/*
 *  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.
 *
 */

package org.apache.tools.zip;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.util.Calendar;
import java.util.Date;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import java.util.zip.ZipException;

/**
 * Replacement for <code>java.util.ZipFile</code>.
 *
 * <p>This class adds support for file name encodings other than UTF-8
 * (which is required to work on ZIP files created by native zip tools
 * and is able to skip a preamble like the one found in self
 * extracting archives.  Furthermore it returns instances of
 * <code>org.apache.tools.zip.ZipEntry</code> instead of
 * <code>java.util.zip.ZipEntry</code>.</p>
 *
 * <p>It doesn't extend <code>java.util.zip.ZipFile</code> as it would
 * have to reimplement all methods anyway.  Like
 * <code>java.util.ZipFile</code>, it uses RandomAccessFile under the
 * covers and supports compressed and uncompressed entries.</p>
 *
 * <p>The method signatures mimic the ones of
 * <code>java.util.zip.ZipFile</code>, with a couple of exceptions:
 *
 * <ul>
 *   <li>There is no getName method.</li>
 *   <li>entries has been renamed to getEntries.</li>
 *   <li>getEntries and getEntry return
 *   <code>org.apache.tools.zip.ZipEntry</code> instances.</li>
 *   <li>close is allowed to throw IOException.</li>
 * </ul>
 *
 */
public class ZipFile {
    private static final int HASH_SIZE = 509;
    private static final int SHORT     =   2;
    private static final int WORD      =   4;
    private static final int NIBLET_MASK = 0x0f;
    private static final int BYTE_SHIFT = 8;
    private static final int POS_0 = 0;
    private static final int POS_1 = 1;
    private static final int POS_2 = 2;
    private static final int POS_3 = 3;

    /**
     * Maps ZipEntrys to Longs, recording the offsets of the local
     * file headers.
     */
    private Hashtable entries = new Hashtable(HASH_SIZE);

    /**
     * Maps String to ZipEntrys, name -> actual entry.
     */
    private Hashtable nameMap = new Hashtable(HASH_SIZE);

    private static final class OffsetEntry {
        private long headerOffset = -1;
        private long dataOffset = -1;
    }

    /**
     * The encoding to use for filenames and the file comment.
     *
     * <p>For a list of possible values see <a
     * href="http://java.sun.com/j2se/1.5.0/docs/guide/intl/encoding.doc.html">http://java.sun.com/j2se/1.5.0/docs/guide/intl/encoding.doc.html</a>.
     * Defaults to the platform's default character encoding.</p>
     */
    private String encoding = null;

    /**
     * The actual data source.
     */
    private RandomAccessFile archive;

    /**
     * Opens the given file for reading, assuming the platform's
     * native encoding for file names.
     *
     * @param f the archive.
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(File f) throws IOException {
        this(f, null);
    }

    /**
     * Opens the given file for reading, assuming the platform's
     * native encoding for file names.
     *
     * @param name name of the archive.
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(String name) throws IOException {
        this(new File(name), null);
    }

    /**
     * Opens the given file for reading, assuming the specified
     * encoding for file names.
     *
     * @param name name of the archive.
     * @param encoding the encoding to use for file names
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(String name, String encoding) throws IOException {
        this(new File(name), encoding);
    }

    /**
     * Opens the given file for reading, assuming the specified
     * encoding for file names.
     *
     * @param f the archive.
     * @param encoding the encoding to use for file names
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(File f, String encoding) throws IOException {
        this.encoding = encoding;
        archive = new RandomAccessFile(f, "r");
        try {
            populateFromCentralDirectory();
            resolveLocalFileHeaderData();
        } catch (IOException e) {
            try {
                archive.close();
            } catch (IOException e2) {
                // swallow, throw the original exception instead
            }
            throw e;
        }
    }

    /**
     * The encoding to use for filenames and the file comment.
     *
     * @return null if using the platform's default character encoding.
     */
    public String getEncoding() {
        return encoding;
    }

    /**
     * Closes the archive.
     * @throws IOException if an error occurs closing the archive.
     */
    public void close() throws IOException {
        archive.close();
    }

