/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.optimizer;

import java.util.HashMap;
import java.util.Map;

import org.apache.flink.api.common.io.statistics.BaseStatistics;

/**
 * The collection of access methods that can be used to retrieve statistical information about the
 * data processed in a job. Currently this method acts as an entry point only for obtaining cached
 * statistics.
 */
public class DataStatistics {
	
	private final Map<String, BaseStatistics> baseStatisticsCache;
	
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Creates a new statistics object, with an empty cache. 
	 */
	public DataStatistics() {
		this.baseStatisticsCache = new HashMap<String, BaseStatistics>();
	}
	
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Gets the base statistics for the input identified by the given identifier.
	 *  
	 * @param inputIdentifier The identifier for the input.
	 * @return The statistics that were cached for this input.
	 */
	public BaseStatistics getBaseStatistics(String inputIdentifier) {
		synchronized (this.baseStatisticsCache) {
			return this.baseStatisticsCache.get(inputIdentifier);
		}
	}
	
	/**
	 * Caches the given statistics. They are later retrievable under the given identifier.
	 * 
	 * @param statistics The statistics to cache.
	 * @param identifier The identifier which may be later used to retrieve the statistics.
	 */
	public void cacheBaseStatistics(BaseStatistics statistics, String identifier) {
		synchronized (this.baseStatisticsCache) {
			this.baseStatisticsCache.put(identifier, statistics);
		}
	}
}