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Apache Storm API Implementation for Cassandra CQL
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/**
 * 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 com.github.fhuss.storm.cassandra.query;

import backtype.storm.tuple.ITuple;
import com.datastax.driver.core.Session;
import com.datastax.driver.core.Statement;
import static com.datastax.driver.core.querybuilder.QueryBuilder.*;
import com.datastax.driver.core.querybuilder.Insert;

import java.io.Serializable;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Optional;

/**
 * Default interface to map a {@link backtype.storm.tuple.ITuple} to a CQL {@link com.datastax.driver.core.Statement}.
 *
 * @author fhussonnois
 */
@FunctionalInterface
public interface CQLStatementTupleMapper extends Serializable {

    public static final String FIELD_KEYSPACE =  "keyspace";
    public static final String FIELD_TABLE    =  "table";
    public static final String FIELD_VALUES   =  "value";

    /**
     * Maps a given tuple to one or multiple CQL statements.
     *
     * @param conf the storm configuration map.
     * @param session the cassandra session.
     * @param tuple the incoming tuple to map.
     * @return a list of {@link com.datastax.driver.core.Statement}.
     */
    List map(Map conf, Session session, ITuple tuple);

    public static CQLStatementTupleMapper identity() {
        return (conf, session, tuple) -> {
            Optional ks = Optional.ofNullable(tuple.contains(FIELD_KEYSPACE) ? tuple.getStringByField(FIELD_KEYSPACE) : null);
            String table = tuple.getStringByField(FIELD_TABLE);
            Map values = (Map) tuple.getValueByField(FIELD_VALUES);

            final Insert stmt = (ks.isPresent()) ? insertInto(ks.get(), table) : insertInto(table);
            values.forEach( (key, value) -> stmt.value(key, value));

            return Arrays.asList(stmt);
        };
    }

}