package org.codehaus.plexus.archiver.tar;

/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  Licensed 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.
 *
 */

/*
 * This package is based on the work done by Timothy Gerard Endres
 * (time@ice.com) to whom the Ant project is very grateful for his great code.
 */

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * The TarInputStream reads a UNIX tar archive as an InputStream.
 * methods are provided to position at each successive entry in
 * the archive, and the read each entry as a normal input stream
 * using read().
 *
 * @version $Revision$ $Date$
 *          from org.apache.ant.tools.tar.TarInputStream v1.16
 */
public class TarInputStream
    extends FilterInputStream
{
    protected boolean debug;

    protected boolean hasHitEOF;

    protected int entrySize;

    protected int entryOffset;

    protected byte[] oneBuf;

    protected byte[] readBuf;

    protected TarBuffer buffer;

    protected TarEntry currEntry;

    public TarInputStream( InputStream is )
    {
        this( is, TarBuffer.DEFAULT_BLKSIZE, TarBuffer.DEFAULT_RCDSIZE );
    }

    public TarInputStream( InputStream is, int blockSize )
    {
        this( is, blockSize, TarBuffer.DEFAULT_RCDSIZE );
    }

    public TarInputStream( InputStream is, int blockSize, int recordSize )
    {
        super( is );

        this.buffer = new TarBuffer( is, blockSize, recordSize );
        this.readBuf = null;
        this.oneBuf = new byte[1];
        this.debug = false;
        this.hasHitEOF = false;
    }

    /**
     * Sets the debugging flag.
     *
     * @param debug True to turn on debugging.
     */
    public void setDebug( boolean debug )
    {
        this.debug = debug;
        this.buffer.setDebug( debug );
    }

    /**
     * Closes this stream. Calls the TarBuffer's close() method.
     */
    public void close()
        throws IOException
    {
        this.buffer.close();
    }

    /**
     * Get the record size being used by this stream's TarBuffer.
     *
     * @return The TarBuffer record size.
     */
    public int getRecordSize()
    {
        return this.buffer.getRecordSize();
    }

    /**
     * Get the available data that can be read from the current
     * entry in the archive. This does not indicate how much data
     * is left in the entire archive, only in the current entry.
     * This value is determined from the entry's size header field
     * and the amount of data already read from the current entry.
     *
     * @return The number of available bytes for the current entry.
     */
    public int available()
        throws IOException
    {
        return this.entrySize - this.entryOffset;
    }

    /**
     * Skip bytes in the input buffer. This skips bytes in the
     * current entry's data, not the entire archive, and will
     * stop at the end of the current entry's data if the number
     * to skip extends beyond that point.
     *
     * @param numToSkip The number of bytes to skip.
     */
    public long skip( long numToSkip )
        throws IOException
    {
        // REVIEW
        // This is horribly inefficient, but it ensures that we
        // properly skip over bytes via the TarBuffer...
        //
        byte[] skipBuf = new byte[8 * 1024];
        long skip = numToSkip;
        while ( skip > 0 )
        {
            int realSkip = (int) ( skip > skipBuf.length ? skipBuf.length : skip );
            int numRead = this.read( skipBuf, 0, realSkip );
            if ( numRead == -1 )
            {
                break;
            }
            skip -= numRead;
        }
        return ( numToSkip - skip );
    }

    /**
     * Since we do not support marking just yet, we return false.
     *
     * @return False.
     */
    public boolean markSupported()
    {
        return false;
    }

    /**
     * Since we do not support marking just yet, we do nothing.
     *
     * @param markLimit The limit to mark.
     */
    public void mark( int markLimit )
    {
    }

    /**
     * Since we do not support marking just yet, we do nothing.
     */
    public void reset()
    {
    }

    /**
     * Get the next entry in this tar archive. This will skip
     * over any remaining data in the current entry, if there
     * is one, and place the input stream at the header of the
     * next entry, and read the header and instantiate a new
     * TarEntry from the header bytes and return that entry.
     * If there are no more entries in the archive, null will
     * be returned to indicate that the end of the archive has
     * been reached.
     *
     * @return The next TarEntry in the archive, or null.
     */
    public TarEntry getNextEntry()
        throws IOException
    {
        if ( this.hasHitEOF )
        {
            return null;
        }

        if ( this.currEntry != null )
        {
            int numToSkip = this.entrySize - this.entryOffset;

            if ( this.debug )
            {
                System.err.println( "TarInputStream: SKIP currENTRY '" + this.currEntry.getName() + "' SZ "
                    + this.entrySize + " OFF " + this.entryOffset + "  skipping " + numToSkip + " bytes" );
            }

            if ( numToSkip > 0 )
            {
                this.skip( numToSkip );
            }

            this.readBuf = null;
        }

        byte[] headerBuf = this.buffer.readRecord();

        if ( headerBuf == null )
        {
            if ( this.debug )
            {
                System.err.println( "READ NULL RECORD" );
            }
            this.hasHitEOF = true;
        }
        else if ( this.buffer.isEOFRecord( headerBuf ) )
        {
            if ( this.debug )
            {
                System.err.println( "READ EOF RECORD" );
            }
            this.hasHitEOF = true;
        }

        if ( this.hasHitEOF )
        {
            this.currEntry = null;
        }
        else
        {
            this.currEntry = new TarEntry( headerBuf );

            if ( this.debug )
            {
                System.err.println( "TarInputStream: SET CURRENTRY '" + this.currEntry.getName() + "' size = "
                    + this.currEntry.getSize() );
            }

            this.entryOffset = 0;

