/*
    * ====================================================================
    * 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.hc.core5.http.impl.io;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.List;
  
  import org.apache.hc.core5.function.Supplier;
  import org.apache.hc.core5.http.FormattedHeader;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.StreamClosedException;
  import org.apache.hc.core5.http.io.SessionOutputBuffer;
  import org.apache.hc.core5.http.message.BasicLineFormatter;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.CharArrayBuffer;
  
  /**
   * Implements chunked transfer coding. The content is sent in small chunks.
   * Entities transferred using this output stream can be of unlimited length.
   * Writes are buffered to an internal buffer (2048 default size).
   * <p>
   * Note that this class NEVER closes the underlying stream, even when close
   * gets called.  Instead, the stream will be marked as closed and no further
   * output will be permitted.
   *
   *
   * @since 4.0
   */
  public class ChunkedOutputStream extends OutputStream {
  
      private final SessionOutputBuffer buffer;
      private final OutputStream outputStream;
  
      private final byte[] cache;
      private int cachePosition = 0;
      private boolean wroteLastChunk = false;
      private boolean closed = false;
      private final CharArrayBuffer lineBuffer;
      private final Supplier<List<? extends Header>> trailerSupplier;
  
      /**
       * Default constructor.
       *
       * @param buffer Session output buffer
       * @param outputStream Output stream
       * @param chunkSizeHint minimal chunk size hint
       * @param trailerSupplier Trailer supplier. May be {@code null}
       *
       * @since 5.0
       */
      public ChunkedOutputStream(
              final SessionOutputBuffer buffer,
              final OutputStream outputStream,
              final int chunkSizeHint,
              final Supplier<List<? extends Header>> trailerSupplier) {
          super();
          this.buffer = Args.notNull(buffer, "Session output buffer");
          this.outputStream = Args.notNull(outputStream, "Output stream");
          this.cache = new byte[chunkSizeHint > 0 ? chunkSizeHint : 2048];
          this.lineBuffer = new CharArrayBuffer(32);
          this.trailerSupplier = trailerSupplier;
      }
  
      /**
       * Constructor with no trailers.
       *
       * @param buffer Session output buffer
       * @param outputStream Output stream
       * @param chunkSizeHint minimal chunk size hint
       */
      public ChunkedOutputStream(final SessionOutputBuffer buffer, final OutputStream outputStream, final int chunkSizeHint) {
          this(buffer, outputStream, chunkSizeHint, null);
      }
 
     /**
      * Writes the cache out onto the underlying stream
      */
     private void flushCache() throws IOException {
         if (this.cachePosition > 0) {
             this.lineBuffer.clear();
             this.lineBuffer.append(Integer.toHexString(this.cachePosition));
             this.buffer.writeLine(this.lineBuffer, this.outputStream);
             this.buffer.write(this.cache, 0, this.cachePosition, this.outputStream);
             this.lineBuffer.clear();
             this.buffer.writeLine(this.lineBuffer, this.outputStream);
             this.cachePosition = 0;
         }
     }
 
     /**
      * Writes the cache and bufferToAppend to the underlying stream
      * as one large chunk
      */
     private void flushCacheWithAppend(final byte[] bufferToAppend, final int off, final int len) throws IOException {
         this.lineBuffer.clear();
         this.lineBuffer.append(Integer.toHexString(this.cachePosition + len));
         this.buffer.writeLine(this.lineBuffer, this.outputStream);
         this.buffer.write(this.cache, 0, this.cachePosition, this.outputStream);
         this.buffer.write(bufferToAppend, off, len, this.outputStream);
         this.lineBuffer.clear();
         this.buffer.writeLine(this.lineBuffer, this.outputStream);
         this.cachePosition = 0;
     }
 
     private void writeClosingChunk() throws IOException {
         // Write the final chunk.
         this.lineBuffer.clear();
         this.lineBuffer.append('0');
         this.buffer.writeLine(this.lineBuffer, this.outputStream);
         writeTrailers();
         this.lineBuffer.clear();
         this.buffer.writeLine(this.lineBuffer, this.outputStream);
     }
 
     private void writeTrailers() throws IOException {
         final List<? extends Header> trailers = this.trailerSupplier != null ? this.trailerSupplier.get() : null;
         if (trailers != null) {
             for (int i = 0; i < trailers.size(); i++) {
                 final Header header = trailers.get(i);
                 if (header instanceof FormattedHeader) {
                     final CharArrayBuffer chbuffer = ((FormattedHeader) header).getBuffer();
                     this.buffer.writeLine(chbuffer, this.outputStream);
                 } else {
                     this.lineBuffer.clear();
                     BasicLineFormatter.INSTANCE.formatHeader(this.lineBuffer, header);
                     this.buffer.writeLine(this.lineBuffer, this.outputStream);
                 }
             }
         }
     }
 
     // ----------------------------------------------------------- Public Methods
     /**
      * Must be called to ensure the internal cache is flushed and the closing
      * chunk is written.
      * @throws IOException in case of an I/O error
      */
     public void finish() throws IOException {
         if (!this.wroteLastChunk) {
             flushCache();
             writeClosingChunk();
             this.wroteLastChunk = true;
         }
     }
 
     // -------------------------------------------- OutputStream Methods
     @Override
     public void write(final int b) throws IOException {
         if (this.closed) {
             throw new StreamClosedException();
         }
         this.cache[this.cachePosition] = (byte) b;
         this.cachePosition++;
         if (this.cachePosition == this.cache.length) {
             flushCache();
         }
     }
 
     /**
      * Writes the array. If the array does not fit within the buffer, it is
      * not split, but rather written out as one large chunk.
      */
     @Override
     public void write(final byte[] b) throws IOException {
         write(b, 0, b.length);
     }
 
     /**
      * Writes the array. If the array does not fit within the buffer, it is
      * not split, but rather written out as one large chunk.
      */
     @Override
     public void write(final byte[] src, final int off, final int len) throws IOException {
         if (this.closed) {
             throw new StreamClosedException();
         }
         if (len >= this.cache.length - this.cachePosition) {
             flushCacheWithAppend(src, off, len);
         } else {
             System.arraycopy(src, off, cache, this.cachePosition, len);
             this.cachePosition += len;
         }
     }
 
     /**
      * Flushes the content buffer and the underlying stream.
      */
     @Override
     public void flush() throws IOException {
         flushCache();
         this.buffer.flush(this.outputStream);
     }
 
     /**
      * Finishes writing to the underlying stream, but does NOT close the underlying stream.
      */
     @Override
     public void close() throws IOException {
         if (!this.closed) {
             this.closed = true;
             finish();
             this.buffer.flush(this.outputStream);
         }
     }
 }