import re
import argparse

parser = argparse.ArgumentParser()
parser.add_argument("filename", help="the file from which to take data")
args = parser.parse_args()

with open(args.filename, "r") as f: commands = f.readlines()

visited = {(0,0)}
head = (0, 0)
tails = (0, 0)

def walk(command, head, tail, visited):
	direction, repeats = command.split(" ")
	repeats = int(repeats)
	first = True
	while repeats > 0:
		head = step(direction, head, tail)
		tail = follow(head, tail)
		first = False
		visited = visited | {tail}

		repeats -= 1

		print("walking {} while head is {} and tail is {}".format(command, head, tail))
	return head, tail, visited

def follow(head, tail):
	if head[0] < tail[0]-1 or head[0] > tail[0]+1 or \
		head[1] < tail[1]-1 or head[1] > tail[1]+1:
		if head[0] < tail[0]: tail = (tail[0]-1, tail[1])
		if head[0] > tail[0]: tail = (tail[0]+1, tail[1])
		if head[1] < tail[1]: tail = (tail[0], tail[1]-1)
		if head[1] > tail[1]: tail = (tail[0], tail[1]+1)
	return tail

def step(direction, head, tail):
	match direction:
		case 'R': return (head[0]+1, head[1])
		case 'L': return (head[0]-1, head[1])
		case 'U': return (head[0], head[1]+1)
		case 'D': return (head[0], head[1]-1)
		case _: return head

print("{}".format(visited))

for command in commands:
	head, tail, visited = walk(command, head, tail, visited)

print("{}".format(visited))

print("visited {} locations".format(len(visited)))