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/*
 * Copyright 2016-2023 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.data.cassandra.repository.query;

import reactor.core.publisher.Mono;

import org.reactivestreams.Publisher;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.cassandra.ReactiveResultSet;
import org.springframework.data.cassandra.core.CassandraOperations;
import org.springframework.data.cassandra.core.ReactiveCassandraOperations;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.CollectionExecution;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.ExistsExecution;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.ResultProcessingConverter;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.ResultProcessingExecution;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.SingleEntityExecution;
import org.springframework.data.cassandra.repository.query.ReactiveCassandraQueryExecution.SlicedExecution;
import org.springframework.data.repository.query.ParameterAccessor;
import org.springframework.data.repository.query.RepositoryQuery;
import org.springframework.data.repository.query.ResultProcessor;

import com.datastax.oss.driver.api.core.cql.SimpleStatement;

/**
 * Base class for reactive {@link RepositoryQuery} implementations for Cassandra.
 *
 * @author Mark Paluch
 * @author Hleb Albau
 * @see org.springframework.data.cassandra.repository.query.CassandraRepositoryQuerySupport
 * @since 2.0
 */
public abstract class AbstractReactiveCassandraQuery extends CassandraRepositoryQuerySupport {

	private final ReactiveCassandraOperations operations;

	/**
	 * Create a new {@link AbstractReactiveCassandraQuery} from the given {@link CassandraQueryMethod} and
	 * {@link CassandraOperations}.
	 *
	 * @param method must not be {@literal null}.
	 * @param operations must not be {@literal null}.
	 */
	public AbstractReactiveCassandraQuery(ReactiveCassandraQueryMethod method, ReactiveCassandraOperations operations) {

		super(method, operations.getConverter().getMappingContext());

		this.operations = operations;
	}

	@Override
	public ReactiveCassandraQueryMethod getQueryMethod() {
		return (ReactiveCassandraQueryMethod) super.getQueryMethod();
	}

	@Override
	public Object execute(Object[] parameters) {

		ReactiveCassandraParameterAccessor parameterAccessor = new ReactiveCassandraParameterAccessor(getQueryMethod(),
				parameters);

		Mono resolved = parameterAccessor.resolveParameters();

		return resolved.flatMapMany(this::executeLater);
	}

	private Publisher executeLater(ReactiveCassandraParameterAccessor parameterAccessor) {

		Mono statement = createQuery(parameterAccessor);
		ResultProcessor resultProcessor = getQueryMethod().getResultProcessor().withDynamicProjection(parameterAccessor);
		ReactiveCassandraQueryExecution queryExecution = getExecution(parameterAccessor,
				new ResultProcessingConverter(resultProcessor, getMappingContext(), getEntityInstantiators()));

		Class resultType = resolveResultType(resultProcessor);

		return statement.flatMapMany(it -> queryExecution.execute(it, resultType));
	}

	private Class resolveResultType(ResultProcessor resultProcessor) {

		CassandraReturnedType returnedType = new CassandraReturnedType(resultProcessor.getReturnedType(),
				getReactiveCassandraOperations().getConverter().getCustomConversions());

		return returnedType.getResultType();
	}

	/**
	 * Creates a string query using the given {@link ParameterAccessor}
	 *
	 * @param accessor must not be {@literal null}.
	 */
	protected abstract Mono createQuery(CassandraParameterAccessor accessor);

	protected ReactiveCassandraOperations getReactiveCassandraOperations() {
		return this.operations;
	}

	/**
	 * Returns the execution instance to use.
	 *
	 * @param parameterAccessor must not be {@literal null}.
	 * @param resultProcessing must not be {@literal null}.
	 */
	private ReactiveCassandraQueryExecution getExecution(ReactiveCassandraParameterAccessor parameterAccessor,
			Converter resultProcessing) {
		return new ResultProcessingExecution(getExecutionToWrap(parameterAccessor), resultProcessing);
	}

	private ReactiveCassandraQueryExecution getExecutionToWrap(CassandraParameterAccessor parameterAccessor) {

		if (getQueryMethod().isSliceQuery()) {
			return new SlicedExecution(getReactiveCassandraOperations(), parameterAccessor.getPageable());
		} else if (getQueryMethod().isCollectionQuery()) {
			return new CollectionExecution(getReactiveCassandraOperations());
		} else if (isCountQuery()) {
			return ((statement, type) -> new SingleEntityExecution(getReactiveCassandraOperations(), false).execute(statement,
					Long.class));
		} else if (isExistsQuery()) {
			return new ExistsExecution(getReactiveCassandraOperations());
		} else if (isModifyingQuery()) {

			return (statement, type) -> getReactiveCassandraOperations().execute(statement)
					.map(ReactiveResultSet::wasApplied);
		} else {
			return new SingleEntityExecution(getReactiveCassandraOperations(), isLimiting());
		}
	}

	/**
	 * Returns whether the query should get a count projection applied.
	 *
	 * @return a boolean value indicating whether the query is a count projection.
	 * @since 2.1
	 */
	protected abstract boolean isCountQuery();

	/**
	 * Returns whether the query should get an exists projection applied.
	 *
	 * @return a boolean value indicating whether the query is an exists projection.
	 * @since 2.1
	 */
	protected abstract boolean isExistsQuery();

	/**
	 * Return whether the query has an explicit limit set.
	 *
	 * @return a boolean value indicating whether the query has an explicit limit set.
	 * @since 2.0.4
	 */
	protected abstract boolean isLimiting();

	/**
	 * Returns whether the query is a modifying query.
	 *
	 * @return a boolean value indicating whether the query is a modifying query.
	 * @since 2.2
	 */
	protected abstract boolean isModifyingQuery();

}
 















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