// SimplexNoise for C#
// Author: Benjamin Ward
// Originally authored by Heikki Törmälä
//
// Modified by Josh Bothun to produce values from [0, 1)
//
// https://github.com/WardBenjamin/SimplexNoise/blob/master/SimplexNoise/Noise.cs
//
//BSD 3-Clause License

//Copyright(c) 2019, Benjamin Ward
//All rights reserved.

//Redistribution and use in source and binary forms, with or without
//modification, are permitted provided that the following conditions are met:

//* Redistributions of source code must retain the above copyright notice, this
//  list of conditions and the following disclaimer.

//* Redistributions in binary form must reproduce the above copyright notice,
//  this list of conditions and the following disclaimer in the documentation
//  and/or other materials provided with the distribution.

//* Neither the name of the copyright holder nor the names of its
//  contributors may be used to endorse or promote products derived from
//  this software without specific prior written permission.

//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
//AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
//IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
//DISCLAIMED.IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
//FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
//DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
//SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
//CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
//OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
//OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

using System;

namespace SimplexNoise {
  /// <summary>
  /// Implementation of the Perlin simplex noise, an improved Perlin noise algorithm.
  /// Based loosely on SimplexNoise1234 by Stefan Gustavson <http://staffwww.itn.liu.se/~stegu/aqsis/aqsis-newnoise/>
  /// </summary>
  public class Noise {
    public static float[] Calc1D(int width, float scale) {
      float[] values = new float[width];
      for (int i = 0; i < width; i++)
        values[i] = Generate(i * scale) * 0.5f + 0.5f;
      return values;
    }

    public static float[,] Calc2D(int width, int height, float scale) {
      float[,] values = new float[width, height];
      for (int i = 0; i < width; i++)
        for (int j = 0; j < height; j++)
          values[i, j] = Generate(i * scale, j * scale) * 0.5f + 0.5f;
      return values;
    }

    public static float[,,] Calc3D(int width, int height, int length, float scale) {
      float[,,] values = new float[width, height, length];
      for (int i = 0; i < width; i++)
        for (int j = 0; j < height; j++)
          for (int k = 0; k < length; k++)
            values[i, j, k] = Generate(i * scale, j * scale, k * scale) * 0.5f + 0.5f;
      return values;
    }

    public static float CalcPixel1D(int x, float scale) {
      return Generate(x * scale) * 0.5f + 0.5f;
    }

    public static float CalcPixel2D(int x, int y, float scale) {
      return Generate(x * scale, y * scale) * 0.5f + 0.5f;
    }

    public static float CalcPixel2DFloat(float x, float y, float scale) {
      return Generate(x * scale, y * scale) * 0.5f + 0.5f;
    }

    public static float CalcPixel3D(int x, int y, int z, float scale) {
      return Generate(x * scale, y * scale, z * scale) * 0.5f + 0.5f;
    }

    public static float CalcPixel3DFloat(float x, float y, float z, float scale) {
      return (Generate(x * scale, y * scale, z * scale) + 1) * .5f;
    }

    static Noise() {
      perm = new byte[permOriginal.Length];
      SimplexNoise.Noise.permOriginal.CopyTo(perm, 0);
    }

    public static int Seed {
      get { return seed; }
      set {
        if (value == 0) {
          perm = new byte[permOriginal.Length];
          SimplexNoise.Noise.permOriginal.CopyTo(perm, 0);
        } else {
          perm = new byte[512];
          Random random = new Random(value);
          random.NextBytes(perm);
        }
      }
    }
    private static int seed = 0;

    /// <summary>
    /// 1D simplex noise
    /// </summary>
    /// <param name="x"></param>
    /// <returns></returns>
    internal static float Generate(float x) {
      int i0 = FastFloor(x);
      int i1 = i0 + 1;
      float x0 = x - i0;
      float x1 = x0 - 1.0f;

      float n0, n1;

      float t0 = 1.0f - x0 * x0;
      t0 *= t0;
      n0 = t0 * t0 * grad(perm[i0 & 0xff], x0);

      float t1 = 1.0f - x1 * x1;
      t1 *= t1;
      n1 = t1 * t1 * grad(perm[i1 & 0xff], x1);
      // The maximum value of this noise is 8*(3/4)^4 = 2.53125
      // A factor of 0.395 scales to fit exactly within [-1,1]
      return 0.395f * (n0 + n1);
    }

