/*
    * 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.zip;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  import org.apache.commons.compress.utils.ExactMath;
  import org.apache.commons.compress.utils.InputStreamStatistics;
  import org.apache.commons.io.input.BoundedInputStream;
  import org.apache.commons.io.input.CloseShieldInputStream;
  
  /**
   * The implode compression method was added to PKZIP 1.01 released in 1989. It was then dropped from PKZIP 2.0 released in 1993 in favor of the deflate method.
   * <p>
   * The algorithm is described in the ZIP File Format Specification.
   *
   * @see <a href="https://www.pkware.com/documents/casestudies/APPNOTE.TXT">ZIP File Format Specification</a>
   *
   * @since 1.7
   */
  final class ExplodingInputStream extends InputStream implements InputStreamStatistics {
  
      /** The underlying stream containing the compressed data */
      private final InputStream in;
  
      /** The stream of bits read from the input stream */
      private BitStream bits;
  
      /** The size of the sliding dictionary (4K or 8K) */
      private final int dictionarySize;
  
      /** The number of Shannon-Fano trees (2 or 3) */
      private final int numberOfTrees;
  
      private final int minimumMatchLength;
  
      /** The binary tree containing the 256 encoded literals (null when only two trees are used) */
      private BinaryTree literalTree;
  
      /** The binary tree containing the 64 encoded lengths */
      private BinaryTree lengthTree;
  
      /** The binary tree containing the 64 encoded distances */
      private BinaryTree distanceTree;
  
      /** Output buffer holding the decompressed data */
      private final CircularBuffer buffer = new CircularBuffer(32 * 1024);
  
      private long uncompressedCount;
  
      private long treeSizes;
  
      /**
       * Constructs a new stream decompressing the content of the specified stream using the explode algorithm.
       *
       * @param dictionarySize the size of the sliding dictionary (4096 or 8192)
       * @param numberOfTrees  the number of trees (2 or 3)
       * @param in             the compressed data stream
       */
      ExplodingInputStream(final int dictionarySize, final int numberOfTrees, final InputStream in) {
          if (dictionarySize != 4096 && dictionarySize != 8192) {
              throw new IllegalArgumentException("The dictionary size must be 4096 or 8192");
          }
          if (numberOfTrees != 2 && numberOfTrees != 3) {
              throw new IllegalArgumentException("The number of trees must be 2 or 3");
          }
          this.dictionarySize = dictionarySize;
          this.numberOfTrees = numberOfTrees;
          this.minimumMatchLength = numberOfTrees;
          this.in = in;
      }
  
      /**
       * @since 1.17
       */
      @Override
      public void close() throws IOException {
          in.close();
      }
  
      /**
      * Fill the sliding dictionary with more data.
      *
      * @throws IOException on error.
      */
     private void fillBuffer() throws IOException {
         init();
 
         final int bit = bits.nextBit();
         if (bit == -1) {
             // EOF
             return;
         }
         if (bit == 1) {
             // literal value
             final int literal;
             if (literalTree != null) {
                 literal = literalTree.read(bits);
             } else {
                 literal = bits.nextByte();
             }
 
             if (literal == -1) {
                 // end of stream reached, nothing left to decode
                 return;
             }
 
             buffer.put(literal);
 
         } else {
             // back reference
             final int distanceLowSize = dictionarySize == 4096 ? 6 : 7;
             final int distanceLow = (int) bits.nextBits(distanceLowSize);
             final int distanceHigh = distanceTree.read(bits);
             if (distanceHigh == -1 && distanceLow <= 0) {
                 // end of stream reached, nothing left to decode
                 return;
             }
             final int distance = distanceHigh << distanceLowSize | distanceLow;
 
             int length = lengthTree.read(bits);
             if (length == 63) {
                 final long nextByte = bits.nextBits(8);
                 if (nextByte == -1) {
                     // EOF
                     return;
                 }
                 length = ExactMath.add(length, nextByte);
             }
             length += minimumMatchLength;
 
             buffer.copy(distance + 1, length);
         }
     }
 
     /**
      * @since 1.17
      */
     @Override
     public long getCompressedCount() {
         return bits.getBytesRead() + treeSizes;
     }
 
     /**
      * @since 1.17
      */
     @Override
     public long getUncompressedCount() {
         return uncompressedCount;
     }
 
     /**
      * Reads the encoded binary trees and prepares the bit stream.
      *
      * @throws IOException
      */
     private void init() throws IOException {
         if (bits == null) {
             // we do not want to close in
             try (BoundedInputStream cis = BoundedInputStream.builder().setInputStream(CloseShieldInputStream.wrap(in)).get()) {
                 if (numberOfTrees == 3) {
                     literalTree = BinaryTree.decode(cis, 256);
                 }
 
                 lengthTree = BinaryTree.decode(cis, 64);
                 distanceTree = BinaryTree.decode(cis, 64);
                 treeSizes += cis.getCount();
             }
 
             bits = new BitStream(in);
         }
     }
 
     @Override
     public int read() throws IOException {
         if (!buffer.available()) {
             try {
                 fillBuffer();
             } catch (final IllegalArgumentException ex) {
                 throw new IOException("bad IMPLODE stream", ex);
             }
         }
 
         final int ret = buffer.get();
         if (ret > -1) {
             uncompressedCount++;
         }
         return ret;
     }
 
 }