tapestry-framework/src/java/org/apache/tapestry/script/LetToken.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// Licensed 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.tapestry.script;

import java.util.Map;

import org.apache.hivemind.Location;

/**
 * Allows for the creation of new symbols that can be used in the script or
 * returned to the caller.
 * <p>
 * The &lt;let&gt; tag wraps around static text and &lt;insert&gt; elements. The
 * results are trimmed.
 * 
 * @author Howard Lewis Ship
 * @since 0.2.9
 */

class LetToken extends AbstractToken
{

    private String _key;
    private boolean _unique;
    private int _bufferLengthHighwater = 20;

    public LetToken(String key, boolean unique, Location location)
    {
        super(location);

        _key = key;
        _unique = unique;
    }

    public void write(StringBuffer buffer, ScriptSession session)
    {
        if (buffer != null) throw new IllegalArgumentException();

        StringBuffer useBuffer = new StringBuffer(_bufferLengthHighwater);

        writeChildren(useBuffer, session);

        // Store the symbol back into the root set of symbols.

        Map symbols = session.getSymbols();

        String value = useBuffer.toString().trim();

        if (_unique) {
            value = session.getUniqueString(value);
            
            // unique in scripts is mostly used to generate javascript identifiers
            value = makeValidIdentifier(value);
        }

        symbols.put(_key, value);

        // Store the buffer length from this run for the next run, since its
        // going to be approximately the right size.

        _bufferLengthHighwater = Math.max(_bufferLengthHighwater, useBuffer
                .length());
    }
    
    /**
     * Replaces hyphens, colons and periods (which are allowed in html 
     * but not in javascript identifiers) with underscores.
     */
    private static String makeValidIdentifier(String id) {
        char[] chars = id.toCharArray();
        for (int i=0; i<chars.length; i++) {
            char c = chars[i];
            if (c==':' || c=='-' || c=='.')
                chars[i]='_';
        }
        return new String(chars);
    }
}