package twilightforest.util;

import net.minecraft.core.BlockPos;
import net.minecraft.util.Mth;

/**
 * A speed-improved simplex noise algorithm for 3D in Java.
 * <p>
 * Based on example code by Stefan Gustavson (stegu@itn.liu.se).
 * Optimisations by Peter Eastman (peastman@drizzle.stanford.edu).
 * Better rank ordering method for 4D by Stefan Gustavson in 2012.
 * <p>
 * This could be speeded up even further, but it's useful as it is.
 * <p>
 * Version 2012-03-09
 * <p>
 * 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.
 * <p>
 * <a href="https://github.com/SRombauts/SimplexNoise/blob/master/references/SimplexNoise.java">https://github.com/SRombauts/SimplexNoise/blob/master/references/SimplexNoise.java</a>
 * <p>
 * TODO There's multiple SimplexNoise classes, would be great to benchmark all 3 implementations and see which one's the fastest
 *  @see org.joml.SimplexNoise
 *  @see net.minecraft.world.level.levelgen.synth.SimplexNoise
 */
public class SimplexNoiseHelper {  // Simplex noise in 2D, 3D and 4D
	public static float rippleFractalNoise(int iterations, float size, BlockPos pos, float minimum, float maximum, float frequency) {
		float i = maximum - minimum;
		return Math.abs(((getFractalNoise(iterations, size, pos) * frequency) % (2 * i)) - i) + minimum;
	}

	public static float getFractalNoise(int iteration, float size, BlockPos pos) {
		return iteration == 0 ? 0 : ((noise(
			(pos.getX() + (iteration * size)) / size,
			(pos.getY() + (iteration * size)) / size,
			(pos.getZ() + (iteration * size)) / size)
			+ 1.0f) * 0.5f) + getFractalNoise(iteration - 1, size, pos);
	}

	public static float fractalNoise(int iterations, float size, BlockPos pos) {
		return getFractalNoise(iterations, size, pos) / iterations;
	}

	@Deprecated
	public static int calcVariant(BlockPos pos) {
		return calcVariant(pos, 16);
	}

	public static int calcVariant(BlockPos pos, int variants) {
		return Mth.floor(Mth.positiveModulo(fractalNoise(3, 48.0f, pos) * 120.0f, variants));
	}

	private static final 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 final short[] p = {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};

	// To remove the need for index wrapping, double the permutation table length
	private static final short[] perm = new short[512];
	private static final short[] permMod12 = new short[512];

	static {
		for (int i = 0; i < 512; i++) {
			perm[i] = p[i & 255];
			permMod12[i] = (short) (perm[i] % 12);
		}
	}

	// Skewing and unskewing factors for 2, 3, and 4 dimensions
	private static final float F3 = 1.0f / 3.0f;
	private static final float G3 = 1.0f / 6.0f;

	// This method is a *lot* faster than using (int)Math.floor(x)
	private static int fastfloor(float x) {
		int xi = (int) x;
		return x < xi ? xi - 1 : xi;
	}

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

	// 3D simplex noise
	static float noise(float xin, float yin, float zin) {
		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 = (xin + yin + zin) * F3; // Very nice and simple skew factor for 3D
		int i = fastfloor(xin + s);
		int j = fastfloor(yin + s);
		int k = fastfloor(zin + s);
		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 = xin - X0; // The x,y,z distances from the cell origin
		float y0 = yin - Y0;
		float z0 = zin - 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
		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;
		// Work out the hashed gradient indices of the four simplex corners
		int ii = i & 255;
		int jj = j & 255;
		int kk = k & 255;
		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);
	}

	// Inner class to speed upp gradient computations
	// (In Java, array access is a lot slower than member access)
	private static class Grad {
		final float x;
		final float y;
		final float z;

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