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andkerosine/fen.rb

Created August 24, 2012 21:30
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  1. andkerosine created this gist Aug 24, 2012.
    36 changes: 36 additions & 0 deletions fen.rb
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,36 @@
    def side piece
    piece == ' ' ? -1 : piece =~ /[a-z]/
    end

    fen = File.read ARGV.shift
    board = [*'1'..'8'].reverse.product [*'a'..'h']
    from, to = *ARGV.map { |a| board.index a.reverse.split // }
    raise 'Wat.' if from == to

    board, act, _ = fen.split
    board.gsub!(/(\d|\/)/) { ' ' * $1.to_i }
    raise 'No piece.' if board[from] == ' '
    raise 'Not your turn.' if side board[from] != side(act.tr 'w', 'W')
    raise 'Mutiny!' if side(board[from]) == side(board[to])

    a, b = [from, to].minmax
    dir = [*7..9].find { |n| (b - a) % n == 0 } || 1
    clear = (a + dir...b).step(dir).map { |s| board [s] }.join.strip.empty?

    rook = ([*-7..7] + (-56..56).step(8).to_a).include? to
    bishop = [7, 9].include? dir
    queen = clear and rook or bishop
    pawn = [*7..9, 16]

    puts case board[from]
    when /r/i then clear and rook
    when /b/i then clear and bishop
    when /q/i then queen
    when /k/i then queen and [1, *7..9].include?(b - a)
    when /n/i then [6, 10, 15, 17].include?(b - a)
    when /p/i then
    pawn.map!(&:-@) if $~[0] == 'P'
    pawn.select! { |s| board[from + s].send s.odd? ? :!= : :==, ' ' }
    pawn.pop unless [*8..15, *47..55].include? from
    pawn.map { |s| from + s }.include? to
    end