/*
    * ====================================================================
    * 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.io;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CoderResult;
  import java.nio.charset.CodingErrorAction;
  
  import org.apache.http.annotation.NotThreadSafe;
  import org.apache.http.io.BufferInfo;
  import org.apache.http.io.SessionOutputBuffer;
  import org.apache.http.io.HttpTransportMetrics;
  import org.apache.http.params.CoreConnectionPNames;
  import org.apache.http.params.HttpParams;
  import org.apache.http.params.HttpProtocolParams;
  import org.apache.http.protocol.HTTP;
  import org.apache.http.util.ByteArrayBuffer;
  import org.apache.http.util.CharArrayBuffer;
  
  /**
   * Abstract base class for session output buffers that stream data to
   * an arbitrary {@link OutputStream}. This class buffers small chunks of
   * output data in an internal byte array for optimal output performance.
   * <p>
   * {@link #writeLine(CharArrayBuffer)} and {@link #writeLine(String)} methods
   * of this class use CR-LF as a line delimiter.
   * <p>
   * The following parameters can be used to customize the behavior of this
   * class:
   * <ul>
   *  <li>{@link org.apache.http.params.CoreProtocolPNames#HTTP_ELEMENT_CHARSET}</li>
   *  <li>{@link org.apache.http.params.CoreConnectionPNames#MIN_CHUNK_LIMIT}</li>
   * </ul>
   * <p>
   *
   * @since 4.0
   */
  @NotThreadSafe
  public abstract class AbstractSessionOutputBuffer implements SessionOutputBuffer, BufferInfo {
  
      private static final Charset ASCII = Charset.forName("US-ASCII");
      private static final byte[] CRLF = new byte[] {HTTP.CR, HTTP.LF};
  
      private OutputStream outstream;
      private ByteArrayBuffer buffer;
  
      private Charset charset;
      private CharsetEncoder encoder;
      private ByteBuffer bbuf;
      private boolean ascii = true;
      private int minChunkLimit = 512;
  
      private HttpTransportMetricsImpl metrics;
  
      private CodingErrorAction onMalformedInputAction;
      private CodingErrorAction onUnMappableInputAction;
  
      /**
       * Initializes this session output buffer.
       *
       * @param outstream the destination output stream.
       * @param buffersize the size of the internal buffer.
       * @param params HTTP parameters.
       */
      protected void init(final OutputStream outstream, int buffersize, final HttpParams params) {
          if (outstream == null) {
              throw new IllegalArgumentException("Input stream may not be null");
          }
          if (buffersize <= 0) {
             throw new IllegalArgumentException("Buffer size may not be negative or zero");
         }
         if (params == null) {
             throw new IllegalArgumentException("HTTP parameters may not be null");
         }
         this.outstream = outstream;
         this.buffer = new ByteArrayBuffer(buffersize);
         this.charset = Charset.forName(HttpProtocolParams.getHttpElementCharset(params));
         this.ascii = this.charset.equals(ASCII);
         this.encoder = null;
         this.minChunkLimit = params.getIntParameter(CoreConnectionPNames.MIN_CHUNK_LIMIT, 512);
         this.metrics = createTransportMetrics();
         this.onMalformedInputAction = HttpProtocolParams.getMalformedInputAction(params);
         this.onUnMappableInputAction = HttpProtocolParams.getUnmappableInputAction(params);
     }
 
     /**
      * @since 4.1
      */
     protected HttpTransportMetricsImpl createTransportMetrics() {
         return new HttpTransportMetricsImpl();
     }
 
     /**
      * @since 4.1
      */
     public int capacity() {
         return this.buffer.capacity();
     }
 
     /**
      * @since 4.1
      */
     public int length() {
         return this.buffer.length();
     }
 
