/*
 * Copyright 2013 MovingBlocks
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.terasology.utilities.procedural;

import org.terasology.math.TeraMath;
import org.terasology.utilities.random.FastRandom;

/**
 * A speed-improved simplex noise algorithm for Simplex noise in 2D, 3D and 4D.
 * <br><br>
 * Based on example code by Stefan Gustavson (stegu@itn.liu.se).
 * Optimisations by Peter Eastman (peastman@drizzle.stanford.edu).
 * Better rank ordering method by Stefan Gustavson in 2012.
 * <br><br>
 * This could be speeded up even further, but it's useful as it is.
 * <br><br>
 * Version 2012-03-09
 * <br><br>
 * This code was placed in the public domain by its original author,
 * Stefan Gustavson. You may use it as you see fit, but
 * attribution is appreciated.
 * <br><br>
 * See http://staffwww.itn.liu.se/~stegu/
 * <br><br>
 * msteiger: Introduced seed value
 */
public class SimplexNoise extends AbstractNoise implements Noise2D, Noise3D {

    /**
     * Multiply this with the gridDim provided and noise(x,x) will give tileable 1D noise which will tile
     * when x crosses a multiple of (this * gridDim)
     */
    public static final float TILEABLE1DMAGICNUMBER = 0.5773502691896258f;

    private static Grad[] grad3 = {
            new Grad(1, 1, 0), new Grad(-1, 1, 0), new Grad(1, -1, 0), new Grad(-1, -1, 0),
            new Grad(1, 0, 1), new Grad(-1, 0, 1), new Grad(1, 0, -1), new Grad(-1, 0, -1),
            new Grad(0, 1, 1), new Grad(0, -1, 1), new Grad(0, 1, -1), new Grad(0, -1, -1)};

    private static Grad[] grad4 = {
            new Grad(0, 1, 1, 1), new Grad(0, 1, 1, -1), new Grad(0, 1, -1, 1), new Grad(0, 1, -1, -1),
            new Grad(0, -1, 1, 1), new Grad(0, -1, 1, -1), new Grad(0, -1, -1, 1), new Grad(0, -1, -1, -1),
            new Grad(1, 0, 1, 1), new Grad(1, 0, 1, -1), new Grad(1, 0, -1, 1), new Grad(1, 0, -1, -1),
            new Grad(-1, 0, 1, 1), new Grad(-1, 0, 1, -1), new Grad(-1, 0, -1, 1), new Grad(-1, 0, -1, -1),
            new Grad(1, 1, 0, 1), new Grad(1, 1, 0, -1), new Grad(1, -1, 0, 1), new Grad(1, -1, 0, -1),
            new Grad(-1, 1, 0, 1), new Grad(-1, 1, 0, -1), new Grad(-1, -1, 0, 1), new Grad(-1, -1, 0, -1),
            new Grad(1, 1, 1, 0), new Grad(1, 1, -1, 0), new Grad(1, -1, 1, 0), new Grad(1, -1, -1, 0),
            new Grad(-1, 1, 1, 0), new Grad(-1, 1, -1, 0), new Grad(-1, -1, 1, 0), new Grad(-1, -1, -1, 0)};

    // Skewing and unskewing factors for 2, 3, and 4 dimensions
    private static final float F2 = 0.5f * (float) (Math.sqrt(3.0f) - 1.0f);
    private static final float G2 = (3.0f - (float) Math.sqrt(3.0f)) / 6.0f;
    private static final float F3 = 1.0f / 3.0f;
    private static final float G3 = 1.0f / 6.0f;
    private static final float F4 = ((float) Math.sqrt(5.0f) - 1.0f) / 4.0f;
    private static final float G4 = (5.0f - (float) Math.sqrt(5.0f)) / 20.0f;

    private final short[] perm;
    private final short[] permMod12;
    private final int permCount;
    /**
     * Initialize permutations with a given seed and grid dimension.
     *
     * @param seed a seed value used for permutation shuffling
     */
    public SimplexNoise(long seed) {
        this(seed, 256);
    }

    /**
     * Initialize permutations with a given seed and grid dimension.
     * Supports 1D tileable noise
     * @see SimplexNoise#tileable1DMagicNumber
     *
     * @param seed a seed value used for permutation shuffling
     * @param gridDim gridDim x gridDim will be the number of squares in the square grid formed after skewing the simplices belonging to once "tile"
     */
    public SimplexNoise(long seed, int gridDim) {
        FastRandom rand = new FastRandom(seed);

        permCount = gridDim;

        perm = new short[permCount * 2];
        permMod12 = new short[permCount * 2];
        short[] p = new short[permCount];

        // Initialize with all values [0..(permCount-1)]
        for (short i = 0; i < permCount; i++) {
            p[i] = i;
        }

