import os, argparse

def solve_task(lines):
    messages = []
    for line in lines:
        if line == "":
            continue
        else:
            messages.append(Packet(line))
    
    d1 = Packet("[[2]]")
    d2 = Packet("[[6]]")
    messages.append(d1)
    messages.append(d2)
    messages.sort()
    
    i1 = messages.index(d1)+1
    i2 = messages.index(d2)+1
    print(f"Divider packages at index {i1} and {i2}")
    print(f"Decoder key: {i1*i2}")

class Packet:
    def __init__(self, line) -> None:
        self.package = eval(line)
    
    def __lt__(self, other):
        return compare(self.package, other.package)

def compare(left,right):
    if isinstance(left, int) and isinstance(right, int):
        if left == right:
            return "undetermined"
        else:
            return left < right
    elif isinstance(left, int):
        return compare([left], right)
    elif isinstance(right, int):
        return compare(left, [right])
    else:
        for i in range(min(len(left), len(right))):
            comp = compare(left[i], right[i])
            if comp == "undetermined":
                continue
            else:
                return comp
        if len(left) < len(right):
            return True
        elif len(right) < len(left):
            return False
        else:
            return "undetermined"

def read_lines(filename):
    lines = []
    with open(filename) as infile:
        for raw_line in infile:
            line = raw_line.rstrip()
            lines.append(line)
    return lines

def parse_arguments():
    parser = argparse.ArgumentParser(description="Script that solves the case",epilog="Have a nice day!")
    parser.add_argument('filename', nargs='?', default="example.txt", help='Input file')
    args = parser.parse_args()
    return args

def main():
    args = parse_arguments()
    lines = read_lines(args.filename)
    solve_task(lines)

if __name__ == "__main__":
    main()