/*
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.mail;

import java.lang.*;
import java.lang.reflect.*;
import java.io.*;
import java.net.*;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Properties;
import java.util.StringTokenizer;
import java.util.Vector;

import javax.activation.*;

import com.sun.mail.util.LineInputStream;

/**
 * The Session class represents a mail session and is not subclassed.
 * It collects together properties and defaults used by the mail API's.
 * A single default session can be shared by multiple applications on the
 * desktop.  Unshared sessions can also be created.
 *
 * @version 1.47, 00/10/23
 * @author John Mani
 * @author Bill Shannon
 * @author Max Spivak
 */

public final class Session {

    private Properties props;
    private Authenticator authenticator;
    private Hashtable authTable = new Hashtable();
    private boolean debug = false;
    private Vector providers = new Vector();
    private Hashtable providersByProtocol = new Hashtable();
    private Hashtable providersByClassName = new Hashtable();
    private Properties addressMap = new Properties();  // maps type to protocol
    private static Method getResources = null;
    private static Method getSystemResources = null;

    static {
	try {
	    Class c = java.lang.ClassLoader.class;
	    // assume both succeed or both fail
	    getResources = c.getMethod("getResources",
				    new Class[] { String.class });
	    getSystemResources = c.getMethod("getSystemResources",
				    new Class[] { String.class });
	} catch (Throwable t) { }	// ignore any errors
    }
    
    // The default session.
    private static Session defaultSession = null;

    // Constructor is not public
    private Session(Properties props, Authenticator authenticator) {
	this.props = props;
	this.authenticator = authenticator;

	if (Boolean.valueOf(props.getProperty("mail.debug")).booleanValue())
	    debug = true;

	// get the Class associated with the Authenticator
	Class cl;
	if (authenticator != null)
	    cl = authenticator.getClass();
	else
	    cl = this.getClass();
	// load the resources
	loadProviders(cl);
	loadAddressMap(cl);
    }

    /**
     * Get a new Session object.
     *
     * @param	props	Properties object that hold relevant properties.<br>
     *                  It is expected that the client supplies values
     *                  for the properties listed in Appendix A of the
     *                  JavaMail spec (particularly  mail.store.protocol, 
     *                  mail.transport.protocol, mail.host, mail.user, 
     *                  and mail.from) as the defaults are unlikely to 
     *                  work in all cases.
     * @param	authenticator Authenticator object used to call back to
     *			the application when a user name and password is
     *			needed.
     * @return		a new Session object
     * @see	javax.mail.Authenticator
     */
    public static Session getInstance(Properties props,
					Authenticator authenticator) {
	return new Session(props, authenticator);
    }

    /**
     * Get a new Session object.
     *
     * @param	props	Properties object that hold relevant properties.<br>
     *                  It is expected that the client supplies values
     *                  for the properties listed in Appendix A of the
     *                  JavaMail spec (particularly  mail.store.protocol, 
     *                  mail.transport.protocol, mail.host, mail.user, 
     *                  and mail.from) as the defaults are unlikely to 
     *                  work in all cases.
     * @return		a new Session object
     * @since		JavaMail 1.2
     */
    public static Session getInstance(Properties props) {
	return new Session(props, null);
    }

