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.crdt.hash;
  
  import io.activej.async.function.AsyncRunnable;
  import io.activej.async.function.AsyncRunnables;
  import io.activej.async.service.ReactiveService;
  import io.activej.common.Checks;
  import io.activej.crdt.storage.ICrdtStorage;
  import io.activej.datastream.consumer.StreamConsumers;
  import io.activej.promise.Promise;
  import io.activej.reactor.AbstractReactive;
  import io.activej.reactor.Reactor;
  import org.jetbrains.annotations.Nullable;
  
  import java.util.Map;
  import java.util.TreeMap;
  import java.util.function.BinaryOperator;
  
  import static io.activej.reactor.Reactive.checkInReactorThread;
  
  public class JavaCrdtMap<K extends Comparable<K>, S> extends AbstractReactive
  	implements ICrdtMap<K, S>, ReactiveService {
  
  	private static final boolean CHECKS = Checks.isEnabled(JavaCrdtMap.class);
  
  	private final Map<K, S> map = new TreeMap<>();
  
  	private final BinaryOperator<S> mergeFn;
  
  	private final AsyncRunnable refresh;
  
  	public JavaCrdtMap(Reactor reactor, BinaryOperator<S> mergeFn) {
  		super(reactor);
  		this.mergeFn = mergeFn;
  		this.refresh = Promise::complete;
  	}
  
  	public JavaCrdtMap(Reactor reactor, BinaryOperator<S> mergeFn, ICrdtStorage<K, S> storage) {
  		super(reactor);
  		this.mergeFn = mergeFn;
  		this.refresh = AsyncRunnables.reuse(() -> doRefresh(storage));
  	}
  
  	@Override
  	public Promise<@Nullable S> get(K key) {
  		if (CHECKS) checkInReactorThread(this);
  		return Promise.of(map.get(key));
  	}
  
  	@Override
  	public Promise<Void> refresh() {
  		checkInReactorThread(this);
  		return refresh.run();
  	}
  
  	@Override
  	public Promise<@Nullable S> put(K key, S value) {
  		if (CHECKS) checkInReactorThread(this);
  		return Promise.of(map.merge(key, value, mergeFn));
  	}
  
  	@Override
  	public Promise<?> start() {
  		checkInReactorThread(this);
  		return refresh();
  	}
  
  	@Override
  	public Promise<?> stop() {
  		checkInReactorThread(this);
  		return Promise.complete();
  	}
  
  	private Promise<Void> doRefresh(ICrdtStorage<K, S> storage) {
  		assert storage != null;
  		return storage.download()
  			.then(supplier -> supplier.streamTo(StreamConsumers.ofConsumer(crdtData -> map.put(crdtData.getKey(), crdtData.getState()))));
  	}
  }
  