/*
 * 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.juneau.serializer;

import static org.apache.juneau.common.utils.IOUtils.*;
import static org.apache.juneau.common.utils.ThrowableUtils.*;
import static org.apache.juneau.internal.ClassUtils.*;

import java.io.*;
import java.nio.charset.*;

import org.apache.juneau.*;
import org.apache.juneau.common.utils.*;
import org.apache.juneau.internal.*;

/**
 * A wrapper around an object that a serializer sends its output to.
 *
 * <p>
 * For character-based serializers, the output object can be any of the following:
 * <ul>
 *    <li>{@link Writer}
 *    <li>{@link OutputStream} - Output will be written as UTF-8 encoded stream.
 *    <li>{@link File} - Output will be written as system-default encoded stream.
 *    <li>{@link StringBuilder}
 * </ul>
 *
 * <p>
 * For stream-based serializers, the output object can be any of the following:
 * <ul>
 *    <li>{@link OutputStream}
 *    <li>{@link File}
 * </ul>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/SerializersAndParsers">Serializers and Parsers</a>
 * </ul>
 */
public class SerializerPipe implements Closeable {

   private final Object output;
   private final boolean autoClose;

   private OutputStream outputStream;
   private Writer writer;
   private Charset charset;

   /**
    * Writer-based constructor.
    *
    * @param output The object to pipe the serializer output to.
    */
   SerializerPipe(Object output, Charset streamCharset, Charset fileCharset) {
      boolean isFile = (output instanceof File);
      this.output = output;
      this.autoClose = isFile;
      Charset cs = isFile ? fileCharset : streamCharset;
      if (cs == null)
         cs = isFile ? Charset.defaultCharset() : UTF8;
      this.charset = cs;
   }

   /**
    * Stream-based constructor.
    *
    * @param output The object to pipe the serializer output to.
    */
   SerializerPipe(Object output) {
      this.output = output;
      this.autoClose = false;
      this.charset = null;
   }

   /**
    * Wraps the specified output object inside an output stream.
    *
    * <p>
    * Subclasses can override this method to implement their own specialized output streams.
    *
    * <p>
    * This method can be used if the output object is any of the following class types:
    * <ul>
    *    <li>{@link OutputStream}
    *    <li>{@link File}
    * </ul>
    *
    * @return
    *    The output object wrapped in an output stream.
    *    Calling {@link OutputStream#close()} on the returned object simply flushes the response and does not close
    *    the underlying stream.
    * @throws IOException If object could not be converted to an output stream.
    */
   public OutputStream getOutputStream() throws IOException {
      if (output == null)
         throw new IOException("Output cannot be null.");

      if (output instanceof OutputStream)
         outputStream = (OutputStream)output;
      else if (output instanceof File)
         outputStream = new BufferedOutputStream(new FileOutputStream((File)output));
      else
         throw new IOException("Cannot convert object of type "+className(output)+" to an OutputStream.");

      return new NoCloseOutputStream(outputStream);
   }


   /**
    * Wraps the specified output object inside a writer.
    *
    * <p>
    * Subclasses can override this method to implement their own specialized writers.
    *
    * <p>
    * This method can be used if the output object is any of the following class types:
    * <ul>
    *    <li>{@link Writer}
    *    <li>{@link OutputStream} - Output will be written as UTF-8 encoded stream.
    *    <li>{@link File} - Output will be written as system-default encoded stream.
    * </ul>
    *
    * @return
    *    The output object wrapped in a writer.
    *    Calling {@link Writer#close()} on the returned object simply flushes the response and does not close
    *    the underlying writer.
    * @throws SerializeException If object could not be converted to a writer.
    */
   public Writer getWriter() throws SerializeException {
      if (output == null)
         throw new SerializeException("Output cannot be null.");

      try {
         if (output instanceof Writer)
            writer = (Writer)output;
         else if (output instanceof OutputStream)
            writer = new OutputStreamWriter((OutputStream)output, charset);
         else if (output instanceof File)
            writer = new OutputStreamWriter(new BufferedOutputStream(new FileOutputStream((File)output)));
         else if (output instanceof StringBuilder)
            writer = new StringBuilderWriter((StringBuilder)output);
         else
            throw new SerializeException("Cannot convert object of type "+className(output)+" to a Writer.");
      } catch (FileNotFoundException e) {
         throw cast(SerializeException.class, e);
      }

      return new NoCloseWriter(writer);
   }

   /**
    * Overwrites the writer in this pipe.
    *
    * <p>
    * Used when wrapping the writer returned by {@link #getWriter()} so that the wrapped writer will be flushed
    * and closed when {@link #close()} is called.
    *
    * @param writer The wrapped writer.
    */
   public void setWriter(Writer writer) {
      this.writer = writer;
   }

   /**
    * Overwrites the output stream in this pipe.
    *
    * <p>
    * Used when wrapping the stream returned by {@link #getOutputStream()} so that the wrapped stream will be flushed
    * when {@link #close()} is called.
    *
    * @param outputStream The wrapped stream.
    */
   public void setOutputStream(OutputStream outputStream) {
      this.outputStream = outputStream;
   }

   /**
    * Returns the raw output object passed into this session.
    *
    * @return The raw output object passed into this session.
    */
   public Object getRawOutput() {
      return output;
   }

   /**
    * Closes the output pipe.
    */
   @Override /* Closeable */
   public void close() {
      try {
         IOUtils.flush(writer, outputStream);
         if (autoClose)
            IOUtils.close(writer, outputStream);
      } catch (IOException e) {
         throw new BeanRuntimeException(e);
      }
   }
}