gist/20200510/epidemic.js

const WIDTH = 8;
const HEIGHT = 8;

// https://www.coding-dojo-silesia.pl/golf

function point_free(x, y, people) {
	const pLength = people.length;
	for (let i = 0; i < pLength; i++) {
		const person = people[i];
		if (x === person.x && y === person.y)
			return false;
	}

	return true;
}

function check_neighborhood(person, people) {
	const pLength = people.length;
	for (let i = 0; i < pLength; i++) {
		const otherPerson = people[i];
		if ((otherPerson.x >= person.x-1 && otherPerson.x <= person.x+1) && (otherPerson.y >= person.y-1 && otherPerson.y <= person.y+1) && otherPerson.s === 'S') {
			return true;
		}
	}

	return false;
}

function next_iteration(people) {
	people.forEach(function(person, _) { // iterate in a sequence
		cure(person);

		if (person.s === 'S') person.i++;

		person.n = gen_n(person.n);
		[new_x, new_y] = gen_new_cords(person);
		if (point_free(new_x, new_y, people) && person.q === 0) {
			person.x = new_x;
			person.y = new_y;
		}

		if (person.s === 'H' && check_neighborhood(person, people)) {
			// https://en.wikipedia.org/wiki/Moore_neighborhood
			person.s = 'S';
		}
	});

	return people;
}

function cure(person) {
	if (person.s === 'S' && person.i > 13) {
		person.s = 'R';
		person.i = 1;
	}
}

function gen_n(n) {
	n ^= n << BigInt(13);
	n ^= n >> BigInt(17);
	n ^= n << BigInt(5);
	return n % BigInt(1 << 30);
}

function gen_new_cords(person) {
	x = person.x;
	y = person.y;
	switch(person.n % BigInt(4)) {
		case BigInt(0): x++; break;
		case BigInt(1): x--; break;
		case BigInt(2): y++; break;
		case BigInt(3): y--; break;
	}
	// wrap points, like in pacman game
	if (x >= WIDTH) {
		x -= WIDTH;
	} else if (x < 0) {
		x += WIDTH;
	}

	if (y >= HEIGHT) {
		y -= HEIGHT;
	} else if (y < 0) {
		y += HEIGHT;
	}

	return [x, y];
}

function get_people(peopleString) {
	peopleUnparsed = peopleString.split(",");

	let people = [];
	peopleUnparsed.forEach(function(item, _) {
		let person = {};
		person.x = Number(item[0]);
		person.y = Number(item[1]);
		person.s = item[2];
		person.q = Number(item[3]);

		person.n = BigInt((person.x << 2) ^ 7 * (person.y << 3) ^ 5);
		person.i = 1;

		people.push(person);
	});

	return people;
}

function print_field(P) {
	for (let i = 0; i < HEIGHT; i++) {
		let string = '';
		for (let j = 0; j < WIDTH; j++) {
			const person = P.find(p => p.x === j && p.y === i);
			if (person === undefined)
				string += '.';
			else
				string += person.s;
		}
		console.log(string);
	}
}

function main() {
	const iterations = process.argv[2];
	const peopleUnparsed = process.argv[3];

	let people = get_people(peopleUnparsed);

	for (let i = 0; i < iterations; i++) {
		people = next_iteration(people);
	}
	print_field(people);
}

main();