rope simluation thingy

from pathlib import Path

def parse(line):
    direction, amount = line.split(" ")
    return direction.lower(), int(amount)

offsets = {"u": (0, 1), "d": (0, -1), "l": (-1, 0), "r": (1, 0)}


class Coord:
    x, y = 0, 0

    def __init__(self, x=0, y=0):
        self.x, self.y = x, y

    def move(self, tx, ty):
        self.x += tx
        self.y += ty

    def carry(self, other):
        if abs(self.x - other.x) > 0:
            other.x += (1 if self.x > other.x else -1)

        if abs(self.y - other.y) > 0:
            other.y += (1 if self.y > other.y else -1)

        return Coord(other.x, other.y)

    def distance(self, other):
        return max(abs(self.x - other.x), abs(self.y - other.y))


class Rope:
    head = Coord(0,0)
    knots = []
    visited = {(0,0)}

    def __init__(self, knots=2):
        # head is a knot
        for n in range(knots-1):
            self.knots.append(Coord(0,0))

    def move(self, direction, amount):
        for _ in range(amount):
            self.head.move(*offsets[direction])

            # each knot "carries" the next one
            current = self.head
            for knot in self.knots:
                while current.distance(knot) > 1:
                    current.carry(knot)
                current = knot

            tail = self.knots[-1]
            self.visited.add((tail.x, tail.y))


if __name__ == '__main__':
    data = Path("input.txt").read_text().splitlines()

    rope = Rope(knots=10)
    for line in data:
        direction, amount = parse(line)
        rope.move(direction, amount)

    print(f"visited: {len(rope.visited)}")