Class: JustXiangqi::GameState

Inherits:
Object
  • Object
show all
Defined in:
lib/just_xiangqi/game_state.rb

Overview

Game State

Represents a game of Xiangqi in progress.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(current_player_number:, squares: []) ⇒ GameState

Returns a new instance of GameState.



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# File 'lib/just_xiangqi/game_state.rb', line 17

def initialize(current_player_number: , squares: [])
  @current_player_number = current_player_number
  @squares = if squares.is_a?(SquareSet)
               squares
             else
               SquareSet.new(squares: squares)
             end
end

Instance Attribute Details

#current_player_number ⇒ Object (readonly)

Returns the value of attribute current_player_number.



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# File 'lib/just_xiangqi/game_state.rb', line 26

def current_player_number
  @current_player_number
end

#errors ⇒ Object (readonly)

Returns the value of attribute errors.



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# File 'lib/just_xiangqi/game_state.rb', line 26

def errors
  @errors
end

#squares ⇒ Object (readonly)

Returns the value of attribute squares.



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# File 'lib/just_xiangqi/game_state.rb', line 26

def squares
  @squares
end

Class Method Details

.default ⇒ GameState

Instantiates a new GameState object in the starting position.

Returns:



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# File 'lib/just_xiangqi/game_state.rb', line 31

def self.default
  new(
    current_player_number: 1,
    squares: [
      { id: 'a10', x: 0, y: 0, piece: { id: 1, player_number: 2, type: 'ju' } },
      { id: 'b10', x: 1, y: 0, piece: { id: 2, player_number: 2, type: 'ma' } },
      { id: 'c10', x: 2, y: 0, piece: { id: 3, player_number: 2, type: 'xiang' } },
      { id: 'd10', x: 3, y: 0, piece: { id: 4, player_number: 2, type: 'shi' } },
      { id: 'e10', x: 4, y: 0, piece: { id: 5, player_number: 2, type: 'jiang' } },
      { id: 'f10', x: 5, y: 0, piece: { id: 6, player_number: 2, type: 'shi' } },
      { id: 'g10', x: 6, y: 0, piece: { id: 7, player_number: 2, type: 'xiang' } },
      { id: 'h10', x: 7, y: 0, piece: { id: 8, player_number: 2, type: 'ma' } },
      { id: 'i10', x: 8, y: 0, piece: { id: 9, player_number: 2, type: 'ju' } },

      { id: 'a9', x: 0, y: 1, piece: nil },
      { id: 'b9', x: 1, y: 1, piece: nil },
      { id: 'c9', x: 2, y: 1, piece: nil },
      { id: 'd9', x: 3, y: 1, piece: nil },
      { id: 'e9', x: 4, y: 1, piece: nil },
      { id: 'f9', x: 5, y: 1, piece: nil },
      { id: 'g9', x: 6, y: 1, piece: nil },
      { id: 'h9', x: 7, y: 1, piece: nil },
      { id: 'i9', x: 8, y: 1, piece: nil },

      { id: 'a8', x: 0, y: 2, piece: nil },
      { id: 'b8', x: 1, y: 2, piece: { id: 10, player_number: 2, type: 'pao' } },
      { id: 'c8', x: 2, y: 2, piece: nil },
      { id: 'd8', x: 3, y: 2, piece: nil },
      { id: 'e8', x: 4, y: 2, piece: nil },
      { id: 'f8', x: 5, y: 2, piece: nil },
      { id: 'g8', x: 6, y: 2, piece: nil },
      { id: 'h8', x: 7, y: 2, piece: { id: 11, player_number: 2, type: 'pao' } },
      { id: 'i8', x: 8, y: 2, piece: nil },

      { id: 'a7', x: 0, y: 3, piece: { id: 12, player_number: 2, type: 'zu' } },
      { id: 'b7', x: 1, y: 3, piece: nil },
      { id: 'c7', x: 2, y: 3, piece: { id: 13, player_number: 2, type: 'zu' } },
      { id: 'd7', x: 3, y: 3, piece: nil },
      { id: 'e7', x: 4, y: 3, piece: { id: 14, player_number: 2, type: 'zu' } },
      { id: 'f7', x: 5, y: 3, piece: nil },
      { id: 'g7', x: 6, y: 3, piece: { id: 15, player_number: 2, type: 'zu' } },
      { id: 'h7', x: 7, y: 3, piece: nil },
      { id: 'i7', x: 8, y: 3, piece: { id: 16, player_number: 2, type: 'zu' } },

