/*
    * ====================================================================
    * 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.nio.client.methods;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import java.nio.charset.CoderResult;
  
  import org.apache.http.HttpEntity;
  import org.apache.http.entity.ContentType;
  import org.apache.http.nio.ContentDecoder;
  import org.apache.http.nio.IOControl;
  import org.apache.http.nio.protocol.AbstractAsyncResponseConsumer;
  import org.apache.http.protocol.HTTP;
  import org.apache.http.util.Asserts;
  
  /**
   * {@link org.apache.http.nio.protocol.HttpAsyncResponseConsumer} implementation that
   * provides convenience methods for processing of textual content entities enclosed
   * in an HTTP response.
   *
   * @since 4.0
   */
  public abstract class AsyncCharConsumer<T> extends AbstractAsyncResponseConsumer<T> {
  
      private final ByteBuffer bbuf;
      private final CharBuffer cbuf;
  
      private CharsetDecoder charDecoder;
  
      public AsyncCharConsumer(final int bufSize) {
          super();
          this.bbuf = ByteBuffer.allocate(bufSize);
          this.cbuf = CharBuffer.allocate(bufSize);
      }
  
      public AsyncCharConsumer() {
          this(8 * 1024);
      }
  
      /**
       * Invoked to process a {@link CharBuffer chunk} of content.
       * The {@link IOControl} interface can be used to suspend input events
       * if the consumer is temporarily unable to consume more content.
       *
       * @param buf chunk of content.
       * @param ioControl I/O control of the underlying connection.
       * @throws IOException in case of an I/O error
       */
      protected abstract void onCharReceived(
              CharBuffer buf, IOControl ioControl) throws IOException;
  
      /**
       * Invoked to create a @{link CharsetDecoder} for contentType.
       * This allows to use different default charsets for different content
       * types and set appropriate coding error actions.
       *
       * @param contentType response Content-Type or null if not specified.
       * @return content decoder.
       *
       * @since 4.1
       */
      protected CharsetDecoder createDecoder(final ContentType contentType) {
          Charset charset = contentType != null ? contentType.getCharset() : null;
          if (charset == null) {
              charset = HTTP.DEF_CONTENT_CHARSET;
          }
          return charset.newDecoder();
      }
  
      @Override
      protected final void onEntityEnclosed(
             final HttpEntity entity, final ContentType contentType) throws IOException {
         this.charDecoder = createDecoder(contentType != null ? contentType : ContentType.DEFAULT_TEXT);
     }
 
     @Override
     protected final void onContentReceived(
             final ContentDecoder decoder, final IOControl ioControl) throws IOException {
         Asserts.notNull(this.bbuf, "Byte buffer");
 
         final int bytesRead = decoder.read(this.bbuf);
         if (bytesRead <= 0) {
             return;
         }
         this.bbuf.flip();
         final boolean completed = decoder.isCompleted();
         CoderResult result = this.charDecoder.decode(this.bbuf, this.cbuf, completed);
         handleDecodingResult(result, ioControl);
         this.bbuf.compact();
         if (completed) {
             result = this.charDecoder.flush(this.cbuf);
             handleDecodingResult(result, ioControl);
         }
     }
 
     private void handleDecodingResult(
             final CoderResult result, final IOControl ioControl) throws IOException {
         if (result.isError()) {
             result.throwException();
         }
         this.cbuf.flip();
         if (this.cbuf.hasRemaining()) {
             onCharReceived(this.cbuf, ioControl);
         }
         this.cbuf.clear();
     }
 
     @Override
     protected void releaseResources() {
     }
 
 }