// TryManyPooled by Rowland http://home.comcast.net/~rowland3/
// Base class to attempt connections on many possible servers at a given port.
// Useful for finding a usable server on an IRC net, for example.
// This version uses a thread pool.

import java.io.*;
import java.net.*;
import java.util.*;

/** FileEntriesIterator reads a file of tokens as an Iterator **/
class FileEntriesIterator implements Iterator {
    protected final FileReader fr;
    protected final StreamTokenizer in;
    protected int token;
    protected boolean gotToken;

    public FileEntriesIterator(String fileSpec) throws Exception {
	fr= new FileReader(fileSpec);
	in= new StreamTokenizer(fr);  in.resetSyntax();  in.wordChars(33, 127);
	token= 0;  gotToken= false;
    }

    protected final void getnext() {
	if (!gotToken)
	    try {
		do {
		    token= in.nextToken();
		}  while (token!=in.TT_EOF && token!=in.TT_WORD); // skip over all else
	    } catch (Exception E) {
		System.err.println("ERR FileEntriesIterator: "+ E.toString());
		token= in.TT_EOF; // encourage caller to can halt gracefully
	    }
	gotToken= true;
    }

    public final boolean hasNext() {
	if (in== null)  return false;
	getnext();
	if (token== in.TT_EOF)  return false;
	return true;
    } 

    public final Object next() {
	Object result= null;
	if (in== null)  return null;
	getnext();
	if (token== in.TT_EOF)  result= null;
	else  result= in.sval;
	gotToken= false;
	return result;
    }

    public void remove() {   }  // not implemented
}


/** TryMany tries to connect to many possible servers on a given port.
    Override callbackGotOne() to get useful behavior. **/
public class TryManyPooled  implements Runnable {
    protected final Iterator candidates;
    final int port;
    int timeout= 15000;
    protected boolean debug= false;
    /** set scanning to false if you want to stop trying for more connections **/
    protected boolean scanning= false;
    protected Thread[] pool= new Thread[10];

    class TryThread implements Runnable {
	public void run() {
	    scanning= true;
	    if (candidates== null) {
		println("ERR: TryMany: no candidates");
		return;
	    }
	    while (candidates.hasNext()) {
		String candidate= (String)candidates.next();
		tryCandidate(candidate);
		if (!scanning)  return;
	    }
	}
    }

    /** constructor to read in candidates from a file **/
    public TryManyPooled(String fileSpec, int _port) throws Exception {
	candidates= new FileEntriesIterator(fileSpec);
	port= _port;
    }
    /** A more general constructor that will use any Iterator **/
    public TryManyPooled(Iterator _candidates, int _port)  {
	candidates= _candidates;
	port= _port;
    }

    public void setDebug(boolean _debug) { debug= _debug; }
    public void setTimeout(int _timeout) { timeout= _timeout; }

    synchronized boolean hasNext() { return candidates.hasNext(); }
    synchronized Object next() { return candidates.next(); }

    public void run() {
	for (int i=0; i<pool.length; i++) {
	    Thread t= new Thread(new TryThread());
	    pool[i]= t;
	    t.start();
	}
    }

    /** println is for debug output, controlled by setDebug() **/
    protected final void println(String line) {
	if (debug)  System.out.println(line);
    }

    protected boolean tryCandidate(String candidate) {
	println("\n\nTRYING: "+ candidate);
	Socket socket= null;
	try {
	    InetAddress addr = InetAddress.getByName(candidate);
	    SocketAddress sockaddr = new InetSocketAddress(addr, port);
	    socket = new Socket();
	    socket.connect(sockaddr, timeout);
	    println("  ...connected");
	    socket.setSoTimeout(timeout);
	} catch (Exception E) {
	    callbackFailed(candidate, E);
	    socket= null;
	    return false;
	}

	if (socket!= null)  try {
	    callbackGotOne(candidate, socket);
	} catch (Exception E) {
	    println("ERR from callback: "+ E.toString());
	    return false;
	}
	return true;
    }

    /** callbackGotOne called when a connection succeeeds.  override in derived class.  */
    protected synchronized void callbackGotOne(String host, Socket socket) throws Exception {
	System.out.println("CONNECT: "+ host);
    }

    /** callbackFailed called when a connection fails.  override in derived class.  */
    protected synchronized void callbackFailed(String host, Exception E)  {
	println("ERR TryMany connect: "+ E.toString());
    }


    /** main routine for testing. Pass file with list of IRC servers as command line argument. **/
    public static void main(String args[]) {
	try {
	    String fileSpec= args[0];
	    TryManyPooled tm= new TryManyPooled(fileSpec, 6667);
	    tm.run();
	} catch (Exception E) {
	    System.err.println("ERR: "+ E.toString());
	}
    }
}