    /// <summary>
    /// 2D simplex noise
    /// </summary>
    /// <param name="x"></param>
    /// <param name="y"></param>
    /// <returns></returns>
    internal static float Generate(float x, float y) {
      const float F2 = 0.366025403f; // F2 = 0.5*(sqrt(3.0)-1.0)
      const float G2 = 0.211324865f; // G2 = (3.0-Math.sqrt(3.0))/6.0

      float n0, n1, n2; // Noise contributions from the three corners

      // Skew the input space to determine which simplex cell we're in
      float s = (x + y) * F2; // Hairy factor for 2D
      float xs = x + s;
      float ys = y + s;
      int i = FastFloor(xs);
      int j = FastFloor(ys);

      float t = (float)(i + j) * G2;
      float X0 = i - t; // Unskew the cell origin back to (x,y) space
      float Y0 = j - t;
      float x0 = x - X0; // The x,y distances from the cell origin
      float y0 = y - Y0;

      // For the 2D case, the simplex shape is an equilateral triangle.
      // Determine which simplex we are in.
      int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
      if (x0 > y0) { i1 = 1; j1 = 0; } // lower triangle, XY order: (0,0)->(1,0)->(1,1)
      else { i1 = 0; j1 = 1; }      // upper triangle, YX order: (0,0)->(0,1)->(1,1)

      // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
      // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
      // c = (3-sqrt(3))/6

      float x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
      float y1 = y0 - j1 + G2;
      float x2 = x0 - 1.0f + 2.0f * G2; // Offsets for last corner in (x,y) unskewed coords
      float y2 = y0 - 1.0f + 2.0f * G2;

      // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
      int ii = i % 256;
      int jj = j % 256;

      // Calculate the contribution from the three corners
      float t0 = 0.5f - x0 * x0 - y0 * y0;
      if (t0 < 0.0f) n0 = 0.0f;
      else {
        t0 *= t0;
        n0 = t0 * t0 * grad(perm[ii + perm[jj]], x0, y0);
      }

      float t1 = 0.5f - x1 * x1 - y1 * y1;
      if (t1 < 0.0f) n1 = 0.0f;
      else {
        t1 *= t1;
        n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1]], x1, y1);
      }

      float t2 = 0.5f - x2 * x2 - y2 * y2;
      if (t2 < 0.0f) n2 = 0.0f;
      else {
        t2 *= t2;
        n2 = t2 * t2 * grad(perm[ii + 1 + perm[jj + 1]], x2, y2);
      }

      // Add contributions from each corner to get the final noise value.
      // The result is scaled to return values in the interval [-1,1].
      return 40.0f * (n0 + n1 + n2); // TODO: The scale factor is preliminary!
    }


    internal static float Generate(float x, float y, float z) {
      // Simple skewing factors for the 3D case
      const float F3 = 0.333333333f;
      const float G3 = 0.166666667f;

      float n0, n1, n2, n3; // Noise contributions from the four corners

      // Skew the input space to determine which simplex cell we're in
      float s = (x + y + z) * F3; // Very nice and simple skew factor for 3D
      float xs = x + s;
      float ys = y + s;
      float zs = z + s;
      int i = FastFloor(xs);
      int j = FastFloor(ys);
      int k = FastFloor(zs);

      float t = (float)(i + j + k) * G3;
      float X0 = i - t; // Unskew the cell origin back to (x,y,z) space
      float Y0 = j - t;
      float Z0 = k - t;
      float x0 = x - X0; // The x,y,z distances from the cell origin
      float y0 = y - Y0;
      float z0 = z - Z0;

      // For the 3D case, the simplex shape is a slightly irregular tetrahedron.
      // Determine which simplex we are in.
      int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
      int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords

      /* This code would benefit from a backport from the GLSL version! */
      if (x0 >= y0) {
        if (y0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // X Y Z order
        else if (x0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 0; k2 = 1; } // X Z Y order
        else { i1 = 0; j1 = 0; k1 = 1; i2 = 1; j2 = 0; k2 = 1; } // Z X Y order
      } else { // x0<y0
        if (y0 < z0) { i1 = 0; j1 = 0; k1 = 1; i2 = 0; j2 = 1; k2 = 1; } // Z Y X order
        else if (x0 < z0) { i1 = 0; j1 = 1; k1 = 0; i2 = 0; j2 = 1; k2 = 1; } // Y Z X order
        else { i1 = 0; j1 = 1; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // Y X Z order
      }

      // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
      // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
      // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
      // c = 1/6.

      float x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
      float y1 = y0 - j1 + G3;
      float z1 = z0 - k1 + G3;
      float x2 = x0 - i2 + 2.0f * G3; // Offsets for third corner in (x,y,z) coords
      float y2 = y0 - j2 + 2.0f * G3;
      float z2 = z0 - k2 + 2.0f * G3;
      float x3 = x0 - 1.0f + 3.0f * G3; // Offsets for last corner in (x,y,z) coords
      float y3 = y0 - 1.0f + 3.0f * G3;
      float z3 = z0 - 1.0f + 3.0f * G3;

      // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
      int ii = Mod(i, 256);
      int jj = Mod(j, 256);
      int kk = Mod(k, 256);

      // Calculate the contribution from the four corners
      float t0 = 0.6f - x0 * x0 - y0 * y0 - z0 * z0;
      if (t0 < 0.0f) n0 = 0.0f;
      else {
        t0 *= t0;
        n0 = t0 * t0 * grad(perm[ii + perm[jj + perm[kk]]], x0, y0, z0);
      }

      float t1 = 0.6f - x1 * x1 - y1 * y1 - z1 * z1;
      if (t1 < 0.0f) n1 = 0.0f;
      else {
        t1 *= t1;
        n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1 + perm[kk + k1]]], x1, y1, z1);
      }

      float t2 = 0.6f - x2 * x2 - y2 * y2 - z2 * z2;
      if (t2 < 0.0f) n2 = 0.0f;
      else {
        t2 *= t2;
        n2 = t2 * t2 * grad(perm[ii + i2 + perm[jj + j2 + perm[kk + k2]]], x2, y2, z2);
      }

      float t3 = 0.6f - x3 * x3 - y3 * y3 - z3 * z3;
      if (t3 < 0.0f) n3 = 0.0f;
      else {
        t3 *= t3;
        n3 = t3 * t3 * grad(perm[ii + 1 + perm[jj + 1 + perm[kk + 1]]], x3, y3, z3);
      }

      // Add contributions from each corner to get the final noise value.
      // The result is scaled to stay just inside [-1,1]
      return 32.0f * (n0 + n1 + n2 + n3); // TODO: The scale factor is preliminary!
    }

    private static byte[] perm;

    private static readonly byte[] permOriginal = new byte[]
    {
            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,
            151,160,137,91,90,15,
            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
    };

    private static int FastFloor(float x) {
      return (x > 0) ? ((int)x) : (((int)x) - 1);
    }

    private static int Mod(int x, int m) {
      int a = x % m;
      return a < 0 ? a + m : a;
    }

    private static float grad(int hash, float x) {
      int h = hash & 15;
      float grad = 1.0f + (h & 7);   // Gradient value 1.0, 2.0, ..., 8.0
      if ((h & 8) != 0) grad = -grad;         // Set a random sign for the gradient
      return (grad * x);           // Multiply the gradient with the distance
    }

    private static float grad(int hash, float x, float y) {
      int h = hash & 7;      // Convert low 3 bits of hash code
      float u = h < 4 ? x : y;  // into 8 simple gradient directions,
      float v = h < 4 ? y : x;  // and compute the dot product with (x,y).
      return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -2.0f * v : 2.0f * v);
    }

    private static float grad(int hash, float x, float y, float z) {
      int h = hash & 15;     // Convert low 4 bits of hash code into 12 simple
      float u = h < 8 ? x : y; // gradient directions, and compute dot product.
      float v = h < 4 ? y : h == 12 || h == 14 ? x : z; // Fix repeats at h = 12 to 15
      return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v);
    }

    private static float grad(int hash, float x, float y, float z, float t) {
      int h = hash & 31;      // Convert low 5 bits of hash code into 32 simple
      float u = h < 24 ? x : y; // gradient directions, and compute dot product.
      float v = h < 16 ? y : z;
      float w = h < 8 ? z : t;
      return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v) + ((h & 4) != 0 ? -w : w);
    }
  }
}