            // REVIEW How do we resolve this discrepancy?!
            this.entrySize = (int) this.currEntry.getSize();
        }

        if ( this.currEntry != null && this.currEntry.isGNULongNameEntry() )
        {
            // read in the name
            StringBuffer longName = new StringBuffer();
            byte[] buffer = new byte[256];
            int length;
            while ( ( length = read( buffer ) ) >= 0 )
            {
                longName.append( new String( buffer, 0, length ) );
            }
            getNextEntry();

            // remove trailing null terminator
            if ( longName.length() > 0
                 && longName.charAt( longName.length() - 1 ) == 0 )
            {
                longName.deleteCharAt( longName.length() - 1 );
            }
            this.currEntry.setName( longName.toString() );
        }

        return this.currEntry;
    }

    /**
     * Reads a byte from the current tar archive entry.
     * <p/>
     * This method simply calls read( byte[], int, int ).
     *
     * @return The byte read, or -1 at EOF.
     */
    public int read()
        throws IOException
    {
        int num = this.read( this.oneBuf, 0, 1 );

        if ( num == -1 )
        {
            return num;
        }
        else
        {
            return (int) this.oneBuf[ 0 ];
        }
    }

    /**
     * Reads bytes from the current tar archive entry.
     * <p/>
     * This method simply calls read( byte[], int, int ).
     *
     * @param buf The buffer into which to place bytes read.
     * @return The number of bytes read, or -1 at EOF.
     */
    public int read( byte[] buf )
        throws IOException
    {
        return this.read( buf, 0, buf.length );
    }

    /**
     * Reads bytes from the current tar archive entry.
     * <p/>
     * This method is aware of the boundaries of the current
     * entry in the archive and will deal with them as if they
     * were this stream's start and EOF.
     *
     * @param buf       The buffer into which to place bytes read.
     * @param offset    The offset at which to place bytes read.
     * @param numToRead The number of bytes to read.
     * @return The number of bytes read, or -1 at EOF.
     */
    public int read( byte[] buf, int offset, int numToRead )
        throws IOException
    {
        int totalRead = 0;

        if ( this.entryOffset >= this.entrySize )
        {
            return -1;
        }

        if ( ( numToRead + this.entryOffset ) > this.entrySize )
        {
            numToRead = ( this.entrySize - this.entryOffset );
        }

        if ( this.readBuf != null )
        {
            int sz = ( numToRead > this.readBuf.length ) ? this.readBuf.length : numToRead;

            System.arraycopy( this.readBuf, 0, buf, offset, sz );

            if ( sz >= this.readBuf.length )
            {
                this.readBuf = null;
            }
            else
            {
                int newLen = this.readBuf.length - sz;
                byte[] newBuf = new byte[newLen];

                System.arraycopy( this.readBuf, sz, newBuf, 0, newLen );

                this.readBuf = newBuf;
            }

            totalRead += sz;
            numToRead -= sz;
            offset += sz;
        }

        while ( numToRead > 0 )
        {
            byte[] rec = this.buffer.readRecord();

            if ( rec == null )
            {
                // Unexpected EOF!
                throw new IOException( "unexpected EOF with " + numToRead + " bytes unread" );
            }

            int sz = numToRead;
            int recLen = rec.length;

            if ( recLen > sz )
            {
                System.arraycopy( rec, 0, buf, offset, sz );

                this.readBuf = new byte[recLen - sz];

                System.arraycopy( rec, sz, this.readBuf, 0, recLen - sz );
            }
            else
            {
                sz = recLen;

                System.arraycopy( rec, 0, buf, offset, recLen );
            }

            totalRead += sz;
            numToRead -= sz;
            offset += sz;
        }

        this.entryOffset += totalRead;

        return totalRead;
    }

    /**
     * Copies the contents of the current tar archive entry directly into
     * an output stream.
     *
     * @param out The OutputStream into which to write the entry's data.
     */
    public void copyEntryContents( OutputStream out )
        throws IOException
    {
        byte[] buf = new byte[32 * 1024];

        while ( true )
        {
            int numRead = this.read( buf, 0, buf.length );

            if ( numRead == -1 )
            {
                break;
            }

            out.write( buf, 0, numRead );
        }
    }
}
