/**
 * barnsley-fern.js
 * Plot a Barnsley fern to the JXG Board
 */
import "./lib/dfhi.js";
import * as JXG from "jsxgraph" ;
import {exportBoard} from "./lib/dfhi-plot";

/**
 * the JXG Board
 * */
let board = undefined;
/**
 * called only once, as page loaded, as required by "lib/dfhi.js" API
 * */
window.init = function() {
	board = initBoard();
	function exportSvg(event) {
		exportBoard(board);
	}
	document.getElementById("export")
		.addEventListener("click", exportSvg);
};

/**
 * called every time user clicks on the #run Button, as required by "lib/dfhi.js"
 * */
window.main = function(...argv) {
	if (board) {
		try {
			JXG.JSXGraph.freeBoard(board);
			board = undefined;// remove all child of boad
			board = initBoard();
		}catch (e) {
			console.log(e);
			console.log(board);
		}
	}
	let n = Number.parseInt(argv[0]);
	let points = barnsley(n);
	let opt = {withLabel:false, fixed:true, size:0.001, fillColor:"#00aa00", strokeWidth:0};
	plotBarnsley(board, points, opt);
};

/**
 * init board, called at least once by window.init
 * */
function initBoard() {
	return JXG.JSXGraph.initBoard('plotter', {
		boundingbox: [-6, 12, 6, -1],
		axis: false,
		keepAspectRatio:true
	});
}


/**
 * generates points of Barnsley Fern.
 * */
function barnsley(n) {
	const m = [
		[ 0    ,  0    , 0     , 0.16 , 0.500   , 0    , 0.01],
		[ 0.85 ,  0.04 , -0.04 , 0.85 , 0.075   , 1.60 , 0.85],
		[ 0.20 , -0.26 , 0.23  , 0.22 , 0.400   , 1.60 , 0.07],
		[-0.15 ,  0.28 , 0.26  , 0.24 , 0.575   , 0.44 , 0.07]
	];
	const p = [ m[0][6], m[0][6] + m[1][6], m[0][6] + m[1][6] + m[2][6] ];
	let x = 0, y = 0;
	const points = [ [x, y] ];
	for(let i = 0; i < n; ++i) {
		let r = Math.random();
		let f = 0;
		if (r < p[0]) {
			f = 0;
		}else if (r < p[1]) {
			f = 1;
		}else if (r < p[2]) {
			f = 2;
		} else {
			f = 3;
		}
		let nX = (m[f][0] * x) + (m[f][1] * y) + m[f][4];
		y =  (m[f][2] * x) + (m[f][3] * y) + m[f][5];
		x = nX;
		points.push([x,y]);
	}
	return points;
}

/**
 *
 * @param board
 * @param points
 * @param attr
 *
 * */
function  plotBarnsley(board, points, attr ) {
	for(let p of points) {
		board.create('point', p, attr );
	}
}