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The module for FunctionalJ Core.
There is a newer version: 1.0.17
// ============================================================================
// Copyright (c) 2017-2021 Nawapunth Manusitthipol (NawaMan - http://nawaman.net).
// ----------------------------------------------------------------------------
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
// ============================================================================
package functionalj.stream;

import static functionalj.function.Func.f;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;

import functionalj.function.aggregator.Aggregation;
import functionalj.list.FuncList;
import functionalj.map.FuncMap;
import functionalj.map.ImmutableFuncMap;
import lombok.val;

public interface AsStreamPlusWithGroupingBy {
    
    public StreamPlus streamPlus();
    
    /** Group the elements by determining the grouping keys */
    public default  FuncMap> groupingBy(Function keyMapper) {
        val toFuncList = f((ArrayList array) -> FuncList.from(array));
        val newArray   = f(() -> new ArrayList());
        val streamPlus = this.streamPlus();
        Supplier  >>                                    supplier;
        BiConsumer>, ? super DATA>                      accumulator;
        BiConsumer>, Map>> combiner;
        
        supplier = LinkedHashMap::new;
        accumulator = (map, each) -> {
            val key = keyMapper.apply(each);
            map.compute(key, (k, a)->{
                if (a == null) {
                    a = newArray.get();
                }
                a.add(each);
                return a;
            });
        };
        combiner = (map1, map2) -> map1.putAll(map2);
        
        val theMap = streamPlus.collect(supplier, accumulator, combiner);
        return ImmutableFuncMap
                    .from    (theMap)
                    .mapValue(toFuncList);
    }
    
    /** Group the elements by determining the grouping keys */
    public default  FuncMap> groupingBy(Aggregation keyAggregation) {
        val keyMapper = keyAggregation.newAggregator();
        return groupingBy(keyMapper);
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public default  FuncMap groupingBy(
            Function                 keyMapper,
            Function, VALUE> aggregate) {
        FuncMap> groupingBy = groupingBy(keyMapper);
        return (FuncMap) groupingBy.mapValue((Function)aggregate);
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    public default  FuncMap groupingBy(
            Aggregation              keyAggregation,
            Function, VALUE> aggregate) {
        val keyMapper = keyAggregation.newAggregator();
        return groupingBy(keyMapper, aggregate);
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    public default  FuncMap groupingBy(
            Function              keyMapper,
            Aggregation aggregation) {
        return groupingBy(keyMapper, stream -> stream.aggregate(aggregation));
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    public default  FuncMap groupingBy(
            Aggregation           keyAggregation,
            Aggregation aggregation) {
        val keyMapper = keyAggregation.newAggregator();
        return groupingBy(keyMapper, stream -> stream.aggregate(aggregation));
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public default  FuncMap groupingBy(
            Function                                   keyMapper,
            Supplier> collectorSupplier) {
        val valueMapper = f((FuncList list) -> list.collect(collectorSupplier.get()));
        return ((FuncMap)
                groupingBy(keyMapper)
                .mapValue(valueMapper));
    }
    
    /** Group the elements by determining the grouping keys and aggregate the result */
    public default  FuncMap groupingBy(
            Aggregation                                keyAggregation,
            Supplier> collectorSupplier) {
        val keyMapper = keyAggregation.newAggregator();
        return groupingBy(keyMapper, collectorSupplier);
    }
    
}