package pool

const Infinite = -1
const Empty = 0

type Pool struct {
	OverflowsTo *Pool `json:"-"`
	SubtractsTo *Pool `json:"-"`
	Max         int
	Value       int
}

func (p *Pool) Add(amount int) {
	p.Value += amount
	if p.Max == Infinite {
		return
	}

	if p.Value > p.Max {
		overflow := p.Value - p.Max
		p.Value = p.Max
		if p.OverflowsTo != nil {
			p.OverflowsTo.Add(overflow)
		}
	}
}

func (p *Pool) Subtract(amount int) {
	if p.SubtractsTo != nil {
		forward := amount
		if forward > p.Value {
			forward = p.Value
		}
		p.SubtractsTo.Add(forward)
	}

	if p.Value == Infinite {
		return
	}

	p.Value -= amount
	if p.Value < 0 {
		p.Value = 0
	}
}

func (p *Pool) Fits(amount int) bool {
	return p.Value+amount <= p.Max
}

func (p *Pool) Has(amount int) bool {
	return p.Value >= amount
}

func New(start, max int) *Pool {
	return &Pool{
		Max:   max,
		Value: start,
	}
}