// ProxyNewsDb - proxy netnews database
//
// Copyright (C) 1996 by Jef Poskanzer <jef@mail.acme.com>.  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.Nnrpd;

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

/// Proxy netnews database.
// <P>
// This is a news database that forwards requests to a remote news server.
// <P>
// <A HREF="/resources/classes/Acme/Nnrpd/ProxyNewsDb.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class ProxyNewsDb extends NewsDb
    {

    // This switch is for getting around the "LIKE_PULLERS DONT" option
    // in INN 1.5+.  In INN 1.5.1 the option is completely broken, and
    // admins have to set "LIKE_PULLERS DO" in order to get acceptable
    // reader performance.  In versions after that, ...?
    private static final boolean avoidArticleHack = false;

    private String host;
    private int port;
    private Socket socket;
    private boolean postingOk;
    private String[] overviewFmt = null;
    private OverviewCache overviewCache;

    // The object's synchronization is basically on the I/O streams.
    private DataInputStream din;
    private PrintStream pout;

    // Group cache.
    private Hashtable groupTable = null;
    private long groupsFetched;

    // Group descriptions cache.
    private Hashtable groupDescsTable = null;
    private long groupDescsFetched;

    // State variables.
    private NewsDbGroup currentGroup = null;
    private int currentArtNum = -1;

    /// Constructor.
    // The proxyHost string should be "hostname:portnum", or just a
    // hostname in which case the default netnews port will be used.
    // @param proxyHost the remote news server to connect to
    // @param oCacheSize how many overview entries to save in the cache
    // @exception NewsDbException if something goes wrong
    public ProxyNewsDb( String proxyHost, int oCacheSize ) throws NewsDbException
	{
	int colon = proxyHost.indexOf( ':' );
	if ( colon == -1 )
	    {
	    host = proxyHost;
	    port = NnrpdUtils.DEFAULT_PORT;
	    }
	else
	    {
	    host = proxyHost.substring( 0, colon );
	    port = Utils.parseInt(
		proxyHost.substring( colon + 1 ), NnrpdUtils.DEFAULT_PORT );
	    }

	try
	    {
	    socket = new Socket( host, port );
	    din = new DataInputStream( new BufferedInputStream(
		socket.getInputStream() ) );
	    pout = new PrintStream( new CrLfOutputStream(
		new BufferedOutputStream( socket.getOutputStream() ) ) );
	    }
	catch ( IOException e )
	    {
	    throw new NewsDbException(
		"problem opening socket to " + host + ": " + e );
	    }

	// Read initial response.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 200:
	    postingOk = true;
	    break;
	    case 201:
	    postingOk = false;
	    break;
	    case 502:
	    throw new NewsDbException( "no read permission on " + host );
	    default:
	    throw new NewsDbException(
		"unexpected response to " + host + " initial connect: " +
		Utils.flattenStrarr( resp ) );
	    }

	// Do SLAVE command - it probably does nothing, but it's in the spec.
	pout.println( NnrpdUtils.CMD_SLAVE );
	resp = readResp();
	// Ignore response.

	// See if there's an overview database.  First try a LIST schema.
	pout.println( NnrpdUtils.CMD_LIST + " schema" );
	resp = readResp();
	respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 215:
	    try
		{
		overviewFmt = Utils.splitStr( NnrpdUtils.readText( din ) );
		}
	    catch ( IOException ignore ) {}
	    break;
	    default:
	    // That didn't work.  Now try a LIST overview.fmt.
	    pout.println( NnrpdUtils.CMD_LIST + " overview.fmt" );
	    resp = readResp();
	    respNum = Utils.parseInt( resp[0], -1 );
	    switch ( respNum )
		{
		case 215:
		try
		    {
		    overviewFmt = Utils.splitStr( NnrpdUtils.readText( din ) );
		    }
		catch ( IOException ignore ) {}
		break;
		default:
		break;
		}
	    break;
	    }
	if ( overviewFmt != null )
	    {
	    for ( int i = 0; i < overviewFmt.length; ++i )
		if ( overviewFmt[i].endsWith( ":" ) )
		    overviewFmt[i] = overviewFmt[i].substring(
			0, overviewFmt[i].length() - 1 );
	    overviewCache = new OverviewCache( oCacheSize );
	    }
	}