    /**
     * close a zipfile quietly; throw no io fault, do nothing
     * on a null parameter
     * @param zipfile file to close, can be null
     */
    public static void closeQuietly(ZipFile zipfile) {
        if (zipfile != null) {
            try {
                zipfile.close();
            } catch (IOException e) {
                //ignore
            }
        }
    }

    /**
     * Returns all entries.
     * @return all entries as {@link ZipEntry} instances
     */
    public Enumeration getEntries() {
        return entries.keys();
    }

    /**
     * Returns a named entry - or <code>null</code> if no entry by
     * that name exists.
     * @param name name of the entry.
     * @return the ZipEntry corresponding to the given name - or
     * <code>null</code> if not present.
     */
    public ZipEntry getEntry(String name) {
        return (ZipEntry) nameMap.get(name);
    }

    /**
     * Returns an InputStream for reading the contents of the given entry.
     * @param ze the entry to get the stream for.
     * @return a stream to read the entry from.
     * @throws IOException if unable to create an input stream from the zipenty
     * @throws ZipException if the zipentry has an unsupported compression method
     */
    public InputStream getInputStream(ZipEntry ze)
        throws IOException, ZipException {
        OffsetEntry offsetEntry = (OffsetEntry) entries.get(ze);
        if (offsetEntry == null) {
            return null;
        }
        long start = offsetEntry.dataOffset;
        BoundedInputStream bis =
            new BoundedInputStream(start, ze.getCompressedSize());
        switch (ze.getMethod()) {
            case ZipEntry.STORED:
                return bis;
            case ZipEntry.DEFLATED:
                bis.addDummy();
                return new InflaterInputStream(bis, new Inflater(true));
            default:
                throw new ZipException("Found unsupported compression method "
                                       + ze.getMethod());
        }
    }

    private static final int CFH_LEN =
        /* version made by                 */ SHORT
        /* version needed to extract       */ + SHORT
        /* general purpose bit flag        */ + SHORT
        /* compression method              */ + SHORT
        /* last mod file time              */ + SHORT
        /* last mod file date              */ + SHORT
        /* crc-32                          */ + WORD
        /* compressed size                 */ + WORD
        /* uncompressed size               */ + WORD
        /* filename length                 */ + SHORT
        /* extra field length              */ + SHORT
        /* file comment length             */ + SHORT
        /* disk number start               */ + SHORT
        /* internal file attributes        */ + SHORT
        /* external file attributes        */ + WORD
        /* relative offset of local header */ + WORD;

    /**
     * Reads the central directory of the given archive and populates
     * the internal tables with ZipEntry instances.
     *
     * <p>The ZipEntrys will know all data that can be obtained from
     * the central directory alone, but not the data that requires the
     * local file header or additional data to be read.</p>
     */
    private void populateFromCentralDirectory()
        throws IOException {
        positionAtCentralDirectory();

        byte[] cfh = new byte[CFH_LEN];

        byte[] signatureBytes = new byte[WORD];
        archive.readFully(signatureBytes);
        long sig = ZipLong.getValue(signatureBytes);
        final long cfhSig = ZipLong.getValue(ZipOutputStream.CFH_SIG);
        while (sig == cfhSig) {
            archive.readFully(cfh);
            int off = 0;
            ZipEntry ze = new ZipEntry();

            int versionMadeBy = ZipShort.getValue(cfh, off);
            off += SHORT;
            ze.setPlatform((versionMadeBy >> BYTE_SHIFT) & NIBLET_MASK);

            off += WORD; // skip version info and general purpose byte

            ze.setMethod(ZipShort.getValue(cfh, off));
            off += SHORT;

            // FIXME this is actually not very cpu cycles friendly as we are converting from
            // dos to java while the underlying Sun implementation will convert
            // from java to dos time for internal storage...
            long time = dosToJavaTime(ZipLong.getValue(cfh, off));
            ze.setTime(time);
            off += WORD;

            ze.setCrc(ZipLong.getValue(cfh, off));
            off += WORD;

            ze.setCompressedSize(ZipLong.getValue(cfh, off));
            off += WORD;

            ze.setSize(ZipLong.getValue(cfh, off));
            off += WORD;

            int fileNameLen = ZipShort.getValue(cfh, off);
            off += SHORT;

            int extraLen = ZipShort.getValue(cfh, off);
            off += SHORT;

            int commentLen = ZipShort.getValue(cfh, off);
            off += SHORT;

            off += SHORT; // disk number

            ze.setInternalAttributes(ZipShort.getValue(cfh, off));
            off += SHORT;

            ze.setExternalAttributes(ZipLong.getValue(cfh, off));
            off += WORD;

            byte[] fileName = new byte[fileNameLen];
            archive.readFully(fileName);
            ze.setName(getString(fileName));


