zkoss/zk

/* MessageConst.java


    Purpose: Defines message types
    Description:
    History:
     2001/4/2 2001/4/2, Tom M. Yeh: Created.


Copyright (C) 2001 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
    This program is distributed under LGPL Version 2.1 in the hope that
    it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.mesg;

import java.util.Map;
import java.util.HashMap;

/**
 * Defines the constants of message codes.
 *
 * @author tomyeh
 * @see Messages
 */
public interface MessageConst {
    /** Denotes a non-existent code. */
    public static final int NULL_CODE = 0;

    /** The info of each message bundle.
     * <p>Each bundle is associated with a class and a set of files.
     */
    /*package*/ static class BundleInfo {
        public final Class klass;
        public final String filename;

        private BundleInfo(Class klass, String filename) {
            this.klass = klass;
            this.filename = filename;
        }
        public String toString() {
            return "[" + this.klass.getName() + ", " + this.filename + ']';
        }
    }

    /** Used to handle the mapping of a message code to a filename.
     *
     * <p>FUTURE: we might consider to use hashCode or other to represents
     * the identifier such that the client will have the same code as the server.
     */
    public static class Aide {
        private static Map<Integer, BundleInfo> _bis = new HashMap<Integer, BundleInfo>(4);

        /** Registers a message filename, and returns an identifier to
         * represent it.
         *
         * <p>The path is assumed to be /metainfo/mesg.
         *
         * @param filename the filename without path and extension, e.g, "msgacc"
         * @return an identifier to represent this message file.
         */
        public static final int register(Class klass, String filename) {
            if (filename.indexOf('/') >= 0 || filename.indexOf('.') >= 0)
                throw new IllegalArgumentException("Neither path nor extension is allowed: "+filename);

            //The algorithm is to make id as deterministic as possible
            //though not really necessary
            final BundleInfo bi = new BundleInfo(klass, "/metainfo/mesg/" + filename);
            String sID = klass.getName();
            int id = getId(sID);
            synchronized (Aide.class) {
                Integer iID;
                final Map<Integer, BundleInfo> bis = new HashMap<Integer, BundleInfo>(_bis);
                while (bis.containsKey(iID = new Integer(id)))
                    ++id; //not deterministic
                bis.put(iID, bi);
                _bis = bis; //_bis itself is readonly (so no sync required)
            }
            return id << 16; //as the high word
        }
        private static final int getId(String sID) {
            final int id = sID.hashCode();
            return (id >= 0 ? id: -id) & 0x3fff;
        }
        /** Returns the filename with path, but without extension, of the
         * specified message code.
         */
        /*package*/ static final BundleInfo getBundleInfo(int code) {
            final int id = code >>> 16;
            final BundleInfo bi = _bis.get(new Integer(id));
            if (bi == null)
                throw new IllegalArgumentException("Wrong message ID: "+id
                    +" ("+code+")\nRegistered: "+_bis);
            return bi;
        }
    }
}