// Random number generation and noise functions for WGSL shaders.
// Collection of hash functions and noise generators.

// ============================================
// Hash Functions (Float Input)
// ============================================

// Hash: f32 -> f32
// Fast fractional hash for floats
fn hash_1f(x: f32) -> f32 {
  var v = fract(x * 0.3351);
  v *= v + 33.33;
  v *= v + v;
  return fract(v);
}

// Hash: vec2<f32> -> f32
// 2D coordinate to single hash value
fn hash_2f(p: vec2<f32>) -> f32 {
  var h = dot(p, vec2<f32>(127.1, 311.7));
  return fract(sin(h) * 43758.5453123);
}

// Hash: vec2<f32> -> vec2<f32>
// 2D coordinate to 2D hash (from Shadertoy 4djSRW)
fn hash_2f_2f(p: vec2<f32>) -> vec2<f32> {
  var p3 = fract(vec3<f32>(p.x, p.y, p.x) * vec3<f32>(0.1021, 0.1013, 0.0977));
  p3 += dot(p3, p3.yzx + 33.33);
  return fract((p3.xx + p3.yz) * p3.zy);
}

// Hash: vec3<f32> -> f32
// 3D coordinate to single hash value
fn hash_3f(p: vec3<f32>) -> f32 {
  var h = dot(p, vec3<f32>(127.1, 311.7, 74.7));
  return fract(sin(h) * 43758.5453123);
}

// Hash: vec3<f32> -> vec3<f32>
// 3D coordinate to 3D hash
fn hash_3f_3f(p: vec3<f32>) -> vec3<f32> {
  var v = fract(p);
  v += dot(v, v.yxz + 32.41);
  return fract((v.xxy + v.yzz) * v.zyx);
}

// ============================================
// Hash Functions (Integer Input)
// ============================================

// Hash: u32 -> f32
// Integer hash with bit operations (high quality)
fn hash_1u(p: u32) -> f32 {
  var P = (p << 13u) ^ p;
  P = P * (P * P * 15731u + 789221u) + 1376312589u;
  return bitcast<f32>((P >> 9u) | 0x3f800000u) - 1.0;
}

// Hash: u32 -> vec2<f32>
fn hash_1u_2f(p: u32) -> vec2<f32> {
  return vec2<f32>(hash_1u(p), hash_1u(p + 1423u));
}

// Hash: u32 -> vec3<f32>
fn hash_1u_3f(p: u32) -> vec3<f32> {
  return vec3<f32>(hash_1u(p), hash_1u(p + 1423u), hash_1u(p + 124453u));
}

// ============================================
// Noise Functions
// ============================================

// Value Noise: 2D
// Interpolated grid noise using smoothstep
fn noise_2d(p: vec2<f32>) -> f32 {
  let i = floor(p);
  let f = fract(p);
  let u = f * f * (3.0 - 2.0 * f);
  let n0 = hash_2f(i + vec2<f32>(0.0, 0.0));
  let n1 = hash_2f(i + vec2<f32>(1.0, 0.0));
  let n2 = hash_2f(i + vec2<f32>(0.0, 1.0));
  let n3 = hash_2f(i + vec2<f32>(1.0, 1.0));
  let ix0 = mix(n0, n1, u.x);
  let ix1 = mix(n2, n3, u.x);
  return mix(ix0, ix1, u.y);
}

// Value Noise: 3D
fn noise_3d(p: vec3<f32>) -> f32 {
  let i = floor(p);
  let f = fract(p);
  let u = f * f * (3.0 - 2.0 * f);
  let n000 = hash_3f(i + vec3<f32>(0.0, 0.0, 0.0));
  let n100 = hash_3f(i + vec3<f32>(1.0, 0.0, 0.0));
  let n010 = hash_3f(i + vec3<f32>(0.0, 1.0, 0.0));
  let n110 = hash_3f(i + vec3<f32>(1.0, 1.0, 0.0));
  let n001 = hash_3f(i + vec3<f32>(0.0, 0.0, 1.0));
  let n101 = hash_3f(i + vec3<f32>(1.0, 0.0, 1.0));
  let n011 = hash_3f(i + vec3<f32>(0.0, 1.0, 1.0));
  let n111 = hash_3f(i + vec3<f32>(1.0, 1.0, 1.0));
  let ix00 = mix(n000, n100, u.x);
  let ix10 = mix(n010, n110, u.x);
  let ix01 = mix(n001, n101, u.x);
  let ix11 = mix(n011, n111, u.x);
  let iy0 = mix(ix00, ix10, u.y);
  let iy1 = mix(ix01, ix11, u.y);
  return mix(iy0, iy1, u.z);
}

// ============================================
// Special Functions
// ============================================

// Gyroid function (periodic triply-orthogonal minimal surface)
// Useful for procedural patterns and cellular structures
fn gyroid(p: vec3<f32>) -> f32 {
  return abs(0.04 + dot(sin(p), cos(p.zxy)));
}

// Fractional Brownian Motion (FBM) 2D
// Multi-octave noise for natural-looking variation
fn fbm_2d(p: vec2<f32>, octaves: i32) -> f32 {
  var value = 0.0;
  var amplitude = 0.5;
  var frequency = 1.0;
  var pos = p;
  for (var i = 0; i < octaves; i++) {
    value += amplitude * noise_2d(pos * frequency);
    frequency *= 2.0;
    amplitude *= 0.5;
  }
  return value;
}

// Fractional Brownian Motion (FBM) 3D
fn fbm_3d(p: vec3<f32>, octaves: i32) -> f32 {
  var value = 0.0;
  var amplitude = 0.5;
  var frequency = 1.0;
  var pos = p;
  for (var i = 0; i < octaves; i++) {
    value += amplitude * noise_3d(pos * frequency);
    frequency *= 2.0;
    amplitude *= 0.5;
  }
  return value;
}