    /**
     * Get the default Session object. If a default has not yet been
     * setup, a new Session object is created and installed as the 
     * default. <p>
     *
     * Since the default session is potentially available to all
     * code executing in the same Java virtual machine, and the session
     * can contain security sensitive information such as user names
     * and passwords, access to the default session is restricted.
     * The Authenticator object, which must be created by the caller,
     * is used indirectly to check access permission.  The Authenticator
     * object passed in when the session is created is compared with
     * the Authenticator object passed in to subsequent requests to
     * get the default session.  If both objects are the same, or are
     * from the same ClassLoader, the request is allowed.  Otherwise,
     * it is denied.  <p>
     *
     * Note that if the Authenticator object used to create the session
     * is null, anyone can get the default session by passing in null.  <p>
     *
     * In JDK 1.2, additional security Permission objects may be used to
     * control access to the default session.
     *
     * @param	props	Properties object. Used only if a new Session
     *			object is created.<br>
     *                  It is expected that the client supplies values
     *                  for the properties listed in Appendix A of the
     *                  JavaMail spec (particularly  mail.store.protocol, 
     *                  mail.transport.protocol, mail.host, mail.user, 
     *                  and mail.from) as the defaults are unlikely to 
     *                  work in all cases.
     * @param	authenticator Authenticator object.  Used only if a
     *			new Session object is created.  Otherwise, 
     *			it must match the Authenticator used to create
     *			the Session.
     * @return		the default Session object
     */
    public static Session getDefaultInstance(Properties props,
					Authenticator authenticator) {
	if (defaultSession == null)
	    defaultSession = new Session(props, authenticator);
	else {
	    // have to check whether caller is allowed to see default session
	    if (defaultSession.authenticator == authenticator)
		;	// either same object or both null, either way OK
	    else if (defaultSession.authenticator != null &&
		    authenticator != null &&
		    defaultSession.authenticator.getClass().getClassLoader() ==
			authenticator.getClass().getClassLoader())
		;	// both objects came from the same class loader, OK
	    else
		// anything else is not allowed
		throw new SecurityException("Access to default session denied");
	}

	return defaultSession;
    }

    /**
     * Get the default Session object. If a default has not yet been
     * setup, a new Session object is created and installed as the 
     * default. <p>
     *
     * Note that a default session created with no Authenticator is
     * available to all code executing in the same Java virtual
     * machine, and the session can contain security sensitive
     * information such as user names and passwords.
     *
     * @param	props	Properties object. Used only if a new Session
     *			object is created.<br>
     *                  It is expected that the client supplies values
     *                  for the properties listed in Appendix A of the
     *                  JavaMail spec (particularly  mail.store.protocol, 
     *                  mail.transport.protocol, mail.host, mail.user, 
     *                  and mail.from) as the defaults are unlikely to 
     *                  work in all cases.
     * @return		the default Session object
     * @since		JavaMail 1.2
     */
    public static Session getDefaultInstance(Properties props) {
        return getDefaultInstance(props, null);
    }

    /**
     * Set the debug setting for this Session.
     * <p>
     * Since the debug setting can be turned on only after the Session
     * has been created, to turn on debugging in the Session
     * constructor, set the property <code>mail.debug</code> in the
     * Properties object passed in to the constructor to true.  The
     * value of the <code>mail.debug</code> property is used to
     * initialize the per-Session debugging flag.  Subsequent calls to
     * the <code>setDebug</code> method manipulate the per-Session
     * debugging flag and have no affect on the <code>mail.debug</code>
     * property.
     *
     * @param debug	Debug setting
     */
    public void setDebug(boolean debug) {
	this.debug = debug;
    }

    /**
     * Get the debug setting for this Session.
     *
     * @return current debug setting
     */
    public boolean getDebug() {
	return debug;
    }

    /**
     * This method returns an array of all the implementations installed 
     * via the javamail.[default.]providers files that can
     * be loaded using the ClassLoader available to this application.
     *
     * @return Array of configured providers
     */
    public Provider[] getProviders() {
	Provider[] _providers = new Provider[providers.size()];
	providers.copyInto(_providers);
	return _providers;
    }

    /**
     * Returns the default Provider for the protocol
     * specified. Checks mail.<protocol>.class property
     * first and if it exists, returns the Provider
     * associated with this implementation. If it doesn't exist, 
     * returns the Provider that appeared first in the 
     * configuration files. If an implementation for the protocol 
     * isn't found, throws NoSuchProviderException
     *
     * @param  protocol  Configured protocol (i.e. smtp, imap, etc)
     * @return Currently configured Provider for the specified protocol
     * @exception	NoSuchProviderException If a provider for the given
     *			protocol is not found.
     */
    public Provider getProvider(String protocol)
	                                throws NoSuchProviderException {

	if (protocol == null || protocol.length() <= 0) {
	    throw new NoSuchProviderException("Invalid protocol: null");
	}

