package download

// GlobalDownloadGate wraps a GatedSemaphore for download-specific concurrency control.
// See internal/middleware/rate_limit.go for the underlying GatedSemaphore implementation.
//
// The gate ensures that the total number of concurrent download streams never exceeds
// the configured limit (default 50), which keeps total bandwidth usage under 10 Mbps
// when each stream is throttled to ~25 KB/s.
type GlobalDownloadGate struct {
	sem chan struct{}
}

func NewGlobalDownloadGate(maxConcurrent int) *GlobalDownloadGate {
	return &GlobalDownloadGate{sem: make(chan struct{}, maxConcurrent)}
}

func (g *GlobalDownloadGate) Acquire()       { g.sem <- struct{}{} }
func (g *GlobalDownloadGate) Release()       { <-g.sem }
func (g *GlobalDownloadGate) Available() int { return cap(g.sem) - len(g.sem) }