/*
    * 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.log4j;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import org.apache.log4j.helpers.LogLog;
  
  /**
    * ConsoleAppender appends log events to <code>System.out</code> or
    * <code>System.err</code> using a layout specified by the user. The
    * default target is <code>System.out</code>.
    *
    * @author Ceki G&uuml;lc&uuml; 
    * @author Curt Arnold
    * @since 1.1 */
  public class ConsoleAppender extends WriterAppender {
  
    public static final String SYSTEM_OUT = "System.out";
    public static final String SYSTEM_ERR = "System.err";
  
    protected String target = SYSTEM_OUT;
  
    /**
     *  Determines if the appender honors reassignments of System.out
     *  or System.err made after configuration.
     */
    private boolean follow = false;
  
    /**
      * Constructs an unconfigured appender.
      */
    public ConsoleAppender() {
    }
  
      /**
       * Creates a configured appender.
       *
       * @param layout layout, may not be null.
       */
    public ConsoleAppender(Layout layout) {
      this(layout, SYSTEM_OUT);
    }
  
      /**
       *   Creates a configured appender.
       * @param layout layout, may not be null.
       * @param target target, either "System.err" or "System.out".
       */
    public ConsoleAppender(Layout layout, String target) {
      setLayout(layout);
      setTarget(target);
      activateOptions();
    }
  
    /**
     *  Sets the value of the <b>Target</b> option. Recognized values
     *  are "System.out" and "System.err". Any other value will be
     *  ignored.  
     * */
    public
    void setTarget(String value) {
      String v = value.trim();
  
      if (SYSTEM_OUT.equalsIgnoreCase(v)) {
        target = SYSTEM_OUT;
      } else if (SYSTEM_ERR.equalsIgnoreCase(v)) {
        target = SYSTEM_ERR;
      } else {
        targetWarn(value);
      }
    }
  
    /**
     * Returns the current value of the <b>Target</b> property. The
     * default value of the option is "System.out".
     *
     * See also {@link #setTarget}.
     * */
    public
    String getTarget() {
      return target;
    }
    
   /**
    *  Sets whether the appender honors reassignments of System.out
    *  or System.err made after configuration.
    *  @param newValue if true, appender will use value of System.out or
    *  System.err in force at the time when logging events are appended.
    *  @since 1.2.13
    */
   public final void setFollow(final boolean newValue) {
      follow = newValue;
   }
   
   /**
    *  Gets whether the appender honors reassignments of System.out
    *  or System.err made after configuration.
    *  @return true if appender will use value of System.out or
    *  System.err in force at the time when logging events are appended.
    *  @since 1.2.13
    */
   public final boolean getFollow() {
       return follow;
   }
 
   void targetWarn(String val) {
     LogLog.warn("["+val+"] should be System.out or System.err.");
     LogLog.warn("Using previously set target, System.out by default.");
   }
 
   /**
     *   Prepares the appender for use.
     */
    public void activateOptions() {
         if (follow) {
             if (target.equals(SYSTEM_ERR)) {
                setWriter(createWriter(new SystemErrStream()));
             } else {
                setWriter(createWriter(new SystemOutStream()));
             }
         } else {
             if (target.equals(SYSTEM_ERR)) {
                setWriter(createWriter(System.err));
             } else {
                setWriter(createWriter(System.out));
             }
         }
 
         super.activateOptions();
   }
   
   /**
    *  {@inheritDoc}
    */
   protected
   final
   void closeWriter() {
      if (follow) {
         super.closeWriter();
      }
   }
   
 
     /**
      * An implementation of OutputStream that redirects to the
      * current System.err.
      *
      */
     private static class SystemErrStream extends OutputStream {
         public SystemErrStream() {
         }
 
         public void close() {
         }
 
         public void flush() {
             System.err.flush();
         }
 
         public void write(final byte[] b) throws IOException {
             System.err.write(b);
         }
 
         public void write(final byte[] b, final int off, final int len)
             throws IOException {
             System.err.write(b, off, len);
         }
 
         public void write(final int b) throws IOException {
             System.err.write(b);
         }
     }
 
     /**
      * An implementation of OutputStream that redirects to the
      * current System.out.
      *
      */
     private static class SystemOutStream extends OutputStream {
         public SystemOutStream() {
         }
 
         public void close() {
         }
 
         public void flush() {
             System.out.flush();
         }
 
         public void write(final byte[] b) throws IOException {
             System.out.write(b);
         }
 
         public void write(final byte[] b, final int off, final int len)
             throws IOException {
             System.out.write(b, off, len);
         }
 
         public void write(final int b) throws IOException {
             System.out.write(b);
         }
     }
 
 }