package com.generation;

import java.util.Random;

/**
 * Implementation of a simplex noise octave.
 */
public class SimplexNoiseOctave {

    private static final Gradient[] GRADIENTS = {

            new Gradient(1, 1, 0), new Gradient(-1, 1, 0), new Gradient(1, -1, 0),
            new Gradient(-1, -1, 0), new Gradient(1, 0, 1), new Gradient(-1, 0, 1),
            new Gradient(1, 0, -1), new Gradient(-1, 0, -1), new Gradient(0, 1, 1),
            new Gradient(0, -1, 1), new Gradient(0, 1, -1), new Gradient(0, -1, -1)
    };
    private static final short[] P_SUPPLY = {

            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 final int LENGTH = P_SUPPLY.length * 2;
    private static final int SWAP_COUNT = 20;
    private static final double F2 = 0.5D * (Math.sqrt(3.0D) - 1.0D);
    private static final double G2 = (3.0D - Math.sqrt(3.0D)) / 6.0D;
    private static final double F3 = 1.0D / 3.0D;
    private static final double G3 = 1.0D / 6.0D;

    private final short[] p = P_SUPPLY.clone();
    private final short[] perm = new short[LENGTH];
    private final short[] permMod12 = new short[LENGTH];

    /**
     * @param seed the seed that this octave uses to generate pseudo random numbers
     */
    public SimplexNoiseOctave(long seed) {

        Random random = new Random(seed);

        for (int index = 0; index < SWAP_COUNT; index++) {

            int swapFrom = random.nextInt(this.p.length);
            int swapTo = random.nextInt(this.p.length);

            short temp = this.p[swapFrom];
            this.p[swapFrom] = this.p[swapTo];
            this.p[swapTo] = temp;
        }

        for (int index = 0; index < LENGTH; index++) {

            this.perm[index] = this.p[index & 255];
            this.permMod12[index] = (short) (this.perm[index] % 12);
        }
    }

    /**
     * A method with the functionality of {@link Math#floor(double)} but it is faster.
     *
     * @param x the value
     * @return the result
     * @see Math#floor(double)
     */
    private static final int fastfloor(double x) {

        int xAsInt = (int) x;
        return x < xAsInt ? xAsInt - 1 : xAsInt;
    }

    /**
     * Dot function for a gradient.
     *
     * @param gradient the gradient
     * @param x        X
     * @param y        Y
     * @return the dot value
     */
    private static final double dot(Gradient gradient, double x, double y) {

        return gradient.x * x + gradient.y * y;
    }

    /**
     * Dot function for a gradient.
     *
     * @param gradient the gradient
     * @param x        X
     * @param y        Y
     * @param z        Z
     * @return the dot value
     */
    private static final double dot(Gradient gradient, double x, double y, double z) {

        return gradient.x * x + gradient.y * y + gradient.z * z;
    }

    /**
     * Makes a two dimensional noise.
     *
     * @param x X
     * @param y Y
     * @return the noise
     */
    public double noise(double x, double y) {

        double n0;
        double n1;
        double n2;

        double s = (x + y) * F2;

        int i = fastfloor(x + s);
        int j = fastfloor(y + s);

        double t = (i + j) * G2;

        double X0 = i - t;
        double Y0 = j - t;

        double x0 = x - X0;
        double y0 = y - Y0;

        int i1;
        int j1;

        if (x0 > y0) {

            i1 = 1;
            j1 = 0;

        } else {

            i1 = 0;
            j1 = 1;
        }

        double x1 = x0 - i1 + G2;
        double y1 = y0 - j1 + G2;
        double x2 = x0 - 1.0D + 2.0D * G2;
        double y2 = y0 - 1.0D + 2.0D * G2;

        int ii = i & 0xFF;
        int jj = j & 0xFF;

        int gi0 = this.permMod12[ii + this.perm[jj]];
        int gi1 = this.permMod12[ii + i1 + this.perm[jj + j1]];
        int gi2 = this.permMod12[ii + 1 + this.perm[jj + 1]];

        double t0 = 0.5D - x0 * x0 - y0 * y0;

        if (t0 < 0) {

            n0 = 0.0;

        } else {

            t0 *= t0;
            n0 = t0 * t0 * dot(GRADIENTS[gi0], x0, y0);
        }

        double t1 = 0.5D - x1 * x1 - y1 * y1;

        if (t1 < 0.0D) {

            n1 = 0.0;

        } else {

            t1 *= t1;
            n1 = t1 * t1 * dot(GRADIENTS[gi1], x1, y1);
        }

        double t2 = 0.5D - x2 * x2 - y2 * y2;

        if (t2 < 0.0D) {

            n2 = 0.0D;

