content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * 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 io.activej.cube.attributes;
  
  import io.activej.promise.Promise;
  import io.activej.reactor.AbstractReactive;
  import io.activej.reactor.Reactor;
  
  import java.util.List;
  
  import static io.activej.reactor.Reactive.checkInReactorThread;
  
  public abstract class AbstractAttributeResolver<K, A> extends AbstractReactive
  	implements IAttributeResolver {
  
  	public AbstractAttributeResolver(Reactor reactor) {
  		super(reactor);
  	}
  
  	protected abstract K toKey(Object[] keyArray);
  
  	protected abstract Object[] toAttributes(A attributes);
  
  	protected abstract A resolveAttributes(K key);
  
  	@SuppressWarnings("unused")
  	protected Promise<Void> prepareToResolveAttributes(List<Object> results, KeyFunction keyFunction, AttributesFunction attributesFunction) {
  		assert reactor.inReactorThread();
  		return Promise.complete();
  	}
  
  	private Promise<Void> doResolveAttributes(List<Object> results, KeyFunction keyFunction, AttributesFunction attributesFunction) {
  		for (Object result : results) {
  			K key = toKey(keyFunction.extractKey(result));
  			A attributes = resolveAttributes(key);
  			if (attributes != null) {
  				attributesFunction.applyAttributes(result, toAttributes(attributes));
  			}
  		}
  		return Promise.complete();
  	}
  
  	@Override
  	public final Promise<Void> resolveAttributes(List<Object> results, KeyFunction keyFunction, AttributesFunction attributesFunction) {
  		checkInReactorThread(this);
  		return prepareToResolveAttributes(results, keyFunction, attributesFunction)
  			.then(() -> doResolveAttributes(results, keyFunction, attributesFunction));
  	}
  }
  