external/storm-cassandra/src/main/java/org/apache/storm/cassandra/trident/state/SimpleStateMapper.java

/**
 * 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.storm.cassandra.trident.state;

import java.util.List;
import org.apache.storm.trident.state.OpaqueValue;
import org.apache.storm.trident.state.StateType;
import org.apache.storm.trident.state.TransactionalValue;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Values;

public class SimpleStateMapper<T> implements StateMapper<T> {

    private final Fields fields;
    private final StateType stateType;

    public SimpleStateMapper(Fields fields, StateType stateType) {
        this.fields = fields;
        this.stateType = stateType;
    }

    public static <U> StateMapper<OpaqueValue<U>> opaque(String txIdField, String previousField, String field) {
        return new SimpleStateMapper<>(new Fields(txIdField, field, previousField), StateType.OPAQUE);
    }

    public static <U> StateMapper<TransactionalValue<U>> opaque(String txIdField, String field) {
        return new SimpleStateMapper<>(new Fields(txIdField, field), StateType.TRANSACTIONAL);
    }

    public static <U> StateMapper<U> nontransactional(String field) {
        return new SimpleStateMapper<>(new Fields(field), StateType.NON_TRANSACTIONAL);
    }

    @Override
    public Fields getStateFields() {
        return fields;
    }

    @Override
    public Values toValues(T value) {
        if (value == null) {
            return null;
        }
        switch (stateType) {
            case NON_TRANSACTIONAL:
                return new Values(value);
            case TRANSACTIONAL:
                TransactionalValue transactional = (TransactionalValue) value;
                return new Values(transactional.getTxid(), transactional.getVal());
            case OPAQUE:
                OpaqueValue opaque = (OpaqueValue) value;
                return new Values(opaque.getCurrTxid(), opaque.getCurr(), opaque.getPrev());
            default:
                throw new IllegalStateException("Unknown state type " + stateType);
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    public T fromValues(List<Values> valuesSet) {
        if (valuesSet == null || valuesSet.size() == 0) {
            return null;
        } else if (valuesSet.size() == 1) {
            Values values = valuesSet.get(0);
            if (values == null) {
                return null;
            }
            switch (stateType) {
                case NON_TRANSACTIONAL:
                    return (T) values.get(0);
                case TRANSACTIONAL:
                    return (T) new TransactionalValue((Long) values.get(0), values.get(1));
                case OPAQUE:
                    return (T) new OpaqueValue((Long) values.get(0), values.get(1), values.get(2));
                default:
                    throw new IllegalStateException("Unknown state type " + stateType);
            }
        }
        throw new IllegalStateException("State query returned multiple results.");
    }

    @Override
    public String toString() {
        return String.format("{type: %s, fields: %s, stateType: %s}", this.getClass().getSimpleName(), fields, stateType);
    }
}