/**
   Connects a phone to the mail system. The purpose of this
   class is to keep track of the state of a connection, since
    the phone itself is just a source of individual key presses.
 */
 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;
       phone = 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)
    {
       if (state == RECORDING || state == CHANGE_GREETING)
          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;
       phone.speak(INITIAL_PROMPT);
    }
 
    /**
       Try to connect the user with the specified mailbox.
       @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;
             phone.speak(currentMailbox.getGreeting());
          }
          else
             phone.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;
             phone.speak(MAILBOX_MENU_TEXT);
          }
          else
             phone.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;
          phone.speak(MAILBOX_MENU_TEXT);
         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;
          phone.speak(MAILBOX_MENU_TEXT);
      }
    }
 
   /**
       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;
          phone.speak(MESSAGE_MENU_TEXT);
       }
       else if (key.equals("2"))
       {
          state = CHANGE_PASSCODE;
          phone.speak("Enter new passcode followed by the # key");
       }
       else if (key.equals("3"))
       {
          state = CHANGE_GREETING;
          phone.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 += MESSAGE_MENU_TEXT;
         phone.speak(output);
       }
       else if (key.equals("2"))
      {
        currentMailbox.saveCurrentMessage();
          phone.speak(MESSAGE_MENU_TEXT);
       }
       else if (key.equals("3"))
       {
          currentMailbox.removeCurrentMessage();
          phone.speak(MESSAGE_MENU_TEXT);
       }
       else if (key.equals("4"))
       {
          state = MAILBOX_MENU;
          phone.speak(MAILBOX_MENU_TEXT);
       }
    }
 
    private MailSystem system;
    private Mailbox currentMailbox;
    private String currentRecording;
    private String accumulatedKeys;
    private Telephone phone;
    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 INITIAL_PROMPT = 
       "Enter mailbox number followed by #";      
    private static final String MAILBOX_MENU_TEXT = 
       "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 MESSAGE_MENU_TEXT = 
       "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";
 }