/*
 * 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.usergrid.mq.cassandra.io;


import java.util.List;
import java.util.UUID;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.usergrid.mq.Message;
import org.apache.usergrid.mq.QueueQuery;
import org.apache.usergrid.mq.QueueResults;

import me.prettyprint.hector.api.Keyspace;

import static org.apache.usergrid.mq.cassandra.CassandraMQUtils.getConsumerId;
import static org.apache.usergrid.mq.cassandra.CassandraMQUtils.getQueueId;


/**
 * Reads from the queue without starting transactions.
 *
 * @author tnine
 */
public class NoTransactionSearch extends AbstractSearch
{

    private static final Logger logger = LoggerFactory.getLogger( NoTransactionSearch.class );

    protected static final int DEFAULT_READ = 1;


    /**
     * @param ko
     */
    public NoTransactionSearch( Keyspace ko )
    {
        super( ko );
    }


    /*
     * (non-Javadoc)
     *
     * @see org.apache.usergrid.mq.cassandra.io.QueueSearch#getResults(java.lang.String,
     * org.apache.usergrid.mq.QueueQuery)
     */
    @Override
    public QueueResults getResults( String queuePath, QueueQuery query )
    {

        UUID queueId = getQueueId( queuePath );
        UUID consumerId = getConsumerId( queueId, query );
        QueueBounds bounds = getQueueBounds( queueId );
        SearchParam params = getParams( queueId, consumerId, query );

        List<UUID> ids = getIds( queueId, consumerId, bounds, params );

        List<Message> messages = loadMessages( ids, params.reversed );

        QueueResults results = createResults( messages, queuePath, queueId, consumerId );

        writeClientPointer( queueId, consumerId, results.getLast() );

        return results;
    }


    /** Get information for reading no transactionally from the query. Subclasses can override this behavior */
    protected SearchParam getParams( UUID queueId, UUID consumerId, QueueQuery query )
    {
        UUID lastReadMessageId = getConsumerQueuePosition( queueId, consumerId );

        if ( logger.isDebugEnabled() )
        {
            logger.debug( "Last message id is '{}' for queueId '{}' and clientId '{}'",
                    lastReadMessageId, queueId, consumerId );
        }

        return new SearchParam( lastReadMessageId, false, lastReadMessageId != null, query.getLimit( DEFAULT_READ ) );
    }


    /** Get the list of ids we should load and return to the client. Message ids should be in order on return */
    protected List<UUID> getIds( UUID queueId, UUID consumerId, QueueBounds bounds, SearchParam params )
    {
        return getQueueRange( queueId, bounds, params );
    }


    protected static class SearchParam
    {

        /** The uuid to start seeking from */
        protected final UUID startId;

        /** true if we should seek from high to low */
        protected final boolean reversed;
        /** The number of results to include */
        protected final int limit;
        /** true if the first result should be skipped. Useful for paging from a previous result */
        protected final boolean skipFirst;


        /**
         * @param startId
         * @param reversed
         * @param count
         */
        public SearchParam( UUID startId, boolean reversed, boolean skipFirst, int count )
        {
            this.startId = startId;
            this.reversed = reversed;
            this.skipFirst = skipFirst;
            this.limit = count;
        }
    }
}