	Provider _provider = null;

	// check if the mail.<protocol>.class property exists
	String _className = props.getProperty("mail."+protocol+".class");
	if (_className != null) {
	    if (debug) {
		System.out.println("DEBUG: mail."+protocol+
				   ".class property exists and points to " + 
				   _className);
	    }
	    _provider = (Provider)providersByClassName.get(_className);
	} 

	if (_provider != null) {
	    return _provider;
	} else {
	    // returning currently default protocol in providersByProtocol
	    _provider = (Provider)providersByProtocol.get(protocol);
	}

	if (_provider == null) {
	    throw new NoSuchProviderException("No provider for " + protocol);
	} else {
	    if (debug) {
		System.out.println("\nDEBUG: getProvider() returning " + 
				   _provider.toString());
	    }
	    return _provider;
	}
    }

    /**
     * Set the passed Provider to be the default implementation
     * for the protocol in Provider.protocol overriding any previous values.
     *
     * @param provider Currently configured Provider which will be 
     * set as the default for the protocol
     * @exception	NoSuchProviderException If the provider passed in
     *			is invalid.
     */
    public void setProvider(Provider provider) throws NoSuchProviderException {
	if (provider == null) {
	    throw new NoSuchProviderException("Can't set null provider");
	}
	providersByProtocol.put(provider.getProtocol(), provider);
	props.put("mail." + provider.getProtocol() + ".class", 
		  provider.getClassName());
    }


    /**
     * Get a Store object that implements this user's desired Store
     * protocol. The <code>mail.store.protocol</code> property specifies the
     * desired protocol. If an appropriate Store object is not obtained, 
     * NoSuchProviderException is thrown
     *
     * @return 		a Store object 
     * @exception	NoSuchProviderException If a provider for the given
     *			protocol is not found.
     */
    public Store getStore() throws NoSuchProviderException {
	return getStore(getProperty("mail.store.protocol"));
    }

    /**
     * Get a Store object that implements the specified protocol. If an
     * appropriate Store object cannot be obtained, 
     * NoSuchProviderException is thrown.
     *
     * @param	        protocol
     * @return		a Store object 
     * @exception	NoSuchProviderException If a provider for the given
     *			protocol is not found.
     */
    public Store getStore(String protocol) throws NoSuchProviderException {
	return getStore(new URLName(protocol, null, -1, null, null, null));
    }


    /**
     * Get a Store object for the given URLName. If the requested Store
     * object cannot be obtained, NoSuchProviderException is thrown.
     *
     * The "scheme" part of the URL string (Refer RFC 1738) is used 
     * to locate the Store protocol. <p>
     *
     * @param	url	URLName that represents the desired Store
     * @return		a closed Store object
     * @see		#getFolder(URLName)
     * @see		javax.mail.URLName
     * @exception	NoSuchProviderException If a provider for the given
     *			URLName is not found.
     */
    public Store getStore(URLName url) throws NoSuchProviderException {
	String protocol = url.getProtocol();
	Provider p = getProvider(protocol);
	return getStore(p, url);
    }

    /**
     * Get an instance of the store specified by Provider. Instantiates
     * the store and returns it.
     * 
     * @param provider Store Provider that will be instantiated
     * @return Instantiated Store
     * @exception	NoSuchProviderException If a provider for the given
     *			Provider is not found.
     */
    public Store getStore(Provider provider) throws NoSuchProviderException {
	return getStore(provider, null);
    }


