Class: PGN::Game

Inherits:
Object
  • Object
show all
Defined in:
lib/pgn/game.rb

Overview

Game holds all of the information about a game. It is either the result of parsing a PGN file, or created by hand.

A Game has an interactive #play method, and can also return a list of positions in Position format or FEN.

Constant Summary collapse

LEFT = 
/(a|\x1B\[D)\z/
RIGHT = 
/(d|\x1B\[C)\z/
EXIT = 
/(q|\x03)\z/

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(moves, tags = nil, result = nil, pgn = nil, comment = nil) ⇒ Game

Returns a new instance of Game.

Parameters:

  • moves (Array<String>) —

    a list of moves in SAN

  • tags (Hash<String, String>) (defaults to: nil) —

    metadata about the game

  • result (String) (defaults to: nil) —

    the outcome of the game



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# File 'lib/pgn/game.rb', line 78

def initialize(moves, tags = nil, result = nil, pgn = nil, comment = nil)
  self.moves   = moves
  self.tags    = tags
  self.result  = result
  self.pgn     = pgn
  self.comment = comment
end

Instance Attribute Details

#comment ⇒ Object

Returns the value of attribute comment.



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# File 'lib/pgn/game.rb', line 67

def comment
  @comment
end

#moves ⇒ Array<String>

Returns a list of the moves in standard algebraic notation.

Examples:

game.moves #=> ["e4", "c5", "Nf3", "d6", "d4", "cxd4"]

Returns:

  • (Array<String>) —

    a list of the moves in standard algebraic notation



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# File 'lib/pgn/game.rb', line 66

class Game
  attr_accessor :tags, :result, :pgn, :comment
  attr_reader :moves

  LEFT  = /(a|\x1B\[D)\z/
  RIGHT = /(d|\x1B\[C)\z/
  EXIT  = /(q|\x03)\z/

  # @param moves [Array<String>] a list of moves in SAN
  # @param tags [Hash<String, String>] metadata about the game
  # @param result [String] the outcome of the game
  #
  def initialize(moves, tags = nil, result = nil, pgn = nil, comment = nil)
    self.moves   = moves
    self.tags    = tags
    self.result  = result
    self.pgn     = pgn
    self.comment = comment
  end

  # @param moves [Array<String>] a list of moves in SAN
  #
  # Standardize castling moves to use O's instead of 0's
  #
  def moves=(moves)
    @moves = moves.map { |m| standardize_castling(m) }
  end

  # @return [String] a canonical PGN string for this game, ending with a
  #   trailing newline.
  #
  def to_pgn
    PGN::Serializer.new(self).to_s
  end

  def initial_fen
    tags && tags['FEN']
  end

  def starting_position
    @starting_position ||= if initial_fen
                             PGN::FEN.new(initial_fen).to_position
                           else
                             PGN::Position.start
                           end
  end

  # @return [Array<PGN::Position>] list of the {PGN::Position}s in the game
  #
  def positions
    @positions ||= each_position.to_a
  end

  # @return [Enumerator, self] with a block: yields each {PGN::Position}
  #   in order (starting position, then one per move) and returns self.
  #   Without a block: returns an Enumerator that yields the same.
  #
  # The replay loop is shared with {#positions} so eager and lazy paths
  # produce identical position objects in identical order.
  def each_position
    return enum_for(:each_position) unless block_given?

    position = starting_position
    yield position
    moves.each do |move|
      position = position.move(move.notation)
      yield position
    end
    self
  end

  # @return [Array<String>] list of the fen representations of the positions
  #
  def fen_list
    positions.map { |p| p.to_fen.inspect }
  end

  # The current {PGN::Position} (the last position after replaying all
  # moves), or the starting position when there are no moves.
  #
  # @return [PGN::Position]
  def current_position
    positions.last
  end

  # Append a move in SAN, validating legality when the native engine is
  # available. Raises ArgumentError for an illegal move (when the engine is
  # loaded) and invalidates the memoized position list.
  #
  # @param san [String, PGN::MoveText] the move to append
  # @return [self]
  def push(san)
    move = standardize_castling(san)
    if PGN::Bitboard.const_defined?(:Engine, false) && !current_position.legal?(move.notation)
      raise ArgumentError, "illegal move: #{san}"
    end

    @moves << move
    @positions = nil
    self
  end

  # Remove and return the last move, or nil if there are none. Invalidates
  # the memoized position list.
  #
  # @return [PGN::MoveText, nil]
  def pop
    return nil if @moves.empty?

