/*
    * Copyright (c) 2001-2004,
    * RedVerst Group, ISP RAS http://www.ispras.ru
    * All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions are met:
    *
    * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * 3. The names "ATP", "TreeDL", "RedVerst", "ISP RAS"
   *    may not be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
   * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package com.unitesk.atp.text.filters;
  
  import java.util.Stack;
  
  /***
   * This filter manages indent levels and inserts spaces according
   * to the current indent level at the start of every line.
   *
   * @author <A href="mailto:demakov@ispras.ru">Alexey Demakov</A>
   * @version $Id: IndentFilter.java,v 1.1 2004/10/09 06:36:40 all-x Exp $
   */
  public class IndentFilter extends Filter
  {
      /***
       * The default value of indent step.
       */
      public static final int DEFAULT_INDENT_STEP = 4;
  
      /***
       * Constructs indent filter with default indent step.
       *
       * @see #DEFAULT_INDENT_STEP
       */
      public IndentFilter( TextReceiver client )
      {
          super( client );
  
          indent_stack.push( new Integer( 0 ) );
      }
  
      /***
       * Constructs indent server with given indent step.
       *
       * @param indent_step   the indent step value
       * @throws IllegalArgumentException
       *         <code>if indent_step &lt;= 0</code>
       */
      public IndentFilter( TextReceiver client, int indent_step )
      {
          this( client );
  
          if( indent_step <= 0 )
          {
              throw
              new IllegalArgumentException( Integer.toString( indent_step ) );
          }
  
          this.indent_step = indent_step;
      }
  
      /***
       * Returns the indent step.
       */
      public int getIndentStep()
      {
          return indent_step;
      }
  
      /***
       * Pushes in stack new indent level.
       *
       * @param indent   the new indent level
       * @throws IllegalArgumentException
       *         if <code>indent</code> is negative
       */
      public void pushIndent( int indent )
      {
          if( indent < 0 )
         {
             throw new IllegalArgumentException( Integer.toString( indent ) );
         }
         indent_stack.push( new Integer( indent ) );
     }
 
     /***
      * Returns the current indent level.
      *
      * @throws java.util.EmptyStackException
      *         if no indent level is in stack.
      */
     public int getIndent()
     {
         return ((Integer)indent_stack.peek()).intValue();
     }
 
     /***
      * Restores the previous indent level.
      *
      * @throws java.util.EmptyStackException
      *                 if no indent level is in stack.
      */
     public void popIndent()
     {
         indent_stack.pop();
     }
 
     /***
      * Receives string and passes it to the client inserting appropriate
      * number of spaces at the start of each line
      *
      * @param str   the string to receive
      *
      * @throws NullPointerException
      *         if <code>str</code> is <code>null</code>
      */
     public void txt( String str )
     {
         if( str.length() == 0 ) return;
 
         if( is_line_start )
         {
             int indent = ((Integer)indent_stack.peek()).intValue();
             client.txt( fill( ' ', indent ) );
             is_line_start = false;
         }
         client.txt( str );
     }
 
     /***
      * Receives line separator and passes it to the client.
      * The next string received by {@link TextReceiver#txt(String)} will be
      * prefixed by indent.
      *
      * @throws NullPointerException
      *         if <code>c</code> is <code>null</code>
      */
     public void nl()
     {
         client.nl();
         is_line_start = true;
     }
 
     /***
      * Returns the current state of the line start indicator.
      */
     public boolean isLineStart()
     {
         return is_line_start;
     }
 
     /***
      * Fills a string with characters.
      *
      * @param c   the character to fill
      * @param l   the length of the string
      * @return The string of the length <code>l</code> filled by <code>c</code>.
      *         If <code>l &lt; 0</code> empty string is returned.
      */
     public static String fill( char c, int l )
     {
         StringBuffer sb = new StringBuffer( l );
 
         while( l-- > 0 )
         {
             sb.append( c );
         }
 
         return sb.toString();
     }
 
     //--------------------------------------------------------------------------
     // implementation
 
     /***
      * The line start indicator.
      */
     private boolean is_line_start = true;
 
     /***
      * The stack of indent levels.
      */
     private Stack/*Integer*/ indent_stack = new Stack/*Integer*/();
 
     /***
      * The current step of indentation.
      *
      * @see #DEFAULT_INDENT_STEP
      */
     private int indent_step = DEFAULT_INDENT_STEP;
 }