/*****************************************************************
 *   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.cayenne.cache;

import java.util.List;
import java.util.Map;

import org.apache.cayenne.map.DataMap;
import org.apache.cayenne.map.DbEntity;
import org.apache.cayenne.map.ObjEntity;
import org.apache.cayenne.map.Procedure;
import org.apache.cayenne.query.PrefetchTreeNode;
import org.apache.cayenne.query.Query;
import org.apache.cayenne.query.QueryCacheStrategy;
import org.apache.cayenne.query.QueryMetadata;
import org.apache.cayenne.reflect.ClassDescriptor;

/**
 * A {@link QueryCache} wrapper that introduces a key namespace on top of a delegate
 * shared cache. This way multiple cache users can share the same underlying cache without
 * a possibility of key conflicts, yet refresh the cache groups in a coordinated fashion.
 * 
 * @since 3.0
 */
public class NestedQueryCache implements QueryCache {

    private static volatile int currentId;

    protected QueryCache delegate;
    protected String namespace;

    private static final int nextInt() {
        if (currentId == Integer.MAX_VALUE) {
            currentId = 0;
        }

        return currentId++;
    }

    public NestedQueryCache(QueryCache delegate) {
        this.delegate = delegate;
        this.namespace = getClass().getName() + nextInt() + ":";
    }

    /**
     * Returns the actual implementation of the query cache that is wrapped by this
     * NestedQueryCache.
     */
    public QueryCache getDelegate() {
        return delegate;
    }

    /**
     * Clears the underlying shared cache.
     */
    public void clear() {
        delegate.clear();
    }

    @SuppressWarnings("unchecked")
    public List get(QueryMetadata metadata, QueryCacheEntryFactory factory) {
        return delegate.get(qualifiedMetadata(metadata), factory);
    }

    @SuppressWarnings("unchecked")
    public List get(QueryMetadata metadata) {
        return delegate.get(qualifiedMetadata(metadata));
    }

    @SuppressWarnings("unchecked")
    public void put(QueryMetadata metadata, List results) {
        delegate.put(qualifiedMetadata(metadata), results);
    }

    /**
     * Removes an entry for key in the current namespace.
     */
    public void remove(String key) {
        delegate.remove(qualifiedKey(key));
    }

    /**
     * Invalidates a shared cache group.
     */
    public void removeGroup(String groupKey) {
        delegate.removeGroup(groupKey);
    }

    /**
     * Returns a shared cache size.
     */
    public int size() {
        return delegate.size();
    }

    private String qualifiedKey(String key) {
        return key != null ? namespace + key : null;
    }

    private QueryMetadata qualifiedMetadata(QueryMetadata md) {
        return new QualifiedKeyQueryMetadata(md);
    }

    final class QualifiedKeyQueryMetadata implements QueryMetadata {

        private QueryMetadata mdDelegate;

        QualifiedKeyQueryMetadata(QueryMetadata mdDelegate) {
            this.mdDelegate = mdDelegate;
        }

        public String[] getCacheGroups() {
            return mdDelegate.getCacheGroups();
        }

        public String getCacheKey() {
            return qualifiedKey(mdDelegate.getCacheKey());
        }

        /**
         * @deprecated since 3.0 in favor of 'getCacheStrategy'.
         */
        public String getCachePolicy() {
            return mdDelegate.getCachePolicy();
        }

        public QueryCacheStrategy getCacheStrategy() {
            return mdDelegate.getCacheStrategy();
        }

        public ClassDescriptor getClassDescriptor() {
            return mdDelegate.getClassDescriptor();
        }

        public DataMap getDataMap() {
            return mdDelegate.getDataMap();
        }

        public DbEntity getDbEntity() {
            return mdDelegate.getDbEntity();
        }

        public int getFetchLimit() {
            return mdDelegate.getFetchLimit();
        }

        public int getFetchOffset() {
            return mdDelegate.getFetchOffset();
        }

        /**
         * @deprecated since 3.0
         */
        public int getFetchStartIndex() {
            return mdDelegate.getFetchStartIndex();
        }

        public ObjEntity getObjEntity() {
            return mdDelegate.getObjEntity();
        }

        public Query getOrginatingQuery() {
            return mdDelegate.getOrginatingQuery();
        }

        public int getPageSize() {
            return mdDelegate.getPageSize();
        }

        public PrefetchTreeNode getPrefetchTree() {
            return mdDelegate.getPrefetchTree();
        }

        public Map<String, String> getPathSplitAliases() {
            return mdDelegate.getPathSplitAliases();
        }

        public Procedure getProcedure() {
            return mdDelegate.getProcedure();
        }

        public List<Object> getResultSetMapping() {
            return mdDelegate.getResultSetMapping();
        }

        public boolean isFetchingDataRows() {
            return mdDelegate.isFetchingDataRows();
        }

        public boolean isRefreshingObjects() {
            return mdDelegate.isRefreshingObjects();
        }

        public boolean isResolvingInherited() {
            return mdDelegate.isResolvingInherited();
        }
    }
}