      { id: 'a6', x: 0, y: 4, piece: nil },
      { id: 'b6', x: 1, y: 4, piece: nil },
      { id: 'c6', x: 2, y: 4, piece: nil },
      { id: 'd6', x: 3, y: 4, piece: nil },
      { id: 'e6', x: 4, y: 4, piece: nil },
      { id: 'f6', x: 5, y: 4, piece: nil },
      { id: 'g6', x: 6, y: 4, piece: nil },
      { id: 'h6', x: 7, y: 4, piece: nil },
      { id: 'i6', x: 8, y: 4, piece: nil },

      { id: 'a5', x: 0, y: 5, piece: nil },
      { id: 'b5', x: 1, y: 5, piece: nil },
      { id: 'c5', x: 2, y: 5, piece: nil },
      { id: 'd5', x: 3, y: 5, piece: nil },
      { id: 'e5', x: 4, y: 5, piece: nil },
      { id: 'f5', x: 5, y: 5, piece: nil },
      { id: 'g5', x: 6, y: 5, piece: nil },
      { id: 'h5', x: 7, y: 5, piece: nil },
      { id: 'i5', x: 8, y: 5, piece: nil },

      { id: 'a4', x: 0, y: 6, piece: { id: 17, player_number: 1, type: 'zu' } },
      { id: 'b4', x: 1, y: 6, piece: nil },
      { id: 'c4', x: 2, y: 6, piece: { id: 17, player_number: 1, type: 'zu' } },
      { id: 'd4', x: 3, y: 6, piece: nil },
      { id: 'e4', x: 4, y: 6, piece: { id: 17, player_number: 1, type: 'zu' } },
      { id: 'f4', x: 5, y: 6, piece: nil },
      { id: 'g4', x: 6, y: 6, piece: { id: 17, player_number: 1, type: 'zu' } },
      { id: 'h4', x: 7, y: 6, piece: nil },
      { id: 'i4', x: 8, y: 6, piece: { id: 17, player_number: 1, type: 'zu' } },

      { id: 'a3', x: 0, y: 7, piece: nil },
      { id: 'b3', x: 1, y: 7, piece: { id: 18, player_number: 1, type: 'pao' } },
      { id: 'c3', x: 2, y: 7, piece: nil },
      { id: 'd3', x: 3, y: 7, piece: nil },
      { id: 'e3', x: 4, y: 7, piece: nil },
      { id: 'f3', x: 5, y: 7, piece: nil },
      { id: 'g3', x: 6, y: 7, piece: nil },
      { id: 'h3', x: 7, y: 7, piece: { id: 19, player_number: 1, type: 'pao' } },
      { id: 'i3', x: 8, y: 7, piece: nil },

      { id: 'a2', x: 0, y: 8, piece: nil },
      { id: 'b2', x: 1, y: 8, piece: nil },
      { id: 'c2', x: 2, y: 8, piece: nil },
      { id: 'd2', x: 3, y: 8, piece: nil },
      { id: 'e2', x: 4, y: 8, piece: nil },
      { id: 'f2', x: 5, y: 8, piece: nil },
      { id: 'g2', x: 6, y: 8, piece: nil },
      { id: 'h2', x: 7, y: 8, piece: nil },
      { id: 'i2', x: 8, y: 8, piece: nil },

