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/*
 * Copyright (c) 2021 dzikoysk
 *
 * 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 panda.std.stream;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.ToLongFunction;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

public final class StreamUtils {

    private static final Map, Class> PRIMITIVE_TO_WRAPPER;

    static {
        Map, Class> primitiveToWrapper = new HashMap<>();

        primitiveToWrapper.put(boolean.class, Boolean.class);
        primitiveToWrapper.put(byte.class, Byte.class);
        primitiveToWrapper.put(char.class, Character.class);
        primitiveToWrapper.put(short.class, Short.class);
        primitiveToWrapper.put(int.class, Integer.class);
        primitiveToWrapper.put(long.class, Long.class);
        primitiveToWrapper.put(float.class, Float.class);
        primitiveToWrapper.put(double.class, Double.class);
        primitiveToWrapper.put(void.class, Void.class);

        PRIMITIVE_TO_WRAPPER = Collections.unmodifiableMap(primitiveToWrapper);
    }

    private StreamUtils() { }

    @SuppressWarnings("unchecked")
    static  Class convertPrimitiveToWrapper(Class type) {
        return (Class) PRIMITIVE_TO_WRAPPER.getOrDefault(type, type);
    }

    public static  long sum(Iterable iterable, ToLongFunction function) {
        return stream(iterable).mapToLong(function).sum();
    }

    public static  long sumLongs(Iterable iterable, ToLongFunction function) {
        return stream(iterable).mapToLong(function).sum();
    }

    public static  long count(Iterable iterable, Predicate filter) {
        return stream(iterable).filter(filter).count();
    }

    public static  Optional findFirst(Iterable iterable, Predicate filter) {
        return stream(iterable).filter(filter).findFirst();
    }

    public static  Collection map(Iterable iterable, Function mapper) {
        return stream(iterable).map(mapper).collect(Collectors.toList());
    }

    private static  Stream stream(Iterable iterable) {
        return StreamSupport.stream(iterable.spliterator(), false);
    }

    public static  BinaryOperator emptyBinaryOperator() {
        return (a, b) -> {
            throw new RuntimeException("Empty binary operator called by parallel stream");
        };
    }

}