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/*
 * Copyright 2019 Immutables Authors and Contributors
 *
 * 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
 *
 *  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.immutables.criteria.repository.reactive;

import org.immutables.criteria.backend.Backend;
import org.immutables.criteria.expression.Query;
import org.immutables.criteria.repository.Fetcher;
import org.reactivestreams.Publisher;

import java.util.function.Function;

/**
 * Reactive interface for fetcher
 */
public interface ReactiveFetcher extends Fetcher {

  /**
   * Fetch all results
   */
  Publisher fetch();

  /**
   * Check that exactly one element is matched by current query and return it.
   * @return Publisher with single element, or Publisher that throws {@link org.immutables.criteria.backend.NonUniqueResultException}
   */
  Publisher one();

  /**
   * Check that at most one element is matched by current query and return it (if available).
   * @return Publisher with zero or one element, or Publisher that throws {@link org.immutables.criteria.backend.NonUniqueResultException}
   */
  Publisher oneOrNone();

  /**
   * Check that current query matches any elements.
   * @return Publisher with single boolean ({@code true / false} if there is a match)
   */
  Publisher exists();

  /**
   * Applies a mapping function to each element emitted by current fetcher
   */
   ReactiveFetcher map(Function mapFn);

  /**
   * Factory method
   */
  static  ReactiveFetcher of(Query query, Backend.Session session) {
    return ReactiveFetcherDelegate.of(query, session);
  }

}