import { Skia } from "@shopify/react-native-skia";

// Color Shift: cyclic hue/saturation breathing effect
// Uniforms: time, intensity, speed
export const colorShiftShader = Skia.RuntimeEffect.Make(`
  uniform shader image;
  uniform float2 resolution;
  uniform float time;
  uniform float intensity;
  uniform float speed;

  // RGB to HSL conversion
  float3 rgb2hsl(float3 c) {
    float mx = max(c.r, max(c.g, c.b));
    float mn = min(c.r, min(c.g, c.b));
    float l = (mx + mn) * 0.5;
    float s = 0.0;
    float h = 0.0;

    if (mx != mn) {
      float d = mx - mn;
      s = l > 0.5 ? d / (2.0 - mx - mn) : d / (mx + mn);

      if (mx == c.r) {
        h = (c.g - c.b) / d + (c.g < c.b ? 6.0 : 0.0);
      } else if (mx == c.g) {
        h = (c.b - c.r) / d + 2.0;
      } else {
        h = (c.r - c.g) / d + 4.0;
      }
      h /= 6.0;
    }

    return float3(h, s, l);
  }

  float hue2rgb(float p, float q, float t) {
    float tt = t;
    if (tt < 0.0) tt += 1.0;
    if (tt > 1.0) tt -= 1.0;
    if (tt < 1.0/6.0) return p + (q - p) * 6.0 * tt;
    if (tt < 1.0/2.0) return q;
    if (tt < 2.0/3.0) return p + (q - p) * (2.0/3.0 - tt) * 6.0;
    return p;
  }

  float3 hsl2rgb(float3 hsl) {
    float h = hsl.x;
    float s = hsl.y;
    float l = hsl.z;

    if (s == 0.0) return float3(l);

    float q = l < 0.5 ? l * (1.0 + s) : l + s - l * s;
    float p = 2.0 * l - q;

    return float3(
      hue2rgb(p, q, h + 1.0/3.0),
      hue2rgb(p, q, h),
      hue2rgb(p, q, h - 1.0/3.0)
    );
  }

  half4 main(float2 coord) {
    half4 color = image.eval(coord);
    float3 hsl = rgb2hsl(float3(color.rgb));

    float t = time * speed * 0.15;

    // Shift hue cyclically
    hsl.x = fract(hsl.x + intensity * 0.1 * sin(t));

    // Pulse saturation
    hsl.y = clamp(hsl.y + intensity * 0.15 * sin(t * 1.3), 0.0, 1.0);

    // Subtle luminance breathing
    hsl.z = clamp(hsl.z + intensity * 0.03 * sin(t * 0.8), 0.0, 1.0);

    float3 rgb = hsl2rgb(hsl);
    return half4(half3(rgb), color.a);
  }
`)!;