import { perlinNoiseData } from "./perlin_noise_data";
import { Math_sqrt } from "./builtins";

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

    dot2(x, y) {
        return this.x * x + this.y * y;
    }

    dot3(x, y, z) {
        return this.x * x + this.y * y + this.z * z;
    }
}

function fade(t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
}

function lerp(a, b, t) {
    return (1 - t) * a + t * b;
}

const F2 = 0.5 * (Math_sqrt(3) - 1);
const G2 = (3 - Math_sqrt(3)) / 6;

const F3 = 1 / 3;
const G3 = 1 / 6;

export class PerlinNoise {
    constructor(seed) {
        this.perm = new Array(512);
        this.gradP = new Array(512);
        this.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),
        ];

        this.seed = seed;
        this.initializeFromSeed(seed);
    }

    initializeFromSeed(seed) {
        const P = perlinNoiseData;

        if (seed > 0 && seed < 1) {
            // Scale the seed out
            seed *= 65536;
        }

        seed = Math.floor(seed);
        if (seed < 256) {
            seed |= seed << 8;
        }

        for (let i = 0; i < 256; i++) {
            let v;
            if (i & 1) {
                v = P[i] ^ (seed & 255);
            } else {
                v = P[i] ^ ((seed >> 8) & 255);
            }

            this.perm[i] = this.perm[i + 256] = v;
            this.gradP[i] = this.gradP[i + 256] = this.grad3[v % 12];
        }
    }

    /**
     * 2d Perlin Noise
     * @param {number} x
     * @param {number} y
     * @returns {number}
     */
    computePerlin2(x, y) {
        // Find unit grid cell containing point
        let X = Math.floor(x),
            Y = Math.floor(y);

        // Get relative xy coordinates of point within that cell
        x = x - X;
        y = y - Y;

        // Wrap the integer cells at 255 (smaller integer period can be introduced here)
        X = X & 255;
        Y = Y & 255;

        // Calculate noise contributions from each of the four corners
        let n00 = this.gradP[X + this.perm[Y]].dot2(x, y);
        let n01 = this.gradP[X + this.perm[Y + 1]].dot2(x, y - 1);
        let n10 = this.gradP[X + 1 + this.perm[Y]].dot2(x - 1, y);
        let n11 = this.gradP[X + 1 + this.perm[Y + 1]].dot2(x - 1, y - 1);

        // Compute the fade curve value for x
        let u = fade(x);

        // Interpolate the four results
        return lerp(lerp(n00, n10, u), lerp(n01, n11, u), fade(y));
    }

    computeSimplex2(xin, yin) {
        var n0, n1, n2; // Noise contributions from the three corners
        // Skew the input space to determine which simplex cell we're in
        var s = (xin + yin) * F2; // Hairy factor for 2D
        var i = Math.floor(xin + s);
        var j = Math.floor(yin + s);
        var t = (i + j) * G2;
        var x0 = xin - i + t; // The x,y distances from the cell origin, unskewed.
        var y0 = yin - j + t;
        // For the 2D case, the simplex shape is an equilateral triangle.
        // Determine which simplex we are in.
        var i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
        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
        var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
        var y1 = y0 - j1 + G2;
        var x2 = x0 - 1 + 2 * G2; // Offsets for last corner in (x,y) unskewed coords
        var y2 = y0 - 1 + 2 * G2;
        // Work out the hashed gradient indices of the three simplex corners
        i &= 255;
        j &= 255;
        var gi0 = this.gradP[i + this.perm[j]];
        var gi1 = this.gradP[i + i1 + this.perm[j + j1]];
        var gi2 = this.gradP[i + 1 + this.perm[j + 1]];
        // Calculate the contribution from the three corners
        var t0 = 0.5 - x0 * x0 - y0 * y0;
        if (t0 < 0) {
            n0 = 0;
        } else {
            t0 *= t0;
            n0 = t0 * t0 * gi0.dot2(x0, y0); // (x,y) of grad3 used for 2D gradient
        }
        var t1 = 0.5 - x1 * x1 - y1 * y1;
        if (t1 < 0) {
            n1 = 0;
        } else {
            t1 *= t1;
            n1 = t1 * t1 * gi1.dot2(x1, y1);
        }
        var t2 = 0.5 - x2 * x2 - y2 * y2;
        if (t2 < 0) {
            n2 = 0;
        } else {
            t2 *= t2;
            n2 = t2 * t2 * gi2.dot2(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 * (n0 + n1 + n2);
    }
}