package balancer

import "sync/atomic"

type roundRobin struct {
	counter atomic.Uint64
}

// RoundRobin returns a strategy that cycles through healthy endpoints
// sequentially using an atomic counter.
func RoundRobin() Strategy {
	return &roundRobin{}
}

func (r *roundRobin) Next(healthy []Endpoint) (Endpoint, error) {
	if len(healthy) == 0 {
		return Endpoint{}, ErrNoHealthy
	}
	idx := r.counter.Add(1) - 1
	return healthy[idx%uint64(len(healthy))], nil
}