/*
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  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 end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
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 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS 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
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 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package com.sun.faces.el.impl;

/**
 * <p>An expression representing a String literal value.
 *
 * @author Nathan Abramson - Art Technology Group
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: rlubke $
 */

public class StringLiteral
    extends Literal {

    //-------------------------------------
    /**
     * Constructor
     */
    StringLiteral(Object pValue) {
        super(pValue);
    }

    //-------------------------------------
    /**
     * Returns a StringLiteral parsed from the given token (enclosed by
     * single or double quotes)
     */
    public static StringLiteral fromToken(String pToken) {
        return new StringLiteral(getValueFromToken(pToken));
    }

    //-------------------------------------
    /**
     * Returns a StringLiteral with the given string value
     */
    public static StringLiteral fromLiteralValue(String pValue) {
        return new StringLiteral(pValue);
    }

    //-------------------------------------
    /**
     * Parses the given token into the literal value
     */
    public static String getValueFromToken(String pToken) {
        StringBuffer buf = new StringBuffer();
        int len = pToken.length() - 1;
        boolean escaping = false;
        for (int i = 1; i < len; i++) {
            char ch = pToken.charAt(i);
            if (escaping) {
                buf.append(ch);
                escaping = false;
            } else if (ch == '\\') {
                escaping = true;
            } else {
                buf.append(ch);
            }
        }
        return buf.toString();
    }

    //-------------------------------------
    /**
     * Converts the specified value to a String token, using " as the
     * enclosing quotes and escaping any characters that need escaping.
     */
    public static String toStringToken(String pValue) {
        // See if any escaping is needed
        if (pValue.indexOf('\"') < 0 &&
            pValue.indexOf('\\') < 0) {
            return "\"" + pValue + "\"";
        }

        // Escaping is needed
        else {
            StringBuffer buf = new StringBuffer();
            buf.append('\"');
            int len = pValue.length();
            for (int i = 0; i < len; i++) {
                char ch = pValue.charAt(i);
                if (ch == '\\') {
                    buf.append('\\');
                    buf.append('\\');
                } else if (ch == '\"') {
                    buf.append('\\');
                    buf.append('\"');
                } else {
                    buf.append(ch);
                }
            }
            buf.append('\"');
            return buf.toString();
        }
    }

    //-------------------------------------
    /**
     * Converts the specified value to an identifier token, escaping it
     * as a string literal if necessary.
     */
    public static String toIdentifierToken(String pValue) {
        // See if it's a valid java identifier
        if (isJavaIdentifier(pValue)) {
            return pValue;
        }

        // Return as a String literal
        else {
            return toStringToken(pValue);
        }
    }

    //-------------------------------------
    /**
     * Returns true if the specified value is a legal java identifier
     */
    static boolean isJavaIdentifier(String pValue) {
        int len = pValue.length();
        if (len == 0) {
            return false;
        } else {
            if (!Character.isJavaIdentifierStart(pValue.charAt(0))) {
                return false;
            } else {
                for (int i = 1; i < len; i++) {
                    if (!Character.isJavaIdentifierPart(pValue.charAt(i))) {
                        return false;
                    }
                }
                return true;
            }
        }
    }

    //-------------------------------------
    // Expression methods
    //-------------------------------------
    /**
     * Returns the expression in the expression language syntax
     */
    public String getExpressionString() {
        return toStringToken((String) getValue());
    }

    //-------------------------------------
}