     /**
      * @since 4.1
      */
     public int available() {
         return capacity() - length();
     }
 
     protected void flushBuffer() throws IOException {
         int len = this.buffer.length();
         if (len > 0) {
             this.outstream.write(this.buffer.buffer(), 0, len);
             this.buffer.clear();
             this.metrics.incrementBytesTransferred(len);
         }
     }
 
     public void flush() throws IOException {
         flushBuffer();
         this.outstream.flush();
     }
 
     public void write(final byte[] b, int off, int len) throws IOException {
         if (b == null) {
             return;
         }
         // Do not want to buffer large-ish chunks
         // if the byte array is larger then MIN_CHUNK_LIMIT
         // write it directly to the output stream
         if (len > this.minChunkLimit || len > this.buffer.capacity()) {
             // flush the buffer
             flushBuffer();
             // write directly to the out stream
             this.outstream.write(b, off, len);
             this.metrics.incrementBytesTransferred(len);
         } else {
             // Do not let the buffer grow unnecessarily
             int freecapacity = this.buffer.capacity() - this.buffer.length();
             if (len > freecapacity) {
                 // flush the buffer
                 flushBuffer();
             }
             // buffer
             this.buffer.append(b, off, len);
         }
     }
 
     public void write(final byte[] b) throws IOException {
         if (b == null) {
             return;
         }
         write(b, 0, b.length);
     }
 
     public void write(int b) throws IOException {
         if (this.buffer.isFull()) {
             flushBuffer();
         }
         this.buffer.append(b);
     }
 
     /**
      * Writes characters from the specified string followed by a line delimiter
      * to this session buffer.
      * <p>
      * This method uses CR-LF as a line delimiter.
      *
      * @param      s   the line.
      * @exception  IOException  if an I/O error occurs.
      */
     public void writeLine(final String s) throws IOException {
         if (s == null) {
             return;
         }
         if (s.length() > 0) {
             if (this.ascii) {
                 for (int i = 0; i < s.length(); i++) {
                     write(s.charAt(i));
                 }
             } else {
                 CharBuffer cbuf = CharBuffer.wrap(s);
                 writeEncoded(cbuf);
             }
         }
         write(CRLF);
     }
 
     /**
      * Writes characters from the specified char array followed by a line
      * delimiter to this session buffer.
      * <p>
      * This method uses CR-LF as a line delimiter.
      *
      * @param      charbuffer the buffer containing chars of the line.
      * @exception  IOException  if an I/O error occurs.
      */
     public void writeLine(final CharArrayBuffer charbuffer) throws IOException {
         if (charbuffer == null) {
             return;
         }
         if (this.ascii) {
             int off = 0;
             int remaining = charbuffer.length();
             while (remaining > 0) {
                 int chunk = this.buffer.capacity() - this.buffer.length();
                 chunk = Math.min(chunk, remaining);
                 if (chunk > 0) {
                     this.buffer.append(charbuffer, off, chunk);
                 }
                 if (this.buffer.isFull()) {
                     flushBuffer();
                 }
                 off += chunk;
                 remaining -= chunk;
             }
         } else {
             CharBuffer cbuf = CharBuffer.wrap(charbuffer.buffer(), 0, charbuffer.length());
             writeEncoded(cbuf);
         }
         write(CRLF);
     }
 
     private void writeEncoded(final CharBuffer cbuf) throws IOException {
         if (!cbuf.hasRemaining()) {
             return;
         }
         if (this.encoder == null) {
             this.encoder = this.charset.newEncoder();
             this.encoder.onMalformedInput(this.onMalformedInputAction);
             this.encoder.onUnmappableCharacter(this.onUnMappableInputAction);
         }
         if (this.bbuf == null) {
             this.bbuf = ByteBuffer.allocate(1024);
         }
         this.encoder.reset();
         while (cbuf.hasRemaining()) {
             CoderResult result = this.encoder.encode(cbuf, this.bbuf, true);
             handleEncodingResult(result);
         }
         CoderResult result = this.encoder.flush(this.bbuf);
         handleEncodingResult(result);
         this.bbuf.clear();
     }
 
     private void handleEncodingResult(final CoderResult result) throws IOException {
         if (result.isError()) {
             result.throwException();
         }
         this.bbuf.flip();
         while (this.bbuf.hasRemaining()) {
             write(this.bbuf.get());
         }
         this.bbuf.compact();
     }
 
     public HttpTransportMetrics getMetrics() {
         return this.metrics;
     }
 
 }