#!/usr/bin/env python

# Remove all instances of ### from the code
# to view Part 1 interactively

my_plane = None

with open("/home/login/bin/advent17/input19.txt") as f:
	my_plane = f.readlines() #(x,y) on my_plane is my_plane[-y][x]

plane_width = len(my_plane[0])
plane_height = len(my_plane)

direction_guide = {'|': (0,1), '-':(1,0)}
neighbour_guide = (lambda x,y: [(y,x),(-y,-x)])

def direction_change(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag):
	global direction_guide, neighbour_guide
	check_position = None
	for item in neighbour_guide(*current_direction):
		check_position = tuple(map(lambda x,y: x+y, current_position, item))
		if plane_yx[-check_position[1]][check_position[0]] in direction_guide:
			current_direction[0],current_direction[1] = tuple(x*sum(item) for x in direction_guide[plane_yx[-check_position[1]][check_position[0]]])
			###print(">\tDirection changed to " + str(current_direction))
			move(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag)
			return

def move(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag):
	current_position[0] += current_direction[0]
	current_position[1] += current_direction[1]

def stop(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag):
	stop_flag[0] = True

def add_letter(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag):
	letter_list.append(current_character)
	move(plane_yx, current_position, current_direction, current_character, letter_list, stop_flag)

navigate = {' ': stop,'|': move, '-': move, '+': direction_change, 'A': add_letter, 'B': add_letter, 'C': add_letter, 'D': add_letter, 'E': add_letter, 'F': add_letter, 'G': add_letter, 'H': add_letter, 'I': add_letter, 'J': add_letter, 'K': add_letter, 'L': add_letter, 'M': add_letter, 'N': add_letter, 'O': add_letter, 'P': add_letter, 'Q': add_letter, 'R': add_letter, 'S': add_letter, 'T': add_letter, 'U': add_letter, 'V': add_letter, 'W': add_letter, 'X': add_letter, 'Y': add_letter, 'Z': add_letter}

letters = [] # to store alphabets seen on path

current_position = [0,0] #[x,y]

current_direction = [0,-1] #[x,y]

# Finding starting position
for x in range(0, plane_width):
	if my_plane[0][x]=='|':
		current_position = [x,0]
		break

stop_flag = [False]
steps = 0
while not stop_flag[0]:
	navigate[my_plane[-current_position[1]][current_position[0]]](plane_yx=my_plane, current_position=current_position, current_direction=current_direction, current_character=my_plane[-current_position[1]][current_position[0]], letter_list=letters, stop_flag=stop_flag)
	steps+=1
	###print((steps, current_position, current_direction, my_plane[-current_position[1]][current_position[0]], letters, stop_flag))
	###print("(Press enter key to continue...)")
	###raw_input()
	###print(" ")

steps-=1 # to uncount stepping into " " in the end
print("Letters seen: " + ''.join(letters))
print("Steps taken: " + str(steps))