/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.http.impl.io;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  import org.apache.http.ConnectionClosedException;
  import org.apache.http.Header;
  import org.apache.http.HttpException;
  import org.apache.http.MalformedChunkCodingException;
  import org.apache.http.TruncatedChunkException;
  import org.apache.http.config.MessageConstraints;
  import org.apache.http.io.BufferInfo;
  import org.apache.http.io.SessionInputBuffer;
  import org.apache.http.util.Args;
  import org.apache.http.util.CharArrayBuffer;
  
  /**
   * Implements chunked transfer coding. The content is received in small chunks.
   * Entities transferred using this input stream can be of unlimited length.
   * After the stream is read to the end, it provides access to the trailers,
   * if any.
   * <p>
   * Note that this class NEVER closes the underlying stream, even when close
   * gets called.  Instead, it will read until the "end" of its chunking on
   * close, which allows for the seamless execution of subsequent HTTP 1.1
   * requests, while not requiring the client to remember to read the entire
   * contents of the response.
   *
   *
   * @since 4.0
   *
   */
  public class ChunkedInputStream extends InputStream {
  
      private static final int CHUNK_LEN               = 1;
      private static final int CHUNK_DATA              = 2;
      private static final int CHUNK_CRLF              = 3;
      private static final int CHUNK_INVALID           = Integer.MAX_VALUE;
  
      private static final int BUFFER_SIZE = 2048;
  
      /** The session input buffer */
      private final SessionInputBuffer in;
      private final CharArrayBuffer buffer;
      private final MessageConstraints constraints;
  
      private int state;
  
      /** The chunk size */
      private long chunkSize;
  
      /** The current position within the current chunk */
      private long pos;
  
      /** True if we've reached the end of stream */
      private boolean eof = false;
  
      /** True if this stream is closed */
      private boolean closed = false;
  
      private HeaderHeader">Header[] footers = new Header[] {};
  
      /**
       * Wraps session input stream and reads chunk coded input.
       *
       * @param in The session input buffer
       * @param constraints Message constraints. If {@code null}
       *   {@link MessageConstraints#DEFAULT} will be used.
       *
       * @since 4.4
       */
      public ChunkedInputStream(final SessionInputBuffer in, final MessageConstraints constraints) {
         super();
         this.in = Args.notNull(in, "Session input buffer");
         this.pos = 0L;
         this.buffer = new CharArrayBuffer(16);
         this.constraints = constraints != null ? constraints : MessageConstraints.DEFAULT;
         this.state = CHUNK_LEN;
     }
 
     /**
      * Wraps session input stream and reads chunk coded input.
      *
      * @param in The session input buffer
      */
     public ChunkedInputStream(final SessionInputBuffer in) {
         this(in, null);
     }
 
     @Override
     public int available() throws IOException {
         if (this.in instanceof BufferInfo) {
             final int len = ((BufferInfo) this.in).length();
             return (int) Math.min(len, this.chunkSize - this.pos);
         }
         return 0;
     }
 
     /**
      * <p> Returns all the data in a chunked stream in coalesced form. A chunk
      * is followed by a CRLF. The method returns -1 as soon as a chunksize of 0
      * is detected.</p>
      *
      * <p> Trailer headers are read automatically at the end of the stream and
      * can be obtained with the getResponseFooters() method.</p>
      *
      * @return -1 of the end of the stream has been reached or the next data
      * byte
      * @throws IOException in case of an I/O error
      */
     @Override
     public int read() throws IOException {
         if (this.closed) {
             throw new IOException("Attempted read from closed stream.");
         }
         if (this.eof) {
             return -1;
         }
         if (state != CHUNK_DATA) {
             nextChunk();
             if (this.eof) {
                 return -1;
             }
         }
         final int b = in.read();
         if (b != -1) {
             pos++;
             if (pos >= chunkSize) {
                 state = CHUNK_CRLF;
             }
         }
         return b;
     }
 
