Provi Code Challenge

provi_code_challenge.js

function decodeInt(text) {
  const index = text.indexOf("e");
  const integer = text.slice(1, index);
  return [index + 1, integer];
}

function decodeString(text) {
  const [textLength] = text.split(":");
  const length = Number(textLength);
  return [2 + length, text.slice(2, 2 + length)];
}

function decodeList(text) {
  const list = [];
  let currentChar;
  let position = 1;
  while (position < text.length) {
    currentChar = text[position];
    if (currentChar == "e") {
      position += 1;
      break;
    }
    const [_position, _result] = decode(text.slice(position));
    list.push(_result);
    position += _position;
  }

  return [position, list];
}

function decodeMap(text) {
  const map = {};
  let currentChar;
  let position = 1;
  while (position < text.length) {
    currentChar = text[position];
    if (currentChar == "e") {
      position += 1;
      break;
    }
    const [_position1, _keyName] = decode(text.slice(position));
    const [_position2, _value] = decode(text.slice(position + _position1));
    map[_keyName] = _value;
    position += _position1 + _position2;
  }
  return [position, map];
}

function decode(text) {
  let position = 0;
  let result = [];

  while (text.length > position) {
    const letter = text[position];
    switch (letter) {
      case "i": {
        const [_position, _result] = decodeInt(text.slice(position));
        position += _position;
        result = [_position, _result];
        return result;
      }
      case "l": {
        const [_position, _result] = decodeList(text.slice(position));
        position += _position;
        result = [_position, _result];
        return result;
      }
      case "d": {
        const [_position, _result] = decodeMap(text.slice(position));
        position += _position;
        result = [_position, _result];
        return result;
      }
      default: {
        const [_position, _result] = decodeString(text.slice(position));
        position += _position;
        result = [_position, _result];
        return result;
      }
    }
  }

  return result;
}

function bencode(text) {
  return decode(text)[1];
}

console.log("result -> ", bencode("i10e"));
console.log("result -> ", bencode("le"));
console.log("result -> ", bencode("li10ee"));
console.log("result -> ", bencode("li10ei15ee"));
console.log("result -> ", bencode("lleli8eee"));
console.log("result -> ", bencode("l4:star3:foxe"));
console.log("result -> ", bencode("d3:bar4:spam3:fooi42ee"));