/*
    * 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.commons.compress.archivers.ar;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.StandardCharsets;
  import java.util.Arrays;
  import java.util.regex.Pattern;
  
  import org.apache.commons.compress.archivers.ArchiveInputStream;
  import org.apache.commons.compress.utils.ArchiveUtils;
  import org.apache.commons.compress.utils.IOUtils;
  import org.apache.commons.compress.utils.ParsingUtils;
  
  /**
   * Implements the "ar" archive format as an input stream.
   *
   * @NotThreadSafe
   */
  public class ArArchiveInputStream extends ArchiveInputStream<ArArchiveEntry> {
  
      // offsets and length of meta data parts
      private static final int NAME_OFFSET = 0;
      private static final int NAME_LEN = 16;
      private static final int LAST_MODIFIED_OFFSET = NAME_LEN;
  
      private static final int LAST_MODIFIED_LEN = 12;
  
      private static final int USER_ID_OFFSET = LAST_MODIFIED_OFFSET + LAST_MODIFIED_LEN;
  
      private static final int USER_ID_LEN = 6;
  
      private static final int GROUP_ID_OFFSET = USER_ID_OFFSET + USER_ID_LEN;
      private static final int GROUP_ID_LEN = 6;
      private static final int FILE_MODE_OFFSET = GROUP_ID_OFFSET + GROUP_ID_LEN;
      private static final int FILE_MODE_LEN = 8;
      private static final int LENGTH_OFFSET = FILE_MODE_OFFSET + FILE_MODE_LEN;
      private static final int LENGTH_LEN = 10;
      static final String BSD_LONGNAME_PREFIX = "#1/";
      private static final int BSD_LONGNAME_PREFIX_LEN = BSD_LONGNAME_PREFIX.length();
      private static final Pattern BSD_LONGNAME_PATTERN = Pattern.compile("^" + BSD_LONGNAME_PREFIX + "\\d+");
      private static final String GNU_STRING_TABLE_NAME = "//";
      private static final Pattern GNU_LONGNAME_PATTERN = Pattern.compile("^/\\d+");
  
      /**
       * Does the name look like it is a long name (or a name containing spaces) as encoded by BSD ar?
       * <p>
       * From the FreeBSD ar(5) man page:
       * </p>
       * <pre>
       * BSD   In the BSD variant, names that are shorter than 16
       *       characters and without embedded spaces are stored
       *       directly in this field.  If a name has an embedded
       *       space, or if it is longer than 16 characters, then
       *       the string "#1/" followed by the decimal represen-
       *       tation of the length of the file name is placed in
       *       this field. The actual file name is stored immedi-
       *       ately after the archive header.  The content of the
       *       archive member follows the file name.  The ar_size
       *       field of the header (see below) will then hold the
       *       sum of the size of the file name and the size of
       *       the member.
       * </pre>
       *
       * @since 1.3
       */
      private static boolean isBSDLongName(final String name) {
          return name != null && BSD_LONGNAME_PATTERN.matcher(name).matches();
      }
  
      /**
       * Is this the name of the "Archive String Table" as used by SVR4/GNU to store long file names?
       * <p>
       * GNU ar stores multiple extended file names in the data section of a file with the name "//", this record is referred to by future headers.
       * </p>
       * <p>
       * A header references an extended file name by storing a "/" followed by a decimal offset to the start of the file name in the extended file name data
       * section.
       * </p>
       * <p>
       * The format of the "//" file itself is simply a list of the long file names, each separated by one or more LF characters. Note that the decimal offsets
      * are number of characters, not line or string number within the "//" file.
      * </p>
      */
     private static boolean isGNUStringTable(final String name) {
         return GNU_STRING_TABLE_NAME.equals(name);
     }
 
     /**
      * Checks if the signature matches ASCII "!&lt;arch&gt;" followed by a single LF control character
      *
      * @param signature the bytes to check
      * @param length    the number of bytes to check
      * @return true, if this stream is an Ar archive stream, false otherwise
      */
     public static boolean matches(final byte[] signature, final int length) {
         // 3c21 7261 6863 0a3e
         // @formatter:off
         return length >= 8 &&
                 signature[0] == 0x21 &&
                 signature[1] == 0x3c &&
                 signature[2] == 0x61 &&
                 signature[3] == 0x72 &&
                 signature[4] == 0x63 &&
                 signature[5] == 0x68 &&
                 signature[6] == 0x3e &&
                 signature[7] == 0x0a;
         // @formatter:on
     }
 
     private long offset;
 
     private boolean closed;
 
     /*
      * If getNextEntry has been called, the entry metadata is stored in currentEntry.
      */
     private ArArchiveEntry currentEntry;
 
     /** Storage area for extra long names (GNU ar). */
     private byte[] namebuffer;
 
