/*

  * 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.

  */

 package org.apache.commons.io.output;

 import java.io.File;

 import java.io.FileNotFoundException;

 import java.io.FileOutputStream;

 import java.io.IOException;

 import java.io.OutputStream;

 import java.io.OutputStreamWriter;

 import java.io.StringWriter;

 import java.io.Writer;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 import org.apache.commons.io.input.XmlStreamReader;

 /**

  * Character stream that handles all the necessary Voodo to figure out the

  * charset encoding of the XML document written to the stream.

  *

  * @version $Id: XmlStreamWriter.java 1415850 2012-11-30 20:51:39Z ggregory $

  * @see XmlStreamReader

  * @since 2.0

  */

 public class XmlStreamWriter extends Writer {

     private static final int BUFFER_SIZE = 4096;

     private final OutputStream out;

     private final String defaultEncoding;

     private StringWriter xmlPrologWriter = new StringWriter(BUFFER_SIZE);

     private Writer writer;

     private String encoding;

     /**

      * Construct an new XML stream writer for the specified output stream

      * with a default encoding of UTF-8.

      *

      * @param out The output stream

      */

     public XmlStreamWriter(final OutputStream out) {

         this(out, null);

     }

     /**

      * Construct an new XML stream writer for the specified output stream

      * with the specified default encoding.

      *

      * @param out The output stream

      * @param defaultEncoding The default encoding if not encoding could be detected

      */

     public XmlStreamWriter(final OutputStream out, final String defaultEncoding) {

         this.out = out;

         this.defaultEncoding = defaultEncoding != null ? defaultEncoding : "UTF-8";

     }

     /**

      * Construct an new XML stream writer for the specified file

      * with a default encoding of UTF-8.

      * 

      * @param file The file to write to

      * @throws FileNotFoundException if there is an error creating or

      * opening the file

      */

     public XmlStreamWriter(final File file) throws FileNotFoundException {

         this(file, null);

     }

     /**

      * Construct an new XML stream writer for the specified file

      * with the specified default encoding.

      * 

      * @param file The file to write to

      * @param defaultEncoding The default encoding if not encoding could be detected

      * @throws FileNotFoundException if there is an error creating or

      * opening the file

      */

     public XmlStreamWriter(final File file, final String defaultEncoding) throws FileNotFoundException {

         this(new FileOutputStream(file), defaultEncoding);

     }

     /**

      * Return the detected encoding.

      *

      * @return the detected encoding

      */

     public String getEncoding() {

         return encoding;

     }

     /**

      * Return the default encoding.

      *

      * @return the default encoding

      */

     public String getDefaultEncoding() {

         return defaultEncoding;

     }

     /**

      * Close the underlying writer.

      *

      * @throws IOException if an error occurs closing the underlying writer

      */

     @Override

     public void close() throws IOException {

         if (writer == null) {

             encoding = defaultEncoding;

             writer = new OutputStreamWriter(out, encoding);

             writer.write(xmlPrologWriter.toString());

         }

         writer.close();

     }

     /**

      * Flush the underlying writer.

      *

      * @throws IOException if an error occurs flushing the underlying writer

      */

     @Override

     public void flush() throws IOException {

         if (writer != null) {

             writer.flush();

         }

     }

     /**

      * Detect the encoding.

      *

      * @param cbuf the buffer to write the characters from

      * @param off The start offset

      * @param len The number of characters to write

      * @throws IOException if an error occurs detecting the encoding

      */

     private void detectEncoding(final char[] cbuf, final int off, final int len)

             throws IOException {

         int size = len;

         final StringBuffer xmlProlog = xmlPrologWriter.getBuffer();

         if (xmlProlog.length() + len > BUFFER_SIZE) {

             size = BUFFER_SIZE - xmlProlog.length();

         }

         xmlPrologWriter.write(cbuf, off, size);

         // try to determine encoding

         if (xmlProlog.length() >= 5) {

             if (xmlProlog.substring(0, 5).equals("<?xml")) {

                 // try to extract encoding from XML prolog

                 final int xmlPrologEnd = xmlProlog.indexOf("?>");

                 if (xmlPrologEnd > 0) {

                     // ok, full XML prolog written: let's extract encoding

                     final Matcher m = ENCODING_PATTERN.matcher(xmlProlog.substring(0,

                             xmlPrologEnd));

                     if (m.find()) {

                         encoding = m.group(1).toUpperCase();

                         encoding = encoding.substring(1, encoding.length() - 1);

                     } else {

                         // no encoding found in XML prolog: using default

                         // encoding

                         encoding = defaultEncoding;

                     }

                 } else {

                     if (xmlProlog.length() >= BUFFER_SIZE) {

                         // no encoding found in first characters: using default

                         // encoding

                         encoding = defaultEncoding;

                     }

                 }

             } else {

                 // no XML prolog: using default encoding

                 encoding = defaultEncoding;

             }

             if (encoding != null) {

                 // encoding has been chosen: let's do it

                 xmlPrologWriter = null;

                 writer = new OutputStreamWriter(out, encoding);

                 writer.write(xmlProlog.toString());

                 if (len > size) {

                     writer.write(cbuf, off + size, len - size);

                 }

             }

         }

     }

     /**

      * Write the characters to the underlying writer, detecing encoding.

      * 

      * @param cbuf the buffer to write the characters from

      * @param off The start offset

      * @param len The number of characters to write

      * @throws IOException if an error occurs detecting the encoding

      */

     @Override

     public void write(final char[] cbuf, final int off, final int len) throws IOException {

         if (xmlPrologWriter != null) {

             detectEncoding(cbuf, off, len);

         } else {

             writer.write(cbuf, off, len);

         }

     }

     static final Pattern ENCODING_PATTERN = XmlStreamReader.ENCODING_PATTERN;

 }