Canvas.setpenopacity(0.85);

const turtle = new Turtle();
const polygons = new Polygons();
const gridType = 2; // min=1, max=6, step=1
const grid = 9; // min=5, max=35, step=2
const scale = 175 / grid;

const diamondWidth = 75; // min=5, max=100, step=1
const diamondHeight = 50; // min=5, max=100, step=1

const sizeX = diamondWidth / grid;
const sizeY = diamondHeight / grid;

const layers = 6; // min=1, max=40, step=1
const layerDistance = 0.5; // min=0.1, max=1.75, step=0.001

const hatchType = 1; // min=0, max=4, step=1
const minHatching = 1.0;
const maxHatching = 0.275;
const useOutline = 1; // min=0, max=1, step=1

// The walk function will be called until it returns false.
function walk(i) {
    let gridX = (i % grid) - (grid/2|0);
    let gridY = grid - (i/grid|0) - (grid/2|0);
    gridY -= 0.5; 
    if (gridX % 2 == 0) {
    } else {
        gridY -= 0.5; 
    }
    const x = gridX * scale;
    const y = gridY * scale;
    
    let totalLayers = layers;
    switch (gridType) {
        case 1:
            totalLayers = layers; 
            break;
        case 2: 
            totalLayers = (1 - Math.sqrt( (x)** 2 + (y)**2) / 100) * layers | 0;
            break;
        case 3:
            totalLayers = (1 - Math.sqrt( (x+y)** 2 + (y+x)**2) / 100) * layers | 0;
            break;
        case 4: 
            totalLayers = lerp(1, layers, (Math.cos(gridY * 5 + gridX * 10)/2 + 0.5) ) | 0;
            break;
        case 5:
            totalLayers = lerp(1, layers, (Math.sin(gridX + gridY*5)/2 + 0.5) * (Math.sin(gridY + gridX*5)/2 + 0.5) ) | 0; 
            break;
        case 6: 
            totalLayers = lerp(1, layers, Math.random() ) | 0;
            break;
    }
    
    for (let idx=0; idx<totalLayers; idx++) {
        const t = idx / (totalLayers-1);
        let id = totalLayers - idx;
        const offset = [0, id * sizeY * -layerDistance];
  	    const rect = polygons.create();
  	    rect.addPoints(add2([ x - sizeX, y + 0 ], offset));
  	    rect.addPoints(add2([ x - 0, y - sizeY ], offset));
  	    rect.addPoints(add2([ x + sizeX, y + 0 ], offset));
  	    rect.addPoints(add2([ x + 0, y + sizeY ], offset));
  	    if (useOutline) rect.addOutline();
  	    
  	    if (hatchType) {
  	        if (hatchType === 1 && t > 0) {
  	            if (t > 0.75) rect.addHatching(Math.atan2(diamondHeight, diamondWidth), 0.5)   
      	        if (t >= 0.5) rect.addHatching(Math.PI/2, 0.75 )   
      	        if (t > 0) rect.addHatching(0, 0.75 )   
  	        } else if (hatchType == 2 && t > 0) {
  	            rect.addHatching(Math.atan2(diamondHeight, diamondWidth *  (idx % 2 ==0 ? 1 : -1)), lerp(minHatching, maxHatching, t))
  	        } else if (hatchType === 3) {
  	            if (Math.random() > 0.5) rect.addHatching(Math.atan2(diamondHeight, diamondWidth), 0.75);
  	            if (Math.random() > 0.5) rect.addHatching(Math.atan2(diamondHeight, -diamondWidth), 0.75);
  	            if (Math.random() > 0.5) rect.addHatching(0, 0.75);
  	            if (Math.random() > 0.5) rect.addHatching(Math.PI/2, 0.75);
  	        }  else if (hatchType === 4) {
  	            if (Math.random() > 0.5) rect.addHatching(Math.random() * Math.PI, lerp(minHatching * 0.5, maxHatching, t));
  	        }
  	    }
  	    
        polygons.draw(turtle, rect);
    }
    
    
    return i < grid*grid-1;
}

const lerp=(a,b,t)=>a+(b-a)*t;
const add2=(a,b)=>[a[0]+b[0],a[1]+b[1]];

////////////////////////////////////////////////////////////////
// Polygon Clipping utility code - Created by Reinder Nijhoff 2019
// https://turtletoy.net/turtle/a5befa1f8d
////////////////////////////////////////////////////////////////