     /**
      * The offset where the current entry started. -1 if no entry has been called
      */
     private long entryOffset = -1;
 
     /** Cached buffer for meta data - must only be used locally in the class (COMPRESS-172 - reduce garbage collection). */
     private final byte[] metaData = new byte[NAME_LEN + LAST_MODIFIED_LEN + USER_ID_LEN + GROUP_ID_LEN + FILE_MODE_LEN + LENGTH_LEN];
 
     /**
      * Constructs an Ar input stream with the referenced stream
      *
      * @param inputStream the ar input stream
      */
     public ArArchiveInputStream(final InputStream inputStream) {
         super(inputStream, StandardCharsets.US_ASCII.name());
     }
 
     private int asInt(final byte[] byteArray, final int offset, final int len) throws IOException {
         return asInt(byteArray, offset, len, 10, false);
     }
 
     private int asInt(final byte[] byteArray, final int offset, final int len, final boolean treatBlankAsZero) throws IOException {
         return asInt(byteArray, offset, len, 10, treatBlankAsZero);
     }
 
     private int asInt(final byte[] byteArray, final int offset, final int len, final int base) throws IOException {
         return asInt(byteArray, offset, len, base, false);
     }
 
     private int asInt(final byte[] byteArray, final int offset, final int len, final int base, final boolean treatBlankAsZero) throws IOException {
         final String string = ArchiveUtils.toAsciiString(byteArray, offset, len).trim();
         if (string.isEmpty() && treatBlankAsZero) {
             return 0;
         }
         return ParsingUtils.parseIntValue(string, base);
     }
 
     private long asLong(final byte[] byteArray, final int offset, final int len) throws IOException {
         return ParsingUtils.parseLongValue(ArchiveUtils.toAsciiString(byteArray, offset, len).trim());
     }
 
     /*
      * (non-Javadoc)
      *
      * @see java.io.InputStream#close()
      */
     @Override
     public void close() throws IOException {
         if (!closed) {
             closed = true;
             in.close();
         }
         currentEntry = null;
     }
 
     /**
      * Reads the real name from the current stream assuming the very first bytes to be read are the real file name.
      *
      * @see #isBSDLongName
      *
      * @since 1.3
      */
     private String getBSDLongName(final String bsdLongName) throws IOException {
         final int nameLen = ParsingUtils.parseIntValue(bsdLongName.substring(BSD_LONGNAME_PREFIX_LEN));
         final byte[] name = IOUtils.readRange(in, nameLen);
         final int read = name.length;
         trackReadBytes(read);
         if (read != nameLen) {
             throw new EOFException();
         }
         return ArchiveUtils.toAsciiString(name);
     }
 
     /**
      * Gets an extended name from the GNU extended name buffer.
      *
      * @param offset pointer to entry within the buffer
      * @return the extended file name; without trailing "/" if present.
      * @throws IOException if name not found or buffer not set up
      */
     private String getExtendedName(final int offset) throws IOException {
         if (namebuffer == null) {
             throw new IOException("Cannot process GNU long file name as no // record was found");
         }
         for (int i = offset; i < namebuffer.length; i++) {
             if (namebuffer[i] == '\012' || namebuffer[i] == 0) {
                 // Avoid array errors
                 if (i == 0) {
                     break;
                 }
                 if (namebuffer[i - 1] == '/') {
                     i--; // drop trailing /
                 }
                 // Check there is a something to return, otherwise break out of the loop
                 if (i - offset > 0) {
                     return ArchiveUtils.toAsciiString(namebuffer, offset, i - offset);
                 }
                 break;
             }
         }
         throw new IOException("Failed to read entry: " + offset);
     }
 
     /**
      * Returns the next AR entry in this stream.
      *
      * @return the next AR entry.
      * @throws IOException if the entry could not be read
      * @deprecated Use {@link #getNextEntry()}.
      */
     @Deprecated
     public ArArchiveEntry getNextArEntry() throws IOException {
         if (currentEntry != null) {
             final long entryEnd = entryOffset + currentEntry.getLength();
             final long skipped = org.apache.commons.io.IOUtils.skip(in, entryEnd - offset);
             trackReadBytes(skipped);
             currentEntry = null;
         }
         if (offset == 0) {
             final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.HEADER);
             final byte[] realized = IOUtils.readRange(in, expected.length);
             final int read = realized.length;
             trackReadBytes(read);
             if (read != expected.length) {
                 throw new IOException("Failed to read header. Occurred at byte: " + getBytesRead());
             }
             if (!Arrays.equals(expected, realized)) {
                 throw new IOException("Invalid header " + ArchiveUtils.toAsciiString(realized));
             }
         }
         if (offset % 2 != 0) {
             if (in.read() < 0) {
                 // hit eof
                 return null;
             }
             trackReadBytes(1);
         }
         {
             final int read = IOUtils.readFully(in, metaData);
             trackReadBytes(read);
             if (read == 0) {
                 return null;
             }
             if (read < metaData.length) {
                 throw new IOException("Truncated ar archive");
             }
         }
         {
             final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.TRAILER);
             final byte[] realized = IOUtils.readRange(in, expected.length);
             final int read = realized.length;
             trackReadBytes(read);
             if (read != expected.length) {
                 throw new IOException("Failed to read entry trailer. Occurred at byte: " + getBytesRead());
             }
             if (!Arrays.equals(expected, realized)) {
                 throw new IOException("Invalid entry trailer. not read the content? Occurred at byte: " + getBytesRead());
             }
         }
 
