// #define Day16
#if Day16
var line = File.ReadAllText("day16/input");
Console.WriteLine(line);

// line = "8A004A801A8002F478";

string binarystring = String.Join(String.Empty,
    line.Where(c => !Char.IsWhiteSpace(c)).Select(
        c => Convert.ToString(Convert.ToInt32(c.ToString(), 16), 2).PadLeft(4, '0')
    )
);
Console.WriteLine(binarystring);

int pos = 0;
long versionSum = 0;
Console.WriteLine(ParsePackage(ref pos, binarystring));

Console.WriteLine(versionSum);

long ParsePackage(ref int pos, string binary) {
    var version = ParseTypeOrVersionId(ref pos, binary);
    versionSum += version;
    var type = ParseTypeOrVersionId(ref pos, binary);

    if (type == 4) {
        return ParseLiteral(ref pos, binary);
    } else {
        var lengthTypeId = ParseLength(ref pos, binary, 1);
        if (lengthTypeId == 1) {
            return ParseOperatorType1(ref pos, binary, type);
        } else {
            return ParseOperatorType0(ref pos, binary, type);
        }
    }
}

long ParseTypeOrVersionId(ref int pos, string binary) {
    return ParseLength(ref pos, binary, 3);
}

long ParseLiteral(ref int pos, string binary) {
    string res = String.Empty;
    while (binary[pos] == '1') {
        res += binary.Substring(pos + 1, 4);
        pos += 5;
    }
    res += binary.Substring(pos + 1, 4);
    pos += 5;
    return Convert.ToInt64(res, 2);
}

long ParseLength(ref int pos, string binary, int length)  {
    var id = binary.Substring(pos, length);
    pos += length;
    return Convert.ToInt64(id, 2);
}

long ParseOperatorType0(ref int pos, string binary, long type) {
    long length = ParseLength(ref pos, binary, 15);
    long originalPos = pos;
    List<long> values = new List<long>();
    while (originalPos+length > pos) {
        values.Add(ParsePackage(ref pos, binary));
    }
    return Calculate(type, values);
}

long ParseOperatorType1(ref int pos, string binary, long type) {
    long numberOfSubPackages = ParseLength(ref pos, binary, 11);
    List<long> values = new List<long>();
    for (int i = 0; i < numberOfSubPackages; i++) {
        values.Add(ParsePackage(ref pos, binary));
    }
    return Calculate(type, values);
}

long Calculate(long type, List<long> values) => (type) switch {
    0 => values.Sum(),
    1 => values.Aggregate(1L, (acc, val) => acc * val),
    2 => values.Min(),
    3 => values.Max(),
    5 => values[0] > values[1] ? 1 : 0,
    6 => values[0] < values[1] ? 1 : 0,
    7 => values[0] == values[1] ? 1 : 0,
    _ => throw new ArgumentException("not defined")
};
#endif