module YWF
  class Board
    ROW_MIN = 1
    ROW_MAX = 9
    COL_MIN = 1
    COL_MAX = 9

    WALL = -1
    EMPTY = 0
    BLACK = 1
    GRAY = 2
    WHITE = 3

    Direction = [
      [-1, -1], [-1,  0], [-1,  1],
      [ 0, -1],           [ 0,  1],
      [ 1, -1], [ 1,  0], [ 1,  1],
    ]

    def initialize(other=nil)
      @board = [
        [WALL, WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, GRAY , BLACK, WHITE, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, WHITE, GRAY , BLACK, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, BLACK, WHITE, GRAY , EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, WALL],
        [WALL, WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL , WALL],
      ]
      @move = 1
      @turn = BLACK
      @token = GRAY
      if other
        copy(other)
      end
    end

    attr_reader :move, :turn, :token

    def opponent
      (@turn + 2) % 4
    end

    def color(row, col)
      if (row < ROW_MIN) || (ROW_MAX < row)
        raise "invalid row. [row: #{row}]"
      end
      if (col < COL_MIN) || (COL_MAX < col)
        raise "invalid col. [col: #{col}]"
      end
      @board[row][col]
    end

    def count(color)
      if (color != EMPTY) && (color != BLACK) && (color != GRAY) && (color != WHITE)
        raise "invalid color. [color: #{color}]"
      end

      count = 0
      (ROW_MIN..ROW_MAX).each do |row|
        (COL_MIN..COL_MAX).each do |col|
          if self.color(row, col) == color
            count += 1
          end
        end
      end

      count
    end

    def playable?(row, col)
      if self.color(row, col) != EMPTY
        return false
      end

      has_color_from?(row, col)
    end

    def changeable?(row, col)
      if self.color(row, col) != GRAY
        return false
      end

      if (@token != GRAY) && (@token != @turn)
        return false
      end

      has_color_from?(row, col)
    end

    def must_pass?
      (self.playable_places.size == 0) && (self.changeable_places.size == 0)
    end

    def playable_places
      places = []
      (ROW_MIN..ROW_MAX).each do |row|
        (COL_MIN..COL_MAX).each do |col|
          if self.playable?(row, col)
            places.push [row, col]
          end
        end
      end
      places
    end

    def changeable_places
      places = []
      if @token != opponent
        (ROW_MIN..ROW_MAX).each do |row|
          (COL_MIN..COL_MAX).each do |col|
            if self.changeable?(row, col)
              places.push [row, col]
            end
          end
        end
      end
      places
    end

    def legal_actions
      actions = Array.new
      if self.must_pass?
        actions.push [:pass, nil]
      else
        self.playable_places.each do |place|
          actions.push [:play, place]
        end
        self.changeable_places.each do |place|
          actions.push [:change, place]
        end
      end
      actions
    end

    def play(row, col)
      unless self.playable?(row, col)
        raise "not playable. [row: #{row}, col: #{col}]"
      end

      new_board = self.class.new(self)
      new_board.put_piece(row, col)
      new_board.change_turn
      new_board.add_move

      new_board
    end

    def change(row, col)
      unless self.changeable?(row, col)
        raise "not changeable. [row: #{row}, col: #{col}]"
      end

      new_board = self.class.new(self)
      new_board.put_piece(row, col)
      new_board.change_token
      new_board.change_turn
      new_board.add_move

      new_board
    end

    def pass
      unless self.must_pass?
        raise "cannot pass."
      end

      new_board = self.class.new(self)
      new_board.change_turn
      new_board.add_move

      new_board
    end

    def game_end?
      if self.count(EMPTY) == 0
        return true
      end

      if self.must_pass?
        passed = self.pass
        if passed.must_pass?
          return true
        end
      end

      false
    end

    def win?(color)
      if (color != BLACK) && (color != WHITE)
        raise "invalid color. [color: #{color}]"
      end

      unless self.game_end?
        return false
      end

      if color == BLACK
        (self.count(BLACK) > self.count(WHITE)) ||
          ((self.count(BLACK) == self.count(WHITE)) && (@token == BLACK))
      else
        (self.count(BLACK) < self.count(WHITE)) ||
          ((self.count(BLACK) == self.count(WHITE)) && (@token == WHITE))
      end
    end

    protected

    def put_piece(row, col)
      @board[row][col] = @turn

      color_diff = (@turn == BLACK) ? -1 : +1
      Direction.each do |direction|
        if has_color_from_to?(row, col, direction)
          traverse_to(row, col, direction) do |step_count, traverse_row, traverse_col, traverse_color|
            if traverse_color == @turn
              break
            else
              @board[traverse_row][traverse_col] += color_diff
            end
          end
        end
      end
    end

    def change_turn
      @turn = self.opponent
    end

    def change_token
      @token += (@turn == BLACK) ? +1 : -1
    end

    def add_move
      @move += 1
    end

    private

    def copy(other)
      (ROW_MIN..ROW_MAX).each do |row|
        (COL_MIN..COL_MAX).each do |col|
          @board[row][col] = other.color(row, col)
        end
      end
      @move = other.move
      @turn = other.turn
      @token = other.token
    end

    def has_color_from?(row, col)
      Direction.each do |direction|
        if has_color_from_to?(row, col, direction)
          return true
        end
      end
      return false
    end

    def has_color_from_to?(row, col, direction)
      traverse_to(row, col, direction) do |step_count, traverse_row, traverse_col, traverse_color|
        if traverse_color == @turn
          if step_count == 1
            return false
          else
            return true
          end
        end
      end
      return false
    end

    def traverse_to(row, col, direction, &block)
      # NOTE:
      # 'traverse_to' accesses to 'WALL',
      # so 'color' cannot be used.
      traverse_row = row + direction[0]
      traverse_col = col + direction[1]
      traverse_color = @board[traverse_row][traverse_col]
      step_count = 1
      while (traverse_color != WALL) && (traverse_color != EMPTY)
        block.call(step_count, traverse_row, traverse_col, traverse_color)
        traverse_row += direction[0]
        traverse_col += direction[1]
        traverse_color = @board[traverse_row][traverse_col]
        step_count += 1
      end
    end
  end

  module BoardViewer
    COL_INDEX = "     1   2   3   4   5   6   7   8   9"
    LINE      = "   +---+---+---+---+---+---+---+---+---+"

    def view(board)
      puts "[#{sprintf '%03d', board.move}] turn: #{mark(board.turn)}, token: #{mark(board.token)}"
      puts COL_INDEX
      puts LINE
      (Board::ROW_MIN..Board::ROW_MAX).each do |row|
        print " #{row} "
        (Board::COL_MIN..Board::COL_MAX).each do |col|
          color = board.color(row, col)
          print "| #{mark(color)} "
        end
        puts "|"
        puts LINE
      end
    end

    def mark(color)
      case color
      when Board::EMPTY
        " "
      when Board::BLACK
        "O"
      when Board::GRAY
        "-"
      when Board::WHITE
        "X"
      else
        raise "invalid color. [color: #{color}]"
      end
    end

    module_function :view, :mark
  end
end