        // Shuffle the array
        for (int i = 0; i < permCount; i++) {
            int j = rand.nextInt(permCount);

            short swap = p[i];
            p[i] = p[j];
            p[j] = swap;
        }

        for (int i = 0; i < permCount * 2; i++) {
            perm[i] = p[i % permCount];
            permMod12[i] = (short) (perm[i] % 12);
        }
    }

    private static float dot(Grad g, float x, float y) {
        return g.x * x + g.y * y;
    }

    private static float dot(Grad g, float x, float y, float z) {
        return g.x * x + g.y * y + g.z * z;
    }

    private static float dot(Grad g, float x, float y, float z, float w) {
        return g.x * x + g.y * y + g.z * z + g.w * w;
    }

    /**
     * 2D simplex noise
     *
     * @param xin the x input coordinate
     * @param yin the y input coordinate
     * @return a noise value in the interval [-1,1]
     */
    @Override
    public float noise(float xin, float yin) {
        float n0;
        float n1;
        float n2; // Noise contributions from the three corners

        // Skew the input space to determine which simplex cell we're in
        float s = (xin + yin) * F2; // Hairy factor for 2D
        int i = TeraMath.floorToInt(xin + s);
        int j = TeraMath.floorToInt(yin + s);
        float t = (i + j) * G2;
        float xo0 = i - t; // Unskew the cell origin back to (x,y) space
        float yo0 = j - t;
        float x0 = xin - xo0; // The x,y distances from the cell origin
        float y0 = yin - yo0;

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

        // Work out the hashed gradient indices of the three simplex corners
        int ii = Math.floorMod(i, permCount);
        int jj = Math.floorMod(j, permCount);
        int gi0 = permMod12[ii + perm[jj]];
        int gi1 = permMod12[ii + i1 + perm[jj + j1]];
        int gi2 = permMod12[ii + 1 + perm[jj + 1]];

        // Calculate the contribution from the three corners
        float t0 = 0.5f - x0 * x0 - y0 * y0;
        if (t0 < 0) {
            n0 = 0.0f;
        } else {
            t0 *= t0;
            n0 = t0 * t0 * dot(grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient
        }
        float t1 = 0.5f - x1 * x1 - y1 * y1;
        if (t1 < 0) {
            n1 = 0.0f;
        } else {
            t1 *= t1;
            n1 = t1 * t1 * dot(grad3[gi1], x1, y1);
        }
        float t2 = 0.5f - x2 * x2 - y2 * y2;
        if (t2 < 0) {
            n2 = 0.0f;
        } else {
            t2 *= t2;
            n2 = t2 * t2 * dot(grad3[gi2], 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 70.0f * (n0 + n1 + n2);
    }

    /**
     * 3D simplex noise
     *
     * @param xin the x input coordinate
     * @param yin the y input coordinate
     * @param zin the z input coordinate
     * @return a noise value in the interval [-1,1]
     */
    @Override
    public float noise(float xin, float yin, float zin) {
        float n0;
        float n1;
        float n2;
        float n3; // Noise contributions from the four corners

        // Skew the input space to determine which simplex cell we're in
        float s = (xin + yin + zin) * F3; // Very nice and simple skew factor for 3D
        int i = TeraMath.floorToInt(xin + s);
        int j = TeraMath.floorToInt(yin + s);
        int k = TeraMath.floorToInt(zin + s);
        float t = (i + j + k) * G3;
        float xo0 = i - t; // Unskew the cell origin back to (x,y,z) space
        float yo0 = j - t;
        float zo0 = k - t;
        float x0 = xin - xo0; // The x,y,z distances from the cell origin
        float y0 = yin - yo0;
        float z0 = zin - zo0;

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

        int i2;
        int j2;
        int k2; // Offsets for third corner of simplex in (i,j,k) coords

        if (x0 >= y0) {
            if (y0 >= z0) {         // X Y Z order
                i1 = 1;
                j1 = 0;
                k1 = 0;
                i2 = 1;
                j2 = 1;
                k2 = 0;
            } else if (x0 >= z0) {  // X Z Y order
                i1 = 1;
                j1 = 0;
                k1 = 0;
                i2 = 1;
                j2 = 0;
                k2 = 1;
            } else {                // Z X Y order
                i1 = 0;
                j1 = 0;
                k1 = 1;
                i2 = 1;
                j2 = 0;
                k2 = 1;
            }
        } else { // x0<y0
            if (y0 < z0) {          // Z Y X order
                i1 = 0;
                j1 = 0;
                k1 = 1;
                i2 = 0;
                j2 = 1;
                k2 = 1;
            } else if (x0 < z0) {   // Y Z X order
                i1 = 0;
                j1 = 1;
                k1 = 0;
                i2 = 0;
                j2 = 1;
                k2 = 1;
            } else {                // Y X Z order
                i1 = 0;
                j1 = 1;
                k1 = 0;
                i2 = 1;
                j2 = 1;
                k2 = 0;
            }
        }
        // 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;

