/**
   Represents a single message, and handles the details of
   the made-up protocol that we are using.
   
   @author Tom Austin
 */
public class Message
{
   //text of the message.
   private String text;
   
   //These two fields tag the message and make it unique
   private String senderID;
   private int sequenceNum;
   
   //Pattern of our made up "protocol".
   private final static String pattern = "(.*?)\\|\\|sender:(.*?),seq:(\\d+)";
   
   /**
      Constructor for a new message.  At its creation, the message
      is tagged with the ID of the sender and the number that indicates
      the order that the message was sent.
      
      @param text
      @param senderID
      @param sequenceNum
    */
   public Message(String text, String senderID, int sequenceNum)
   {
      this.text = text;
      this.senderID = senderID;
      this.sequenceNum = sequenceNum;
   }
   
   /**
      This will take a transmissionString (in our made up protocol)
      and construct a new message object from it.
      
      @param receivedText  Text received from a broadcast message.
    */
   public static Message parseTransmissionString(String receivedText)
   {
      assert(receivedText.matches(pattern));
      String text = receivedText.replaceFirst(pattern, "$1");
      String ID = receivedText.replaceFirst(pattern, "$2");
      int seq = Integer.parseInt(receivedText.replaceFirst(pattern, "$3"));
      return new Message(text, ID, seq);
   }
   
   /**
      @return  ID of the original broadcaster of this message.
    */
   public String getSenderID()
   {
      return senderID;
   }
   
   /**
      @return  The sequence number of this message.
    */
   public int getSequenceNumber()
   {
      return sequenceNum;
   }
   
   /**
      Two messages are equal if the sender and sequence number are the same.
      
      @see java.lang.Object#equals(java.lang.Object)
    */
   public boolean equals(Object o)
   {
      if (!(o instanceof Message)) return false;
      Message other = (Message)o;
      return this.senderID.equals(other.senderID) && this.sequenceNum==other.sequenceNum;
   }
   
   /**
      Returns the text of the message;
      @see java.lang.Object#toString()
    */
   public String toString()
   {
      return text;
   }
   
   /**
      Returns a transmission String for use in our protocol.
      @return
    */
   public String transmissionString()
   {
      return text + "||sender:" + senderID + ",seq:" + sequenceNum;
   }
   
   /**
      Test main method for this class.  You can run this to verify
      that a message is not distorted after its reconstruction.
      
      @param args
    */
   public static void main(String [] args)
   {
      Message m1 = new Message("Hola.", "Alpha", 0);
      System.out.println(m1.transmissionString());
      Message m2 = Message.parseTransmissionString(m1.transmissionString());
      System.out.println("m1 eq? m2: " + m1.equals(m2));
   }
}