    move = @moves.pop
    @positions = nil
    move
  end

  # Whether any position has occurred three times in this game (the
  # threefold-repetition draw). Uses {PGN::Position#hash} (the Zobrist
  # hash of the FEN-relevant state), streaming {#each_position} so the
  # full position array need not be materialized for this check.
  #
  # @return [Boolean]
  def threefold?
    counts = Hash.new(0)
    each_position { |position| counts[position.hash] += 1 }
    counts.any? { |_, count| count >= 3 }
  end

  # The terminal status of the game: :checkmate, :stalemate, or :draw
  # (insufficient material, 50-move rule, or threefold repetition). nil
  # if the game is still in progress. Requires the native extension for
  # checkmate/stalemate detection.
  #
  # @return [Symbol, nil]
  def outcome
    final = positions.last
    result = final&.outcome
    return result if result
    return :draw if threefold?

    nil
  end

  # Interactively step through the game
  #
  # Use +d+ to move forward, +a+ to move backward, and +^C+ to exit.
  #
  def play
    index = 0
    hist = Array.new(3, '')

    loop do
      puts "\e[H\e[2J"
      puts positions[index].inspect
      hist[0..2] = (hist[1..2] << $stdin.getch)

      case hist.join
      when LEFT
        index -= 1 if index.positive?
      when RIGHT
        index += 1 if index < moves.length
      when EXIT
        break
      end
    end
  end

  # Build a fresh, navigable {PGN::Node} tree over the mainline. The tree
  # is a live view of the underlying +MoveText+ structure; mutate it
  # through the node API, then call +#root+ again for a fresh tree.
  def root
    PGN::Node.new(
      move: nil, parent: nil, line: @moves, index: -1,
      starting_position: starting_position, game: self
    )
  end

  private

  # A MoveText is reused as-is (no new object) when its notation needs no
  # '0'->'O' fix; otherwise a new MoveText is built. clean_text is idempotent
  # (it only strips a *single* outermost brace pair), so reusing or rebuilding
  # a MoveText never corrupts a comment that still contains inner braces.
  def standardize_castling(entry)
    return MoveText.new(entry.include?('0') ? entry.gsub('0', 'O') : entry) if entry.is_a?(String)

    notation = entry.notation.include?('0') ? entry.notation.gsub('0', 'O') : entry.notation
    return entry if notation.equal?(entry.notation)

    MoveText.new(notation, entry.annotation, entry.comment, entry.variations)
  end
end

#pgn ⇒ Object

Returns the value of attribute pgn.



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# File 'lib/pgn/game.rb', line 67

def pgn
  @pgn
end

#result ⇒ String

Returns the outcome of the game.

Examples:

game.result #=> "1-0"

Returns:

  • (String) —

    the outcome of the game



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# File 'lib/pgn/game.rb', line 66

class Game
  attr_accessor :tags, :result, :pgn, :comment
  attr_reader :moves

  LEFT  = /(a|\x1B\[D)\z/
  RIGHT = /(d|\x1B\[C)\z/
  EXIT  = /(q|\x03)\z/

  # @param moves [Array<String>] a list of moves in SAN
  # @param tags [Hash<String, String>] metadata about the game
  # @param result [String] the outcome of the game
  #
  def initialize(moves, tags = nil, result = nil, pgn = nil, comment = nil)
    self.moves   = moves
    self.tags    = tags
    self.result  = result
    self.pgn     = pgn
    self.comment = comment
  end

  # @param moves [Array<String>] a list of moves in SAN
  #
  # Standardize castling moves to use O's instead of 0's
  #
  def moves=(moves)
    @moves = moves.map { |m| standardize_castling(m) }
  end

  # @return [String] a canonical PGN string for this game, ending with a
  #   trailing newline.
  #
  def to_pgn
    PGN::Serializer.new(self).to_s
  end

  def initial_fen
    tags && tags['FEN']
  end

  def starting_position
    @starting_position ||= if initial_fen
                             PGN::FEN.new(initial_fen).to_position
                           else
                             PGN::Position.start
                           end
  end

  # @return [Array<PGN::Position>] list of the {PGN::Position}s in the game
  #
  def positions
    @positions ||= each_position.to_a
  end

  # @return [Enumerator, self] with a block: yields each {PGN::Position}
  #   in order (starting position, then one per move) and returns self.
  #   Without a block: returns an Enumerator that yields the same.
  #
  # The replay loop is shared with {#positions} so eager and lazy paths
  # produce identical position objects in identical order.
  def each_position
    return enum_for(:each_position) unless block_given?

    position = starting_position
    yield position
    moves.each do |move|
      position = position.move(move.notation)
      yield position
    end
    self
  end

