package ass.sivakfil.cvi5.task3;

import java.util.List;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Task3 {

    public static void main(String[] args) {
        List<Integer> numbers = IntStream.range(0, 10).boxed().collect(Collectors.toList());
        System.out.println(sumEvenNumbers(numbers));
        System.out.println(sumOddNumbers(numbers));
        System.out.println(mulEvenNumbers(numbers));

        System.out.println(genericAggregate1(numbers, (a,b) -> a+b, (i) -> (i % 2) == 0));
        System.out.println(genericAggregate2(numbers, (a,b) -> a+b, (i) -> (i % 2) == 0));
    }

    // possible solution 1
    private static int genericAggregate1(List<Integer> nums, BinaryOperator<Integer> aggregation, Predicate<Integer> filter) {
        return nums.stream()
        .filter(filter)
        .reduce(aggregation)
        .orElse(0);
    }

    // possible solution 2
    private static int genericAggregate2(List<Integer> nums, BinaryOperator<Integer> aggregation, Predicate<Integer> filter) {
        int acc = 0;
        for(Integer i : nums) {
            if(filter.test(i)) {
                acc += aggregation.apply(acc, i);
            }
        }
        return acc;
    }

    private static int sumEvenNumbers(List<Integer> numbers) {
        int acc = 0;
        for(int i : numbers) {
            if(i % 2 == 0) {
                acc += i;
            }
        }
        return acc;
    }

    private static int sumOddNumbers(List<Integer> numbers) {
        int acc = 0;
        for(int i : numbers) {
            if(i % 2 != 0) {
                acc += i;
            }
        }
        return acc;
    }

    private static int mulEvenNumbers(List<Integer> numbers) {
        int acc = 1;
        for(int i : numbers) {
            if(i % 2 == 0) {
                acc *= i;
            }
        }
        return acc;
    }

}