Re: A WM brain bender: The solution

/*
 * Copyright (C) 2005.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted under the terms of either of the following
 * Open Source licenses:
 *
 * The GNU General Public License, version 2, or any later version, as
 * published by the Free Software Foundation
 * (http://www.fsf.org/copyleft/gpl.html);
 *
 * This software is provided "as is", with NO WARRANTY, not even the
 * implied warranties of fitness to purpose, or merchantability. You
 * assume all risks and liabilities associated with its use.
 *
 * See www.webmacro.org for more information on the WebMacro project.
 *
 * @author Mike Weerdenburg
 *
 * @version	14-01-2005
 *
 */

package org.webmacro.directive;

import org.webmacro.*;
import org.webmacro.engine.*;

/**
 * EvalStringTemplateDirective allows you to evaluate a string just like it is a include / template against the current context.<p>
 *
 * Syntax:<pre>
 *    #EvalStringTemplate $valueToEvaluateAsString [to $variable]
 *</pre>
 *
 */
public class EvalStringTemplateDirective extends Directive
{
    /* the argument is NOT a file, but a string represending the template! */
    private static final int PARSE_VALUE = 1;
    private static final int PARSE_TO = 2;
    private static final int PARSE_TO_VARIABLE = 3;

    private Variable _varTarget = null;

    private static final UndefinedMacro UNDEF = UndefinedMacro.getInstance();

    private static final ArgDescriptor[] _args = new ArgDescriptor[]
    {
        new StringArg(PARSE_VALUE),
        new OptionalGroup(2),
        new KeywordArg(PARSE_TO, "to"),
        new LValueArg(PARSE_TO_VARIABLE),
    };

    private static final DirectiveDescriptor _desc = new DirectiveDescriptor("evalStringTemplate", null, _args, null);

    public static DirectiveDescriptor getDescriptor ()
    {
        return _desc;
    }

    //
    // these values are customized for this directive during build()
    //

    /** Logging can be good */
    protected Log _log;

    /** the value as a Macro, if the value arg is a Macro */
    protected Macro _macroValue;

    /**
     * the name given to the directive by webmacro configuration.
     */
    protected String _directiveName;

    public final Object build (DirectiveBuilder builder, BuildContext bc) throws BuildException
    {
        // Get a log-instance.
        // In webmacro.properties : LogLevel.directive=DEBUG
        _log = bc.getLog("directive");

        // name of this directive
        _directiveName = builder.getName();

        // if a target provided, then output to the target!
        if (builder.getArg(PARSE_TO_VARIABLE, bc) != null)
        {
            try
            {
                _varTarget = (Variable) builder.getArg(PARSE_TO_VARIABLE, bc);
            }
            catch (ClassCastException e)
            {
               // throw new NotVariableBuildException(myDescr.name, e);
            }
        }

        Object o = builder.getArg(PARSE_VALUE, bc);
        if (o instanceof Macro)
        {
            // The value passed to us was a Macro (needs to be evaluated later).
            // If u use : #evalStringTemplate $myDatabaseFilledStringToEvaluate
            _macroValue = (Macro) o;
        }
        else
        {
            // If it's not a Macro, then generate an BuildException.
            // If u use : #evalStringTemplate "This is a string with nothing to parse!"
            throw new BuildException("#" + _directiveName + " was expecting a non-static value to evaluate, example: #" + _directiveName + " \"$myDatabaseFilledStringToEvaluate is very interesting!\"");
        }

        return this;
    }

    /**
     * Write out the included file to the specified FastWriter.  If the
     * included file is actually a template, it is evaluated against the
     * <code>context</code> parameter before being written to the FastWriter
     */
    public void write (FastWriter out, Context context) throws PropertyException
    {
        Broker broker = context.getBroker();
        String strValue = null;

        // the value arg passed to us was a Macro, so evaluate and check it now.
        if (_macroValue != null)
        {
            Object obValue = _macroValue.evaluate(context);

            // Only set the value if the macro provided not is null and not Undefined.
            if ( (obValue != null) && (obValue != UNDEF) )
            {
                strValue = obValue.toString();
            }
        }

        if (strValue == null)
        {
            throw new PropertyException("#" + _directiveName + " value cannot be undefined or null");
        }

        // Use the current templateName as templateName for the StringTemplate.
        // exampl. c:/wwwroot/templates/test.wm
        String templateName = context.getTemplateEvaluationContext()._templateName;

        // Use the current template location & directive name, so whe can re-trace error's.
        // exampl. c:/wwwroot/templates/test.wm:46.2 #evalStringTemplate
        if (templateName.indexOf(" #" + _directiveName) == -1) templateName = context.getCurrentLocation() + " #" + _directiveName;

        if (_log.loggingDebug())
        {
            _log.debug("#" + _directiveName + " \"valueToEvaluateAsStringTemplate\""
                    + ((_varTarget == null) ? ""
                    : " to $" + _varTarget.getVariableName()));
        }

        if (_log.loggingWarning())
        {
            if (strValue.indexOf("#" + _directiveName) > -1)
            {
                // when in debug or warning  mode, output a warning if a evalStringTemplate tries to use a evalStringTemplate
                // there could be situtations where this is desired, but it's good to make
                // the user aware of what they're doing
                _log.warning("#" + _directiveName + " uses a #" + _directiveName + ", maybe itself? (endless loop!) at " + context.getCurrentLocation());
            }
        }

        // Create the new StringTemplate.
        Template tmplTemplate = new StringTemplate (broker, strValue, templateName);

        if (_varTarget != null)
        {
            // if a target variable provided, then output to the target.
            _varTarget.setValue(context, tmplTemplate.evaluateAsString(context));
        }
        else
        {
            // else output to the specified FastWriter.
            out.write(tmplTemplate.evaluateAsBytes(out.getEncoding(), context));
        }
    }

    public void accept (TemplateVisitor v)
    {
        v.beginDirective(_desc.name);
        v.visitDirectiveArg("EvalStringTemplate", _macroValue);
        if (_varTarget != null) v.visitDirectiveArg("EvalStringTemplateTarget", _varTarget);
        v.endDirective();
    }
}

#set $Response.ContentType = "text/html; charset=$CharSet"
$HTMLCopyright
<META HTTP-EQUIV="expires" CONTENT="NOW">
<html>
	<head>
		<title></title>
	</head>
<BODY>

#set $myVar1 = "number 1"
#set $myVar2 = "number 2"

#setblock $myEvalVar #begin
	#text #begin
	#foreach $item in ["aap (monkey)","noot (nut)","mies (girls name)"]
	{
		item : $item<BR>
	}
	
	myVar1 : $myVar1<BR>
	myVar2 : $myVar2<BR>
	#end
#end

<HR><PRE>$myEvalVar</PRE><HR>

#evalStringTemplate $myEvalVar

<BR><HR><BR>

## Output to a variable...
#evalStringTemplate $myEvalVar to $myOutput
\myOutput :<BR>$myOutput

#include as template "$(EngineTemplateDir)_includes/footer.inc"
</BODY>
</HTML>