  # @return [Array<String>] list of the fen representations of the positions
  #
  def fen_list
    positions.map { |p| p.to_fen.inspect }
  end

  # The current {PGN::Position} (the last position after replaying all
  # moves), or the starting position when there are no moves.
  #
  # @return [PGN::Position]
  def current_position
    positions.last
  end

  # Append a move in SAN, validating legality when the native engine is
  # available. Raises ArgumentError for an illegal move (when the engine is
  # loaded) and invalidates the memoized position list.
  #
  # @param san [String, PGN::MoveText] the move to append
  # @return [self]
  def push(san)
    move = standardize_castling(san)
    if PGN::Bitboard.const_defined?(:Engine, false) && !current_position.legal?(move.notation)
      raise ArgumentError, "illegal move: #{san}"
    end

    @moves << move
    @positions = nil
    self
  end

  # Remove and return the last move, or nil if there are none. Invalidates
  # the memoized position list.
  #
  # @return [PGN::MoveText, nil]
  def pop
    return nil if @moves.empty?

    move = @moves.pop
    @positions = nil
    move
  end

  # Whether any position has occurred three times in this game (the
  # threefold-repetition draw). Uses {PGN::Position#hash} (the Zobrist
  # hash of the FEN-relevant state), streaming {#each_position} so the
  # full position array need not be materialized for this check.
  #
  # @return [Boolean]
  def threefold?
    counts = Hash.new(0)
    each_position { |position| counts[position.hash] += 1 }
    counts.any? { |_, count| count >= 3 }
  end

  # The terminal status of the game: :checkmate, :stalemate, or :draw
  # (insufficient material, 50-move rule, or threefold repetition). nil
  # if the game is still in progress. Requires the native extension for
  # checkmate/stalemate detection.
  #
  # @return [Symbol, nil]
  def outcome
    final = positions.last
    result = final&.outcome
    return result if result
    return :draw if threefold?

    nil
  end

  # Interactively step through the game
  #
  # Use +d+ to move forward, +a+ to move backward, and +^C+ to exit.
  #
  def play
    index = 0
    hist = Array.new(3, '')

    loop do
      puts "\e[H\e[2J"
      puts positions[index].inspect
      hist[0..2] = (hist[1..2] << $stdin.getch)

      case hist.join
      when LEFT
        index -= 1 if index.positive?
      when RIGHT
        index += 1 if index < moves.length
      when EXIT
        break
      end
    end
  end

  # Build a fresh, navigable {PGN::Node} tree over the mainline. The tree
  # is a live view of the underlying +MoveText+ structure; mutate it
  # through the node API, then call +#root+ again for a fresh tree.
  def root
    PGN::Node.new(
      move: nil, parent: nil, line: @moves, index: -1,
      starting_position: starting_position, game: self
    )
  end

  private

  # A MoveText is reused as-is (no new object) when its notation needs no
  # '0'->'O' fix; otherwise a new MoveText is built. clean_text is idempotent
  # (it only strips a *single* outermost brace pair), so reusing or rebuilding
  # a MoveText never corrupts a comment that still contains inner braces.
  def standardize_castling(entry)
    return MoveText.new(entry.include?('0') ? entry.gsub('0', 'O') : entry) if entry.is_a?(String)

    notation = entry.notation.include?('0') ? entry.notation.gsub('0', 'O') : entry.notation
    return entry if notation.equal?(entry.notation)

    MoveText.new(notation, entry.annotation, entry.comment, entry.variations)
  end
end

#tags ⇒ Hash<String, String>

Returns metadata about the game.

Examples:

game.tags #=> {"White" => "Kasparov", "Black" => "Deep Blue"}

Returns:

  • (Hash<String, String>) —

    metadata about the game



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# File 'lib/pgn/game.rb', line 66

class Game
  attr_accessor :tags, :result, :pgn, :comment
  attr_reader :moves

  LEFT  = /(a|\x1B\[D)\z/
  RIGHT = /(d|\x1B\[C)\z/
  EXIT  = /(q|\x03)\z/

  # @param moves [Array<String>] a list of moves in SAN
  # @param tags [Hash<String, String>] metadata about the game
  # @param result [String] the outcome of the game
  #
  def initialize(moves, tags = nil, result = nil, pgn = nil, comment = nil)
    self.moves   = moves
    self.tags    = tags
    self.result  = result
    self.pgn     = pgn
    self.comment = comment
  end

  # @param moves [Array<String>] a list of moves in SAN
  #
  # Standardize castling moves to use O's instead of 0's
  #
  def moves=(moves)
    @moves = moves.map { |m| standardize_castling(m) }
  end