            // LFH offset,
            OffsetEntry offset = new OffsetEntry();
            offset.headerOffset = ZipLong.getValue(cfh, off);
            // data offset will be filled later
            entries.put(ze, offset);

            nameMap.put(ze.getName(), ze);

            archive.skipBytes(extraLen);

            byte[] comment = new byte[commentLen];
            archive.readFully(comment);
            ze.setComment(getString(comment));

            archive.readFully(signatureBytes);
            sig = ZipLong.getValue(signatureBytes);
        }
    }

    private static final int MIN_EOCD_SIZE =
        /* end of central dir signature    */ WORD
        /* number of this disk             */ + SHORT
        /* number of the disk with the     */
        /* start of the central directory  */ + SHORT
        /* total number of entries in      */
        /* the central dir on this disk    */ + SHORT
        /* total number of entries in      */
        /* the central dir                 */ + SHORT
        /* size of the central directory   */ + WORD
        /* offset of start of central      */
        /* directory with respect to       */
        /* the starting disk number        */ + WORD
        /* zipfile comment length          */ + SHORT;

    private static final int CFD_LOCATOR_OFFSET =
        /* end of central dir signature    */ WORD
        /* number of this disk             */ + SHORT
        /* number of the disk with the     */
        /* start of the central directory  */ + SHORT
        /* total number of entries in      */
        /* the central dir on this disk    */ + SHORT
        /* total number of entries in      */
        /* the central dir                 */ + SHORT
        /* size of the central directory   */ + WORD;

    /**
     * Searches for the &quot;End of central dir record&quot;, parses
     * it and positions the stream at the first central directory
     * record.
     */
    private void positionAtCentralDirectory()
        throws IOException {
        boolean found = false;
        long off = archive.length() - MIN_EOCD_SIZE;
        if (off >= 0) {
            archive.seek(off);
            byte[] sig = ZipOutputStream.EOCD_SIG;
            int curr = archive.read();
            while (curr != -1) {
                if (curr == sig[POS_0]) {
                    curr = archive.read();
                    if (curr == sig[POS_1]) {
                        curr = archive.read();
                        if (curr == sig[POS_2]) {
                            curr = archive.read();
                            if (curr == sig[POS_3]) {
                                found = true;
                                break;
                            }
                        }
                    }
                }
                archive.seek(--off);
                curr = archive.read();
            }
        }
        if (!found) {
            throw new ZipException("archive is not a ZIP archive");
        }
        archive.seek(off + CFD_LOCATOR_OFFSET);
        byte[] cfdOffset = new byte[WORD];
        archive.readFully(cfdOffset);
        archive.seek(ZipLong.getValue(cfdOffset));
    }

    /**
     * Number of bytes in local file header up to the &quot;length of
     * filename&quot; entry.
     */
    private static final long LFH_OFFSET_FOR_FILENAME_LENGTH =
        /* local file header signature     */ WORD
        /* version needed to extract       */ + SHORT
        /* general purpose bit flag        */ + SHORT
        /* compression method              */ + SHORT
        /* last mod file time              */ + SHORT
        /* last mod file date              */ + SHORT
        /* crc-32                          */ + WORD
        /* compressed size                 */ + WORD
        /* uncompressed size               */ + WORD;

