/*
 * Copyright (c) 2001 Matthew Feldt. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided the copyright notice above is
 * retained.
 *
 * THIS SOFTWARE IS PROVIDED ''AS IS'' AND WITHOUT ANY EXPRESSED OR
 * IMPLIED WARRANTIES.
 */

/**
 * Checkmail.java
 *
 * Java Examples In A Nutshell Copyright (c) 2000 David Flanagan
 * Exercise 5-4:
 * In the discussion of Example 5-8, GenericClient, there is an example of
 * using that program to communicate with a POP (Post Office Protocol) server
 * to retrieve email. The POP protocol is a simple one; a little experimentation
 * with GenericClient should allow you to figure out how it works. (Be careful
 * not to delete any important email!)
 *
 * For this excercise write a client program named Checkmail that uses the POP
 * protocol to check a user's mail. It should output the number of messages that
 * are waiting to be retrieved and display the From line of each message. This
 * client should not use the POP dele command to delete mail messages from
 * the server; it should simply display a summary of the messages waiting to be
 * retrieved. In order to read mail messages, this client has to know the host-
 * name of the POP server and has to send a username and password to the
 * server. Your program may obtain the hostname, username, and password
 * from the command line or by prompting the user, but should ideally get this
 * information by reading a configuration file. Consider a java.util.Properties
 * object to implement such a configuration file.
 *
 * @author Matthew Feldt <developer@feldt.com>
 * @version 1.1, 04/20/2001 22:17
 */

package com.feldt.examples.net;
import java.io.*;
import java.net.*;
import java.util.*;
import java.text.*;
import javax.mail.internet.MailDateFormat;

public class Checkmail {
	private String mailhost, username, password;
	private int mailport;
	private Socket sock;
	private BufferedReader in;
	private PrintWriter out;
	protected boolean isConnected;
	public static final String MAIL_PORT = "110"; // default mail port

	/** construct a POP connection with the specified properties */
	Checkmail(String host, int port, String user, String pass) {
		mailhost = host;
		mailport = port;
		username = user;
		password = pass;
		isConnected = false;
	}

	/**
	 * construct a POP connection with the specified properties
	 *  and default mail port
	 */
	Checkmail(String host, String user, String pass) {
		this(host, Integer.parseInt(MAIL_PORT), user, pass);
	}

	/** connect and log in to the specified POP server */
	public void connect() throws IOException {
		String response;

		if (isConnected) return;

		// connect to the specified host and port
		sock = new Socket(mailhost, mailport);

		// configure socket io streams
		in = new BufferedReader(new InputStreamReader(sock.getInputStream()));
		out = new PrintWriter(sock.getOutputStream(), true);

		// log in
		response = in.readLine(); // consume welcome banner
		out.println("user " + username); // send username
		response = in.readLine(); // consume "+OK please send PASS command"
		out.println("pass " + password); // send password
		response = in.readLine(); // confirm password accepted
		if (response.substring(0, 3).compareTo("+OK") != 0)
			throw new IOException(response);

		isConnected = true; // set connected flag
	}

	/** close POP connection and update isConnected flag */
	public void close() throws IOException {
		sock.close();
		isConnected = false;
	}

	/** format a decimal with leading spaces */
	private String decimalFormat(long number, int length) {
		DecimalFormat df = new DecimalFormat("###0");
		StringBuffer result = new StringBuffer();
		FieldPosition pos = new FieldPosition(NumberFormat.INTEGER_FIELD);

		df.format(number, result, pos);
		if (pos.getEndIndex() < length) {
			char[] padding = new char[length-pos.getEndIndex()];
			for (int i = 0; i < padding.length; i++) padding[i] = ' ';
			result.insert(0, padding);
		}

		// result.length() can be greater than spaces
		return new String(result);
	}

	/** format email address */
	private String emailFormat(String email, int length) {
		int open, close;
		String result = email;

		if ((open = email.indexOf('<')) != -1) // address bound by <>
			if ((close = email.indexOf('>')) != -1)
				result = email.substring(open+1, close);

		return formatStringLength(result, length, true);
	}

	/** format the date */
	private String dateFormat(String in, int length) {
		MailDateFormat mf = new MailDateFormat();
		SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd yyyy HH:mm");
		Date date = null;

		// trap parse error and continue
		try { date = mf.parse(in); } catch(ParseException e) {}

		// format what we got or return a properly formatted date
		if (date == null) return formatStringLength(in, length, true);
		else return sdf.format(date);
	}

	/** return a string of 'length' length */
	private String formatStringLength(String in, int length, boolean pad) {
		String out = in;

		if (pad) {
			if (out.length() < length) { // pad with spaces if length() < length
				char[] padding = new char[length-out.length()];
				for (int i = 0; i < padding.length; i++) padding[i] = ' ';
				out += new String(padding);
			}
		}

		if (out.length() > length) { // truncate if length() > length
			out = out.substring(0, length);
		}

		return out;
	}

	/** get mail headers from specified pop server (Checkmail object) */
	public void printHeaderSummary() throws IOException {
		final int DATE_LENGTH = 21;
		final int FROM_LENGTH = 20;
		final int MESSAGECOUNT_LENGTH = 4;
		final int SUBJECT_LENGTH = 27;
		String response, from = null, subject = null, date = null;
		int messageCount;
		boolean header;

		if (! isConnected) throw new IOException("not connected.");

