, aspect, hash(grid + 5.1) * TWO_PI);
      } else {
        shapeMask = sparkleShapeMask(cell, grid);
      }
      
      float sparklePower = isCrackedIce ? 4.8 : 3.2;
      float sparkleIntensity = isCrackedIce ? 0.25 : 1.0;
      float sparkleChroma = isCrackedIce ? 0.20 : 0.35;
      float sparkleMask = pow(alignment, sparklePower) * twinkle * rarity * shapeMask;
      vec3 sparkleColor = mix(vec3(1.0), rainbow(sparkleHash + dot(uTilt, vec2(0.2, -0.15)), 0.55, 1.0), sparkleChroma);
      sparkle = sparkleColor * sparkleMask * uSparkle * sparkleIntensity;
    }
  }

  vec3 styleBase;
  // Style bases sample aspect-corrected UVs for stable pattern geometry.
  if (uStyle < 0.5) {
    styleBase = styleHolographicSilver(aspectUV, uTilt, uTime);
  } else if (uStyle < 1.5) {
    styleBase = styleCrackedIce(aspectUV, uTilt, uTime);
  } else if (uStyle < 2.5) {
    styleBase = styleSilverMosaic(aspectUV, uTilt, uTime);
  } else {
    styleBase = styleSuperGoldVinyl(aspectUV, uTilt, uTime);
  }

  float styleLuma = dot(styleBase, vec3(0.299, 0.587, 0.114));
  vec3 chromaAdjusted = mix(vec3(styleLuma), styleBase, 0.2 + 0.8 * uPrismatic);

  // Directional lighting uses center-relative UVs for broad foil gradients.
  vec2 normal2d = normalize(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 microStrength = isCrackedIce ? 0.08 : 0.18;
  
  // Micro diffraction uses aspect-corrected UVs to keep grain isotropic.
  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 * microStrength;
  
  vec3 styleColor = chromaAdjusted + microShimmer + (specular * 0.15) + 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);
}