/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.tomcat.util.http;

import org.apache.tomcat.util.res.StringManager;

/**
 * Handle (internationalized) HTTP messages.
 * 
 * @author James Duncan Davidson [duncan@eng.sun.com]
 * @author James Todd [gonzo@eng.sun.com]
 * @author Jason Hunter [jch@eng.sun.com]
 * @author Harish Prabandham
 * @author costin@eng.sun.com
 */
public class HttpMessages {
    // XXX move message resources in this package
    protected static StringManager sm =
        StringManager.getManager("org.apache.tomcat.util.http.res");
	
    static String st_200=null;
    static String st_302=null;
    static String st_400=null;
    static String st_404=null;
    
    /** Get the status string associated with a status code.
     *  No I18N - return the messages defined in the HTTP spec.
     *  ( the user isn't supposed to see them, this is the last
     *  thing to translate)
     *
     *  Common messages are cached.
     *
     */
    public static String getMessage( int status ) {
	// method from Response.
	
	// Does HTTP requires/allow international messages or
	// are pre-defined? The user doesn't see them most of the time
	switch( status ) {
	case 200:
	    if( st_200==null ) st_200=sm.getString( "sc.200");
	    return st_200;
	case 302:
	    if( st_302==null ) st_302=sm.getString( "sc.302");
	    return st_302;
	case 400:
	    if( st_400==null ) st_400=sm.getString( "sc.400");
	    return st_400;
	case 404:
	    if( st_404==null ) st_404=sm.getString( "sc.404");
	    return st_404;
	}
	return sm.getString("sc."+ status);
    }

    /**
     * Filter the specified message string for characters that are sensitive
     * in HTML.  This avoids potential attacks caused by including JavaScript
     * codes in the request URL that is often reported in error messages.
     *
     * @param message The message string to be filtered
     */
    public static String filter(String message) {

	if (message == null)
	    return (null);

	char content[] = new char[message.length()];
	message.getChars(0, message.length(), content, 0);
	StringBuffer result = new StringBuffer(content.length + 50);
	for (int i = 0; i < content.length; i++) {
	    switch (content[i]) {
	    case '<':
		result.append("&lt;");
		break;
	    case '>':
		result.append("&gt;");
		break;
	    case '&':
		result.append("&amp;");
		break;
	    case '"':
		result.append("&quot;");
		break;
	    default:
		result.append(content[i]);
	    }
	}
	return (result.toString());
    }

    /**
     * Is the provided message safe to use in an HTTP header. Safe messages must
     * meet the requirements of RFC2616 - i.e. must consist only of TEXT.
     * 
     * @param msg   The message to test
     * @return      <code>true</code> if the message is safe to use in an HTTP
     *              header else <code>false</code>
     */
    public static boolean isSafeInHttpHeader(String msg) {
        // Nulls are fine. It is up to the calling code to address any NPE
        // concerns
        if (msg == null) {
            return true;
        }

        // Reason-Phrase is defined as *<TEXT, excluding CR, LF>
        // TEXT is defined as any OCTET except CTLs, but including LWS
        // OCTET is defined as an 8-bit sequence of data
        // CTL is defined as octets 0-31 and 127
        // LWS, if we exclude CR LF pairs, is defined as SP or HT (32, 9)
        final int len = msg.length();
        for (int i = 0; i < len; i++) {
            char c = msg.charAt(i);
            if (32 <= c && c <= 126 || 128 <= c && c <= 255 || c == 9) {
                continue;
            }
            return false;
        }

        return true;
    }
}
