1. Think about which additional fields and types it needs to implement the promised functionality.

2. Write a constructor MarbleSolitaireControllerImpl(Readable rd, Appendable ap) throws IllegalArgumentException. Readable and Appendable are two existing interfaces in Java that abstract input and output respectively. It should throw the IllegalArgumentException if and only if the readable or appendable objects are null.

   Your controller should accept and store these objects for doing input and output. In this implementation, whenever you need to take user input, use the Readable object and whenever you wish to transmit output, use the Appendable object.

   Look at the Readable and Appendable interfaces to see how to read from and write to them. Ultimately you must figure out a way to transmit a String to an Appendable and read suitable data from a Readable object. The Scanner may offer a way out.

3. The void playGame(MarbleSolitaireModel model) method should play a game. It should “run” the game in the following sequence until the game is over:

   1. Transmit game state to the Appendable object exactly as the model provides it.

   2. Transmit "Score: x", replacing x with the actual score. The last line should end with a new line.

   3. If the game is ongoing, wait for user input from the Readable object. A valid user input for a move is a sequence of four inputs (separated by spaces or newlines), asked one at a time:

      1. The row number of the position from where a marble is to be moved.

      2. The column number of the position from where a marble is to be moved.

      3. The row number of the position to where a marble is to be moved.

      4. The column number of the position to where a marble is to be moved.

      To make the inputs more user-friendly, all row and columns numbers in the input begin from 1.

      The controller will parse these inputs and pass the information on to the model to make the move. See below for more detail.

   4. If the game has been won, the method should transmit the following in order,each on a separate line: Message "Game over!", the final game state, "Score: x" with x replaced by the final score. The last line should end with a new line. The method should then end.

      For example:

      Game over!
          X X X
          X X X
      X X X X X X X
      X X X O X X X
      X X X X X X X
          X X X
          X X X
      Score: 1
      

   Key points:

   • Quitting: If at any point, the input is either the letter 'q' or the letter 'Q', the controller should transmit the following in order, each on a separate line: Message "Game quit!", "State of game when quit:", the current game state, "Score: x" with x replaced by the final score. The last line should end with a new line. The method should then end.

     For example:

     Game quit!
     State of game when quit:
         O O O
         O X O
     O O O X O O O
     O O O O O O O
     O O O O O O O
         O O O
         O O O
     Score: 31
     

   • Bad inputs: If an input is unexpected (i.e. something other than 'q', 'Q' or a positive number) it should ask the user to input it again. If the user entered the from-row and from-column correctly but the to-row incorrectly, the controller should ask only for to-row before moving on to to-column. If the move was invalid as signaled by the model, the controller should transmit a message to the Appendable object "Invalid move. Play again." plus any informative message about why the move was invalid (all on one line), and resume waiting for valid input.

   • Error handling: The controller should throw an IllegalArgumentException if a null model is passed to it. The controller should not propagate any exceptions thrown by the model to its caller. If the Appendable object is unable to transmit output, this method should throw an IllegalStateException to its caller. Likewise if it is unable to read from the Readable object (i.e. it ran out of inputs), it should throw an IllegalStateException to its caller.

4. Write sufficient tests to be confident that your code is correct. Note: once the model has been tested thoroughly (which you hopefully did in Assignment 6), all that remains to be tested is whether the controller works correctly in all cases.

Be sure to properly document your code with Javadoc as appropriate. Method implementations that inherit Javadoc need not provide their own unless their contract differs from the inherited documentation.