    /// Attempt authorization.
    // @exception NewsDbException if something goes wrong
    public boolean authorize( String user, String password ) throws NewsDbException
	{
	pout.println( NnrpdUtils.CMD_AUTHINFO + " USER " + user );
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 381:
	    pout.println( NnrpdUtils.CMD_AUTHINFO + " PASS " + password );
	    resp = readResp();
	    respNum = Utils.parseInt( resp[0], -1 );
	    switch ( respNum )
		{
		case 281:
		return true;
		case 502:
		return false;
		default:
		throw new NewsDbException(
		    "unexpected response to AUTHINFO command: " +
		    Utils.flattenStrarr( resp ) );
		}
	    default:
	    throw new NewsDbException(
		"unexpected response to AUTHINFO command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Whether posting is allowed.
    // @exception NewsDbException if something goes wrong
    public boolean getPostingOk() throws NewsDbException
	{
	return postingOk;
	}

    /// Get a group by name.
    // @exception NewsDbException if something goes wrong
    public synchronized NewsDbGroup getGroup( String groupName ) throws NewsDbException
	{
	// First check current group.
	if ( currentGroup != null &&
	     groupName.equals( currentGroup.getName() ) )
	    return currentGroup;
	// Next check group cache.
	checkGroups();
	NewsDbGroup group = (NewsDbGroup) groupTable.get( groupName );
	if ( group != null )
	    return group;
	// Not there.  Try a GROUP command just to be sure.
	return setGroup( groupName );
	}

    /// Set the remote server's current group.
    private synchronized NewsDbGroup setGroup( String groupName ) throws NewsDbException
	{
	pout.println( NnrpdUtils.CMD_GROUP + " " + groupName );
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 211:
	    try
		{
		currentGroup = new NewsDbGroup(
		    dbStamp, resp[4],
		    Integer.parseInt( resp[1] ),
		    Integer.parseInt( resp[2] ),
		    Integer.parseInt( resp[3] ),
		    '?', (String) groupDescsTable.get( groupName ) );
		}
	    catch ( NumberFormatException e )
		{
		throw new NewsDbException(
		    "unparsable numbers in response to GROUP command: " +
		    Utils.flattenStrarr( resp ) );
		}
	    currentArtNum = currentGroup.getFirstArtNum();
	    // Might as well put it in the group cache.
	    groupTable.put( currentGroup.getName(), currentGroup );
	    return currentGroup;
	    case 411:
	    return null;
	    default:
	    throw new NewsDbException(
		"unexpected response to GROUP command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an article by group and number.
    // @exception NewsDbException if something goes wrong
    public synchronized NewsDbArticle getArticle( NewsDbGroup group, int artNum ) throws NewsDbException
	{
	// Check that this group is one of ours.
	if ( group.getDbStamp() != dbStamp )
	    throw new NewsDbException( "mismatched database stamps" );
	// Make sure it's the current group on the remote server.
	if ( currentGroup == null ||
	     ! group.getName().equals( currentGroup.getName() ) )
	    setGroup( group.getName() );
	// Do the ARTICLE command.
	pout.println( NnrpdUtils.CMD_ARTICLE + " " + artNum );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 220:
	    currentArtNum = artNum;
	    String text;
	    try
		{
		text = NnrpdUtils.readText( din );
		}
	    catch ( IOException e )
		{
		throw new NewsDbException( "problem fetching article: " + e );
		}
	    return new NewsDbArticle( dbStamp, text );
	    case 423:
	    return null;
	    default:
	    throw new NewsDbException(
		"unexpected response to ARTICLE command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an article by message-id.
    // @exception NewsDbException if something goes wrong
    public synchronized NewsDbArticle getArticle( String messageId ) throws NewsDbException
	{
	// Do the ARTICLE command.
	pout.println( NnrpdUtils.CMD_ARTICLE + " " + messageId );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 220:
	    String text;
	    try
		{
		text = NnrpdUtils.readText( din );
		}
	    catch ( IOException e )
		{
		throw new NewsDbException( "problem fetching article: " + e );
		}
	    return new NewsDbArticle( dbStamp, text );
	    case 430:
	    return null;
	    default:
	    throw new NewsDbException(
		"unexpected response to ARTICLE command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    // Remember the most recent names array that matched, so we can do
    // a quick address compare instead of a more expensive content compare.
    private String[] lastOkNames = null;

