// ReSharper disable InconsistentNaming

using System;

namespace RGB.NET.Core.Tests.Helper;

// Simplex Noise for C#
// Copyright © Benjamin Ward 2019
// See LICENSE (https://github.com/WardBenjamin/SimplexNoise/blob/2afa9a63483562cc4c0a95bbfa6b183fc256a790/LICENSE.txt)
// Simplex Noise implementation offering 1D, 2D, and 3D forms w/ values in the range of 0 to 255.
// Based on work by Heikki Törmälä (2012) and Stefan Gustavson (2006).

/// <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 static class SimplexNoise
{
    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);
        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);
        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);
        return values;
    }

    public static float CalcPixel1D(int x, float scale) => Generate(x * scale);
    public static float CalcPixel2D(int x, int y, float scale) => Generate(x * scale, y * scale);
    public static float CalcPixel3D(int x, int y, int z, float scale) => Generate(x * scale, y * scale, z * scale);

    static SimplexNoise()
    {
        _perm = new byte[PermOriginal.Length];
        PermOriginal.CopyTo(_perm, 0);
    }

    public static int Seed
    {
        get => _seed;
        set
        {
            if (value == 0)
            {
                _perm = new byte[PermOriginal.Length];
                PermOriginal.CopyTo(_perm, 0);
            }
            else
            {
                _perm = new byte[512];
                Random random = new(value);
                random.NextBytes(_perm);
            }

            _seed = value;
        }
    }

    private static int _seed;

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

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

        float t1 = 1.0f - (x1 * x1);
        t1 *= t1;
        float 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>
    private 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 = (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 = Mod(i, 256);
        int jj = Mod(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);
    }


    private 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 = (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);
    }

    private static byte[] _perm;

    private static readonly byte[] PermOriginal = 
    [
            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);
    }
}