     /**
      * Read some bytes from the stream.
      * @param b The byte array that will hold the contents from the stream.
      * @param off The offset into the byte array at which bytes will start to be
      * placed.
      * @param len the maximum number of bytes that can be returned.
      * @return The number of bytes returned or -1 if the end of stream has been
      * reached.
      * @throws IOException in case of an I/O error
      */
     @Override
     public int read (final byte[] b, final int off, final int len) throws IOException {
 
         if (closed) {
             throw new IOException("Attempted read from closed stream.");
         }
 
         if (eof) {
             return -1;
         }
         if (state != CHUNK_DATA) {
             nextChunk();
             if (eof) {
                 return -1;
             }
         }
         final int readLen = in.read(b, off, (int) Math.min(len, chunkSize - pos));
         if (readLen != -1) {
             pos += readLen;
             if (pos >= chunkSize) {
                 state = CHUNK_CRLF;
             }
             return readLen;
         }
         eof = true;
         throw new TruncatedChunkException("Truncated chunk (expected size: %,d; actual size: %,d)",
                         chunkSize, pos);
     }
 
     /**
      * Read some bytes from the stream.
      * @param b The byte array that will hold the contents from the stream.
      * @return The number of bytes returned or -1 if the end of stream has been
      * reached.
      * @throws IOException in case of an I/O error
      */
     @Override
     public int read (final byte[] b) throws IOException {
         return read(b, 0, b.length);
     }
 
     /**
      * Read the next chunk.
      * @throws IOException in case of an I/O error
      */
     private void nextChunk() throws IOException {
         if (state == CHUNK_INVALID) {
             throw new MalformedChunkCodingException("Corrupt data stream");
         }
         try {
             chunkSize = getChunkSize();
             if (chunkSize < 0L) {
                 throw new MalformedChunkCodingException("Negative chunk size");
             }
             state = CHUNK_DATA;
             pos = 0L;
             if (chunkSize == 0L) {
                 eof = true;
                 parseTrailerHeaders();
             }
         } catch (final MalformedChunkCodingException ex) {
             state = CHUNK_INVALID;
             throw ex;
         }
     }
 
     /**
      * Expects the stream to start with a chunksize in hex with optional
      * comments after a semicolon. The line must end with a CRLF: "a3; some
      * comment\r\n" Positions the stream at the start of the next line.
      */
     private long getChunkSize() throws IOException {
         final int st = this.state;
         switch (st) {
         case CHUNK_CRLF:
             this.buffer.clear();
             final int bytesRead1 = this.in.readLine(this.buffer);
             if (bytesRead1 == -1) {
                 throw new MalformedChunkCodingException(
                     "CRLF expected at end of chunk");
             }
             if (!this.buffer.isEmpty()) {
                 throw new MalformedChunkCodingException(
                     "Unexpected content at the end of chunk");
             }
             state = CHUNK_LEN;
             //$FALL-THROUGH$
         case CHUNK_LEN:
             this.buffer.clear();
             final int bytesRead2 = this.in.readLine(this.buffer);
             if (bytesRead2 == -1) {
                 throw new ConnectionClosedException(
                                 "Premature end of chunk coded message body: closing chunk expected");
             }
             int separator = this.buffer.indexOf(';');
             if (separator < 0) {
                 separator = this.buffer.length();
             }
             final String s = this.buffer.substringTrimmed(0, separator);
             try {
                 return Long.parseLong(s, 16);
             } catch (final NumberFormatException e) {
                 throw new MalformedChunkCodingException("Bad chunk header: " + s);
             }
         default:
             throw new IllegalStateException("Inconsistent codec state");
         }
     }
 
     /**
      * Reads and stores the Trailer headers.
      * @throws IOException in case of an I/O error
      */
     private void parseTrailerHeaders() throws IOException {
         try {
             this.footers = AbstractMessageParser.parseHeaders(in,
                     constraints.getMaxHeaderCount(),
                     constraints.getMaxLineLength(),
                     null);
         } catch (final HttpException ex) {
             final IOException ioe = new MalformedChunkCodingException("Invalid footer: "
                     + ex.getMessage());
             ioe.initCause(ex);
             throw ioe;
         }
     }
 
     /**
      * Upon close, this reads the remainder of the chunked message,
      * leaving the underlying socket at a position to start reading the
      * next response without scanning.
      * @throws IOException in case of an I/O error
      */
     @Override
     public void close() throws IOException {
         if (!closed) {
             try {
                 if (!eof && state != CHUNK_INVALID) {
                     // read and discard the remainder of the message
                     final byte buff[] = new byte[BUFFER_SIZE];
                     while (read(buff) >= 0) {
                     }
                 }
             } finally {
                 eof = true;
                 closed = true;
             }
         }
     }
 
     public Header[] getFooters() {
         return this.footers.clone();
     }
 
 }