    /**
     * Get an instance of the store specified by Provider. If the URLName
     * is not null, uses it, otherwise creates a new one. Instantiates
     * the store and returns it. This is a private method used by
     * getStore(Provider) and getStore(URLName)
     * 
     * @param provider Store Provider that will be instantiated
     * @param url      URLName used to instantiate the Store
     * @return Instantiated Store
     * @exception	NoSuchProviderException If a provider for the given
     *			Provider/URLName is not found.
     */
    private Store getStore(Provider provider, URLName url) 
	throws NoSuchProviderException {

	// make sure we have the correct type of provider
	if (provider == null || provider.getType() != Provider.Type.STORE ) {
	    throw new NoSuchProviderException("invalid provider");
	}
		
	try {
	    return (Store) getService(provider, url);
	} catch (ClassCastException cce) {
	    throw new NoSuchProviderException("incorrect class");
	}
    }

    /**
     * Get a closed Folder object for the given URLName. If the requested
     * Folder object cannot be obtained, null is returned. <p>
     *
     * The "scheme" part of the URL string (Refer RFC 1738) is used
     * to locate the Store protocol. The rest of the URL string (that is,
     * the "schemepart", as per RFC 1738) is used by that Store
     * in a protocol dependent manner to locate and instantiate the
     * appropriate Folder object. <p>
     *
     * Note that RFC 1738 also specifies the syntax for the 
     * "schemepart" for IP-based protocols (IMAP4, POP3, etc.).
     * Providers of IP-based mail Stores should implement that
     * syntax for referring to Folders. <p>
     *
     * @param	url	URLName that represents the desired folder
     * @return		Folder
     * @see		#getStore(URLName)
     * @see		javax.mail.URLName
     * @exception	NoSuchProviderException If a provider for the given
     *			URLName is not found.
     * @exception	MessagingException if the Folder could not be 
     *			located or created.
     */
    public Folder getFolder(URLName url)
		throws MessagingException {
	// First get the Store
	Store store = getStore(url);
	store.connect();
	return store.getFolder(url);
    }

    /**
     * Get a Transport object that implements this user's desired 
     * Transport protcol. The <code>mail.transport.protocol</code> property 
     * specifies the desired protocol. If an appropriate Transport 
     * object cannot be obtained, MessagingException is thrown.
     *
     * @return 		a Transport object 
     * @exception	NoSuchProviderException If the provider is not found.
     */
    public Transport getTransport() throws NoSuchProviderException {
        return getTransport(getProperty("mail.transport.protocol"));
    }

    /**
     * Get a Transport object that implements the specified protocol.
     * If an appropriate Transport object cannot be obtained, null is
     * returned.
     *
     * @return 		a Transport object 
     * @exception	NoSuchProviderException If provider for the given
     *			protocol is not found.
     */
    public Transport getTransport(String protocol)
				throws NoSuchProviderException {
	return getTransport(new URLName(protocol, null, -1, null, null, null));
    }


    /**
     * Get a Transport object for the given URLName. If the requested 
     * Transport object cannot be obtained, NoSuchProviderException is thrown.
     *
     * The "scheme" part of the URL string (Refer RFC 1738) is used 
     * to locate the Transport protocol. <p>
     *
     * @param	url	URLName that represents the desired Transport
     * @return		a closed Transport object
     * @see		javax.mail.URLName
     * @exception	NoSuchProviderException If a provider for the given
     *			URLName is not found.
     */
    public Transport getTransport(URLName url) throws NoSuchProviderException {
	String protocol = url.getProtocol();
	Provider p = getProvider(protocol);
	return getTransport(p, url);
    }

    /**
     * Get an instance of the transport specified in the Provider. Instantiates
     * the transport and returns it.
     * 
     * @param provider Transport Provider that will be instantiated
     * @return Instantiated Transport
     * @exception	NoSuchProviderException If provider for the given
     *			provider is not found.
     */
    public Transport getTransport(Provider provider) 
	                                     throws NoSuchProviderException {
	return getTransport(provider, null);
    }