    /// Get specified headers from a range of articles by group and number.
    // Some implementations have special faster methods for getting
    // headers from articles, e.g. an XOVER command to a remote server
    // or a local overview database.  If no such fast method is available,
    // this returns null and the caller should fall back on conventional
    // means.
    // @exception NewsDbException if something goes wrong
    public synchronized String[][] getHeaders( String[] names, NewsDbGroup group, int firstArtNum, int lastArtNum ) throws NewsDbException
	{
	// Do we have an XOVER database?
	if ( overviewFmt == null )
	    return null;
	// Is the names list the same as overviewFmt?
	if ( names != lastOkNames )
	    {
	    if ( ! Utils.equalsStrings( names, overviewFmt ) )
		return null;
	    lastOkNames = names;
	    }
	// Check that this group is one of ours.
	if ( group.getDbStamp() != dbStamp )
	    throw new NewsDbException( "mismatched database stamps" );
	// Do we need to refresh overview data for this group?
	long now = System.currentTimeMillis();
	long time = overviewCache.getLastTime( group );
	if ( time == -1 || now - time >= NnrpdUtils.INT_CHECKOVERVIEW )
	    {
	    readOverview( group );
	    overviewCache.setLastTime( group );
	    }
	// Now just get articles from the cache.
	int numArts = lastArtNum - firstArtNum + 1;
	String[][] results = new String[numArts][];
	// Check if we already have cached results for any of these articles.
	for ( int i = 0; i < numArts; ++i )
	    {
	    int artNum = firstArtNum + i;
	    results[i] = overviewCache.getEntry( group, artNum );
	    }
	return results;
	}

    private void readOverview( NewsDbGroup group ) throws NewsDbException
	{
	// Make sure it's the current group on the remote server.
	if ( currentGroup == null ||
	     ! group.getName().equals( currentGroup.getName() ) )
	    setGroup( group.getName() );
	// Do the XOVER command.
	pout.println(
	    NnrpdUtils.CMD_XOVER + " " +
	    group.getFirstArtNum() + "-" + group.getLastArtNum() );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 224:
	    while ( true )
		{
		String line;
		try
		    {
		    line = din.readLine();
		    }
		catch ( IOException e )
		    {
		    break;
		    }
		if ( line == null || line.equals( "." ) )
		    break;
		int tab = line.indexOf( '\t' );
		int artNum;
		try
		    {
		    artNum = Integer.parseInt( line.substring( 0, tab ) );
		    }
		catch ( NumberFormatException e )
		    {
		    continue;
		    }
		String[] overviewEntry =
		    Utils.splitStr( line.substring( tab + 1 ), '\t' );
		if ( overviewEntry.length != overviewFmt.length )
		    continue;	// ignore malformed lines
		overviewCache.addEntry( overviewEntry, group, artNum );
		}
	    break;
	    default:
	    throw new NewsDbException(
		"unexpected response to XOVER command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all the groups.
    // @exception NewsDbException if something goes wrong
    public Enumeration getGroups() throws NewsDbException
	{
	checkGroups();
	return groupTable.elements();
	}

    /// Get an enumeration of all groups created after a given time.
    // @exception NewsDbException if something goes wrong
    public synchronized Enumeration getGroups( long since ) throws NewsDbException
	{
	// Do the NEWGROUPS command.
	pout.println(
	    NnrpdUtils.CMD_NEWGROUPS + " " +
	    NnrpdUtils.rfc977DateTime( since ) );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 231:
	    return readGroups().elements();
	    default:
	    throw new NewsDbException(
		"unexpected response to NEWGROUPS command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all groups created after a given time that match
    // a given distributions pattern.
    // @exception NewsDbException if something goes wrong
    public synchronized Enumeration getGroups( long since, String distsPat ) throws NewsDbException
	{
	// Do the NEWGROUPS command.
	pout.println(
	    NnrpdUtils.CMD_NEWGROUPS + " " +
	    NnrpdUtils.rfc977DateTime( since ) + " " + distsPat );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 231:
	    return readGroups().elements();
	    default:
	    throw new NewsDbException(
		"unexpected response to NEWGROUPS command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all message-ids received after a given time
    // in groups matching the given pattern.
    // @exception NewsDbException if something goes wrong
    public Enumeration getMessageIds( String groupsPat, long since ) throws NewsDbException
	{
	// !!! This is purposely not implemented yet, because the NEWNEWS
	// command takes too long and would tie up the connection to the
	// remote server.  At some point I'll do an implementation which
	// opens up a second connection just for this one command.
	Vector messageIds = new Vector();
	return messageIds.elements();
	}

    /// Get an enumeration of all message-ids received after a given time
    // in groups matching the given pattern, that also match the
    // given distributions pattern.
    // @exception NewsDbException if something goes wrong
    public Enumeration getMessageIds( String groupsPat, long since, String distsPat ) throws NewsDbException
	{
	// !!! This is purposely not implemented yet, because the NEWNEWS
	// command takes too long and would tie up the connection to the
	// remote server.  At some point I'll do an implementation which
	// opens up a second connection just for this one command.
	Vector messageIds = new Vector();
	return messageIds.elements();
	}


