package taskscheduler

import "context"

// SingleFlightGate keeps at most one fetched task in flight. Release is
// idempotent so repeated terminal updates cannot increase capacity.
type SingleFlightGate struct {
	token chan struct{}
}

func NewSingleFlightGate() *SingleFlightGate {
	gate := &SingleFlightGate{token: make(chan struct{}, 1)}
	gate.token <- struct{}{}
	return gate
}

func (g *SingleFlightGate) Acquire(ctx context.Context) error {
	select {
	case <-g.token:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}

func (g *SingleFlightGate) Release() {
	select {
	case g.token <- struct{}{}:
	default:
	}
}