#!/usr/bin/env ruby

problem = 4
@input = File.readlines("#{problem}.input").map { _1.chomp.chars }.reject { _1.empty? }
#@input = DATA.read.split("\n").map(&:chars)

def diagnal?(x, y, dx, dy)
  if dx == -1 && dy == -1
    return false unless x >= 3 && y >= 3

    return @input[y][x] + @input[y-1][x-1] + @input[y-2][x-2] + @input[y-3][x-3] == "XMAS"
  elsif dx == -1 && dy == 1
    return false unless x >= 3 && y <= @input.size - 4

    return @input[y][x] + @input[y+1][x-1] + @input[y+2][x-2] + @input[y+3][x-3] == "XMAS"
  elsif dx = 1 && dy == -1
    return false unless x <= @input.first.size - 4 && y >= 3

    return @input[y][x] + @input[y-1][x+1] + @input[y-2][x+2] + @input[y-3][x+3] == "XMAS"
  #elsif dx == 1 && dy == 1 -- SHRUG
  else
    return false unless x <= @input.first.size - 4 && y <= @input.size - 4

    return @input[y][x] + @input[y+1][x+1] + @input[y+2][x+2] + @input[y+3][x+3] == "XMAS"
  end
end

def horizontal?(x, y, dx)
  row = @input[y]

  if dx == -1
    return false unless x >= 3
    return row[x] + row[x-1] + row[x-2] + row[x-3] == "XMAS"
  end

  if dx == 1
    return false unless x <= @input.first.size - 4
    return row[x] + row[x+1] + row[x+2] + row[x+3] == "XMAS"
  end
end

def vertical?(x, y, dy)
  col = @input.transpose[x]

  if dy == -1
    return false unless y >= 3
    return col[y] + col[y-1] + col[y-2] + col[y-3] == "XMAS"
  end

  if dy == 1
    return false unless y <= @input.size - 4
    return col[y] + col[y+1] + col[y+2] + col[y+3] == "XMAS"
  end
end

xmas = 0
h = 0
d = 0
v = 0
puts "Scanning"
puts " - x: #{@input.first.size}"
puts " - y: #{@input.size}"
(0...@input.size).each do |y|
  (0...@input.first.size) .each do |x|
    next unless @input[y][x] == "X"

    if diagnal?(x, y, -1, -1)
      xmas += 1
      d += 1
      puts "Diag LU at #{x}, #{y}"
    end
    if diagnal?(x, y, 1, -1)
      xmas += 1
      d += 1
      puts "Diag RU at #{x}, #{y}"
    end
    if diagnal?(x, y, -1, 1)
      xmas += 1
      d += 1
      puts "Diag LD at #{x}, #{y}"
    end
    if diagnal?(x, y, 1, 1)
      xmas += 1
      d += 1
      puts "Diag RD at #{x}, #{y}"
    end

    if horizontal?(x, y, -1)
      xmas += 1
      h += 1
    end
    if horizontal?(x, y, 1)
      xmas += 1
      h += 1
    end

    if vertical?(x, y, -1)
      xmas += 1
      v += 1
    end
    if vertical?(x, y, 1)
      xmas += 1
      v += 1
    end
  end
end

puts "Diag: #{d}"
puts "Hor: #{h}"
puts "Vert: #{v}"
p xmas

__END__
MMMSXXMASM
MSAMXMSMSA
AMXSXMAAMM
MSAMASMSMX
XMASAMXAMM
XXAMMXXAMA
SMSMSASXSS
SAXAMASAAA
MAMMMXMMMM
MXMXAXMASX