  # @return [String] a canonical PGN string for this game, ending with a
  #   trailing newline.
  #
  def to_pgn
    PGN::Serializer.new(self).to_s
  end

  def initial_fen
    tags && tags['FEN']
  end

  def starting_position
    @starting_position ||= if initial_fen
                             PGN::FEN.new(initial_fen).to_position
                           else
                             PGN::Position.start
                           end
  end

  # @return [Array<PGN::Position>] list of the {PGN::Position}s in the game
  #
  def positions
    @positions ||= each_position.to_a
  end

  # @return [Enumerator, self] with a block: yields each {PGN::Position}
  #   in order (starting position, then one per move) and returns self.
  #   Without a block: returns an Enumerator that yields the same.
  #
  # The replay loop is shared with {#positions} so eager and lazy paths
  # produce identical position objects in identical order.
  def each_position
    return enum_for(:each_position) unless block_given?

    position = starting_position
    yield position
    moves.each do |move|
      position = position.move(move.notation)
      yield position
    end
    self
  end

  # @return [Array<String>] list of the fen representations of the positions
  #
  def fen_list
    positions.map { |p| p.to_fen.inspect }
  end

  # The current {PGN::Position} (the last position after replaying all
  # moves), or the starting position when there are no moves.
  #
  # @return [PGN::Position]
  def current_position
    positions.last
  end

  # Append a move in SAN, validating legality when the native engine is
  # available. Raises ArgumentError for an illegal move (when the engine is
  # loaded) and invalidates the memoized position list.
  #
  # @param san [String, PGN::MoveText] the move to append
  # @return [self]
  def push(san)
    move = standardize_castling(san)
    if PGN::Bitboard.const_defined?(:Engine, false) && !current_position.legal?(move.notation)
      raise ArgumentError, "illegal move: #{san}"
    end

    @moves << move
    @positions = nil
    self
  end

  # Remove and return the last move, or nil if there are none. Invalidates
  # the memoized position list.
  #
  # @return [PGN::MoveText, nil]
  def pop
    return nil if @moves.empty?

    move = @moves.pop
    @positions = nil
    move
  end

  # Whether any position has occurred three times in this game (the
  # threefold-repetition draw). Uses {PGN::Position#hash} (the Zobrist
  # hash of the FEN-relevant state), streaming {#each_position} so the
  # full position array need not be materialized for this check.
  #
  # @return [Boolean]
  def threefold?
    counts = Hash.new(0)
    each_position { |position| counts[position.hash] += 1 }
    counts.any? { |_, count| count >= 3 }
  end

  # The terminal status of the game: :checkmate, :stalemate, or :draw
  # (insufficient material, 50-move rule, or threefold repetition). nil
  # if the game is still in progress. Requires the native extension for
  # checkmate/stalemate detection.
  #
  # @return [Symbol, nil]
  def outcome
    final = positions.last
    result = final&.outcome
    return result if result
    return :draw if threefold?

    nil
  end

  # Interactively step through the game
  #
  # Use +d+ to move forward, +a+ to move backward, and +^C+ to exit.
  #
  def play
    index = 0
    hist = Array.new(3, '')

    loop do
      puts "\e[H\e[2J"
      puts positions[index].inspect
      hist[0..2] = (hist[1..2] << $stdin.getch)

      case hist.join
      when LEFT
        index -= 1 if index.positive?
      when RIGHT
        index += 1 if index < moves.length
      when EXIT
        break
      end
    end
  end

  # Build a fresh, navigable {PGN::Node} tree over the mainline. The tree
  # is a live view of the underlying +MoveText+ structure; mutate it
  # through the node API, then call +#root+ again for a fresh tree.
  def root
    PGN::Node.new(
      move: nil, parent: nil, line: @moves, index: -1,
      starting_position: starting_position, game: self
    )
  end

  private

  # A MoveText is reused as-is (no new object) when its notation needs no
  # '0'->'O' fix; otherwise a new MoveText is built. clean_text is idempotent
  # (it only strips a *single* outermost brace pair), so reusing or rebuilding
  # a MoveText never corrupts a comment that still contains inner braces.
  def standardize_castling(entry)
    return MoveText.new(entry.include?('0') ? entry.gsub('0', 'O') : entry) if entry.is_a?(String)

    notation = entry.notation.include?('0') ? entry.notation.gsub('0', 'O') : entry.notation
    return entry if notation.equal?(entry.notation)

    MoveText.new(notation, entry.annotation, entry.comment, entry.variations)
  end
end

Instance Method Details

#current_position ⇒ PGN::Position

The current Position (the last position after replaying all moves), or the starting position when there are no moves.