        // Work out the hashed gradient indices of the four simplex corners
        int ii = Math.floorMod(i, permCount);
        int jj = Math.floorMod(j, permCount);
        int kk = Math.floorMod(k, permCount);
        int gi0 = permMod12[ii + perm[jj + perm[kk]]];
        int gi1 = permMod12[ii + i1 + perm[jj + j1 + perm[kk + k1]]];
        int gi2 = permMod12[ii + i2 + perm[jj + j2 + perm[kk + k2]]];
        int gi3 = permMod12[ii + 1 + perm[jj + 1 + perm[kk + 1]]];

        // Calculate the contribution from the four corners
        float t0 = 0.6f - x0 * x0 - y0 * y0 - z0 * z0;
        if (t0 < 0) {
            n0 = 0.0f;
        } else {
            t0 *= t0;
            n0 = t0 * t0 * dot(grad3[gi0], x0, y0, z0);
        }
        float t1 = 0.6f - x1 * x1 - y1 * y1 - z1 * z1;
        if (t1 < 0) {
            n1 = 0.0f;
        } else {
            t1 *= t1;
            n1 = t1 * t1 * dot(grad3[gi1], x1, y1, z1);
        }
        float t2 = 0.6f - x2 * x2 - y2 * y2 - z2 * z2;
        if (t2 < 0) {
            n2 = 0.0f;
        } else {
            t2 *= t2;
            n2 = t2 * t2 * dot(grad3[gi2], x2, y2, z2);
        }
        float t3 = 0.6f - x3 * x3 - y3 * y3 - z3 * z3;
        if (t3 < 0) {
            n3 = 0.0f;
        } else {
            t3 *= t3;
            n3 = t3 * t3 * dot(grad3[gi3], 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);
    }


    /**
     * 4D simplex noise, better simplex rank ordering method 2012-03-09
     *
     * @param xin the x input coordinate
     * @param yin the y input coordinate
     * @param zin the z input coordinate
     * @return a noise value in the interval [-1,1]
     */
    public float noise(float xin, float yin, float zin, float win) {

        float n0;
        float n1;
        float n2;
        float n3;
        float n4; // Noise contributions from the five corners

        // Skew the (x,y,z,w) space to determine which cell of 24 simplices we're in
        float s = (xin + yin + zin + win) * F4; // Factor for 4D skewing
        int i = TeraMath.floorToInt(xin + s);
        int j = TeraMath.floorToInt(yin + s);
        int k = TeraMath.floorToInt(zin + s);
        int l = TeraMath.floorToInt(win + s);
        float t = (i + j + k + l) * G4; // Factor for 4D unskewing
        float xo0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
        float yo0 = j - t;
        float zo0 = k - t;
        float wo0 = l - t;
        float x0 = xin - xo0;  // The x,y,z,w distances from the cell origin
        float y0 = yin - yo0;
        float z0 = zin - zo0;
        float w0 = win - wo0;
        // For the 4D case, the simplex is a 4D shape I won't even try to describe.
        // To find out which of the 24 possible simplices we're in, we need to
        // determine the magnitude ordering of x0, y0, z0 and w0.
        // Six pair-wise comparisons are performed between each possible pair
        // of the four coordinates, and the results are used to rank the numbers.
        int rankx = 0;
        int ranky = 0;
        int rankz = 0;
        int rankw = 0;
        if (x0 > y0) {
            rankx++;
        } else {
            ranky++;
        }
        if (x0 > z0) {
            rankx++;
        } else {
            rankz++;
        }
        if (x0 > w0) {
            rankx++;
        } else {
            rankw++;
        }
        if (y0 > z0) {
            ranky++;
        } else {
            rankz++;
        }
        if (y0 > w0) {
            ranky++;
        } else {
            rankw++;
        }
        if (z0 > w0) {
            rankz++;
        } else {
            rankw++;
        }

        int i1;
        int j1;
        int k1;
        int l1; // The integer offsets for the second simplex corner
        int i2;
        int j2;
        int k2;
        int l2; // The integer offsets for the third simplex corner
        int i3;
        int j3;
        int k3;
        int l3; // The integer offsets for the fourth simplex corner

        // simplex[c] is a 4-vector with the numbers 0, 1, 2 and 3 in some order.
        // Many values of c will never occur, since e.g. x>y>z>w makes x<z, y<w and x<w
        // impossible. Only the 24 indices which have non-zero entries make any sense.
        // We use a thresholding to set the coordinates in turn from the largest magnitude.