    /**
     * Get a Transport object that can transport a Message to the
     * specified address type.
     *
     * @param	address
     * @return	A Transport object
     * @see javax.mail.Address
     * @exception	NoSuchProviderException If provider for the 
     *			Address type is not found
     */
    public Transport getTransport(Address address) 
	                                     throws NoSuchProviderException {

	String transportProtocol = (String)addressMap.get(address.getType());
	if (transportProtocol == null) {
	    throw new NoSuchProviderException("No provider for Address type: "+
					      address.getType());
	} else {
	    return getTransport(transportProtocol);
	}
    }

    /**
     * Get a Transport object using the given provider and urlname.
     *
     * @param	provider	the provider to use
     * @param	url		urlname to use (can be null)
     * @return A Transport object
     * @exception	NoSuchProviderException	If no provider or the provider
     *			was the wrong class.	
     */

    private Transport getTransport(Provider provider, URLName url)
					throws NoSuchProviderException {
	// make sure we have the correct type of provider
	if (provider == null || provider.getType() != Provider.Type.TRANSPORT) {
	    throw new NoSuchProviderException("invalid provider");
	}

	try {
	    return (Transport) getService(provider, url);
	} catch (ClassCastException cce) {
	    throw new NoSuchProviderException("incorrect class");
	}
    }

    /**
     * Get a Service object.  Needs a provider object, but will
     * create a URLName if needed.  It attempts to instantiate
     * the correct class.
     *
     * @param provider	which provider to use
     * @param url	which URLName to use (can be null)
     * @exception	NoSuchProviderException	thrown when the class cannot be
     *			found or when it does not have the correct constructor
     *			(Session, URLName), or if it is not derived from
     *			Service.
     */
    private Object getService(Provider provider, URLName url)
					throws NoSuchProviderException {
	// need a provider and url
	if (provider == null) {
	    throw new NoSuchProviderException("null");
	}

	// create a url if needed
	if (url == null) {
	    url = new URLName(provider.getProtocol(), null, -1, 
			      null, null, null);
	}

	Object service = null;
	
	// get the ClassLoader associated with the Authenticator
	ClassLoader cl;
	if (authenticator != null)
	    cl = authenticator.getClass().getClassLoader();
	else
	    cl = this.getClass().getClassLoader();

	// now load the class
	Class serviceClass = null;
	try {
	    // First try the "application's" class loader.
	    // This should eventually be replaced by
	    // Thread.currentThread().getContextClassLoader().
	    serviceClass = cl.loadClass(provider.getClassName());
	} catch (Exception ex1) {
	    // That didn't work, now try the "system" class loader.
	    // (Need both of these because JDK 1.1 class loaders
	    // may not delegate to their parent class loader.)
	    try {
		serviceClass = Class.forName(provider.getClassName());
	    } catch (Exception ex) {
		// Nothing worked, give up.
		if (debug) ex.printStackTrace();
		throw new NoSuchProviderException(provider.getProtocol());
	    }
	}

	// construct an instance of the class
	try {
	    Class[] c = {javax.mail.Session.class, javax.mail.URLName.class};
	    Constructor cons = serviceClass.getConstructor(c);

	    Object[] o = {this, url};
	    service = cons.newInstance(o);

	} catch (Exception ex) {
	    if (debug) ex.printStackTrace();
	    throw new NoSuchProviderException(provider.getProtocol());
	}

	return service;
    }

    /**
     * Save a PasswordAuthentication for this (store or transport) URLName.
     * If pw is null the entry corresponding to the URLName is removed.
     * <p>
     * This is normally used only by the store or transport implementations
     * to allow authentication information to be shared among multiple
     * uses of a session.
     */
    public void setPasswordAuthentication(URLName url,
					  PasswordAuthentication pw) {
	if (pw == null)
	    authTable.remove(url);
	else
	    authTable.put(url, pw);
    }

