/**
   Connect a phone to the mail system.
*/
public class Connection
{
   /**
      Construct a Connection object.
      @param s a MailSystem object
      @param p a Telephone object
   */
   public Connection(MailSystem s, Telephone p)
   {
      system = s;
      thePhone = p;
      resetConnection();
   }

   /**
      Respond to the user's pressing a key on the phone touchpad
      @param key the phone key pressed by the user
   */
   public void dial(String key)
   {
      if (state == CONNECTED)
         connect(key);
      else if (state == RECORDING)
         login(key);
      else if (state == CHANGE_PASSCODE)
         changePasscode(key);
      else if (state == CHANGE_GREETING)
         changeGreeting(key);
      else if (state == MAILBOX_MENU)
         mailboxMenu(key);
      else if (state == MESSAGE_MENU)
         messageMenu(key);
   }

   /**
      Record voice.
      @param voice voice spoken by the user
   */
   public void record(String voice)
   {
      currentRecording += voice;
   }

   /**
      The user hangs up the phone.
   */
   public void hangup()
   {
      if (state == RECORDING)
         currentMailbox.addMessage(new Message(currentRecording));
      resetConnection();
   }

   /**
      Reset the connection to the initial state and prompt
      for mailbox number
   */
   private void resetConnection()
   {
      currentRecording = "";
      accumulatedKeys = "";
      state = CONNECTED;
      thePhone.speak(initialPrompt);
   }

   /**
      Try to connect the user with the specified mail box.
      @param key the phone key pressed by the user
   */
   private void connect(String key)
   {
      if (key.equals("#"))
      {
         currentMailbox = system.findMailbox(accumulatedKeys);
         if (currentMailbox != null)
         {
            state = RECORDING;
            thePhone.speak(currentMailbox.getGreeting());
         }
         else
            thePhone.speak("Incorrect mailbox number. Try again!");
         accumulatedKeys = "";
      }
      else
         accumulatedKeys += key;
   }

   /**
      Try to log in the user.
      @param key the phone key pressed by the user
   */
   private void login(String key)
   {
      if (key.equals("#"))
      {
         if (currentMailbox.checkPasscode(accumulatedKeys))
         {
            state = MAILBOX_MENU;
            thePhone.speak(mailboxMenu);
         }
         else
            thePhone.speak("Incorrect passcode. Try again!");
         accumulatedKeys = "";
      }
      else
         accumulatedKeys += key;
   }

   /**
      Change passcode.
      @param key the phone key pressed by the user
   */
   private void changePasscode(String key)
   {
      if (key.equals("#"))
      {
         currentMailbox.setPasscode(accumulatedKeys);
         state = MAILBOX_MENU;
         thePhone.speak(mailboxMenu);
         accumulatedKeys = "";
      }
      else
         accumulatedKeys += key;
   }

   /**
      Change greeting.
      @param key the phone key pressed by the user
   */
   private void changeGreeting(String key)
   {
      if (key.equals("#"))
      {
         currentMailbox.setGreeting(currentRecording);
         currentRecording = "";
         state = MAILBOX_MENU;
         thePhone.speak(mailboxMenu);
      }
   }

   /**
      Respond to the user's selection from mailbox menu.
      @param key the phone key pressed by the user
   */
   private void mailboxMenu(String key)
   {
      if (key.equals("1"))
      {
         state = MESSAGE_MENU;
         thePhone.speak(messageMenu);
      }
      else if (key.equals("2"))
      {
         state = CHANGE_PASSCODE;
         thePhone.speak("Enter new passcode followed by the # key");
      }
      else if (key.equals("3"))
      {
         state = CHANGE_GREETING;
         thePhone.speak("Record your greeting, then press the # key");
      }
   }

   /**
      Respond to the user's selection from message menu.
      @param key the phone key pressed by the user
   */
   private void messageMenu(String key)
   {
      if (key.equals("1"))
      {
         String output = "";
         Message m = currentMailbox.getCurrentMessage();
         if (m == null) output += "No messages." + "\n";
         else output += m.getText() + "\n";
         output += messageMenu;
         thePhone.speak(output);
      }
      else if (key.equals("2"))
      {
         currentMailbox.saveCurrentMessage();
         thePhone.speak(messageMenu);
      }
      else if (key.equals("3"))
      {
         currentMailbox.removeCurrentMessage();
         thePhone.speak(messageMenu);
      }
      else if (key.equals("4"))
      {
         state = MAILBOX_MENU;
         thePhone.speak(mailboxMenu);
      }
   }

   private MailSystem system;
   private Mailbox currentMailbox;
   private String currentRecording;
   private String accumulatedKeys;
   private Telephone thePhone;
   private int state;

   private static final int DISCONNECTED = 0;
   private static final int CONNECTED = 1;
   private static final int RECORDING = 2;
   private static final int MAILBOX_MENU = 3;
   private static final int MESSAGE_MENU = 4;
   private static final int CHANGE_PASSCODE = 5;
   private static final int CHANGE_GREETING = 6;

   private static final String initialPrompt = 
      "Please enter mailbox number followed by #";      
   private static final String mailboxMenu = 
      "Enter 1 to listen to your messages\n"
      + "Enter 2 to change your passcode\n"
      + "Enter 3 to change your greeting";
   private static final String messageMenu = 
      "Enter 1 to listen to the current message\n"
      + "Enter 2 to save the current message\n"
      + "Enter 3 to delete the current message\n"
      + "Enter 4 to return to the main menu";
}