/*
    * ====================================================================
    * 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.nio.codecs;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.WritableByteChannel;
  
  import org.apache.http.impl.io.HttpTransportMetricsImpl;
  import org.apache.http.io.BufferInfo;
  import org.apache.http.nio.reactor.SessionOutputBuffer;
  import org.apache.http.util.CharArrayBuffer;
  
  /**
   * Implements chunked transfer coding. The content is sent in small chunks.
   * Entities transferred using this decoder can be of unlimited length.
   *
   * @since 4.0
   */
  public class ChunkEncoder extends AbstractContentEncoder {
  
      private final int fragHint;
      private final CharArrayBuffer lineBuffer;
  
      private final BufferInfo bufferinfo;
  
      /**
       * @since 4.3
       *
       * @param channel underlying channel.
       * @param buffer  session buffer.
       * @param metrics transport metrics.
       * @param fragementSizeHint fragment size hint defining an minimal size of a fragment
       *   that should be written out directly to the channel bypassing the session buffer.
       *   Value {@code 0} disables fragment buffering.
       */
      public ChunkEncoder(
              final WritableByteChannel channel,
              final SessionOutputBuffer buffer,
              final HttpTransportMetricsImpl metrics,
              final int fragementSizeHint) {
          super(channel, buffer, metrics);
          this.fragHint = fragementSizeHint > 0 ? fragementSizeHint : 0;
          this.lineBuffer = new CharArrayBuffer(16);
          if (buffer instanceof BufferInfo) {
              this.bufferinfo = (BufferInfo) buffer;
          } else {
              this.bufferinfo = null;
          }
      }
  
      public ChunkEncoder(
              final WritableByteChannel channel,
              final SessionOutputBuffer buffer,
              final HttpTransportMetricsImpl metrics) {
          this(channel, buffer, metrics, 0);
      }
  
      @Override
      public int write(final ByteBuffer src) throws IOException {
          if (src == null) {
              return 0;
          }
          assertNotCompleted();
  
          int total = 0;
          while (src.hasRemaining()) {
              int chunk = src.remaining();
              int avail;
              if (this.bufferinfo != null) {
                  avail = this.bufferinfo.available();
              } else {
                  avail = 4096;
              }
 
             // subtract the length of the longest chunk header
             // 12345678\r\n
             // <chunk-data>\r\n
             avail -= 12;
             if (avail > 0) {
                 if (avail < chunk) {
                     // write no more than 'avail' bytes
                     chunk = avail;
                     this.lineBuffer.clear();
                     this.lineBuffer.append(Integer.toHexString(chunk));
                     this.buffer.writeLine(this.lineBuffer);
                     final int oldlimit = src.limit();
                     src.limit(src.position() + chunk);
                     this.buffer.write(src);
                     src.limit(oldlimit);
                 } else {
                     // write all
                     this.lineBuffer.clear();
                     this.lineBuffer.append(Integer.toHexString(chunk));
                     this.buffer.writeLine(this.lineBuffer);
                     this.buffer.write(src);
                 }
                 this.lineBuffer.clear();
                 this.buffer.writeLine(this.lineBuffer);
                 total += chunk;
             }
             if (this.buffer.length() >= this.fragHint || src.hasRemaining()) {
                 final int bytesWritten = flushToChannel();
                 if (bytesWritten == 0) {
                     break;
                 }
             }
         }
         return total;
     }
 
     @Override
     public void complete() throws IOException {
         assertNotCompleted();
         this.lineBuffer.clear();
         this.lineBuffer.append("0");
         this.buffer.writeLine(this.lineBuffer);
         this.lineBuffer.clear();
         this.buffer.writeLine(this.lineBuffer);
         super.complete();
     }
 
     @Override
     public String toString() {
         final StringBuilder sb = new StringBuilder();
         sb.append("[chunk-coded; completed: ");
         sb.append(isCompleted());
         sb.append("]");
         return sb.toString();
     }
 
 }