const fs = require("fs");

let [rules, messages] = fs
  .readFileSync("input", "utf-8")
  .trim()
  .split("\n\n")
  .map((part) => part.split("\n"));

rules = rules
  .map((line) => line.split(": "))
  .map(([num, rule]) => [parseInt(num), rule])
  .sort((a, b) => a[0] - b[0])
  .map(([_, rule]) => rule);

console.log(rules);

console.log("=");
// console.log(messages);

function getRegex(idx) {
  const rule = rules[idx];
  if (rule.startsWith('"')) {
    return rule.slice(1, rule.length - 1);
  }
  let regex = "";
  let multiple = false;
  for (const symbol of rule.split(" ")) {
    if (symbol === "|") {
      regex = "(" + regex + "|";
      multiple = true;
    } else {
      regex = regex + getRegex(parseInt(symbol));
    }
  }
  regex = multiple ? regex + ")" : regex;
  rules[idx] = '"' + regex + '"';
  return regex;
}

const regex = new RegExp(`^${getRegex(0)}$`);
console.log(rules);
console.log(regex);

let sum = 0;
for (const message of messages) {
  if (regex.test(message)) sum++;
}
console.log(sum);