        // Rank 3 denotes the largest coordinate.
        i1 = rankx >= 3 ? 1 : 0;
        j1 = ranky >= 3 ? 1 : 0;
        k1 = rankz >= 3 ? 1 : 0;
        l1 = rankw >= 3 ? 1 : 0;

        // Rank 2 denotes the second largest coordinate.
        i2 = rankx >= 2 ? 1 : 0;
        j2 = ranky >= 2 ? 1 : 0;
        k2 = rankz >= 2 ? 1 : 0;
        l2 = rankw >= 2 ? 1 : 0;

        // Rank 1 denotes the second smallest coordinate.
        i3 = rankx >= 1 ? 1 : 0;
        j3 = ranky >= 1 ? 1 : 0;
        k3 = rankz >= 1 ? 1 : 0;
        l3 = rankw >= 1 ? 1 : 0;

        // The fifth corner has all coordinate offsets = 1, so no need to compute that.
        float x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
        float y1 = y0 - j1 + G4;
        float z1 = z0 - k1 + G4;
        float w1 = w0 - l1 + G4;
        float x2 = x0 - i2 + 2.0f * G4; // Offsets for third corner in (x,y,z,w) coords
        float y2 = y0 - j2 + 2.0f * G4;
        float z2 = z0 - k2 + 2.0f * G4;
        float w2 = w0 - l2 + 2.0f * G4;
        float x3 = x0 - i3 + 3.0f * G4; // Offsets for fourth corner in (x,y,z,w) coords
        float y3 = y0 - j3 + 3.0f * G4;
        float z3 = z0 - k3 + 3.0f * G4;
        float w3 = w0 - l3 + 3.0f * G4;
        float x4 = x0 - 1.0f + 4.0f * G4; // Offsets for last corner in (x,y,z,w) coords
        float y4 = y0 - 1.0f + 4.0f * G4;
        float z4 = z0 - 1.0f + 4.0f * G4;
        float w4 = w0 - 1.0f + 4.0f * G4;

        // Work out the hashed gradient indices of the five simplex corners
        int ii = Math.floorMod(i, permCount);
        int jj = Math.floorMod(j, permCount);
        int kk = Math.floorMod(k, permCount);
        int ll = Math.floorMod(l, permCount);
        int gi0 = perm[ii + perm[jj + perm[kk + perm[ll]]]] % 32;
        int gi1 = perm[ii + i1 + perm[jj + j1 + perm[kk + k1 + perm[ll + l1]]]] % 32;
        int gi2 = perm[ii + i2 + perm[jj + j2 + perm[kk + k2 + perm[ll + l2]]]] % 32;
        int gi3 = perm[ii + i3 + perm[jj + j3 + perm[kk + k3 + perm[ll + l3]]]] % 32;
        int gi4 = perm[ii + 1 + perm[jj + 1 + perm[kk + 1 + perm[ll + 1]]]] % 32;

        // Calculate the contribution from the five corners
        float t0 = 0.6f - x0 * x0 - y0 * y0 - z0 * z0 - w0 * w0;
        if (t0 < 0) {
            n0 = 0.0f;
        } else {
            t0 *= t0;
            n0 = t0 * t0 * dot(grad4[gi0], x0, y0, z0, w0);
        }
        float t1 = 0.6f - x1 * x1 - y1 * y1 - z1 * z1 - w1 * w1;
        if (t1 < 0) {
            n1 = 0.0f;
        } else {
            t1 *= t1;
            n1 = t1 * t1 * dot(grad4[gi1], x1, y1, z1, w1);
        }
        float t2 = 0.6f - x2 * x2 - y2 * y2 - z2 * z2 - w2 * w2;
        if (t2 < 0) {
            n2 = 0.f;
        } else {
            t2 *= t2;
            n2 = t2 * t2 * dot(grad4[gi2], x2, y2, z2, w2);
        }
        float t3 = 0.6f - x3 * x3 - y3 * y3 - z3 * z3 - w3 * w3;
        if (t3 < 0) {
            n3 = 0.0f;
        } else {
            t3 *= t3;
            n3 = t3 * t3 * dot(grad4[gi3], x3, y3, z3, w3);
        }
        float t4 = 0.6f - x4 * x4 - y4 * y4 - z4 * z4 - w4 * w4;
        if (t4 < 0) {
            n4 = 0.0f;
        } else {
            t4 *= t4;
            n4 = t4 * t4 * dot(grad4[gi4], x4, y4, z4, w4);
        }
        // Sum up and scale the result to cover the range [-1,1]
        return 27.0f * (n0 + n1 + n2 + n3 + n4);
    }

    // Inner class to speed up gradient computations
    // (array access is a lot slower than member access)
    private static class Grad {
        float x;
        float y;
        float z;
        float w;

        Grad(float x, float y, float z) {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        Grad(float x, float y, float z, float w) {
            this.x = x;
            this.y = y;
            this.z = z;
            this.w = w;
        }
    }
}
