initial Go port of streamrip

internal/ratelimit/limiter.go

@@ -0,0 +1,54 @@
+package ratelimit
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+type Limiter struct {
+	interval time.Duration
+
+	mu   sync.Mutex
+	next time.Time
+}
+
+func New(requestsPerMinute int) *Limiter {
+	if requestsPerMinute <= 0 {
+		return &Limiter{}
+	}
+	return &Limiter{interval: time.Minute / time.Duration(requestsPerMinute)}
+}
+
+func (l *Limiter) Wait(ctx context.Context) error {
+	if l.interval <= 0 {
+		return nil
+	}
+
+	l.mu.Lock()
+	now := time.Now()
+	if l.next.IsZero() {
+		l.next = now.Add(l.interval)
+		l.mu.Unlock()
+		return nil
+	}
+
+	wake := l.next
+	if now.After(wake) {
+		l.next = now.Add(l.interval)
+		l.mu.Unlock()
+		return nil
+	}
+	l.next = l.next.Add(l.interval)
+	l.mu.Unlock()
+
+	timer := time.NewTimer(time.Until(wake))
+	defer timer.Stop()
+
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-timer.C:
+		return nil
+	}
+}