// SmtpListener.java - listens for SMTP emails on port 25.
// Adapted by Rowland http://home.comcast.net/~rowland3
// Based (a bit loosely) on a sample from http://www.engr.uconn.edu/~jeffm/ by Jeffrey A. Meunier

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

class MailMessage  {
    String  subject;
    String  date;
    Vector  vbodylines;   // message text is a vector of strings
    public final String sender, recipient;
    TreeMap header= new TreeMap();
    
    public MailMessage(String _sender, String _recipient)   {
	sender= _sender;  recipient= _recipient;
	vbodylines = new Vector();
    }
    public void addHeaderLine(String line)  {
	try {
	    int ix= line.indexOf(": ");
	    if (ix< 0)  return;
	    String key= line.substring(0, ix);
	    String val= line.substring(ix+2);
	    if (val.endsWith("\n"))  val= val.substring(val.length()-1);  // get rid of trailing LF
	    if (val.endsWith("\r"))  val= val.substring(val.length()-1);  // get rid of trailing CRLF
	    header.put(key, val);
	} catch (Exception E) {
	    System.err.println("MailMessage.addheaderLine: "+ line);
	}
    }
    public void addHeaderVal(String key, String val) {
	header.put(key, val);
    }
    public void addMailMessageLine(String _line)  { vbodylines.add(_line); }
    
    public Enumeration getMailMessageLines()  { return vbodylines.elements(); }
    public Iterator getHeaderFields()  { return header.keySet().iterator(); }
    public String getHeaderVal(String key) {
	Object O= header.get(key);
	if (O== null)  return null;
	return (String)O;
    }
    public String toString() {
	String s= "Sender: "+ sender+ "\tRecipient: "+ recipient+ "\n";
	Iterator hi= header.keySet().iterator();
	while (hi.hasNext()) {
	    String key= (String)hi.next();
	    String hline= key+ ": "+ header.get(key)+ "\n";
	    s+= hline;
	}
	s+= "\n";
	Enumeration e= vbodylines.elements();
	while(e.hasMoreElements()) {
	    s+= (String)e.nextElement()+ "\n";
	}
	return s;
    }
}


//------------------------------------------------------------------------------
class SmtpConnHandler implements Runnable  {
    public static String serverName = "emailtest";

    Socket sclient;
    SmtpListener parent;
    Thread thread;
    BufferedReader in;
    OutputStreamWriter out;
    boolean debug= false;

    public SmtpConnHandler(Socket _sclient, SmtpListener _parent)  {
	parent= _parent;
	sclient = _sclient;
	thread = new Thread(this);
	thread.start();
    }

    public void setDebug(boolean _debug) { debug= _debug; }

    public void run()  {
	if (debug)  System.out.println("SMTP: connection from " +
			   sclient.getInetAddress().getHostAddress());
	try  {
	    InputStream inpStream = sclient.getInputStream();
	    out = new OutputStreamWriter(sclient.getOutputStream());
	    in = new BufferedReader(new InputStreamReader(inpStream));
	    writeln("220 " + serverName + " Service ready");
	    String clientcommand;
	    while (true)  {
		clientcommand = readln();
		if (clientcommand == null)
		    return;
		if (clientcommand.startsWith("EHLO"))
		    break;
		else if (clientcommand.startsWith("HELO"))
		    break;
		else if (clientcommand.equals("QUIT"))
		    return;
	    }
	    
	    writeln("250 " + serverName);    
	    while (true)  {
		clientcommand = readln();
		if (clientcommand.startsWith("MAIL"))
		    readMailMessage(clientcommand);
		else if (clientcommand.equals("QUIT"))
		    break;
	    }

	    writeln("221 " + serverName + " closing connection");
	    if (debug)  System.err.println("SMTP: finished session, closing connection\n");
	    sclient.close();
	}   catch(Exception E)   {
	    System.err.println("SMTPHandler: "+ E.toString());
	}
	
    }

    void readMailMessage(String clientcommand) throws IOException   {
	String sSenderEmailAddr = findEmailAddr(clientcommand);
	ack();
	String sRecptEmailAddr = findEmailAddr(readln());
	ack();
	String s = readln();
	if (!s.equals("DATA"))  {
		nak();
		return;
	    }
	writeln("354 Enter mail, end with \".\" on a line by itself");
	MailMessage message = new MailMessage(sSenderEmailAddr, sRecptEmailAddr);
	while (true)  {  // get the message header
	    s = readln();
	    if (s.equals("QUIT"))
		return;
	    else if (s.equals("."))  // shouldn't actually happen
		return;
	    else if (s.length()== 0)
		break;  // end of header
	    if (s.startsWith(".."))
		s= s.substring(1);
	    message.addHeaderLine(s);
	}
	while (true)  { // get the message body
	    s = readln();
	    if (s.equals("QUIT"))
		return;
	    else if (s.equals("."))
		break;
	    message.addMailMessageLine(s);
	}
	writeln("250 Message accepted");
	if (parent!= null)  parent.gotMailMessage(message);
    }

    protected final void writeln(String s)  throws IOException {
	if (debug)  System.err.println("SMTP: server sending (" + s + ")");
	out.write(s+ "\r\n");  out.flush();
    }

    protected final String readln()  throws IOException {
	String s = in.readLine();
	if (debug)  System.err.println("SMTP: client sent    [" + s + "]");
	return s;
    }

    protected final void ack()  throws IOException   { writeln("250 OK");  }

    protected final void nak()  throws IOException  { writeln("451 aborted: local error"); }

    String findEmailAddr(String s)  throws IOException    {
	int ix= s.indexOf('<');
	if (ix< 0)  return s;
	String emailaddr= s.substring(ix+1);
	ix= emailaddr.indexOf('>');
	if (ix< 0)  return emailaddr;
	return emailaddr.substring(0, ix);
    }

}


//-----------------------------------------------------------------------
class SmtpListener implements Runnable  {
    ServerSocket slisten;
    Thread thread;
    boolean debug= false;

    public SmtpListener(boolean _debug)    {
	debug= _debug;
	thread = new Thread(this);
	thread.start();
    }

    public void setDebug(boolean _debug) { debug= _debug; }

    // Callback from SmtpConnHandler
    public synchronized void gotMailMessage(MailMessage m) {
	System.out.println(m.toString());
    }

    public void run()  {
	System.err.println("Starting SMTP listener");
	try {
	    slisten = new ServerSocket(25);  // SMTP port
	    while(true) {
		Socket sconn = slisten.accept();
		SmtpConnHandler smtpHandler = new SmtpConnHandler(sconn, this);  // spawns automatically
		if (debug)  smtpHandler.setDebug(true);
	    }   
	}  catch (Exception E)  {
	    System.err.println("SmtpListener: "+ E.toString());
	}
    }

    public static void main (String args[]) {
	new SmtpListener(true);
    }
}