io.streamthoughts.azkarra.api.query.internal.KeyValueCountQuery Maven / Gradle / Ivy

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/*
 * Copyright 2019-2020 StreamThoughts.
 *
 * 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 io.streamthoughts.azkarra.api.query.internal;

import io.streamthoughts.azkarra.api.model.KV;
import io.streamthoughts.azkarra.api.monad.Reader;
import io.streamthoughts.azkarra.api.monad.Try;
import io.streamthoughts.azkarra.api.query.DecorateQuery;
import io.streamthoughts.azkarra.api.query.LocalExecutableQuery;
import io.streamthoughts.azkarra.api.query.LocalStoreAccessProvider;
import io.streamthoughts.azkarra.api.query.LocalStoreAccessor;
import io.streamthoughts.azkarra.api.query.Query;
import io.streamthoughts.azkarra.api.query.QueryRequest;
import io.streamthoughts.azkarra.api.query.StoreOperation;
import io.streamthoughts.azkarra.api.query.StoreType;
import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;

import java.util.Collections;
import java.util.List;
import java.util.Optional;

public class KeyValueCountQuery extends DecorateQuery implements LocalExecutableQuery {

    private static final String STATIC_KEY = "count";
    
    /**
     * Creates a new {@link KeyValueCountQuery} instance.
     *
     * @param store         the name of the store.
     */
    KeyValueCountQuery(final String store) {
       super(
           new QueryRequest()
           .storeName(store)
           .storeOperation(StoreOperation.COUNT)
           .storeType(StoreType.KEY_VALUE)
       );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Try>> execute(final LocalStoreAccessProvider provider, final long limit) {

        final LocalStoreAccessor> accessor =
                provider.localKeyValueStore(getStoreName());

        Reader, List>> reader = reader()
                .map(value -> Optional.ofNullable(value)
                .map(v -> Collections.singletonList(new KV<>(STATIC_KEY, v)))
                .orElse(Collections.emptyList()));

        return new LocalStoreQueryExecutor<>(accessor).execute(reader);
    }

    private Reader, Long> reader() {
        return Reader.of(ReadOnlyKeyValueStore::approximateNumEntries);
    }
}