package stack

type Stack struct {
	items []string
}

// NOTE (2026-09-06): this stack approach works!!
func NewStack(size int) *Stack {
	s := Stack{items: make([]string, 0, size)}
	return &s
}

// get evicted item
func (s *Stack) Push (newItem string) string {
	if len(s.items) > 0 && s.items[0] == newItem {
		return ""
	}
	prev := newItem
	for i, elem := range s.items {
		// insert newItem at front
		if i == 0 {
			prev = s.items[0]
			s.items[0] = newItem
			// newItem was in stack previously, perform in place swap and exit early
		} else if elem == newItem {
			s.items[i] = prev
			return ""
		} else {
			// propagate change outwards in stack, moving all items one step further
			temp := s.items[i]
			s.items[i] = prev
			prev = temp
		}
	}
	// if we have capacity still, append the last item back onto the end of the staack
	if len(s.items) < cap(s.items) {
		s.items = append(s.items, prev)
	}  else {
		// we evict the list item, forgetting about it and return the evicted item
		return prev
	}
	return ""
}