src/com/ecyrd/jspwiki/VariableManager.java

/* 
    JSPWiki - a JSP-based WikiWiki clone.

    Copyright (C) 2001 Janne Jalkanen (Janne.Jalkanen@iki.fi)

    This program is free software; you can redistribute it and/or modify
    it under the terms of 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.

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package com.ecyrd.jspwiki;

import java.util.Properties;
import java.util.Iterator;
import org.apache.log4j.Category;

/**
 *  Manages variables.  Variables are case-insensitive.  A list of all
 *  available variables is on a Wiki page called "WikiVariables".
 *
 *  @author Janne Jalkanen
 *  @since 1.9.20.
 */
public class VariableManager
{
    private static Category log = Category.getInstance( VariableManager.class );
    
    public VariableManager( Properties props )
    {
    }

    /**
     *  Returns true if the link is really command to insert
     *  a variable.
     *  <P>
     *  Currently we just check if the link starts with "{$".
     */
    public static boolean isVariableLink( String link )
    {
        return link.startsWith("{$");
    }

    /**
     *  Parses the link and finds a value.
     *  <P>
     *  A variable is inserted using the notation [{$variablename}].
     *
     *  @throws IllegalArgumentException If the format is not valid (does not 
     *          start with {$, is zero length, etc.)
     *  @throws NoSuchVariableException If a variable is not known.
     */
    public String parseAndGetValue( WikiContext context,
                                    String link )
        throws IllegalArgumentException,
               NoSuchVariableException
    {
        if( !link.startsWith("{$") )
            throw new IllegalArgumentException( "Link does not start with {$" );

        if( !link.endsWith("}") )
            throw new IllegalArgumentException( "Link does not end with }" );

        String varName = link.substring(2,link.length()-1);

        return getValue( context, varName.trim() );
    }

    /**
     *  This method does in-place expansion of any variables.  However,
     *  the expansion is not done twice, that is, a variable containing text $variable
     *  will not be expanded.
     *  <P>
     *  The variables should be in the same format ({$variablename} as in the web 
     *  pages.
     *
     *  @param context The WikiContext of the current page.
     *  @param source  The source string.
     */
    // FIXME: somewhat slow.
    public String expandVariables( WikiContext context,
                                   String      source )
    {
        StringBuffer result = new StringBuffer();

        for( int i = 0; i < source.length(); i++ )
        {
            if( source.charAt(i) == '{' )
            {
                if( i < source.length()-2 && source.charAt(i+1) == '$' )
                {
                    int end = source.indexOf( '}', i );

                    if( end != -1 )
                    {
                        String varname = source.substring( i+2, end );
                        String value;

                        try
                        {
                            value = getValue( context, varname );
                        }
                        catch( NoSuchVariableException e )
                        {
                            value = e.getMessage();
                        }
                        catch( IllegalArgumentException e )
                        {
                            value = e.getMessage();
                        }

                        result.append( value );
                        i = end;
                        continue;
                    }
                }
                else
                {
                    result.append( '{' );
                }
            }
            else
            {
                result.append( source.charAt(i) );
            }
        }

        return result.toString();
    }

    /**
     *  Returns a value of the named variable.
     *
     *  @param varName Name of the variable.
     *
     *  @throws IllegalArgumentException If the name is somehow broken.
     *  @throws NoSuchVariableException If a variable is not known.
     */
    // FIXME: Currently a bit complicated.  Perhaps should use reflection
    //        or something to make an easy way of doing stuff.
    public String getValue( WikiContext context,
                            String      varName )
        throws IllegalArgumentException,
               NoSuchVariableException
    {
        if( varName == null )
            throw new IllegalArgumentException( "Null variable name." );

        if( varName.length() == 0 )
            throw new IllegalArgumentException( "Zero length variable name." );

        // Faster than doing equalsIgnoreCase()
        String name = varName.toLowerCase();
        String res = "";

        if( name.equals("pagename") )
        {
            res = context.getPage().getName();
        }
        else if( name.equals("applicationname") )
        {
            res = context.getEngine().getApplicationName();
        }
        else if( name.equals("jspwikiversion") )
        {
            res = Release.VERSTR;
        }
        else if( name.equals("encoding") )
        {
            res = context.getEngine().getContentEncoding();
        }
        else if( name.equals("totalpages") )
        {
            res = Integer.toString(context.getEngine().getPageCount());
        }
        else if( name.equals("pageprovider") )
        {
            res = context.getEngine().getCurrentProvider();
        }
        else if( name.equals("pageproviderdescription") )
        {
            res = context.getEngine().getCurrentProviderInfo();
        }
        else if( name.equals("interwikilinks") )
        {
            // FIXME: Use StringBuffer
            for( Iterator i = context.getEngine().getAllInterWikiLinks().iterator(); i.hasNext(); )
            {
                String link = (String) i.next();
                res += link+" --&gt; "+context.getEngine().getInterWikiURL(link)+"<BR>\n";
            }
        }
        else if( name.equals("inlinedimages") )
        {
            // FIXME: Use StringBuffer
            for( Iterator i = context.getEngine().getAllInlinedImagePatterns().iterator(); i.hasNext(); )
            {
                String ptrn = (String) i.next();
                res += ptrn+"<BR>\n";
            }
        }
        else if( name.equals("pluginpath") )
        {
            res = context.getEngine().getPluginSearchPath();

            res = (res == null) ? "-" : res;
        }
        else if( name.equals("baseurl") )
        {
            res = context.getEngine().getBaseURL();
        }
        else
        {
            // 
            // Check if such a context variable exists,
            // returning its string representation.
            //
            if( (context.getVariable( name )) != null )
            {
                return context.getVariable( name ).toString();
            }

            // Final straw: attempt to fetch using property name
            // We don't allow fetching any other properties than those starting
            // with "jspwiki.".  I know my own code, but I can't vouch for bugs
            // in other people's code... :-)
            
            if( varName.startsWith("jspwiki.") )
            {
                Properties props = context.getEngine().getWikiProperties();

                res = props.getProperty( varName );
                if( res != null )
                {
                    return res;
                }
            }
            
            throw new NoSuchVariableException( "No variable "+varName+" defined." );
        }
        
        return res;
    }
}