/*
 * 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.spi.commons.conversion;

import org.apache.jackrabbit.spi.Name;

import javax.jcr.NamespaceException;

/**
 * Name resolver decorator that uses a generational cache to speed up
 * parsing and formatting of JCR names. Uncached names are resolved using
 * the underlying decorated name resolver.
 */
public class CachingNameResolver implements NameResolver {

    /**
     * Decorated name resolver.
     */
    private final NameResolver resolver;

    /**
     * Generational cache.
     */
    private final GenerationalCache cache;

    /**
     * Creates a caching decorator for the given name resolver. The given
     * generational cache is used for caching.
     *
     * @param resolver decorated name resolver
     * @param cache generational cache
     */
    public CachingNameResolver(NameResolver resolver, GenerationalCache cache) {
        this.resolver = resolver;
        this.cache = cache;
    }

    /**
     * Creates a caching decorator for the given name resolver.
     *
     * @param resolver name resolver
     */
    public CachingNameResolver(NameResolver resolver) {
        this(resolver, new GenerationalCache());
    }

    //-------------------------------------------------------< NameResolver >---
    /**
     * Returns a <code>Name</code> for the given prefixed JCR name. The name
     * is first looked up form the generational cache and the call gets
     * delegated to the decorated name resolver only if the cache misses.
     *
     * @param jcrName A JCR name String.
     * @return A <code>Name</code> object.
     * @throws IllegalNameException if the JCR name format is invalid
     * @throws NamespaceException if the namespace prefix can not be resolved
     */
    public Name getQName(String jcrName)
            throws IllegalNameException, NamespaceException {
        Name name = (Name) cache.get(jcrName);
        if (name == null) {
            name = resolver.getQName(jcrName);
            cache.put(jcrName, name);
        }
        return name;
    }


    /**
     * Returns the prefixed JCR name for the given <code>Name</code>. The name
     * is first looked up form the generational cache and the call gets
     * delegated to the decorated name resolver only if the cache misses.
     *
     * @param name The name object.
     * @return qualified JCR name in the form <code>prefix:localName</code>.
     * @throws NamespaceException if the namespace URI can not be resolved
     */
    public String getJCRName(Name name) throws NamespaceException {
        if (name.getNamespaceURI().length() == 0) {
            return name.getLocalName();
        }
        String jcrName = (String) cache.get(name);
        if (jcrName == null) {
            jcrName = resolver.getJCRName(name);
            cache.put(name, jcrName);
        }
        return jcrName;
    }
}