    /**
     * Walks through all recorded entries and adds the data available
     * from the local file header.
     *
     * <p>Also records the offsets for the data to read from the
     * entries.</p>
     */
    private void resolveLocalFileHeaderData()
        throws IOException {
        Enumeration e = getEntries();
        while (e.hasMoreElements()) {
            ZipEntry ze = (ZipEntry) e.nextElement();
            OffsetEntry offsetEntry = (OffsetEntry) entries.get(ze);
            long offset = offsetEntry.headerOffset;
            archive.seek(offset + LFH_OFFSET_FOR_FILENAME_LENGTH);
            byte[] b = new byte[SHORT];
            archive.readFully(b);
            int fileNameLen = ZipShort.getValue(b);
            archive.readFully(b);
            int extraFieldLen = ZipShort.getValue(b);
            archive.skipBytes(fileNameLen);
            byte[] localExtraData = new byte[extraFieldLen];
            archive.readFully(localExtraData);
            ze.setExtra(localExtraData);
            /*dataOffsets.put(ze,
                            new Long(offset + LFH_OFFSET_FOR_FILENAME_LENGTH
                                     + SHORT + SHORT + fileNameLen + extraFieldLen));
            */
            offsetEntry.dataOffset = offset + LFH_OFFSET_FOR_FILENAME_LENGTH
                                     + SHORT + SHORT + fileNameLen + extraFieldLen;
        }
    }

    /**
     * Convert a DOS date/time field to a Date object.
     *
     * @param zipDosTime contains the stored DOS time.
     * @return a Date instance corresponding to the given time.
     */
    protected static Date fromDosTime(ZipLong zipDosTime) {
        long dosTime = zipDosTime.getValue();
        return new Date(dosToJavaTime(dosTime));
    }

    /*
     * Converts DOS time to Java time (number of milliseconds since epoch).
     */
    private static long dosToJavaTime(long dosTime) {
        Calendar cal = Calendar.getInstance();
        // CheckStyle:MagicNumberCheck OFF - no point
        cal.set(Calendar.YEAR, (int) ((dosTime >> 25) & 0x7f) + 1980);
        cal.set(Calendar.MONTH, (int) ((dosTime >> 21) & 0x0f) - 1);
        cal.set(Calendar.DATE, (int) (dosTime >> 16) & 0x1f);
        cal.set(Calendar.HOUR_OF_DAY, (int) (dosTime >> 11) & 0x1f);
        cal.set(Calendar.MINUTE, (int) (dosTime >> 5) & 0x3f);
        cal.set(Calendar.SECOND, (int) (dosTime << 1) & 0x3e);
        // CheckStyle:MagicNumberCheck ON
        return cal.getTime().getTime();
    }


    /**
     * Retrieve a String from the given bytes using the encoding set
     * for this ZipFile.
     *
     * @param bytes the byte array to transform
     * @return String obtained by using the given encoding
     * @throws ZipException if the encoding cannot be recognized.
     */
    protected String getString(byte[] bytes) throws ZipException {
        if (encoding == null) {
            return new String(bytes);
        } else {
            try {
                return new String(bytes, encoding);
            } catch (UnsupportedEncodingException uee) {
                throw new ZipException(uee.getMessage());
            }
        }
    }

    /**
     * InputStream that delegates requests to the underlying
     * RandomAccessFile, making sure that only bytes from a certain
     * range can be read.
     */
    private class BoundedInputStream extends InputStream {
        private long remaining;
        private long loc;
        private boolean addDummyByte = false;

        BoundedInputStream(long start, long remaining) {
            this.remaining = remaining;
            loc = start;
        }

        public int read() throws IOException {
            if (remaining-- <= 0) {
                if (addDummyByte) {
                    addDummyByte = false;
                    return 0;
                }
                return -1;
            }
            synchronized (archive) {
                archive.seek(loc++);
                return archive.read();
            }
        }

        public int read(byte[] b, int off, int len) throws IOException {
            if (remaining <= 0) {
                if (addDummyByte) {
                    addDummyByte = false;
                    b[off] = 0;
                    return 1;
                }
                return -1;
            }

            if (len <= 0) {
                return 0;
            }

            if (len > remaining) {
                len = (int) remaining;
            }
            int ret = -1;
            synchronized (archive) {
                archive.seek(loc);
                ret = archive.read(b, off, len);
            }
            if (ret > 0) {
                loc += ret;
                remaining -= ret;
            }
            return ret;
        }

        /**
         * Inflater needs an extra dummy byte for nowrap - see
         * Inflater's javadocs.
         */
        void addDummy() {
            addDummyByte = true;
        }
    }

}