Returns:



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# File 'lib/pgn/game.rb', line 147

def current_position
  positions.last
end

#each_position {|position| ... } ⇒ Enumerator, self

The replay loop is shared with #positions so eager and lazy paths produce identical position objects in identical order.

Yields:

  • (position)

Returns:

  • (Enumerator, self) —

    with a block: yields each Position in order (starting position, then one per move) and returns self. Without a block: returns an Enumerator that yields the same.



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# File 'lib/pgn/game.rb', line 125

def each_position
  return enum_for(:each_position) unless block_given?

  position = starting_position
  yield position
  moves.each do |move|
    position = position.move(move.notation)
    yield position
  end
  self
end

#fen_list ⇒ Array<String>

Returns list of the fen representations of the positions.

Returns:

  • (Array<String>) —

    list of the fen representations of the positions



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# File 'lib/pgn/game.rb', line 139

def fen_list
  positions.map { |p| p.to_fen.inspect }
end

#initial_fen ⇒ Object 



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# File 'lib/pgn/game.rb', line 101

def initial_fen
  tags && tags['FEN']
end

#outcome ⇒ Symbol?

The terminal status of the game: :checkmate, :stalemate, or :draw (insufficient material, 50-move rule, or threefold repetition). nil if the game is still in progress. Requires the native extension for checkmate/stalemate detection.

Returns:

  • (Symbol, nil) 


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# File 'lib/pgn/game.rb', line 198

def outcome
  final = positions.last
  result = final&.outcome
  return result if result
  return :draw if threefold?

  nil
end

#play ⇒ Object

Interactively step through the game

Use d to move forward, a to move backward, and ^C to exit.



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# File 'lib/pgn/game.rb', line 211

def play
  index = 0
  hist = Array.new(3, '')

  loop do
    puts "\e[H\e[2J"
    puts positions[index].inspect
    hist[0..2] = (hist[1..2] << $stdin.getch)

    case hist.join
    when LEFT
      index -= 1 if index.positive?
    when RIGHT
      index += 1 if index < moves.length
    when EXIT
      break
    end
  end
end

#pop ⇒ PGN::MoveText?

Remove and return the last move, or nil if there are none. Invalidates the memoized position list.

Returns:



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# File 'lib/pgn/game.rb', line 172

def pop
  return nil if @moves.empty?

  move = @moves.pop
  @positions = nil
  move
end

#positions ⇒ Array<PGN::Position>

Returns list of the Positions in the game.

Returns:



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# File 'lib/pgn/game.rb', line 115

def positions
  @positions ||= each_position.to_a
end

#push(san) ⇒ self

Append a move in SAN, validating legality when the native engine is available. Raises ArgumentError for an illegal move (when the engine is loaded) and invalidates the memoized position list.

Parameters:

Returns:

  • (self) 


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# File 'lib/pgn/game.rb', line 157

def push(san)
  move = standardize_castling(san)
  if PGN::Bitboard.const_defined?(:Engine, false) && !current_position.legal?(move.notation)
    raise ArgumentError, "illegal move: #{san}"
  end

  @moves << move
  @positions = nil
  self
end

#root ⇒ Object

Build a fresh, navigable Node tree over the mainline. The tree is a live view of the underlying MoveText structure; mutate it through the node API, then call #root again for a fresh tree.



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# File 'lib/pgn/game.rb', line 234

def root
  PGN::Node.new(
    move: nil, parent: nil, line: @moves, index: -1,
    starting_position: starting_position, game: self
  )
end

#starting_position ⇒ Object 



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# File 'lib/pgn/game.rb', line 105

def starting_position
  @starting_position ||= if initial_fen
                           PGN::FEN.new(initial_fen).to_position
                         else
                           PGN::Position.start
                         end
end

#threefold? ⇒ Boolean

Whether any position has occurred three times in this game (the threefold-repetition draw). Uses Position#hash (the Zobrist hash of the FEN-relevant state), streaming #each_position so the full position array need not be materialized for this check.

Returns:

  • (Boolean) 


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# File 'lib/pgn/game.rb', line 186

def threefold?
  counts = Hash.new(0)
  each_position { |position| counts[position.hash] += 1 }
  counts.any? { |_, count| count >= 3 }
end

#to_pgn ⇒ String

Returns a canonical PGN string for this game, ending with a trailing newline.

Returns:

  • (String) —

    a canonical PGN string for this game, ending with a trailing newline.



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# File 'lib/pgn/game.rb', line 97

def to_pgn
  PGN::Serializer.new(self).to_s
end