    /**
     * Return any saved PasswordAuthentication for this (store or transport)
     * URLName.  Normally used only by store or transport implementations.
     *
     * @return	the PasswordAuthentication corresponding to the URLName
     */
    public PasswordAuthentication getPasswordAuthentication(URLName url) {
	return (PasswordAuthentication)authTable.get(url);
    }

    /**
     * Call back to the application to get the needed user name and password.
     * The application should put up a dialog something like:
     * <p> <pre>
     * Connecting to <protocol> mail service on host <addr>, port <port>.
     * <prompt>
     *
     * User Name: <defaultUserName>
     * Password:
     * </pre>
     *
     * @param	addr		InetAddress of the host.  may be null.
     * @param	protocol	protocol scheme (e.g. imap, pop3, etc.)
     * @param	prompt		any additional String to show as part of
     *                          the prompt; may be null.
     * @param	defaultUserName	the default username. may be null.
     * @return	the authentication which was collected by the authenticator; 
     *          may be null.
     */
    public PasswordAuthentication requestPasswordAuthentication(
	InetAddress addr, int port,
	String protocol, String prompt, String defaultUserName) {

	if (authenticator != null) {
	    return authenticator.requestPasswordAuthentication(
		addr, port, protocol, prompt, defaultUserName);
	} else {
	    return null;
	}
    }

    /**
     * Returns the Properties object associated with this Session
     *
     * @return		Properties object
     */
    public Properties getProperties() { 
   	return props; 
    }

    /**
     * Returns the value of the specified property. Returns null
     * if this property does not exist.
     *
     * @return		String that is the property value
     */
    public String getProperty(String name) { 
   	return props.getProperty(name); 
    }

    private void loadProviders(Class cl) {
	// load system-wide javamail.providers from the <java.home>/lib dir
	// since we have an absolute path to the file, use FileInputStream
	InputStream javahomeProviderStream = null;
	try {
	    String res = System.getProperty("java.home") + 
	    			File.separator + "lib" + 
				File.separator + "javamail.providers";
	    javahomeProviderStream =
		new BufferedInputStream(new FileInputStream(res));
	    if (javahomeProviderStream != null) {
		loadProvidersFromStream(javahomeProviderStream);
		javahomeProviderStream.close();
		if (debug)
		    pr("DEBUG: loaded providers in <java.home>/lib");
	    } else {
		if (debug)
		    pr("DEBUG: not loading system providers in <java.home>/lib");
	    }
	} catch (FileNotFoundException fex) { /*ignore: don't load resource*/ 
	    if (debug)
		pr("DEBUG: not loading system providers in <java.home>/lib");
	} catch (IOException ioex) { /*ignore: don't load resource*/
	    if (debug)
		pr("DEBUG: " + ioex.getMessage());
	} catch (SecurityException sex) { /*ignore: don't load resource*/ 
	    if (debug)
		pr("DEBUG: not loading system providers in <java.home>/lib");
	}
	
	// load the META-INF/javamail.providers file supplied by an application
	// first try loading the resource file using the app classloader
	// if it fails, try loading it as system res.
	InputStream appProviderStream = null;
	final String clappRes = "META-INF/javamail.providers";
	final String appRes = "/" + clappRes;
	boolean anyLoaded = false;

	if (getResources != null) {
	    try {
		Enumeration e;
		ClassLoader cld = cl.getClassLoader();
		if (cld != null)
		    e = (Enumeration)getResources.invoke(
				cld, new String[] { clappRes });
		else
		    e = (Enumeration)getSystemResources.invoke(
				cld, new String[] { clappRes });
		while (e.hasMoreElements()) {
		    URL url = (URL)e.nextElement();
		    appProviderStream = url.openStream();
		    if (appProviderStream != null) {
			try {
			    loadProvidersFromStream(appProviderStream);
			    anyLoaded = true;
			    appProviderStream.close();
			    if (debug)
				pr("DEBUG: successfully loaded " +
				    "optional custom providers from URL: " +
				    url);
			} catch (IOException ioex) {
			    if (debug)
				pr("DEBUG: " + ioex.getMessage());
			}
		    } else {
			if (debug)
			    pr("DEBUG: not loading optional custom providers " +
				"from URL: " + url);
		    }
		}
	    } catch (Exception ex) {
		if (debug)
		    pr("DEBUG: " + ex);
	    }
	}

