package dcj.examples.messageV1;

import java.util.Vector;
import java.lang.*;
import java.io.*;

/**
 * Source code from "Java Distributed Computing", by Jim Farley.
 *
 * Class: BasicMsgHandler
 * Example: 6-2
 * Description: A base class for agents that utilize message-passing.
 */

public abstract class BasicMsgHandler implements Runnable
{
  // Static message handler for applications where only one is used
  // and needs to be globally accessible.
  public static BasicMsgHandler current = null;

  InputStream msgIn;
  OutputStream msgOut;
  StreamTokenizer tokenizer;
  String msgEndToken = "END";

  public BasicMsgHandler(InputStream in, OutputStream out) {
    setStreams(in, out);
    current = this;
  }

  public BasicMsgHandler(InputStream in, OutputStream out,
                         String endToken) {
    msgEndToken = endToken;
    setStreams(in, out);
    current = this;
  }

  protected void setStreams(InputStream in, OutputStream out) {
    msgIn = in;
    msgOut = out;
  }

  public BasicMessage readMsg() throws IOException {
    BasicMessage msg;
    String token;
    DataInputStream din = new DataInputStream(msgIn);

    token = din.readUTF();
    msg = buildMessage(token);

    if (msg != null) {
      boolean msgEnd = false;
      while (!msgEnd) {
        token = din.readUTF();
        if (token.compareTo(msgEndToken) == 0)
          msgEnd = true;
        else {
          msg.addArg(token);
        }
      }
    }
    return msg;
  }

  public void sendMsg(BasicMessage msg) throws IOException {
    boolean success = true;
    DataOutputStream dout = new DataOutputStream(msgOut);

    dout.writeUTF(msg.messageID());

    Vector args = msg.argList();
    int acnt = args.size();
    for (int i = 0; i < acnt; i++) {
      dout.writeUTF((String)args.elementAt(i));
    }

    dout.writeUTF(msgEndToken);
  }

  public void run() {
    try {
      while (true) {
        BasicMessage msg = readMsg();
        if (msg != null)
          msg.Do();
      }
    }
    // Treat an IOException as a termination of the message
    // exchange, and let this message-processing thread die.
    catch (IOException e) {}
  }

  protected abstract BasicMessage buildMessage(String msgId);
}