/*
    * ====================================================================
    * 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.util;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.http.annotation.ThreadSafe;
  import org.apache.http.nio.ContentEncoder;
  import org.apache.http.nio.IOControl;
  
  /**
   * Implementation of the {@link ContentOutputBuffer} interface that can be
   * shared by multiple threads, usually the I/O dispatch of an I/O reactor and
   * a worker thread.
   * <p>
   * The I/O dispatch thread is expected to transfer data from the buffer to
   *   {@link ContentEncoder} by calling {@link #produceContent(ContentEncoder)}.
   * <p>
   * The worker thread is expected to write data to the buffer by calling
   * {@link #write(int)}, {@link #write(byte[], int, int)} or {@link #writeCompleted()}
   * <p>
   * In case of an abnormal situation or when no longer needed the buffer must be
   * shut down using {@link #shutdown()} method.
   *
   * @since 4.0
   */
  @ThreadSafe
  public class SharedOutputBuffer extends ExpandableBuffer implements ContentOutputBuffer {
  
      private final IOControl ioctrl;
      private final ReentrantLock lock;
      private final Condition condition;
  
      private volatile boolean shutdown = false;
      private volatile boolean endOfStream = false;
  
      public SharedOutputBuffer(int buffersize, final IOControl ioctrl, final ByteBufferAllocator allocator) {
          super(buffersize, allocator);
          if (ioctrl == null) {
              throw new IllegalArgumentException("I/O content control may not be null");
          }
          this.ioctrl = ioctrl;
          this.lock = new ReentrantLock();
          this.condition = this.lock.newCondition();
      }
  
      public void reset() {
          if (this.shutdown) {
              return;
          }
          this.lock.lock();
          try {
              clear();
              this.endOfStream = false;
          } finally {
              this.lock.unlock();
          }
      }
  
      @Override
      public boolean hasData() {
          this.lock.lock();
          try {
              return super.hasData();
          } finally {
              this.lock.unlock();
          }
      }
  
      @Override
      public int available() {
          this.lock.lock();
         try {
             return super.available();
         } finally {
             this.lock.unlock();
         }
     }
 
     @Override
     public int capacity() {
         this.lock.lock();
         try {
             return super.capacity();
         } finally {
             this.lock.unlock();
         }
     }
 
     @Override
     public int length() {
         this.lock.lock();
         try {
             return super.length();
         } finally {
             this.lock.unlock();
         }
     }
 
     public int produceContent(final ContentEncoder encoder) throws IOException {
         if (this.shutdown) {
             return -1;
         }
         this.lock.lock();
         try {
             setOutputMode();
             int bytesWritten = 0;
             if (super.hasData()) {
                 bytesWritten = encoder.write(this.buffer);
                 if (encoder.isCompleted()) {
                     this.endOfStream = true;
                 }
             }
             if (!super.hasData()) {
                 // No more buffered content
                 // If at the end of the stream, terminate
                 if (this.endOfStream && !encoder.isCompleted()) {
                     encoder.complete();
                 }
                 if (!this.endOfStream) {
                     // suspend output events
                     this.ioctrl.suspendOutput();
                 }
             }
             this.condition.signalAll();
             return bytesWritten;
         } finally {
             this.lock.unlock();
         }
     }
 
     public void close() {
         shutdown();
     }
 
     public void shutdown() {
         if (this.shutdown) {
             return;
         }
         this.shutdown = true;
         this.lock.lock();
         try {
             this.condition.signalAll();
         } finally {
             this.lock.unlock();
         }
     }
 
     public void write(final byte[] b, int off, int len) throws IOException {
         if (b == null) {
             return;
         }
         this.lock.lock();
         try {
             if (this.shutdown || this.endOfStream) {
                 throw new IllegalStateException("Buffer already closed for writing");
             }
             setInputMode();
             int remaining = len;
             while (remaining > 0) {
                 if (!this.buffer.hasRemaining()) {
                     flushContent();
                     setInputMode();
                 }
                 int chunk = Math.min(remaining, this.buffer.remaining());
                 this.buffer.put(b, off, chunk);
                 remaining -= chunk;
                 off += chunk;
             }
         } finally {
             this.lock.unlock();
         }
     }
 
     public void write(final byte[] b) throws IOException {
         if (b == null) {
             return;
         }
         write(b, 0, b.length);
     }
 
     public void write(int b) throws IOException {
         this.lock.lock();
         try {
             if (this.shutdown || this.endOfStream) {
                 throw new IllegalStateException("Buffer already closed for writing");
             }
             setInputMode();
             if (!this.buffer.hasRemaining()) {
                 flushContent();
                 setInputMode();
             }
             this.buffer.put((byte)b);
         } finally {
             this.lock.unlock();
         }
     }
 
     public void flush() throws IOException {
     }
 
     private void flushContent() throws IOException {
         this.lock.lock();
         try {
             try {
                 while (super.hasData()) {
                     if (this.shutdown) {
                         throw new InterruptedIOException("Output operation aborted");
                     }
                     this.ioctrl.requestOutput();
                     this.condition.await();
                 }
             } catch (InterruptedException ex) {
                 throw new IOException("Interrupted while flushing the content buffer");
             }
         } finally {
             this.lock.unlock();
         }
     }
 
     public void writeCompleted() throws IOException {
         this.lock.lock();
         try {
             if (this.endOfStream) {
                 return;
             }
             this.endOfStream = true;
             this.ioctrl.requestOutput();
         } finally {
             this.lock.unlock();
         }
     }
 
 }