// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(1);

// Global code will be evaluated once.
const turtle = new Turtle();
let seed = 1000; // min=1 max=1000000 step=1
const bits = 20; 
const samples = 150000; 
const mod = 1<<bits;
const x_gap = 10; // min = 0 max = 30 step = 1
const y_gap = 10; // min = 0 max = 30 step = 1
const perlin_magnitude = 7; // min = 1 max = 20 step = 1
const perlin_size_1 = 10; // min = 1 max = 20 step = 1
const perlin_size_2 = 5; // min = 1 max = 20 step = 1

////////////////////////////////////////////////////////////////
// Pseudorandom number generator. Created by Reinder Nijhoff 2024
// https://turtletoy.net/turtle/a2274fd1fe
////////////////////////////////////////////////////////////////
function random() { // returns a number [0, 1[
    let r = 1103515245 * (((seed+=12345) >> 1) ^ seed);
    r = 1103515245 * (r ^ (r >> 3));
    r = r ^ (r >> 16);
    return (r % mod) / mod;
}

////////////////////////////////////////////////////////////////
// Perlin noise field generator. Taken from turtle below
// https://turtletoy.net/turtle/04036becc3
////////////////////////////////////////////////////////////////
class Perlin {
    constructor(size, gridSize) {
        this.size = size;
        this.gridSize = gridSize;
        this.grid = [];

        for (let i = 0; i <= gridSize; i++) {
            let table = [];
            for (let j = 0; j <= gridSize; j++) {
                let angle = random() * 2 * Math.PI;
                let x = Math.cos(angle);
                let y = Math.sin(angle);
                table.push([x, y]);
            }
            this.grid.push(table);
        }
    }

    get(x, y) {
        x = x / 2 + this.size / 2;
        y = y / 2 + this.size / 2;
        if (x < 0) x = 0;
        if (x >= this.size) x = this.size - 0.01;
        if (y < 0) y = 0;
        if (y >= this.size) y = this.size - 0.01;

        let posx = x * this.gridSize / this.size;
        let posy = y * this.gridSize / this.size;

        let x1 = Math.floor(posx);
        let x2 = x1 + 1;
        let y1 = Math.floor(posy);
        let y2 = y1 + 1;

        let scal = [];
        scal.push(this.scalar(posx, posy, x1, y1));
        scal.push(this.scalar(posx, posy, x2, y1));
        scal.push(this.scalar(posx, posy, x1, y2));
        scal.push(this.scalar(posx, posy, x2, y2));

        let int1 = this.interpolate(posx - x1, scal[0], scal[1]);
        let int2 = this.interpolate(posx - x1, scal[2], scal[3]);

        return this.interpolate(posy - y1, int1, int2);
    }

    scalar(x, y, vx, vy) {
        x -= vx;
        y -= vy;
        return x * this.grid[vx][vy][0] + y * this.grid[vx][vy][1];
    }

    smooth(v) {
        if (v < 0) v = 0;
        if (v > 1) v = 1;
        return v ** 2 * (3 - 2 * v);
    }

    interpolate(x, a, b) {
        return a + (b - a) * this.smooth(x);
    }
}

let perlin_1 = new Perlin(100, perlin_size_1);
let perlin_2 = new Perlin(100, perlin_size_2);

for(let i = -100 + x_gap; i < 100 - x_gap; i += 1) {
    for(let j = -100 + y_gap; j < 100 - y_gap; j+= 1) {
        turtle.penup();
        if(true) {
            perlin_mod = perlin_1.get(i,j);
        } else {
            perlin_mod = perlin_2.get(i,j);
        }
        turtle.goto(i, j + perlin_mod * perlin_magnitude);
        turtle.pendown();
        if(false) {
            perlin_mod = perlin_1.get(i+1,j);
        } else {
            perlin_mod = perlin_2.get(i+1,j);
        }
        turtle.goto(i + 1, j + perlin_mod * perlin_magnitude);
    }
}