        } else {

            t2 *= t2;
            n2 = t2 * t2 * dot(GRADIENTS[gi2], x2, y2);
        }

        return 70.0D * (n0 + n1 + n2);
    }

    /**
     * Makes a three dimensional noise.
     *
     * @param x X
     * @param y Y
     * @param z Z
     * @return the noise
     */
    public double noise(double x, double y, double z) {

        double n0;
        double n1;
        double n2;
        double n3;

        double s = (x + y + z) * F3;

        int i = fastfloor(x + s);
        int j = fastfloor(y + s);
        int k = fastfloor(z + s);

        double t = (i + j + k) * G3;

        double X0 = i - t;
        double Y0 = j - t;
        double Z0 = k - t;

        double x0 = x - X0;
        double y0 = y - Y0;
        double z0 = z - Z0;

        int i1;
        int j1;
        int k1;
        int i2;
        int j2;
        int k2;

        if (x0 >= y0) {

            if (y0 >= z0) {

                i1 = 1;
                j1 = 0;
                k1 = 0;
                i2 = 1;
                j2 = 1;
                k2 = 0;

            } else if (x0 >= z0) {

                i1 = 1;
                j1 = 0;
                k1 = 0;
                i2 = 1;
                j2 = 0;
                k2 = 1;

            } else {

                i1 = 0;
                j1 = 0;
                k1 = 1;
                i2 = 1;
                j2 = 0;
                k2 = 1;
            }

        } else {

            if (y0 < z0) {

                i1 = 0;
                j1 = 0;
                k1 = 1;
                i2 = 0;
                j2 = 1;
                k2 = 1;

            } else if (x0 < z0) {

                i1 = 0;
                j1 = 1;
                k1 = 0;
                i2 = 0;
                j2 = 1;
                k2 = 1;

            } else {

                i1 = 0;
                j1 = 1;
                k1 = 0;
                i2 = 1;
                j2 = 1;
                k2 = 0;
            }
        }

        double x1 = x0 - i1 + G3;
        double y1 = y0 - j1 + G3;
        double z1 = z0 - k1 + G3;

        double x2 = x0 - i2 + 2.0D * G3;
        double y2 = y0 - j2 + 2.0D * G3;
        double z2 = z0 - k2 + 2.0D * G3;

        double x3 = x0 - 1.0D + 3.0D * G3;
        double y3 = y0 - 1.0D + 3.0D * G3;
        double z3 = z0 - 1.0D + 3.0D * G3;

        int ii = i & 0xFF;
        int jj = j & 0xFF;
        int kk = k & 0xFF;

        int gi0 = this.permMod12[ii + this.perm[jj + this.perm[kk]]];
        int gi1 = this.permMod12[ii + i1 + this.perm[jj + j1 + this.perm[kk + k1]]];
        int gi2 = this.permMod12[ii + i2 + this.perm[jj + j2 + this.perm[kk + k2]]];
        int gi3 = this.permMod12[ii + 1 + this.perm[jj + 1 + this.perm[kk + 1]]];

        double t0 = 0.6D - x0 * x0 - y0 * y0 - z0 * z0;

        if (t0 < 0) {

            n0 = 0.0D;

        } else {

            t0 *= t0;
            n0 = t0 * t0 * dot(GRADIENTS[gi0], x0, y0, z0);
        }

        double t1 = 0.6D - x1 * x1 - y1 * y1 - z1 * z1;

        if (t1 < 0) {

            n1 = 0.0D;

        } else {

            t1 *= t1;
            n1 = t1 * t1 * dot(GRADIENTS[gi1], x1, y1, z1);
        }

        double t2 = 0.6D - x2 * x2 - y2 * y2 - z2 * z2;

        if (t2 < 0) {

            n2 = 0.0D;

        } else {

            t2 *= t2;
            n2 = t2 * t2 * dot(GRADIENTS[gi2], x2, y2, z2);
        }

        double t3 = 0.6D - x3 * x3 - y3 * y3 - z3 * z3;

        if (t3 < 0) {

            n3 = 0.0D;

        } else {

            t3 *= t3;
            n3 = t3 * t3 * dot(GRADIENTS[gi3], x3, y3, z3);
        }

        return 32.0D * (n0 + n1 + n2 + n3);
    }

    /**
     * Represents a gradient.
     * Inner classes are faster than arrays.
     */
    private static final class Gradient {

        private final double x;
        private final double y;
        private final double z;

        /**
         * @param x X
         * @param y Y
         * @param z Z
         */
        private Gradient(double x, double y, double z) {

            this.x = x;
            this.y = y;
            this.z = z;
        }
    }
}