const grid = 13; //min=1 max=30 step=1
const rotation = -13; //min=-45 max=45 step=1
const perspective = .4 //min=.2 max=1 step=.01
const roughness = .2; //min=0 max=1 step=.01
const tileSize = 9; //min=1 max=20 step=.5
const tileMargin = .25; //min=0 max=.9 step=.01
const style = 1; //min=0 max=2 step=1 (Outline, Hatching, Both)
const gap = 20; //min=1 max=40 step=1
// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(.7);

// Global code will be evaluated once.
const turtle = new Turtle();
const polygons = new Polygons();
const perl = new Perlin(0.01 + roughness * .49);

const tileRatio = 1 - tileMargin;

const rotationMatrix2 = (radians) => [Math.cos(radians), -Math.sin(radians), Math.sin(radians), Math.cos(radians)];
const transform2 = (matrix, a) => [matrix[0]*a[0]+matrix[2]*a[1], matrix[1]*a[0]+matrix[3]*a[1]];
const scale2 = (a, scalar) => [a[0]*scalar,a[1]*scalar];
const add2 = (a,b) => [a[0]+b[0],a[1]+b[1]];

const rot = rotationMatrix2(Math.PI * .75 + (Math.PI * rotation/180));

const gridValues = (() => {
    const gv = Array.from({length: grid}).map((i, x) => Array.from({length: grid}).map((i, y) => perl.get(x+3, y+3)));// Math.random()));
    const minmax = gv.flat().reduce((p, c) => [c<p[0]? c: p[0], c > p[1]? c: p[1]], [100, -100] );
    return gv.map(v => v.map(value => (value - minmax[0]) / (minmax[1] - minmax[0]) ));
})();

// The walk function will be called until it returns false.
function walk(i) {
    const col = i % grid;
    const row = i / grid | 0;
    
    const basicTile = [[-.5, -.5], [.5, -.5], [.5, .5], [-.5, .5]]
        .map(p => scale2(p, tileSize * tileRatio))
        .map(p => add2(p, [tileSize * (col+.5-grid/2), tileSize * (row+.5-grid/2)]))
        .map(p => transform2(rot, p))
        .map(p => transform2([1, 0, 0, perspective], p))

    const ceiling = basicTile.map(p => add2(p, [0, -55]));
    const top = basicTile.map(p => add2(p, [0, 20*gridValues[col][row] -(gap+10)]));
    
    const bottom = basicTile.map(p => add2(p, [0, (gap-10) +  20*gridValues[col][row]]));
    const floor = basicTile.map(p => add2(p, [0, 55]));
    
    drawLayer(ceiling, top);
    drawLayer(bottom, floor);

    return i < grid**2 - 1;
}

const drawLayer = (a, b) => {
    drawPoly(a, .8);
    drawPoly([a[0], a[1], b[1], b[0]], .2);
    drawPoly([a[3], a[0], b[0], b[3]], .5);
}
const drawPoly = (pts, fill = null) => {
    let p = polygons.create();
    p.addPoints(...pts);
    if(style != 1) {
        p.addOutline();
    }
    if(style > 0) {
        p.addHatching(1, fill);
    }
    polygons.draw(turtle, p);
}

