/*
 * 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.jackrabbit.vault.util.xml.serialize;


import java.io.UnsupportedEncodingException;
import java.util.Hashtable;
import java.util.Locale;

import org.apache.jackrabbit.vault.util.xml.xerces.util.EncodingMap;


/**
 * Provides information about encodings. Depends on the Java runtime
 * to provides writers for the different encodings, but can be used
 * to override encoding names and provide the last printable character
 * for each encoding.
 *
 * @author <a href="mailto:arkin@intalio.com">Assaf Arkin</a>
 * @version $Id$
 */
public class Encodings {


    /**
     * The last printable character for unknown encodings.
     */
    static final int DEFAULT_LAST_PRINTABLE = 0x7F;

    // last printable character for Unicode-compatible encodings
    static final int LAST_PRINTABLE_UNICODE = 0xffff;
    // unicode-compliant encodings; can express plane 0
    static final String[] UNICODE_ENCODINGS = {
            "Unicode", "UnicodeBig", "UnicodeLittle", "GB2312", "UTF8",
    };
    // default (Java) encoding if none supplied:
    static final String DEFAULT_ENCODING = "UTF8";

    // note that the size of this Hashtable
    // is bounded by the number of encodings recognized by EncodingMap;
    // therefore it poses no static mutability risk.
    static Hashtable _encodings = new Hashtable();

    /**
     * @param encoding a MIME charset name, or null.
     */
    static EncodingInfo getEncodingInfo(String encoding, boolean allowJavaNames) throws UnsupportedEncodingException {
        EncodingInfo eInfo = null;
        if (encoding == null) {
            if ((eInfo = (EncodingInfo) _encodings.get(DEFAULT_ENCODING)) != null)
                return eInfo;
            eInfo = new EncodingInfo(EncodingMap.getJava2IANAMapping(DEFAULT_ENCODING), DEFAULT_ENCODING, LAST_PRINTABLE_UNICODE);
            _encodings.put(DEFAULT_ENCODING, eInfo);
            return eInfo;
        }
        // need to convert it to upper case:
        encoding = encoding.toUpperCase(Locale.ENGLISH);
        String jName = EncodingMap.getIANA2JavaMapping(encoding);
        if (jName == null) {
            // see if the encoding passed in is a Java encoding name.
            if (allowJavaNames) {
                EncodingInfo.testJavaEncodingName(encoding);
                if ((eInfo = (EncodingInfo) _encodings.get(encoding)) != null)
                    return eInfo;
                // is it known to be unicode-compliant?
                int i = 0;
                for (; i < UNICODE_ENCODINGS.length; i++) {
                    if (UNICODE_ENCODINGS[i].equalsIgnoreCase(encoding)) {
                        eInfo = new EncodingInfo(EncodingMap.getJava2IANAMapping(encoding), encoding, LAST_PRINTABLE_UNICODE);
                        break;
                    }
                }
                if (i == UNICODE_ENCODINGS.length) {
                    eInfo = new EncodingInfo(EncodingMap.getJava2IANAMapping(encoding), encoding, DEFAULT_LAST_PRINTABLE);
                }
                _encodings.put(encoding, eInfo);
                return eInfo;
            } else {
                throw new UnsupportedEncodingException(encoding);
            }
        }
        if ((eInfo = (EncodingInfo) _encodings.get(jName)) != null)
            return eInfo;
        // have to create one...
        // is it known to be unicode-compliant?
        int i = 0;
        for (; i < UNICODE_ENCODINGS.length; i++) {
            if (UNICODE_ENCODINGS[i].equalsIgnoreCase(jName)) {
                eInfo = new EncodingInfo(encoding, jName, LAST_PRINTABLE_UNICODE);
                break;
            }
        }
        if (i == UNICODE_ENCODINGS.length) {
            eInfo = new EncodingInfo(encoding, jName, DEFAULT_LAST_PRINTABLE);
        }
        _encodings.put(jName, eInfo);
        return eInfo;
    }

    static final String JIS_DANGER_CHARS
            = "\\\u007e\u007f\u00a2\u00a3\u00a5\u00ac"
            + "\u2014\u2015\u2016\u2026\u203e\u203e\u2225\u222f\u301c"
            + "\uff3c\uff5e\uffe0\uffe1\uffe2\uffe3";

}
