package parsekit

func (p *P) QueueStates(states ...StateFn) StateFn {
	first, followup := states[0], states[1:]
	for reverse := range followup {
		p.PushState(followup[len(followup)-reverse-1])
	}
	return first
}

func (p *P) ToChildState(state StateFn) StateFn {
	p.PushState(p.state)
	return state
}

func (p *P) ToParentState() StateFn {
	state := p.PopState()
	return state
}

// PushState adds the state function to the state stack.
// This is used for implementing nested parsing.
func (p *P) PushState(state StateFn) {
	p.stack = append(p.stack, state)
}

// PopState pops the last pushed state from the state stack.
func (p *P) PopState() StateFn {
	last := len(p.stack) - 1
	head, tail := p.stack[:last], p.stack[last]
	p.stack = head
	return tail
}