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.etl;
  
  import java.util.*;
  import java.util.function.Function;
  import java.util.stream.Stream;
  
  import static java.util.Collections.emptyList;
  import static java.util.Collections.emptyMap;
  
  public class LogDiff<D> {
  	private final Map<String, LogPositionDiff> positions;
  	private final List<D> diffs;
  
  	private LogDiff(Map<String, LogPositionDiff> positions, List<D> diffs) {
  		this.positions = positions;
  		this.diffs = diffs;
  	}
  
  	public static <D> LogDiff<D> of(Map<String, LogPositionDiff> positions, List<D> diffs) {
  		return new LogDiff<>(positions, diffs);
  	}
  
  	public static <D> LogDiff<D> of(Map<String, LogPositionDiff> positions, D diff) {
  		return of(positions, List.of(diff));
  	}
  
  	public static <D> LogDiff<D> empty() {
  		return of(emptyMap(), emptyList());
  	}
  
  	public static <D> LogDiff<D> reduce(List<LogDiff<D>> logDiffs, Function<List<D>, D> diffsReducer) {
  		Map<String, LogPositionDiff> positions = new LinkedHashMap<>();
  		List<D> diffs = new ArrayList<>();
  		for (var logDiff : logDiffs) {
  			for (var entry : logDiff.getPositions().entrySet()) {
  				positions.compute(entry.getKey(),
  					(partitionId, logPositionDiff) ->
  						logPositionDiff == null ?
  							entry.getValue() :
  							new LogPositionDiff(logPositionDiff.from(), entry.getValue().to())
  				);
  			}
  			diffs.add(diffsReducer.apply(logDiff.getDiffs()));
  		}
  		return LogDiff.of(positions, diffsReducer.apply(diffs));
  	}
  
  
  	public static <D> LogDiff<D> forCurrentPosition(List<D> diffs) {
  		return of(Map.of(), diffs);
  	}
  
  	public static <D> LogDiff<D> forCurrentPosition(D diff) {
  		return forCurrentPosition(List.of(diff));
  	}
  
  	public Map<String, LogPositionDiff> getPositions() {
  		return positions;
  	}
  
  	public List<D> getDiffs() {
  		return diffs;
  	}
  
  	public Stream<D> diffs() {
  		return diffs.stream();
  	}
  
  	@Override
  	public boolean equals(Object o) {
  		if (this == o) return true;
  		if (o == null || getClass() != o.getClass()) return false;
  
  		LogDiff<?> logDiff = (LogDiff<?>) o;
  
  		if (!Objects.equals(positions, logDiff.positions)) return false;
  		return Objects.equals(diffs, logDiff.diffs);
  	}
  
  	@Override
  	public int hashCode() {
  		int result = positions != null ? positions.hashCode() : 0;
  		result = 31 * result + (diffs != null ? diffs.hashCode() : 0);
  		return result;
  	}
  
  	@Override
  	public String toString() {
  		return "{positions:" + positions.keySet() + ", diffs:" + diffs.size() + '}';
  	}
  }
  