/*
    * ====================================================================
    * 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.nio.ContentEncoder;
  import org.apache.http.nio.reactor.SessionOutputBuffer;
  import org.apache.http.util.Args;
  import org.apache.http.util.Asserts;
  
  /**
   * Abstract {@link ContentEncoder} that serves as a base for all content
   * encoder implementations.
   *
   * @since 4.0
   */
  public abstract class AbstractContentEncoder implements ContentEncoder {
  
      protected final WritableByteChannel channel;
      protected final SessionOutputBuffer buffer;
      protected final HttpTransportMetricsImpl metrics;
  
      /**
       * TODO: make private
       */
      protected boolean completed;
  
      /**
       * Creates an instance of this class.
       *
       * @param channel the destination channel.
       * @param buffer the session output buffer that can be used to store
       *    session data for intermediate processing.
       * @param metrics Transport metrics of the underlying HTTP transport.
       */
      public AbstractContentEncoder(
              final WritableByteChannel channel,
              final SessionOutputBuffer buffer,
              final HttpTransportMetricsImpl metrics) {
          super();
          Args.notNull(channel, "Channel");
          Args.notNull(buffer, "Session input buffer");
          Args.notNull(metrics, "Transport metrics");
          this.buffer = buffer;
          this.channel = channel;
          this.metrics = metrics;
      }
  
      @Override
      public boolean isCompleted() {
          return this.completed;
      }
  
      @Override
      public void complete() throws IOException {
          this.completed = true;
      }
  
      protected void assertNotCompleted() {
          Asserts.check(!this.completed, "Encoding process already completed");
      }
  
      /**
       * Flushes content of the session buffer to the channel and updates transport metrics.
       *
       * @return number of bytes written to the channel.
       *
       * @since 4.3
       */
      protected int flushToChannel() throws IOException {
         if (!this.buffer.hasData()) {
             return 0;
         }
         final int bytesWritten = this.buffer.flush(this.channel);
         if (bytesWritten > 0) {
             this.metrics.incrementBytesTransferred(bytesWritten);
         }
         return bytesWritten;
     }
 
     /**
      * Flushes content of the given buffer to the channel and updates transport metrics.
      *
      * @return number of bytes written to the channel.
      *
      * @since 4.3
      */
     protected int writeToChannel(final ByteBuffer src) throws IOException {
         if (!src.hasRemaining()) {
             return 0;
         }
         final int bytesWritten = this.channel.write(src);
         if (bytesWritten > 0) {
             this.metrics.incrementBytesTransferred(bytesWritten);
         }
         return bytesWritten;
     }
 
     /**
      * Transfers content of the source to the channel and updates transport metrics.
      *
      * @param src source.
      * @param limit max number of bytes to transfer.
      * @return number of bytes transferred.
      *
      * @since 4.3
      */
     protected int writeToChannel(final ByteBuffer src, final int limit) throws IOException {
         return doWriteChunk(src, limit, true);
     }
 
     /**
      * Transfers content of the source to the buffer and updates transport metrics.
      *
      * @param src source.
      * @param limit max number of bytes to transfer.
      * @return number of bytes transferred.
      *
      * @since 4.3
      */
     protected int writeToBuffer(final ByteBuffer src, final int limit) throws IOException {
         return doWriteChunk(src, limit, false);
     }
 
     private int doWriteChunk(
         final ByteBuffer src, final int chunk, final boolean direct) throws IOException {
         final int bytesWritten;
         if (src.remaining() > chunk) {
             final int oldLimit = src.limit();
             final int newLimit = oldLimit - (src.remaining() - chunk);
             src.limit(newLimit);
             bytesWritten = doWriteChunk(src, direct);
             src.limit(oldLimit);
         } else {
             bytesWritten = doWriteChunk(src, direct);
         }
         return bytesWritten;
     }
 
     private int doWriteChunk(final ByteBuffer src, final boolean direct) throws IOException {
         if (direct) {
             final int bytesWritten = this.channel.write(src);
             if (bytesWritten > 0) {
                 this.metrics.incrementBytesTransferred(bytesWritten);
             }
             return bytesWritten;
         }
         final int chunk = src.remaining();
         this.buffer.write(src);
         return chunk;
     }
 
 }