part1.ts

import * as fs from 'fs';

const input = fs.readFileSync('input', 'utf8');

const monkeys = input.split('\n\n').map((monkey) => {
	const lines = monkey.split('\n');
	const [, items] = lines[1].split(': ');
	const [safe] = lines[2].match(/(old|\d+) (\*|\+) (old|\d+)$/);
	return {
		items: items.split(', ').map((x) => +x),
		operation: new Function('old', `return ${safe}`),
		divisible: Number(lines[3].match(/\d+$/)[0]),
		yes: Number(lines[4].match(/\d+$/)[0]),
		no: Number(lines[5].match(/\d+$/)[0]),
		business: 0,
	};
});

for (let i = 0; i < 20; i++) {
	for (const monkey of monkeys) {
		while (monkey.items.length > 0) {
			let worry = monkey.operation(monkey.items.shift());
			worry = Math.floor(worry / 3);
			const target = worry % monkey.divisible === 0 ? monkey.yes : monkey.no;
			monkeys[target].items.push(worry);
			monkey.business++;
		}
	}
}

const [top1, top2] = monkeys.sort((a, b) => b.business - a.business);

console.log(top1.business * top2.business);