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/*
 * Copyright © 2009 HotPads ([email protected])
 *
 * 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.datarouter.scanner;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.Supplier;

public class ScannerToGroups,M extends Map> implements Function,M>{

	private final Function keyFunction;
	private final Function valueFunction;
	private final Supplier mapSupplier;
	private final Supplier collectionSupplier;

	private ScannerToGroups(
			Function keyFunction,
			Function valueFunction,
			Supplier mapSupplier,
			Supplier collectionSupplier){
		this.keyFunction = keyFunction;
		this.valueFunction = valueFunction;
		this.mapSupplier = mapSupplier;
		this.collectionSupplier = collectionSupplier;
	}

	@Override
	public M apply(Scanner scanner){
		M map = mapSupplier.get();
		scanner.forEach(item -> {
			K key = keyFunction.apply(item);
			C collection = map.computeIfAbsent(key, $ -> collectionSupplier.get());
			V value = valueFunction.apply(item);
			collection.add(value);
		});
		return map;
	}

	/*--------------- Factories ----------------*/

	public static 
	Function,Map>> of(
			Function keyFunction){
		return new ScannerToGroups<>(keyFunction, Function.identity(), HashMap::new, ArrayList::new);
	}

	public static 
	Function,Map>> of(
			Function keyFunction,
			Function valueFunction){
		return new ScannerToGroups<>(keyFunction, valueFunction, HashMap::new, ArrayList::new);
	}

	public static >>
	Function,M> of(
			Function keyFunction,
			Function valueFunction,
			Supplier mapSupplier){
		return new ScannerToGroups<>(keyFunction, valueFunction, mapSupplier, ArrayList::new);
	}

	public static ,M extends Map>
	Function,M> of(
			Function keyFunction,
			Function valueFunction,
			Supplier mapSupplier,
			Supplier collectionSupplier){
		return new ScannerToGroups<>(keyFunction, valueFunction, mapSupplier, collectionSupplier);
	}

}