/*

  * $Source: /usr/cvsroot/melati/melati/src/main/java/org/melati/template/velocity/WebMacroConverter.java,v $

  * $Revision: 1.9 $

  *

  * Copyright (C) 2006 Tim Pizey

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) the GNU General Public License as published by the Free Software

  *    Foundation; either version 2 of the License, or (at your option)

  *    any later version,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * Contact details for copyright holder:

  *

  *     Tim Pizey <timp At paneris.org>

  */

 package org.melati.template.velocity;

 import java.io.ByteArrayInputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import org.apache.oro.text.perl.Perl5Util;

 import org.melati.util.MelatiBugMelatiException;

 /**

  * Converter from WebMacro templates to Velocity templates.

  * 

  * Note that this does not succeed for modern WebMacro syntax 

  * which uses optionional #begin in #foreach.

  * 

  * @author Tim Pizey based on work by Jason van Zyl and Tim Joyce.

  *

  */

 public final class WebMacroConverter {

   private WebMacroConverter() {}

   /**

    * The regexes to use for substition. The regexes come

    * in pairs. The first is the string to match, the

    * second is the substitution to make.

    */

   public static final String[] regExps = {

         // Make #if directive match the Velocity directive style.

         "#if\\s*[(]\\s*(.*\\S)\\s*[)]\\s*(#begin|{)[ \\t]?",

         "#if( $1 )",

         // Remove the WM #end #else #begin usage.

         "[ \\t]?(#end|})\\s*#else\\s*(#begin|{)[ \\t]?(\\w)",

         "#else#**#$3", // avoid touching a followup word with embedded comment

         "[ \\t]?(#end|})\\s*#else\\s*(#begin|{)[ \\t]?",

         "#else",

         // Convert nulls.

         // This converts

         // $var != null

         // to

         // $var

         "\\s*(\\$[^\\s\\!]+)\\s*!=\\s*null\\s*",

         " $1 ",

         // This converts

         // $var == null

         // to

         // !$var

         "\\s*(\\$[^\\s\\!]+)\\s*==\\s*null\\s*",

         " !$1 ",

         // Convert WM style #foreach to Velocity directive style.

         "#foreach\\s+(\\$\\w+)\\s+in\\s+(\\$[^\\s#]+)\\s*(#begin|{)[ \\t]?",

         "#foreach( $1 in $2 )",

         // Change the "}" to #end. Have to get more

         // sophisticated here. Will assume either {}

         // and no javascript, or #begin/#end with the

         // possibility of javascript.

         "\n}", // assumes that javascript is indented, WMs not!!!

         "\n#end",

         // Convert WM style #set to Velocity directive style.

         //"#set\\s+(\\$[^\\s=]+)\\s*=\\s*(.*\\S)[ \\t]*",

         "#set\\s+(\\$[^\\s=]+)\\s*=\\s*([\\S \\t]+)",

         "#set( $1 = $2 )",

         "(##[# \\t\\w]*)\\)", // fix comments included at end of line

         ")$1",

         // Convert WM style #parse to Velocity directive style.

         "#parse\\s+([^\\s#]+)[ \\t]?",

         "#parse( $1 )",

         // parse is now depricated for web macro

         // include as template is recommended.

         // Velocity supports only parse

         // added for melati conversion

         "#include\\s+as\\s+template\\s+([^\\s#]+)[ \\t]?",

         "#parse( $1 )",

         // Convert WM style #include to Velocity directive style.

         "#include\\s+([^\\s#]+)[ \\t]?",

         "#include( $1 )",

         // Convert WM formal reference to VL syntax.

         "\\$\\(([^\\)]+)\\)",

         "${$1}",

         "\\${([^}\\(]+)\\(([^}]+)}\\)", // fix encapsulated brakets: {(})

         "${$1($2)}",

         // Velocity currently does not permit leading underscore.

         "\\$_",

         "$l_",

         "\\${(_[^}]+)}", // within a formal reference

         "${l$1}",

   };

   /**

    * Do the conversion.

    * 

    * @param in

    * @return the InputStream with substitutions applied

    */

   public static InputStream convert(InputStream in) {

     byte[] ca;

     try {

       ca = new byte[in.available()];

       in.read(ca);

       String contents = new String(ca);

       /* Regular expression tool */

       final Perl5Util perl = new Perl5Util();

       for (int i = 0; i < regExps.length; i += 2) {

         while (perl.match("/" + regExps[i] + "/", contents)) {

           contents = perl.substitute(

               "s/" + regExps[i] + "/" + regExps[i+1] + "/", contents);

         }

       }

       // System.err.println(contents);

       return new ByteArrayInputStream(contents.getBytes());

     } catch (IOException e) {

       throw new MelatiBugMelatiException(

               "Problem loading WebMacro template as a VelocityTemplate", e);

     }

   }

 }