////////////////////////////////////////////////////////////////
// Polygon Clipping utility code - Created by Reinder Nijhoff 2019
// (Polygon binning by Lionel Lemarie 2021)
// https://turtletoy.net/turtle/a5befa1f8d
////////////////////////////////////////////////////////////////
function Polygons(){const t=[],s=25,e=Array.from({length:s**2},t=>[]),n=class{constructor(){this.cp=[],this.dp=[],this.aabb=[]}addPoints(...t){let s=1e5,e=-1e5,n=1e5,h=-1e5;(this.cp=[...this.cp,...t]).forEach(t=>{s=Math.min(s,t[0]),e=Math.max(e,t[0]),n=Math.min(n,t[1]),h=Math.max(h,t[1])}),this.aabb=[s,n,e,h]}addSegments(...t){t.forEach(t=>this.dp.push(t))}addOutline(){for(let t=0,s=this.cp.length;t<s;t++)this.dp.push(this.cp[t],this.cp[(t+1)%s])}draw(t){for(let s=0,e=this.dp.length;s<e;s+=2)t.jump(this.dp[s]),t.goto(this.dp[s+1])}addHatching(t,s){const e=new n;e.cp.push([-1e5,-1e5],[1e5,-1e5],[1e5,1e5],[-1e5,1e5]);const h=Math.sin(t)*s,o=Math.cos(t)*s,a=200*Math.sin(t),i=200*Math.cos(t);for(let t=.5;t<150/s;t++)e.dp.push([h*t+i,o*t-a],[h*t-i,o*t+a]),e.dp.push([-h*t+i,-o*t-a],[-h*t-i,-o*t+a]);e.boolean(this,!1),this.dp=[...this.dp,...e.dp]}inside(t){let s=0;for(let e=0,n=this.cp.length;e<n;e++)this.segment_intersect(t,[.1,-1e3],this.cp[e],this.cp[(e+1)%n])&&s++;return 1&s}boolean(t,s=!0){const e=[];for(let n=0,h=this.dp.length;n<h;n+=2){const h=this.dp[n],o=this.dp[n+1],a=[];for(let s=0,e=t.cp.length;s<e;s++){const n=this.segment_intersect(h,o,t.cp[s],t.cp[(s+1)%e]);!1!==n&&a.push(n)}if(0===a.length)s===!t.inside(h)&&e.push(h,o);else{a.push(h,o);const n=o[0]-h[0],i=o[1]-h[1];a.sort((t,s)=>(t[0]-h[0])*n+(t[1]-h[1])*i-(s[0]-h[0])*n-(s[1]-h[1])*i);for(let n=0;n<a.length-1;n++)(a[n][0]-a[n+1][0])**2+(a[n][1]-a[n+1][1])**2>=.001&&s===!t.inside([(a[n][0]+a[n+1][0])/2,(a[n][1]+a[n+1][1])/2])&&e.push(a[n],a[n+1])}}return(this.dp=e).length>0}segment_intersect(t,s,e,n){const h=(n[1]-e[1])*(s[0]-t[0])-(n[0]-e[0])*(s[1]-t[1]);if(0===h)return!1;const o=((n[0]-e[0])*(t[1]-e[1])-(n[1]-e[1])*(t[0]-e[0]))/h,a=((s[0]-t[0])*(t[1]-e[1])-(s[1]-t[1])*(t[0]-e[0]))/h;return o>=0&&o<=1&&a>=0&&a<=1&&[t[0]+o*(s[0]-t[0]),t[1]+o*(s[1]-t[1])]}};return{list:()=>t,create:()=>new n,draw:(n,h,o=!0)=>{reducedPolygonList=function(n){const h={},o=200/s;for(var a=0;a<s;a++){const c=a*o-100,r=[0,c,200,c+o];if(!(n[3]<r[1]||n[1]>r[3]))for(var i=0;i<s;i++){const c=i*o-100;r[0]=c,r[2]=c+o,n[0]>r[2]||n[2]<r[0]||e[i+a*s].forEach(s=>{const e=t[s];n[3]<e.aabb[1]||n[1]>e.aabb[3]||n[0]>e.aabb[2]||n[2]<e.aabb[0]||(h[s]=1)})}}return Array.from(Object.keys(h),s=>t[s])}(h.aabb);for(let t=0;t<reducedPolygonList.length&&h.boolean(reducedPolygonList[t]);t++);h.draw(n),o&&function(n){t.push(n);const h=t.length-1,o=200/s;e.forEach((t,e)=>{const a=e%s*o-100,i=(e/s|0)*o-100,c=[a,i,a+o,i+o];c[3]<n.aabb[1]||c[1]>n.aabb[3]||c[0]>n.aabb[2]||c[2]<n.aabb[0]||t.push(h)})}(h)}}}


// Adapted from https://github.com/joeiddon/perlin
function Perlin(scale) {
    class Perlin {
        constructor(s) {
            this.gradients = {};
            this.memory = {};
            this.scale = s;
        }
        rand_vect() {
            let theta = Math.random() * 2 * Math.PI;
            return [Math.cos(theta), Math.sin(theta)];
        }
        dot_prod_grid(x, y, vx, vy) {
            let g_vect;
            let d_vect = [x - vx, y - vy];
            if (this.gradients[[vx,vy]]){
                g_vect = this.gradients[[vx,vy]];
            } else {
                g_vect = this.rand_vect();
                this.gradients[[vx, vy]] = g_vect;
            }
            return d_vect[0] * g_vect[0] + d_vect[1] * g_vect[1];
        }
        smootherstep(x) {
            return 6*x**5 - 15*x**4 + 10*x**3;
        }
        interp(x, a, b){
            return a + this.smootherstep(x) * (b-a);
        }
        get(x, y) {
            x *= this.scale;
            y *= this.scale;
            if (this.memory.hasOwnProperty([x,y]))
                return this.memory[[x,y]];
            let xf = Math.floor(x);
            let yf = Math.floor(y);
            //interpolate
            let tl = this.dot_prod_grid(x, y, xf,   yf);
            let tr = this.dot_prod_grid(x, y, xf+1, yf);
            let bl = this.dot_prod_grid(x, y, xf,   yf+1);
            let br = this.dot_prod_grid(x, y, xf+1, yf+1);
            let xt = this.interp(x-xf, tl, tr);
            let xb = this.interp(x-xf, bl, br);
            let v = this.interp(y-yf, xt, xb);
            this.memory[[x,y]] = v;
            return v;
        }
    }
    return new Perlin(scale);
}