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.storage;
  
  import io.activej.common.annotation.ComponentInterface;
  import io.activej.crdt.CrdtData;
  import io.activej.crdt.CrdtTombstone;
  import io.activej.datastream.consumer.StreamConsumer;
  import io.activej.datastream.supplier.StreamSupplier;
  import io.activej.promise.Promise;
  
  /**
   * Interface for various CRDT client implementations.
   * CRDT storage can be seen as SortedMap where put operation is same as merge with CRDT union as combiner.
   *
   * @param <K> type of crdt keys
   * @param <S> type of crdt states
   */
  @ComponentInterface
  public interface ICrdtStorage<K extends Comparable<K>, S> {
  
  	/**
  	 * Returns a promise of a stream consumer of key-state pairs to be added to the CRDT storage.
  	 *
  	 * @return a promise of a stream consumer of key-state pairs.
  	 */
  	Promise<StreamConsumer<CrdtData<K, S>>> upload();
  
  	/**
  	 * Returns a promise of a stream supplier of all key-state pairs in the CRDT storage that were put AFTER given timestamp was received.
  	 * Pairs are sorted by key.
  	 *
  	 * @return a promise of a stream supplier of key-state pairs
  	 */
  	Promise<StreamSupplier<CrdtData<K, S>>> download(long timestamp);
  
  	/**
  	 * Same as above, but downloads all possible key-state pairs.
  	 *
  	 * @return a promise of a stream consumer of all possible key-state pairs
  	 */
  	default Promise<StreamSupplier<CrdtData<K, S>>> download() {
  		return download(0);
  	}
  
  	/**
  	 * Returns a promise of a "destroying" stream supplier of all key-state pairs in the CRDT storage.
  	 * Pairs are sorted by key. After stream supplier is finished, all the returned key-state pairs
  	 * are removed from the CRDT storage.
  	 *
  	 * @return a promise of a "destroying" stream supplier of all possible key-state pairs
  	 */
  	Promise<StreamSupplier<CrdtData<K, S>>> take();
  
  	/**
  	 * Returns a promise of a stream consumer of tombstones (keyus to be removed from the CRDT storage).
  	 * This operation is not persistent and not guaranteed.
  	 *
  	 * @return a promise of a stream consumer of tombstones
  	 */
  	Promise<StreamConsumer<CrdtTombstone<K>>> remove();
  
  	/**
  	 * Marker that this client is functional (server is up, there are enough nodes in cluster etc.)
  	 *
  	 * @return promise that succeeds if this client is up
  	 */
  	Promise<Void> ping();
  }
  