from dataclasses import dataclass
from itertools import count


@dataclass
class Scanner(object):
    depth: int
    period: int
    severity: int

    @classmethod
    def from_line(cls, line):
        depth, range_ = map(int, line.split(":"))
        return cls(depth, (range_ - 1) * 2, depth * range_)

    def catches(self, delay=0):
        return (self.depth + delay) % self.period == 0


def severity(firewall):
    return sum(s.severity for s in firewall if s.catches())


def find_delay(firewall):
    return next(d for d in count() if not any(s.catches(d) for s in firewall))


def read_firewall(lines):
    return [Scanner.from_line(line) for line in lines if line.strip()]

test = read_firewall(
    """\
0: 3
1: 2
4: 4
6: 4
""".splitlines()
)

assert severity(test) == 24
assert find_delay(test) == 10

import aocd

data = aocd.get_data(day=13, year=2017)
firewall = read_firewall(data.splitlines())