/*
    * ====================================================================
    * 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.hc.core5.http.impl.nio;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.channels.ReadableByteChannel;
  import java.nio.channels.WritableByteChannel;
  import java.nio.charset.CharacterCodingException;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CoderResult;
  
  import org.apache.hc.core5.http.Chars;
  import org.apache.hc.core5.http.nio.SessionOutputBuffer;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.CharArrayBuffer;
  
  class SessionOutputBufferImpl extends ExpandableBuffer implements SessionOutputBuffer {
  
      private static final byte[] CRLF = new byte[] {Chars.CR, Chars.LF};
  
      private final CharsetEncoder charEncoder;
      private final int lineBuffersize;
  
      private CharBuffer charbuffer;
  
      /**
       *  Creates SessionOutputBufferImpl instance.
       *
       * @param bufferSize input buffer size
       * @param lineBuffersize buffer size for line operations. Has effect only if
       *   {@code charEncoder} is not {@code null}.
       * @param charEncoder charEncoder to be used for encoding HTTP protocol elements.
       *   If {@code null} simple type cast will be used for char to byte conversion.
       *
       * @since 4.3
       */
      public SessionOutputBufferImpl(
              final int bufferSize,
              final int lineBuffersize,
              final CharsetEncoder charEncoder) {
          super(bufferSize);
          this.lineBuffersize = Args.positive(lineBuffersize, "Line buffer size");
          this.charEncoder = charEncoder;
      }
  
      /**
       * @since 4.3
       */
      public SessionOutputBufferImpl(
              final int bufferSize,
              final int lineBufferSize,
              final Charset charset) {
          this(bufferSize, lineBufferSize, charset != null ? charset.newEncoder() : null);
      }
  
      /**
       * @since 4.3
       */
      public SessionOutputBufferImpl(
              final int bufferSize,
              final int lineBufferSize) {
          this(bufferSize, lineBufferSize, (CharsetEncoder) null);
      }
  
      /**
       * @since 4.3
       */
      public SessionOutputBufferImpl(final int bufferSize) {
          this(bufferSize, 256);
      }
  
     @Override
     public int length() {
         return super.length();
     }
 
     @Override
     public boolean hasData() {
         return super.hasData();
     }
 
     @Override
     public int capacity() {
         return super.capacity();
     }
 
     @Override
     public int flush(final WritableByteChannel channel) throws IOException {
         Args.notNull(channel, "Channel");
         setOutputMode();
         return channel.write(buffer());
     }
 
     @Override
     public void write(final ByteBuffer src) {
         if (src == null) {
             return;
         }
         setInputMode();
         ensureAdjustedCapacity(buffer().position() + src.remaining());
         buffer().put(src);
     }
 
     @Override
     public void write(final ReadableByteChannel src) throws IOException {
         if (src == null) {
             return;
         }
         setInputMode();
         src.read(buffer());
     }
 
     private void write(final byte[] b) {
         if (b == null) {
             return;
         }
         setInputMode();
         final int off = 0;
         final int len = b.length;
         final int requiredCapacity = buffer().position() + len;
         ensureAdjustedCapacity(requiredCapacity);
         buffer().put(b, off, len);
     }
 
     private void writeCRLF() {
         write(CRLF);
     }
 
     @Override
     public void writeLine(final CharArrayBuffer lineBuffer) throws CharacterCodingException {
         if (lineBuffer == null) {
             return;
         }
         setInputMode();
         // Do not bother if the buffer is empty
         if (lineBuffer.length() > 0 ) {
             if (this.charEncoder == null) {
                 final int requiredCapacity = buffer().position() + lineBuffer.length();
                 ensureCapacity(requiredCapacity);
                 if (buffer().hasArray()) {
                     final byte[] b = buffer().array();
                     final int len = lineBuffer.length();
                     final int off = buffer().position();
                     final int arrayOffset = buffer().arrayOffset();
                     for (int i = 0; i < len; i++) {
                         b[arrayOffset + off + i]  = (byte) lineBuffer.charAt(i);
                     }
                     buffer().position(off + len);
                 } else {
                     for (int i = 0; i < lineBuffer.length(); i++) {
                         buffer().put((byte) lineBuffer.charAt(i));
                     }
                 }
             } else {
                 if (this.charbuffer == null) {
                     this.charbuffer = CharBuffer.allocate(this.lineBuffersize);
                 }
                 this.charEncoder.reset();
                 // transfer the string in small chunks
                 int remaining = lineBuffer.length();
                 int offset = 0;
                 while (remaining > 0) {
                     int l = this.charbuffer.remaining();
                     boolean eol = false;
                     if (remaining <= l) {
                         l = remaining;
                         // terminate the encoding process
                         eol = true;
                     }
                     this.charbuffer.put(lineBuffer.array(), offset, l);
                     this.charbuffer.flip();
 
                     boolean retry = true;
                     while (retry) {
                         final CoderResult result = this.charEncoder.encode(this.charbuffer, buffer(), eol);
                         if (result.isError()) {
                             result.throwException();
                         }
                         if (result.isOverflow()) {
                             expand();
                         }
                         retry = !result.isUnderflow();
                     }
                     this.charbuffer.compact();
                     offset += l;
                     remaining -= l;
                 }
                 // flush the encoder
                 boolean retry = true;
                 while (retry) {
                     final CoderResult result = this.charEncoder.flush(buffer());
                     if (result.isError()) {
                         result.throwException();
                     }
                     if (result.isOverflow()) {
                         expand();
                     }
                     retry = !result.isUnderflow();
                 }
             }
         }
         writeCRLF();
     }
 
 }