/*
    * 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.imaging.bytesource;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Arrays;
  import java.util.Objects;
  
  import org.apache.commons.imaging.ImagingException;
  import org.apache.commons.imaging.common.Allocator;
  import org.apache.commons.imaging.common.BinaryFunctions;
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.io.build.AbstractOrigin.InputStreamOrigin;
  
  final class InputStreamByteSource extends ByteSource {
  
      /**
       * A block of bytes (a byte array).
       */
      private final class Block {
  
          final byte[] bytes;
          private Block next;
          private boolean triedNext;
  
          Block(final byte[] bytes) {
              this.bytes = Objects.requireNonNull(bytes);
          }
  
          Block getNext() throws IOException {
              if (next != null) {
                  return next;
              }
              if (triedNext) {
                  return null;
              }
              triedNext = true;
              next = readBlock();
              return next;
          }
  
          int length() {
              return bytes.length;
          }
      }
  
      private final class BlockInputStream extends InputStream {
  
          private Block block;
          private boolean readFirst;
          private int blockIndex;
  
          @Override
          public int read() throws IOException {
              if (block == null) {
                  if (readFirst) {
                      return -1;
                  }
                  block = getFirstBlock();
                  readFirst = true;
              }
              if (block != null && blockIndex >= block.length()) {
                  block = block.getNext();
                  blockIndex = 0;
              }
              if (block == null) {
                  return -1;
              }
              if (blockIndex >= block.length()) {
                  return -1;
              }
              return 0xff & block.bytes[blockIndex++];
          }
  
          @Override
          public int read(final byte[] array, final int off, final int len) throws IOException {
              Objects.requireNonNull(array, "array");
              if (off < 0 || off > array.length || len < 0 || off + len > array.length || off + len < 0) {
                  throw new IndexOutOfBoundsException();
              }
              if (len == 0) {
                  return 0;
             }
             // optimized block read
             if (block == null) {
                 if (readFirst) {
                     return -1;
                 }
                 block = getFirstBlock();
                 readFirst = true;
             }
             if (block != null && blockIndex >= block.length()) {
                 block = block.getNext();
                 blockIndex = 0;
             }
             if (block == null) {
                 return -1;
             }
             if (blockIndex >= block.length()) {
                 return -1;
             }
             final int readSize = Math.min(len, block.length() - blockIndex);
             System.arraycopy(block.bytes, blockIndex, array, off, readSize);
             blockIndex += readSize;
             return readSize;
         }
 
         @Override
         public long skip(final long n) throws IOException {
             long remaining = n;
             if (n <= 0) {
                 return 0;
             }
             while (remaining > 0) {
                 // read the first block
                 if (block == null) {
                     if (readFirst) {
                         return -1;
                     }
                     block = getFirstBlock();
                     readFirst = true;
                 }
                 // get next block
                 if (block != null && blockIndex >= block.length()) {
                     block = block.getNext();
                     blockIndex = 0;
                 }
                 if (block == null) {
                     break;
                 }
                 if (blockIndex >= block.length()) {
                     break;
                 }
                 final int readSize = Math.min((int) Math.min(BLOCK_SIZE, remaining), block.length() - blockIndex);
                 blockIndex += readSize;
                 remaining -= readSize;
             }
             return n - remaining;
         }
     }
 
     private static final int BLOCK_SIZE = IOUtils.DEFAULT_BUFFER_SIZE;
     private final InputStream inputStream;
     private final Block headBlock;
     //private byte[] readBuffer;
     private long streamLength = -1;
 
     InputStreamByteSource(final InputStream inputStream, final String fileName) throws IOException {
         super(new InputStreamOrigin(inputStream), fileName);
         this.inputStream = new BufferedInputStream(inputStream);
         headBlock = readBlock();
     }
 
     @SuppressWarnings("resource") // accesses input stream more than once, don't close here.
     @Override
     public byte[] getByteArray(final long position, final int length) throws IOException {
         // We include a separate check for int overflow.
         if (position < 0 || length < 0 || position + length < 0 || position + length > size()) {
             throw new ImagingException(
                     "Could not read block (block start: " + position + ", block length: " + length + ", data length: " + streamLength + ").");
         }
         final InputStream cis = getInputStream();
         BinaryFunctions.skipBytes(cis, position);
         final byte[] bytes = Allocator.byteArray(length);
         int total = 0;
         while (true) {
             final int read = cis.read(bytes, total, bytes.length - total);
             if (read < 1) {
                 throw new ImagingException("Could not read block.");
             }
             total += read;
             if (total >= length) {
                 return bytes;
             }
         }
     }
 
     private Block getFirstBlock() throws IOException {
         return headBlock;
     }
 
     @Override
     public InputStream getInputStream() throws IOException {
         return new BlockInputStream();
     }
 
     private Block readBlock() throws IOException {
         final byte[] readBuffer = new byte[BLOCK_SIZE];
         final int read = inputStream.read(readBuffer);
         if (read < 1) {
             return null;
         }
         if (read < readBuffer.length) {
             // return a copy.
             return new Block(Arrays.copyOf(readBuffer, read));
         }
         // return current buffer.
         return new Block(readBuffer);
     }
 
     @Override
     public long size() throws IOException {
         if (streamLength >= 0) {
             return streamLength;
         }
         try (InputStream cis = getInputStream()) {
             return streamLength = IOUtils.consume(cis);
         }
     }
 }