package org.apache.maven.it;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PushbackInputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A simple HTTP proxy that only understands the CONNECT method to check HTTPS tunneling.
 *
 * @author Benjamin Bentmann
 */
public class TunnelingProxyServer
    implements Runnable
{

    private int port;

    private volatile ServerSocket server;

    private String targetHost;

    private int targetPort;

    private String connectFilter;

    public TunnelingProxyServer( int port, String targetHost, int targetPort, String connectFilter )
    {
        this.port = port;
        this.targetHost = targetHost;
        this.targetPort = targetPort;
        this.connectFilter = connectFilter;
    }

    public int getPort()
    {
        return ( server != null ) ? server.getLocalPort() : port;
    }

    public void start()
        throws IOException
    {
        server = new ServerSocket( port, 4 );
        new Thread( this ).start();
    }

    public void stop()
        throws IOException
    {
        if ( server != null )
        {
            server.close();
            server = null;
        }
    }

    public void run()
    {
        try
        {
            while ( true )
            {
                new ClientHandler( server.accept() ).start();
            }
        }
        catch ( Exception e )
        {
            // closed
        }
    }

    class ClientHandler
        extends Thread
    {

        private Socket client;

        public ClientHandler( Socket client )
        {
            this.client = client;
        }

        public void run()
        {
            try
            {
                PushbackInputStream is = new PushbackInputStream( client.getInputStream() );

                String dest = null;

                while ( true )
                {
                    String line = readLine( is );
                    if ( line == null || line.length() <= 0 )
                    {
                        break;
                    }
                    Matcher m = Pattern.compile( "CONNECT +([^:]+:[0-9]+) +.*" ).matcher( line );
                    if ( m.matches() )
                    {
                        dest = m.group( 1 );
                    }
                }

                OutputStream os = client.getOutputStream();

                if ( dest == null || ( connectFilter != null && !dest.matches( connectFilter ) ) )
                {
                    os.write( ( "HTTP/1.0 400 Bad request for " + dest + "\r\n\r\n" ).getBytes( "UTF-8" ) );
                    return;
                }

                os.write( "HTTP/1.0 200 Connection established\r\n\r\n".getBytes( "UTF-8" ) );

                Socket server = new Socket( targetHost, targetPort );

                Thread t1 = new StreamPumper( is, server.getOutputStream() );
                t1.start();
                Thread t2 = new StreamPumper( server.getInputStream(), os );
                t2.start();
                t1.join();
                t2.join();

                server.close();
            }
            catch ( Exception e )
            {
                e.printStackTrace();
            }
            finally
            {
                try
                {
                    client.close();
                }
                catch ( IOException e )
                {
                    e.printStackTrace();
                }
            }
        }

        private String readLine( PushbackInputStream is )
            throws IOException
        {
            StringBuilder buffer = new StringBuilder( 1024 );

            while ( true )
            {
                int b = is.read();
                if ( b < 0 )
                {
                    return null;
                }
                else if ( b == '\n' )
                {
                    break;
                }
                else if ( b == '\r' )
                {
                    b = is.read();
                    if ( b != '\n' )
                    {
                        is.unread( b );
                    }
                    break;
                }
                else
                {
                    buffer.append( (char) b );
                }
            }

            return buffer.toString();
        }

    }

    static class StreamPumper
        extends Thread
    {

        private final InputStream is;

        private final OutputStream os;

        public StreamPumper( InputStream is, OutputStream os )
        {
            this.is = is;
            this.os = os;
        }

        public void run()
        {
            try
            {
                for ( byte[] buffer = new byte[1024 * 8]; ; )
                {
                    int n = is.read( buffer );
                    if ( n < 0 )
                    {
                        break;
                    }
                    os.write( buffer, 0, n );
                }
            }
            catch ( IOException e )
            {
                // closed
            }
            finally
            {
                try
                {
                    is.close();
                }
                catch ( IOException e )
                {
                    e.printStackTrace();
                }
                try
                {
                    os.close();
                }
                catch ( IOException e )
                {
                    e.printStackTrace();
                }
            }
        }

    }

}