#!/usr/bin/env ruby

problem = 8
input = File.readlines("#{problem}.input").map(&:strip)
#input = DATA.read.split("\n")

# Find diferent antennas
signals = input.join.chars.uniq
  .reject { _1 == "." }
  .map { [_1, []] }
  .to_h

grid = input.map(&:chars)
# map antenna locations
signals.keys.each do |signal|
  grid.each_with_index do |row, x|
    row.each_with_index do |val, y|
      signals[val] << [x, y] if val == signal
    end
  end
end

# calculate antinodes between all node pairs
antinodes = []
signals.each do |(signal, locations)|
  locations.each { antinodes << _1 }
  locations.combination(2).each do |(first, second)|
    x = (first.first - second.first).abs
    y = (first.last - second.last).abs

    node1, node2 = first, second
    loop do
      if first.first < second.first
        x1 = node1.first - x
      else
        x1 = node1.first + x
      end
      if first.last < second.last
        y1 = node1.last - y
      else
        y1 = node1.last + y
      end
      node1 = [x1, y1]
      break unless x1 >= 0 && y1 >= 0 && x1 < grid.size && y1 < grid.first.size
      antinodes << node1
    end

    loop do
      if first.first < second.first
        x2 = node2.first + x
      else
        x2 = node2.first - x
      end
      if first.last < second.last
        y2 = node2.last + y
      else
        y2 = node2.last - y
      end

      node2 = [x2, y2]
      break unless x2 >= 0 && y2 >= 0 && x2 < grid.size && y2 < grid.first.size
      antinodes << node2
    end
  end
end

p antinodes.uniq.size

grid.each_with_index do |row, x|
  row.each_with_index do |val, y|
    if antinodes.index([x,y])
      print "#"
    else
      print grid[x][y]
    end
  end
  puts
end

__END__
............
........0...
.....0......
.......0....
....0.......
......A.....
............
............
........A...
.........A..
............
............