/*
 * Licensed to STRATIO (C) under one or more contributor license agreements.
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership.  The STRATIO (C) 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 com.stratio.cassandra.lucene.cache;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.db.ClusteringComparator;
import org.apache.cassandra.db.PartitionRangeReadCommand;
import org.apache.cassandra.db.ReadCommand;
import org.apache.lucene.search.Query;

import java.util.Optional;
import java.util.UUID;

/**
 * Search cache to take advantage of Lucene's query cache.
 *
 * @author Andres de la Pena {@literal <adelapena@stratio.com>}
 */
public class SearchCache {

    private final ClusteringComparator comparator;
    private final Cache<UUID, SearchCacheEntry> cache;

    /**
     * Constructor taking the base table metadata and the max number of cache entries.
     *
     * @param metadata the base table metadata
     * @param cacheSize the max number of cache entries
     */
    public SearchCache(CFMetaData metadata, int cacheSize) {
        this.comparator = metadata.comparator;
        this.cache = CacheBuilder.newBuilder().maximumSize(cacheSize).build();
    }

    void put(UUID key, SearchCacheEntry entry) {
        cache.put(key, entry);
    }

    /**
     * Puts a cache entry associating the specified search and {@link ReadCommand} with the specified {@link Query}.
     *
     * @param search the search
     * @param command the read command
     * @param query the cached query
     */
    public void put(String search, ReadCommand command, Query query) {
        if (command instanceof PartitionRangeReadCommand) {
            PartitionRangeReadCommand rangeCommand = (PartitionRangeReadCommand) command;
            put(UUID.randomUUID(), new SearchCacheEntry(this, search, rangeCommand, query));
        }
    }

    /**
     * Returns a {@link SearchCacheUpdater} for updating an entry associating the specified search and {@link
     * ReadCommand} with the specified {@link Query}.
     *
     * @param search the search
     * @param command the read command
     * @param query the cached query
     * @return the cache updater
     */
    public SearchCacheUpdater updater(String search, ReadCommand command, Query query) {
        return new SearchCacheUpdater(this, search, UUID.randomUUID(), command, query);
    }

    /**
     * Discards all cached entries.
     */
    public void invalidate() {
        cache.invalidateAll();
    }

    /**
     * Gets the optional {@link SearchCacheEntry} associated to the specified search and {@link ReadCommand}.
     *
     * @param search the search
     * @param command the read command
     * @return the cache entry, maybe empty
     */
    public Optional<SearchCacheEntry> get(String search, ReadCommand command) {
        if (command instanceof PartitionRangeReadCommand) {
            PartitionRangeReadCommand rangeCommand = (PartitionRangeReadCommand) command;
            return cache.asMap().values().stream().filter(e -> e.isValid(comparator, search, rangeCommand)).findAny();
        }
        return Optional.empty();
    }

}