//
// Perlin noise generator for Unity
// Keijiro Takahashi, 2013, 2015
// https://github.com/keijiro/PerlinNoise
//
// Based on the original implementation by Ken Perlin
// http://mrl.nyu.edu/~perlin/noise/
//
using UnityEngine;

public static class Perlin {
  #region Noise functions

  public static float Noise(float x) {
    var X = Mathf.FloorToInt(x) & 0xff;
    x -= Mathf.Floor(x);
    var u = Fade(x);
    return Lerp(u, Grad(perm[X], x), Grad(perm[X + 1], x - 1)) * 2;
  }

  public static float Noise(float x, float y) {
    var X = Mathf.FloorToInt(x) & 0xff;
    var Y = Mathf.FloorToInt(y) & 0xff;
    x -= Mathf.Floor(x);
    y -= Mathf.Floor(y);
    var u = Fade(x);
    var v = Fade(y);
    var A = (perm[X] + Y) & 0xff;
    var B = (perm[X + 1] + Y) & 0xff;
    return Lerp(v, Lerp(u, Grad(perm[A], x, y), Grad(perm[B], x - 1, y)),
                   Lerp(u, Grad(perm[A + 1], x, y - 1), Grad(perm[B + 1], x - 1, y - 1)));
  }

  public static float Noise(Vector2 coord) {
    return Noise(coord.x, coord.y);
  }

  public static float Noise(float x, float y, float z) {
    var X = Mathf.FloorToInt(x) & 0xff;
    var Y = Mathf.FloorToInt(y) & 0xff;
    var Z = Mathf.FloorToInt(z) & 0xff;
    x -= Mathf.Floor(x);
    y -= Mathf.Floor(y);
    z -= Mathf.Floor(z);
    var u = Fade(x);
    var v = Fade(y);
    var w = Fade(z);
    var A = (perm[X] + Y) & 0xff;
    var B = (perm[X + 1] + Y) & 0xff;
    var AA = (perm[A] + Z) & 0xff;
    var BA = (perm[B] + Z) & 0xff;
    var AB = (perm[A + 1] + Z) & 0xff;
    var BB = (perm[B + 1] + Z) & 0xff;
    return Lerp(w, Lerp(v, Lerp(u, Grad(perm[AA], x, y, z), Grad(perm[BA], x - 1, y, z)),
                           Lerp(u, Grad(perm[AB], x, y - 1, z), Grad(perm[BB], x - 1, y - 1, z))),
                   Lerp(v, Lerp(u, Grad(perm[AA + 1], x, y, z - 1), Grad(perm[BA + 1], x - 1, y, z - 1)),
                           Lerp(u, Grad(perm[AB + 1], x, y - 1, z - 1), Grad(perm[BB + 1], x - 1, y - 1, z - 1))));
  }

  public static float Noise(Vector3 coord) {
    return Noise(coord.x, coord.y, coord.z);
  }

  #endregion

  #region fBm functions

  public static float Fbm(float x, int octave) {
    var f = 0.0f;
    var w = 0.5f;
    for (var i = 0; i < octave; i++) {
      f += w * Noise(x);
      x *= 2.0f;
      w *= 0.5f;
    }
    return f;
  }

  public static float Fbm(Vector2 coord, int octave) {
    var f = 0.0f;
    var w = 0.5f;
    for (var i = 0; i < octave; i++) {
      f += w * Noise(coord);
      coord *= 2.0f;
      w *= 0.5f;
    }
    return f;
  }

  public static float Fbm(float x, float y, int octave) {
    return Fbm(new Vector2(x, y), octave);
  }

  public static float Fbm(Vector3 coord, int octave) {
    var f = 0.0f;
    var w = 0.5f;
    for (var i = 0; i < octave; i++) {
      f += w * Noise(coord);
      coord *= 2.0f;
      w *= 0.5f;
    }
    return f;
  }

  public static float Fbm(float x, float y, float z, int octave) {
    return Fbm(new Vector3(x, y, z), octave);
  }

  #endregion

  #region Private functions

  static float Fade(float t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
  }

  static float Lerp(float t, float a, float b) {
    return a + t * (b - a);
  }

  static float Grad(int hash, float x) {
    return (hash & 1) == 0 ? x : -x;
  }

  static float Grad(int hash, float x, float y) {
    return ((hash & 1) == 0 ? x : -x) + ((hash & 2) == 0 ? y : -y);
  }

  static float Grad(int hash, float x, float y, float z) {
    var h = hash & 15;
    var u = h < 8 ? x : y;
    var v = h < 4 ? y : (h == 12 || h == 14 ? x : z);
    return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
  }

  static int[] perm = {
        151,160,137,91,90,15,
        131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
        190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
        88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
        77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
        102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
        135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
        5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
        223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
        129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
        251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
        49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
        138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180,
        151
    };

  #endregion
}