concat.go

package gcf

type concatIterable[T any] struct {
	itb1 Iterable[T]
	itb2 Iterable[T]
}

type concatIterator[T any] struct {
	it1 Iterator[T]
	it2 Iterator[T]
	iteratorItem[T]
}

// Concat makes Iterable elements concatenated of itb1 and itb2.
//
//	itb1 := gcf.FromSlice([]int{1, 2, 3})
//	itb2 := gcf.FromSlice([]int{4, 5, 6})
//	itbc := gcf.Concat(itb1, itb2)
func Concat[T any](itb1 Iterable[T], itb2 Iterable[T]) Iterable[T] {
	if isEmpty(itb1) && isEmpty(itb2) {
		return orEmpty(itb1)
	}
	if isEmpty(itb2) {
		return itb1
	}
	if isEmpty(itb1) {
		return itb2
	}
	return &concatIterable[T]{itb1, itb2}
}

func (itb *concatIterable[T]) Iterator() Iterator[T] {
	return &concatIterator[T]{
		it1: itb.itb1.Iterator(),
		it2: itb.itb2.Iterator(),
	}
}

func (it *concatIterator[T]) MoveNext() bool {
	if it.done {
		return false
	}
	if it.it1.MoveNext() {
		it.current = it.it1.Current()
		return true
	}
	if it.it2.MoveNext() {
		it.current = it.it2.Current()
		return true
	}
	it.MarkDone()
	return false
}

func (it *concatIterator[T]) Current() T {
	return it.current
}