function Polygons() {
	const polygonList = [];
	const Polygon = class {
		constructor() {
			this.cp = [];       // clip path: array of [x,y] pairs
			this.dp = [];       // 2d lines [x0,y0],[x1,y1] to draw
			this.aabb = [];     // AABB bounding box
		}
		addPoints(...points) {
		    // add point to clip path and update bounding box
		    let xmin = 1e5, xmax = -1e5, ymin = 1e5, ymax = -1e5;
			(this.cp = [...this.cp, ...points]).forEach( p => {
				xmin = Math.min(xmin, p[0]), xmax = Math.max(xmax, p[0]);
				ymin = Math.min(ymin, p[1]), ymax = Math.max(ymax, p[1]);
			});
		    this.aabb = [(xmin+xmax)/2, (ymin+ymax)/2, (xmax-xmin)/2, (ymax-ymin)/2];
		}
		addSegments(...points) {
		    // add segments (each a pair of points)
		    points.forEach(p => this.dp.push(p));
		}
		addOutline() {
			for (let i = 0, l = this.cp.length; i < l; i++) {
				this.dp.push(this.cp[i], this.cp[(i + 1) % l]);
			}
		}
		draw(t) {
			for (let i = 0, l = this.dp.length; i < l; i+=2) {
				t.jump(this.dp[i]), t.goto(this.dp[i + 1]);
			}
		}
		addHatching(a, d) {
			const tp = new Polygon();
			tp.cp.push([-1e5,-1e5],[1e5,-1e5],[1e5,1e5],[-1e5,1e5]);
			const dx = Math.sin(a) * d,   dy = Math.cos(a) * d;
			const cx = Math.sin(a) * 200, cy = Math.cos(a) * 200;
			for (let i = 0.5; i < 150 / d; i++) {
				tp.dp.push([dx * i + cy,   dy * i - cx], [dx * i - cy,   dy * i + cx]);
				tp.dp.push([-dx * i + cy, -dy * i - cx], [-dx * i - cy, -dy * i + cx]);
			}
			tp.boolean(this, false);
			this.dp = [...this.dp, ...tp.dp];
		}
		inside(p) {
			let int = 0; // find number of i ntersection points from p to far away
			for (let i = 0, l = this.cp.length; i < l; i++) {
				if (this.segment_intersect(p, [0.1, -1000], this.cp[i], this.cp[(i + 1) % l])) {
					int++;
				}
			}
			return int & 1; // if even your outside
		}
		boolean(p, diff = true) {
		    // bouding box optimization by ge1doot.
		    if (Math.abs(this.aabb[0] - p.aabb[0]) - (p.aabb[2] + this.aabb[2]) >= 0 &&
				Math.abs(this.aabb[1] - p.aabb[1]) - (p.aabb[3] + this.aabb[3]) >= 0) return this.dp.length > 0;
				
			// polygon diff algorithm (narrow phase)
			const ndp = [];
			for (let i = 0, l = this.dp.length; i < l; i+=2) {
				const ls0 = this.dp[i];
				const ls1 = this.dp[i + 1];
				// find all intersections with clip path
				const int = [];
				for (let j = 0, cl = p.cp.length; j < cl; j++) {
					const pint = this.segment_intersect(ls0, ls1, p.cp[j], p.cp[(j + 1) % cl]);
					if (pint !== false) {
						int.push(pint);
					}
				}
				if (int.length === 0) {
					// 0 intersections, inside or outside?
					if (diff === !p.inside(ls0)) {
						ndp.push(ls0, ls1);
					}
				} else {
					int.push(ls0, ls1);
					// order intersection points on line ls.p1 to ls.p2
					const cmpx = ls1[0] - ls0[0];
					const cmpy = ls1[1] - ls0[1];
					int.sort( (a,b) =>  (a[0] - ls0[0]) * cmpx + (a[1] - ls0[1]) * cmpy - 
					                    (b[0] - ls0[0]) * cmpx - (b[1] - ls0[1]) * cmpy);
					 
					for (let j = 0; j < int.length - 1; j++) {
						if ((int[j][0] - int[j+1][0])**2 + (int[j][1] - int[j+1][1])**2 >= 0.001) {
							if (diff === !p.inside([(int[j][0]+int[j+1][0])/2,(int[j][1]+int[j+1][1])/2])) {
								ndp.push(int[j], int[j+1]);
							}
						}
					}
				}
			}
			return (this.dp = ndp).length > 0;
		}
		//port of http://paulbourke.net/geometry/pointlineplane/Helpers.cs
		segment_intersect(l1p1, l1p2, l2p1, l2p2) {
			const d   = (l2p2[1] - l2p1[1]) * (l1p2[0] - l1p1[0]) - (l2p2[0] - l2p1[0]) * (l1p2[1] - l1p1[1]);
			if (d === 0) return false;
			const n_a = (l2p2[0] - l2p1[0]) * (l1p1[1] - l2p1[1]) - (l2p2[1] - l2p1[1]) * (l1p1[0] - l2p1[0]);
			const n_b = (l1p2[0] - l1p1[0]) * (l1p1[1] - l2p1[1]) - (l1p2[1] - l1p1[1]) * (l1p1[0] - l2p1[0]);
			const ua = n_a / d;
			const ub = n_b / d;
			if (ua >= 0 && ua <= 1 && ub >= 0 && ub <= 1) {
				return [l1p1[0] + ua * (l1p2[0] - l1p1[0]), l1p1[1] + ua * (l1p2[1] - l1p1[1])];
			}
			return false;
		}
	};
	return {
		list: () => polygonList,
		create: () => new Polygon(),
		draw: (turtle, p, addToVisList=true) => {
			for (let j = 0; j < polygonList.length && p.boolean(polygonList[j]); j++);
			p.draw(turtle);
			if (addToVisList) polygonList.push(p);
		}
	};
}