#! /usr/bin/env ruby

if ARGV.length != 1
        abort("Incorrect arguments - needs input file")
elsif not File.exist? (ARGV[0])
	abort("File #{ARGV[0]} did not exist")
end

file = ARGV[0]

OPEN_SPACE = "."
GALAXY = "#"
EXPANSION_FACTOR = 1000000

input_space = File.open(file, "r").each_line(chomp: true).map(&:each_char).map(&:to_a)

first, *rest = input_space
open_columns = first.zip(*rest).each_with_index.map {|col, idx| col.all? {|cell| cell == OPEN_SPACE} ? idx : nil}.compact
open_rows = input_space.each_with_index.map {|row, idx| row.all? {|cell| cell == OPEN_SPACE} ? idx : nil}.compact


galaxies = input_space.each_with_index.flat_map {|row, y| row.each_with_index.map {|cell, x| [x, y] if cell == GALAXY}}.compact
galactic_distances = galaxies.combination(2).map do |a, b|
	x_1, x_2 = [a[0], b[0]].minmax
	y_1, y_2 = [a[1], b[1]].minmax
	expanded_cols = ((x_1..x_2).to_a & open_columns).length
	expanded_rows = ((y_1..y_2).to_a & open_rows).length

	# Avoid double-counting the expanded cell by subtracting the number of columns first rather any complex logic
	x_2 - x_1 + - expanded_cols + (expanded_cols * EXPANSION_FACTOR) + y_2 - y_1 + - expanded_rows + (expanded_rows * EXPANSION_FACTOR)
end
puts galactic_distances.sum