	// if failed to load anything, fall back to old technique, just in case
	if (!anyLoaded) {
	    appProviderStream = cl.getResourceAsStream(appRes);
	    if (appProviderStream != null) {
		try {
		    loadProvidersFromStream(appProviderStream);
		    appProviderStream.close();
		    if (debug)
			pr("DEBUG: successfully loaded " +
			    "optional custom providers: " + appRes);
		} catch (IOException ioex) {
		    if (debug)
			pr("DEBUG: " + ioex);
		}
	    } else {
		if (debug)
		    pr("DEBUG: not loading optional custom providers file: " + 
		       appRes);
	    }
	}

	// load default META-INF/javamail.default.providers from mail.jar file
	InputStream defProviderStream = null;
	String defRes = "/META-INF/javamail.default.providers";
	defProviderStream = cl.getResourceAsStream(defRes);
	if (defProviderStream != null) {
	    try {
		loadProvidersFromStream(defProviderStream);
		defProviderStream.close();
		if (debug)
		    pr("DEBUG: successfully loaded default providers");
	    } catch (IOException ioex) {
		if (debug)
		    pr("DEBUG: " + ioex.getMessage());
	    }
	} else {
	    if (debug)
		pr("DEBUG: can't load default providers file" + defRes);
	}


	if (debug) {
	    System.out.println("\nDEBUG: Tables of loaded providers");
	    // dump the output of the tables for debugging
	    //pr("DEBUG: --- Providers Listed By Class Name --------");
	    //System.out.println("size " + providersByClassName.size());
	    pr("DEBUG: Providers Listed By Class Name: " + 
	       providersByClassName.toString());

	    //pr("\nDEBUG: --- Providers Listed By Protocol ---------");
	    //System.out.println("size " + providersByProtocol.size());
	    pr("DEBUG: Providers Listed By Protocol: " + 
	       providersByProtocol.toString());
	}
    }

    private void loadProvidersFromStream(InputStream is) 
				throws IOException {
	if (is != null) {
	    LineInputStream lis = new LineInputStream(is);
	    String currLine;

	    // load and process one line at a time using LineInputStream
	    while ((currLine = lis.readLine()) != null) {

		if (currLine.startsWith("#"))
		    continue;
		Provider.Type type = null;
		String protocol = null, className = null;
		String vendor = null, version = null;
		    
		// separate line into key-value tuples
		StringTokenizer tuples = new StringTokenizer(currLine,";");
		while (tuples.hasMoreTokens()) {
		    String currTuple = tuples.nextToken().trim();
			
		    // set the value of each attribute based on its key
		    int sep = currTuple.indexOf("=");
		    if (currTuple.startsWith("protocol=")) {
			protocol = currTuple.substring(sep+1);
		    } else if (currTuple.startsWith("type=")) {
			String strType = currTuple.substring(sep+1);
			if (strType.equalsIgnoreCase("store")) {
			    type = Provider.Type.STORE;
			} else if (strType.equalsIgnoreCase("transport")) {
			    type = Provider.Type.TRANSPORT;
		    	}
		    } else if (currTuple.startsWith("class=")) {
			className = currTuple.substring(sep+1);
		    } else if (currTuple.startsWith("vendor=")) {
			vendor = currTuple.substring(sep+1);
		    } else if (currTuple.startsWith("version=")) {
			version = currTuple.substring(sep+1);
		    }
		}

		// check if a valid Provider; else, continue
		if (type == null || protocol == null || className == null 
		    || protocol.length() <= 0 || className.length() <= 0) {
			
		    if (debug)
			System.out.println("DEBUG: Bad provider entry: " + 
					       currLine);
		    continue;
		}
		Provider provider = new Provider(type, protocol, className,
					         vendor, version);

