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.datastream.processor.transformer;
  
  import io.activej.datastream.supplier.StreamDataAcceptor;
  
  public final class StreamCounter<T> extends AbstractStreamTransformer<T, T> {
  	private CounterDataAcceptor acceptor = new CounterDataAcceptor(null, 0L);
  
  	private StreamCounter() {}
  
  	public static <T> StreamCounter<T> create() {
  		return new StreamCounter<>();
  	}
  
  	@Override
  	protected StreamDataAcceptor<T> onResumed(StreamDataAcceptor<T> output) {
  		acceptor = new CounterDataAcceptor(output, acceptor.itemCount);
  		return acceptor;
  	}
  
  	public long getItemCount() {
  		return acceptor.itemCount;
  	}
  
  	public class CounterDataAcceptor implements StreamDataAcceptor<T> {
  		private final StreamDataAcceptor<T> output;
  		private long itemCount;
  
  		public CounterDataAcceptor(StreamDataAcceptor<T> output, long itemCount) {
  			this.output = output;
  			this.itemCount = itemCount;
  		}
  
  		@Override
  		public void accept(T item) {
  			itemCount++;
  			output.accept(item);
  		}
  	}
  }
  