		// set up a flushed system output stream
		PrintWriter sysOutFlushed = new PrintWriter(System.out, true);

		out.println("stat"); // get messages count
		StringTokenizer token = new StringTokenizer(response = in.readLine());
		if ((token.countTokens() != 3) || (token.nextToken().compareTo("-ERR") == 0))
			throw new IOException("stat error: " + response);
		messageCount = Integer.parseInt(token.nextToken());

		// request messages in order and print header summary
		for (int i = 1; i <= messageCount; i++) {
			header = true;
			out.println("retr " + i);
			while (true) {
				response = in.readLine();
				if (response.compareTo(".") == 0) break; // end of message
				// head and body separater by blank line
				if ((header) && (response.compareTo("") == 0)) header = false;
				if (header) { // only review headers
					if (response.startsWith("From: ")) {
						from = response.substring(6);  // remove From:
					}
					if (response.startsWith("Subject: ")) {
						subject = response.substring(9); // remove Subject:
					}
					if (response.startsWith("Date: ")) {
						date = response.substring(6); // remove Date:
					}
				}
			}
			sysOutFlushed.println(decimalFormat(i, MESSAGECOUNT_LENGTH) + " " +
				emailFormat(from, FROM_LENGTH) + "  " +
				dateFormat(date, DATE_LENGTH) + "  \"" +
				formatStringLength(subject, SUBJECT_LENGTH, false) + "\"");
		}
	}


	/**
	 * get configuration from a Properties file, or prompt the user
	 * for missing values. optionally will save queried values to a
	 * Properties file.
	 */
	protected static Checkmail getCheckmailConfig(String filename)
			throws FileNotFoundException, IllegalArgumentException, IOException {
		final String HOST_KEY_STRING = "mailhost"; // property file key strings
		final String USER_KEY_STRING = "username";
		final String PASS_KEY_STRING = "password";
		final String PORT_KEY_STRING = "mailport";
		String host = null, user = null , pass = null, port = null, response;
		BufferedReader userInput = new BufferedReader(
			new InputStreamReader(System.in));
		boolean prompted = false;

		Properties p = new Properties();
		if (filename != null) { // load Properties is filename was supplied
			File f = new File(filename);
			if (! f.exists()) fail(filename + ": no such file.");
			if (! f.canRead()) fail(filename + ": read protected.");
			if (! f.isFile()) fail(filename + ": is not a regular file.");
			p.load(new FileInputStream(f));
			host = p.getProperty(HOST_KEY_STRING);
			port = p.getProperty(PORT_KEY_STRING);
			user = p.getProperty(USER_KEY_STRING);
			pass = p.getProperty(PASS_KEY_STRING);
		}

		if (host == null) {
			System.out.print("Enter mailhost > ");
			host = userInput.readLine();
			p.setProperty(HOST_KEY_STRING, host);
			prompted = true;
		}
		if (port == null) {
			System.out.print("Enter mailport > ");
			port = userInput.readLine();
			p.setProperty(PORT_KEY_STRING, port);
			prompted = true;
		}
		if (user == null) {
			System.out.print("Enter username > ");
			user = userInput.readLine();
			p.setProperty(USER_KEY_STRING, user);
			prompted = true;
		}
		if (pass == null) {
			System.out.print("Enter password > ");
			pass = userInput.readLine();
			p.setProperty(PASS_KEY_STRING, pass);
			prompted = true;
		}

		// if user prompted for input see if they want to save
		if (prompted) {
			System.out.print("Save configuration [y/n] > ");
			response = userInput.readLine();
			if (response.compareToIgnoreCase("y") == 0) {
				System.out.print("Configuration filename > ");
				response = userInput.readLine();
				// currently will overwrite existing file
				p.store(new FileOutputStream(response), null);
				System.out.println("Configuration saved.");
			}
		}
		return new Checkmail(host, Integer.parseInt(port), user, pass);
	}

	/** shorthand method to throw an exception with the appropriate message */
	protected static void fail(String msg) throws IllegalArgumentException {
		throw new IllegalArgumentException(msg);
	}

	/** test class */
	static class Test {
		public static void main(String[] args) throws IOException {
			final String USAGE = "Usage: java Checkmail$Test [<filename>]";
			String configFile = null;
			Checkmail cm;

			// parse the command line
			if (args.length != 0 && args.length != 1) fail(USAGE);
			// config file supplied on command line
			if (args.length == 1) configFile = args[0];

			try {
				cm = Checkmail.getCheckmailConfig(configFile);
				cm.connect(); // open Checkmail connection
				cm.printHeaderSummary(); // print header summary
				cm.close(); // close Checkmail connection
			} catch(FileNotFoundException e){
				System.err.println(e.getMessage());
				System.exit(-1);
			} catch(IllegalArgumentException e) {
				System.err.println(e.getMessage());
				System.exit(-1);
			} catch(IOException e) {
				System.err.println(e.getMessage());
				System.exit(-1);
			}
		}
	}
}