         entryOffset = offset;
         // GNU ar uses a '/' to mark the end of the file name; this allows for the use of spaces without the use of an extended file name.
         // entry name is stored as ASCII string
         String temp = ArchiveUtils.toAsciiString(metaData, NAME_OFFSET, NAME_LEN).trim();
         if (isGNUStringTable(temp)) { // GNU extended file names entry
             currentEntry = readGNUStringTable(metaData, LENGTH_OFFSET, LENGTH_LEN);
             return getNextArEntry();
         }
         long len;
         try {
             len = asLong(metaData, LENGTH_OFFSET, LENGTH_LEN);
         } catch (final NumberFormatException ex) {
             throw new IOException("Broken archive, unable to parse ar_size field as a number", ex);
         }
         if (temp.endsWith("/")) { // GNU terminator
             temp = temp.substring(0, temp.length() - 1);
         } else if (isGNULongName(temp)) {
             final int off = ParsingUtils.parseIntValue(temp.substring(1)); // get the offset
             temp = getExtendedName(off); // convert to the long name
         } else if (isBSDLongName(temp)) {
             temp = getBSDLongName(temp);
             // entry length contained the length of the file name in
             // addition to the real length of the entry.
             // assume file name was ASCII, there is no "standard" otherwise
             final int nameLen = temp.length();
             len -= nameLen;
             entryOffset += nameLen;
         }
         if (len < 0) {
             throw new IOException("broken archive, entry with negative size");
         }
         try {
             currentEntry = new ArArchiveEntry(temp, len, asInt(metaData, USER_ID_OFFSET, USER_ID_LEN, true),
                     asInt(metaData, GROUP_ID_OFFSET, GROUP_ID_LEN, true), asInt(metaData, FILE_MODE_OFFSET, FILE_MODE_LEN, 8),
                     asLong(metaData, LAST_MODIFIED_OFFSET, LAST_MODIFIED_LEN));
             return currentEntry;
         } catch (final NumberFormatException ex) {
             throw new IOException("Broken archive, unable to parse entry metadata fields as numbers", ex);
         }
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.compress.archivers.ArchiveInputStream#getNextEntry()
      */
     @Override
     public ArArchiveEntry getNextEntry() throws IOException {
         return getNextArEntry();
     }
 
     /**
      * Does the name look like it is a long name (or a name containing spaces) as encoded by SVR4/GNU ar?
      *
      * @see #isGNUStringTable
      */
     private boolean isGNULongName(final String name) {
         return name != null && GNU_LONGNAME_PATTERN.matcher(name).matches();
     }
 
     /*
      * (non-Javadoc)
      *
      * @see java.io.InputStream#read(byte[], int, int)
      */
     @Override
     public int read(final byte[] b, final int off, final int len) throws IOException {
         if (len == 0) {
             return 0;
         }
         if (currentEntry == null) {
             throw new IllegalStateException("No current ar entry");
         }
         final long entryEnd = entryOffset + currentEntry.getLength();
         if (len < 0 || offset >= entryEnd) {
             return -1;
         }
         final int toRead = (int) Math.min(len, entryEnd - offset);
         final int ret = this.in.read(b, off, toRead);
         trackReadBytes(ret);
         return ret;
     }
 
     /**
      * Reads the GNU archive String Table.
      *
      * @see #isGNUStringTable
      */
     private ArArchiveEntry readGNUStringTable(final byte[] length, final int offset, final int len) throws IOException {
         int bufflen;
         try {
             bufflen = asInt(length, offset, len); // Assume length will fit in an int
         } catch (final NumberFormatException ex) {
             throw new IOException("Broken archive, unable to parse GNU string table length field as a number", ex);
         }
         namebuffer = IOUtils.readRange(in, bufflen);
         final int read = namebuffer.length;
         trackReadBytes(read);
         if (read != bufflen) {
             throw new IOException("Failed to read complete // record: expected=" + bufflen + " read=" + read);
         }
         return new ArArchiveEntry(GNU_STRING_TABLE_NAME, bufflen);
     }
 
     private void trackReadBytes(final long read) {
         count(read);
         if (read > 0) {
             offset += read;
         }
     }
 }