package lib

// Regression: sovereign (self-mutating) receivers own an arena. Mutations
// through maps, slices and linked pointers must persist across method calls,
// and a map's internal owner arena must survive the receiver.

type Node struct {
	next *Node
	val  int32
}

type Obj interface {
	Key() (s string)
}

type Named struct {
	name string
}

func NewNamed(name string) (n *Named) {
	return &Named{name: name}
}

func (n *Named) Key() (s string) { return n.name }

type Store struct {
	head  *Node
	items []*Node
	byKey map[string]Obj
}

func (s *Store) Add(k string, v int32) {
	n := &Node{val: v}
	n.next = s.head
	s.head = n
	s.items = push(s.items, n)
	if s.byKey == nil {
		s.byKey = map[string]Obj{}
	}
	s.byKey[k] = NewNamed(k)
}

func (s *Store) Sum() (n int32) {
	p := s.head
	for p != nil {
		n += p.val
		p = p.next
	}
	for _, q := range s.items {
		n += q.val
	}
	return n
}

func (s *Store) KeyName(k string) (name string) {
	o := s.byKey[k]
	if o == nil {
		return ""
	}
	return o.Key()
}