      { id: 'a1', x: 0, y: 9, piece: { id: 20, player_number: 1, type: 'ju' } },
      { id: 'b1', x: 1, y: 9, piece: { id: 21, player_number: 1, type: 'ma' } },
      { id: 'c1', x: 2, y: 9, piece: { id: 22, player_number: 1, type: 'xiang' } },
      { id: 'd1', x: 3, y: 9, piece: { id: 23, player_number: 1, type: 'shi' } },
      { id: 'e1', x: 4, y: 9, piece: { id: 24, player_number: 1, type: 'jiang' } },
      { id: 'f1', x: 5, y: 9, piece: { id: 25, player_number: 1, type: 'shi' } },
      { id: 'g1', x: 6, y: 9, piece: { id: 26, player_number: 1, type: 'xiang' } },
      { id: 'h1', x: 7, y: 9, piece: { id: 27, player_number: 1, type: 'ma' } },
      { id: 'i1', x: 8, y: 9, piece: { id: 28, player_number: 1, type: 'ju' } }
    ]
  )
end

Instance Method Details

#as_json ⇒ Hash

serializes the game state as ahash

Returns:

  • (Hash) 


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# File 'lib/just_xiangqi/game_state.rb', line 141

def as_json
  {
    current_player_number: current_player_number,
    squares: squares.as_json,
  }
end

#clone ⇒ GameState

deep clone of the game state

Returns:



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# File 'lib/just_xiangqi/game_state.rb', line 151

def clone
  self.class.new(**as_json)
end

#in_check?(player_number) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/just_xiangqi/game_state.rb', line 235

def in_check?(player_number)
  jiang_square = squares.find_jiang_for_player(player_number)
  threatened_by = squares.threatened_by(opposing_player_number(player_number), self)
  threatened_by.include?(jiang_square)
end

#in_checkmate?(player_number) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/just_xiangqi/game_state.rb', line 241

def in_checkmate?(player_number)
  (in_check?(player_number) || non_jiang_pieces_cannot_move?(player_number)) && jiang_cannot_move?(player_number)
end

#move(player_number, from_id, to_id) ⇒ Boolean

Moves a piece owned by the player, from one square, to another.

It has an option to promote the moving piece. It moves the piece and returns true if the move is valid and it’s the player’s turn. It returns false otherwise.

Example:

# Moves a piece from a square to perform a move
game_state.move(1, '77', '78')

Parameters:

  • player_number (Fixnum) —

    the player number, 1 or 2.

  • from_id (String) —

    the id of the from square

  • to_id (String) —

    the id of the to square

Returns:

  • (Boolean) 


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# File 'lib/just_xiangqi/game_state.rb', line 175

def move(player_number, from_id, to_id)
  @errors = []

  from = squares.find_by_id(from_id)
  to = squares.find_by_id(to_id)

  if current_player_number != player_number
    @errors.push JustXiangqi::NotPlayersTurnError.new
  elsif from.unoccupied?
    @errors.push JustXiangqi::NoPieceError.new
  elsif to.nil?
    @errors.push JustXiangqi::OffBoardError.new
  elsif from.piece.can_move?(from, to, self)

    duplicate = self.clone
    duplicate.perform_complete_move(player_number, from_id, to_id)

    if duplicate.in_check?(current_player_number)
      @errors.push JustXiangqi::MovedIntoCheckError.new
    else
      perform_complete_move(player_number, from_id, to_id)
    end
  else
    @errors.push JustXiangqi::InvalidMoveError.new
  end

  @errors.empty?
end

#perform_complete_move(player_number, from_id, to_id) ⇒ Object

Moves a piece owned by the player, from one square, to another, with the option to promote.

It moves the piece and returns true if the move is valid and it’s the player’s turn. It returns false otherwise.



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# File 'lib/just_xiangqi/game_state.rb', line 222

def perform_complete_move(player_number, from_id, to_id)
  from = squares.find_by_id(from_id)
  to = squares.find_by_id(to_id)

  captured = to.occupied? ? to : nil

  @last_change = { type: 'move', data: { player_number: player_number, from: from_id, to: to_id } }

  perform_move(player_number, from, to, captured)

  pass_turn
end

#winner ⇒ Fixnum, NilClass

The player number of the winner. It returns nil if there is no winner.

Returns:

  • (Fixnum, NilClass) 


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# File 'lib/just_xiangqi/game_state.rb', line 207

def winner
  case
  when in_checkmate?(1)
    2
  when in_checkmate?(2)
    1
  else
    nil
  end
end