backends-common/cassandra/src/main/java/org/apache/james/backends/cassandra/utils/CassandraAsyncExecutor.java

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package org.apache.james.backends.cassandra.utils;

import java.util.Optional;

import javax.inject.Inject;

import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
import com.datastax.driver.core.Statement;
import net.javacrumbs.futureconverter.java8guava.FutureConverter;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;

public class CassandraAsyncExecutor {

    private final Session session;

    @Inject
    public CassandraAsyncExecutor(Session session) {
        this.session = session;
    }

    public Mono<ResultSet> execute(Statement statement) {
        return Mono.defer(() -> Mono.fromFuture(FutureConverter
                .toCompletableFuture(session.executeAsync(statement)))
                .publishOn(Schedulers.elastic()));
    }

    public Mono<Boolean> executeReturnApplied(Statement statement) {
        return execute(statement)
                .map(row -> row.wasApplied());
    }

    public Mono<Void> executeVoid(Statement statement) {
        return execute(statement)
                .then();
    }

    public Mono<Row> executeSingleRow(Statement statement) {
        return executeSingleRowOptional(statement)
                .handle((t, sink) -> t.ifPresent(sink::next));
    }

    public Flux<Row> executeRows(Statement statement) {
        return execute(statement)
            .flatMapMany(Flux::fromIterable);
    }

    public Mono<Optional<Row>> executeSingleRowOptional(Statement statement) {
        return execute(statement)
            .map(resultSet -> Optional.ofNullable(resultSet.one()));
    }

    public Mono<Boolean> executeReturnExists(Statement statement) {
        return executeSingleRow(statement)
                .hasElement();
    }
}