/*
 ** Authored by Timothy Gerard Endres
 ** <mailto:time@gjt.org>  <http://www.trustice.com>
 ** 
 ** This work has been placed into the public domain.
 ** You may use this work in any way and for any purpose you wish.
 **
 ** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
 ** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
 ** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
 ** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
 ** REDISTRIBUTION OF THIS SOFTWARE. 
 ** 
 */

package com.ice.tar;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.GZIPInputStream;

/**
 * Special class designed to parse a Tar archive VERY FAST.
 * This class is not a general Tar archive solution because
 * it does not accomodate TarBuffer, or blocking. It does not
 * allow you to read the entries either. This would not be
 * difficult to add in a subclass.
 *
 * The real purpose of this class is that there are folks out
 * there who wish to parse an ENORMOUS tar archive, and maybe
 * only want to know the filenames, or they wish to locate the
 * offset of a particular entry so that can process that entry
 * with special code.
 *
 * @author Timothy Gerard Endres, <time@gjt.org>
 *
 */

public class FastTarStream
{
    private boolean debug = false;
    private boolean hasHitEOF = false;
    private TarEntry currEntry = null;
    private InputStream inStream = null;
    private int recordSize = TarBuffer.DEFAULT_RCDSIZE;

    public FastTarStream(InputStream in)
    {
        this(in, TarBuffer.DEFAULT_RCDSIZE);
    }

    public FastTarStream(InputStream in, int recordSize)
    {
        this.inStream = in;
        this.hasHitEOF = false;
        this.currEntry = null;
        this.recordSize = recordSize;
    }

    public void setDebug(boolean debug)
    {
        this.debug = debug;
    }

    public TarEntry getNextEntry() throws IOException
    {
        if (this.hasHitEOF)
            return null;

        /**
         * Here I have tried skipping the entry size, I have tried
         * skipping entrysize - header size,
         * entrysize + header, and all seem to skip to some bizzarelocation!
         */
        if (this.currEntry != null && this.currEntry.getSize() > 0)
        {
            // Need to round out the number of records to be read to skip entry...
            int numRecords = ((int) this.currEntry.getSize() + (this.recordSize - 1)) / this.recordSize;

            if (numRecords > 0)
            {
                this.inStream.skip(numRecords * this.recordSize);
            }
        }

        byte[] headerBuf = new byte[this.recordSize];

        // NOTE Apparently (with GZIPInputStream maybe?) we are able to
        //      read less then record size bytes in any given read(). So,
        //      we have to be persistent.

        int bufIndex = 0;
        for (int bytesNeeded = this.recordSize; bytesNeeded > 0;)
        {
            int numRead = this.inStream.read(headerBuf, bufIndex, bytesNeeded);

            if (numRead == -1)
            {
                this.hasHitEOF = true;
                break;
            }

            bufIndex += numRead;
            bytesNeeded -= numRead;
        }

        // Check for "EOF block" of all zeros
        if (!this.hasHitEOF)
        {
            this.hasHitEOF = true;
            for (int i = 0; i < headerBuf.length; ++i)
            {
                if (headerBuf[i] != 0)
                {
                    this.hasHitEOF = false;
                    break;
                }
            }
        }

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

                if (this.debug)
                {
                    byte[] by = new byte[headerBuf.length];
                    for (int i = 0; i < headerBuf.length; i++)
                    {
                        by[i] = (headerBuf[i] == 0 ? 20 : headerBuf[i]);
                    }
                    String s = new String(by);
                    System.out.println("\n" + s);
                }

                if (!(headerBuf[257] == 'u' && headerBuf[258] == 's' && headerBuf[259] == 't' && headerBuf[260] == 'a' && headerBuf[261] == 'r'))
                {
                    throw new InvalidHeaderException("header magic is not'ustar', but '" + headerBuf[257] + headerBuf[258] + headerBuf[259] + headerBuf[260]
                                    + headerBuf[261] + "', or (dec) " + ((int) headerBuf[257]) + ", " + ((int) headerBuf[258]) + ", " + ((int) headerBuf[259])
                                    + ", " + ((int) headerBuf[260]) + ", " + ((int) headerBuf[261]));
                }
            }
            catch (InvalidHeaderException ex)
            {
                this.currEntry = null;
                throw ex;
            }
        }

        return this.currEntry;
    }

    public static void main(String[] args)
    {
        boolean debug = false;
        InputStream in = null;

        try
        {
            int idx = 0;
            if (args.length > 0)
            {
                if (args[idx].equals("-d"))
                {
                    debug = true;
                    idx++;
                }

                if (args[idx].endsWith(".gz") || args[idx].endsWith(".tgz"))
                {
                    in = new GZIPInputStream(new FileInputStream(args[idx]));
                }
                else
                {
                    in = new FileInputStream(args[idx]);
                }
            }
            else
            {
                in = System.in;
            }

            FastTarStream fts = new FastTarStream(in);
            fts.setDebug(debug);

            int nameWidth = 56;
            int sizeWidth = 9;
            int userWidth = 8;
            StringBuilder padBuf = new StringBuilder(128);
            for (;;)
            {
                TarEntry entry = fts.getNextEntry();
                if (entry == null)
                    break;

                if (entry.isDirectory())
                {
                    // TYPE
                    System.out.print("D ");

                    // NAME
                    padBuf.setLength(0);
                    padBuf.append(entry.getName());
                    padBuf.setLength(padBuf.length() - 1); // drop '/'
                    if (padBuf.length() > nameWidth)
                        padBuf.setLength(nameWidth);
                    for (; padBuf.length() < nameWidth;)
                        padBuf.append('_');

                    padBuf.append('_');
                    System.out.print(padBuf.toString());

                    // SIZE
                    padBuf.setLength(0);
                    for (; padBuf.length() < sizeWidth;)
                        padBuf.insert(0, '_');

                    padBuf.append(' ');
                    System.out.print(padBuf.toString());

                    // USER
                    padBuf.setLength(0);
                    padBuf.append(entry.getUserName());
                    if (padBuf.length() > userWidth)
                        padBuf.setLength(userWidth);
                    for (; padBuf.length() < userWidth;)
                        padBuf.append(' ');

                    System.out.print(padBuf.toString());
                }
                else
                {
                    // TYPE
                    System.out.print("F ");

                    // NAME
                    padBuf.setLength(0);
                    padBuf.append(entry.getName());
                    if (padBuf.length() > nameWidth)
                        padBuf.setLength(nameWidth);
                    for (; padBuf.length() < nameWidth;)
                        padBuf.append(' ');

                    padBuf.append(' ');
                    System.out.print(padBuf.toString());

                    // SIZE
                    padBuf.setLength(0);
                    padBuf.append(entry.getSize());
                    if (padBuf.length() > sizeWidth)
                        padBuf.setLength(sizeWidth);
                    for (; padBuf.length() < sizeWidth;)
                        padBuf.insert(0, ' ');

                    padBuf.append(' ');
                    System.out.print(padBuf.toString());

                    // USER
                    padBuf.setLength(0);
                    padBuf.append(entry.getUserName());
                    if (padBuf.length() > userWidth)
                        padBuf.setLength(userWidth);
                    for (; padBuf.length() < userWidth;)
                        padBuf.append(' ');

                    System.out.print(padBuf.toString());
                }

                System.out.println("");
            }
        }
        catch (IOException ex)
        {
            ex.printStackTrace(System.err);
        }
    }
}