Using Pattern Matching to solve Tic Tac Toe

pattern_match_tic_tac_toe.rb

MOVE = /[XO]/.freeze

def board(*rows) = rows.map(&:chars)

def winner(board)
  case board
  in [
    [MOVE => move, ^move, ^move],
    [_, _, _],
    [_, _, _]
  ]
    [:horizontal, move]
  in [
    [_, _, _],
    [MOVE => move, ^move, ^move],
    [_, _, _]
  ]
    [:horizontal, move]
  in [
    [_, _, _],
    [_, _, _],
    [MOVE => move, ^move, ^move]
  ]
    [:horizontal, move]
  in [
    [MOVE => move, _, _],
    [^move, _, _],
    [^move, _, _]
  ]
    [:vertical, move]
  in [
    [_, MOVE => move, _],
    [_, ^move, _],
    [_, ^move, _]
  ]
    [:vertical, move]
  in [
    [_, _, MOVE => move],
    [_, _, ^move],
    [_, _, ^move]
  ]
    [:vertical, move]
  in [
    [MOVE => move, _, _],
    [_, ^move, _],
    [_, _, ^move]
  ]
    [:diagonal, move]
  in [
    [_, _, MOVE => move],
    [_, ^move, _],
    [^move, _, _]
  ]
    [:diagonal, move]
  else
    [:none, false]
  end
end

EXAMPLES = {
  straights: [
    # Win
    board('XXX', '   ', '   '),
    board('   ', 'OOO', '   '),
    board('   ', '   ', 'XXX'),

    # No Win
    board('X X', '   ', '   '),
    board('   ', 'O O', '   '),
    board('   ', '   ', 'X X'),
  ],

  verticals: [
    # Win
    board('X  ', 'X  ', 'X  '),
    board(' O ', ' O ', ' O '),
    board('  X', '  X', '  X'),

    # No Win
    board('   ', 'X  ', 'X  '),
    board(' O ', '   ', ' O '),
    board('  X', '  X', '   '),
  ],

  diagonals: [
    # Win
    board('O  ', ' O ', '  O'),
    board('  X', ' X ', 'X  '),

    # No Win
    board('O  ', ' O ', '   '),
    board('  X', ' X ', '   '),
  ]
}

EXAMPLES.each do |type, boards|
  boards.each do |board|
    puts "type: #{type}, win: #{winner(board)}"
  end
end