		// add the newly-created Provider to the lookup tables
		providers.addElement(provider);
		providersByClassName.put(className, provider);
		if (!providersByProtocol.containsKey(protocol)) {
		    providersByProtocol.put(protocol, provider);
		}
	    }
	}
    }

    // load maps in reverse order of preference so that the preferred
    // map is loaded last since its entries will override the previous ones
    private void loadAddressMap(Class cl) {
	// load default META-INF/javamail.default.address.map from mail.jar
	// first try loading the resource file using the app classloader
	// if it fails, try loading it as system res.
	InputStream defAddressStream = null;
	String defRes = "/META-INF/javamail.default.address.map";
	defAddressStream = cl.getResourceAsStream(defRes);
	if (defAddressStream != null) {
	    try {
		addressMap.load(defAddressStream);
		defAddressStream.close();
	    } catch (IOException ioex) { /* ignore it */ 
	    } catch (SecurityException sex) { /* ignore it */ }
	}
	
	// load the META-INF/javamail.address.map file supplied by an app
	// first try loading the resource file using the app classloader
	// if it fails, try loading it as system res.
	InputStream appAddressStream = null;
	final String clappRes = "META-INF/javamail.address.map";
	final String appRes = "/" + clappRes;
	boolean anyLoaded = false;

	if (getResources != null) {
	    try {
		Enumeration e;
		ClassLoader cld = cl.getClassLoader();
		if (cld != null)
		    e = (Enumeration)getResources.invoke(
				cld, new String[] { clappRes });
		else
		    e = (Enumeration)getSystemResources.invoke(
				cld, new String[] { clappRes });
		while (e.hasMoreElements()) {
		    URL url = (URL)e.nextElement();
		    appAddressStream = url.openStream();
		    if (appAddressStream != null) {
			try {
			    addressMap.load(appAddressStream);
			    anyLoaded = true;
			    appAddressStream.close();
			    if (debug)
				pr("DEBUG: successfully loaded " +
				    "optional address map from URL: " + url);
			} catch (IOException ioex) {
			    if (debug)
				pr("DEBUG: " + ioex.getMessage());
			}
		    } else {
			if (debug)
			    pr("DEBUG: not loading optional address map " +
				"from URL: " + url);
		    }
		}
	    } catch (Exception ex) {
		if (debug)
		    pr("DEBUG: " + ex);
	    }
	}

	// if failed to load anything, fall back to old technique, just in case
	if (!anyLoaded) {
	    appAddressStream = cl.getResourceAsStream(appRes);
	    if (appAddressStream != null) {
		try {
		    addressMap.load(appAddressStream);
		    appAddressStream.close();
		    if (debug)
			pr("DEBUG: successfully loaded " +
			    "optional address map: " + appRes);
		} catch (IOException ioex) {
		    if (debug)
			pr("DEBUG: " + ioex);
		}
	    } else {
		if (debug)
		    pr("DEBUG: not loading optional address map file: " + 
		       appRes);
	    }
	}


	// load system-wide javamail.address.map from the <java.home>/lib dir
	// since we have an absolute path to the file, use FileInputStream
	InputStream javahomeAddressStream = null;
	try {
	    String res = System.getProperty("java.home") + 
				File.separator + "lib" + 
				File.separator + "javamail.address.map";
	    javahomeAddressStream =
		new BufferedInputStream(new FileInputStream(res));
	} catch (FileNotFoundException fex) { 
	    /*ignore: don't load resource*/ 
	} catch (SecurityException sex) { 
	    /*ignore: don't load resource*/ 
	}
	if (javahomeAddressStream != null) {
	    try {
		addressMap.load(javahomeAddressStream);
		javahomeAddressStream.close();
	    } catch (IOException ioex) { /* ignore it */ }
	}
    }

    private static void pr(String str) {
	System.out.println(str);
    }
}