    /// Post an article.
    // @exception NewsDbException if something goes wrong
    public synchronized void post( String artText ) throws NewsDbException
	{
	// Do the POST command.
	pout.println( NnrpdUtils.CMD_POST );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 340:
	    pout.print( artText );
	    pout.println( "." );
	    // Get and interpret results.
	    resp = readResp();
	    respNum = Utils.parseInt( resp[0], -1 );
	    switch ( respNum )
		{
		case 240:
		// Ok!
		break;
		case 441:
		throw new NewsDbException(
		    "post failed: " + Utils.flattenStrarr( resp ) );
		default:
		throw new NewsDbException(
		    "unexpected response to posted article: " +
		    Utils.flattenStrarr( resp ) );
		}
	    break;
	    default:
	    throw new NewsDbException(
		"unexpected response to POST command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Shut down the news database.
    public synchronized void close()
	{
	pout.println( NnrpdUtils.CMD_QUIT );
	try
	    {
	    din.close();
	    pout.flush();
	    pout.close();
	    socket.close();
	    }
	catch ( IOException ignore ) {}
	}


    /// Read a response from the server, and return it split into words.
    private synchronized String[] readResp() throws NewsDbException
	{
	pout.flush();
	String line;
	try
	    {
	    line = din.readLine();
	    }
	catch ( IOException e )
	    {
	    throw new NewsDbException(
		"problem reading remote response: " + e );
	    }
	if ( line == null || line.length() == 0 )
	    throw new NewsDbException( "problem reading remote response" );
	return Utils.splitStr( line );
	}

    /// Read the list of groups, if necessary.
    private synchronized void checkGroups() throws NewsDbException
	{
	checkGroupDescs();	// check group descriptions cache too
	long now = System.currentTimeMillis();
	if ( groupTable != null &&
	     now - groupsFetched < NnrpdUtils.INT_CHECKGROUPS )
	    return;
	// Do the LIST command.
	pout.println( NnrpdUtils.CMD_LIST );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 215:
	    groupTable = readGroups();
	    groupsFetched = now;
	    return;
	    default:
	    throw new NewsDbException(
		"unexpected response to LIST command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Read the list of groups descriptions, if necessary.
    private synchronized void checkGroupDescs() throws NewsDbException
	{
	long now = System.currentTimeMillis();
	if ( groupDescsTable != null &&
	     now - groupDescsFetched < NnrpdUtils.INT_CHECKGROUPDESCS )
	    return;
	// Do the LIST newsgroups command.
	pout.println( NnrpdUtils.CMD_LIST + " newsgroups" );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 215:
	    groupDescsTable = new Hashtable();
	    String line, groupName, groupDesc;
	    int ws, nws;
	    while ( true )
		{
		try
		    {
		    line = din.readLine();
		    }
		catch ( IOException e )
		    {
		    break;
		    }
		if ( line == null || line.equals( "." ) )
		    break;
		ws = Utils.strCSpan( line, " \t" );
		nws = ws + Utils.strSpan( line, " \t", ws );
		groupName = line.substring( 0, ws );
		groupDesc = line.substring( nws );
		groupDescsTable.put( groupName, groupDesc );
		}
	    groupDescsFetched = now;
	    return;
	    default:
	    throw new NewsDbException(
		"unexpected response to LIST newsgroups command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Read a list of groups.
    private synchronized Hashtable readGroups() throws NewsDbException
	{
	Hashtable gt = new Hashtable();
	String line;
	String[] words;
	String groupName;
	int lastArtNum, firstArtNum;
	char flag;
	NewsDbGroup group;
	while ( true )
	    {
	    try
		{
		line = din.readLine();
		}
	    catch ( IOException e )
		{
		break;
		}
	    if ( line == null || line.equals( "." ) )
		break;
	    words = Utils.splitStr( line );
	    groupName = words[0];
	    try
		{
		lastArtNum = Integer.parseInt( words[1] );
		firstArtNum = Integer.parseInt( words[2] );
		}
	    catch ( NumberFormatException e )
		{
		continue;
		}
	    flag = words[3].charAt( 0 );
	    group = new NewsDbGroup(
		dbStamp, groupName, lastArtNum - firstArtNum + 1,
		firstArtNum, lastArtNum, flag,
		(String) groupDescsTable.get( groupName ) );
	    gt.put( group.getName(), group );
	    }
	return gt;
	}

    }