Done

Gemfile.lock

@@ -31,4 +31,5 @@ DEPENDENCIES
   rspec
 
 BUNDLED WITH
-   2.0.1
+   2.1.4
+

lib/board.rb

@@ -0,0 +1,43 @@
+class Board 
+  attr_accessor :cells 
+  def initialize
+    reset!
+  end 
+
+  def reset!
+    @cells = Array.new(9, " ")
+  end 
+
+  def display
+    puts " #{cells[0]} | #{cells[1]} | #{cells[2]} "
+    puts "-------------------------------------------"
+    puts " #{cells[3]} | #{cells[4]} | #{cells[5]} "
+    puts "-------------------------------------------"
+    puts " #{cells[6]} | #{cells[7]} | #{cells[8]} "
+  end 
+
+  def full?
+    cells.all?{|token| token == "X" || token == "O"}
+  end
+
+  def turn_count
+    cells.count{|token| token == "X" || token == "O"}
+  end
+
+  def valid_move?(input)
+    input.to_i.between?(1,9) && !taken?(input)
+  end
+
+  def update(input, player)
+    cells[input.to_i-1] = player.token
+  end
+
+  def position(input)
+    cells[input.to_i-1]
+  end
+
+  def taken?(input)
+    !(position(input) == " " || position(input) == "")
+  end
+end 
+

lib/game.rb

@@ -0,0 +1,71 @@
+class Game
+  attr_accessor :board, :player_1, :player_2
+  WIN_COMBINATIONS = [
+    [0,1,2],
+    [3,4,5],
+    [6,7,8],
+    [0,3,6],
+    [1,4,7],
+    [2,5,8],
+    [0,4,8],
+    [6,4,2]
+  ]
+
+  def initialize(player_1 = Players::Human.new("X"), player_2 = Players::Human.new("O"), board = Board.new)
+    @board = board
+    @player_1 = player_1
+    @player_2 = player_2
+  end
+
+  def over?
+    won? || draw?
+  end
+
+  def current_player
+    @board.turn_count % 2 == 0 ? @player_1 : @player_2
+  end
+
+  def winner
+    if winning_combo = won?
+      @winner = @board.cells[winning_combo.first]
+    end
+  end
+
+  def turn
+    player = current_player
+    current_move = player.move(@board)
+    if [email protected]_move?(current_move)
+      turn
+    else
+      puts "Turn #: #{@board.turn_count+1}\n"
+      @board.display
+      @board.update(current_move, player)
+      puts "#{player.token}: moved #{current_move}"
+      @board.display
+      puts "\n\n"
+    end
+  end
+
+  def play
+    while !over?
+      turn
+    end
+    if won?
+      puts "Congratulations #{winner}!"
+    elsif draw?
+      puts "Cat's Game!"
+    end
+  end
+
+  def won?
+    WIN_COMBINATIONS.detect do |combo|
+      @board.cells[combo[0]] == @board.cells[combo[1]] &&
+      @board.cells[combo[1]] == @board.cells[combo[2]] &&
+      @board.taken?(combo[0]+1)
+    end
+  end
+
+  def draw?
+    @board.full? && !won?
+  end
+end

lib/player.rb

@@ -0,0 +1,7 @@
+class Player
+  attr_reader :token
+
+  def initialize(token)
+    @token = token
+  end
+end

lib/players/computer.rb

@@ -0,0 +1,27 @@
+module Players
+  class Computer < Player
+    def move(board)
+      move = nil
+
+      if !board.taken?(5)
+        move = "5"
+      elsif board.turn_count == 1
+        move = "1"
+      elsif board.turn_count == 2
+        move = [1, 3, 7, 9].detect{|i| !board.taken?(i)}.to_s
+      elsif board.turn_count == 3 && (board.position(1) == board.position(9) || board.position(3) == board.position(7))
+        move = "2"
+
+        Game::WIN_COMBINATIONS.detect do |combo|
+          if combo.select{|i| board.position(i+1) == token}.size == 2 && combo.any?{|i| board.position(i+1) == " "}
+            move = combo.select{|i| !board.taken?(i+1)}.first.to_i.+(1).to_s
+          elsif combo.select{|i| board.position(i+1) != " " && board.position(i+1) != token}.size == 2 && combo.any?{|i| board.position(i+1) == " "}
+            move = combo.select{|i| !board.taken?(i+1)}.first.to_i.+(1).to_s
+          end
+        end
+        move = [1, 3, 7, 9, 2, 4, 6, 8].detect{|i| !board.taken?(i)}.to_s if move == nil
+      end
+      move
+    end
+  end
+end

lib/players/human.rb

@@ -0,0 +1,9 @@
+
+module Players
+  class Human < Player
+    def move(board)
+      puts "Please enter a number between 1 - 9:"
+      gets.strip
+    end
+  end
+end