refactor: split jikan client into transport/cache/rate subpackages

integrations/jikan/rate/limiter.go

@@ -0,0 +1,42 @@
+package rate
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+)
+
+type Limiter struct {
+	mu          sync.Mutex
+	lastReqTime time.Time
+	interval    time.Duration
+}
+
+func NewLimiter(interval time.Duration) *Limiter {
+	return &Limiter{interval: interval}
+}
+
+// Wait enforces minimum spacing between upstream Jikan requests.
+func (l *Limiter) Wait(ctx context.Context) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	now := time.Now()
+	nextAllowed := l.lastReqTime.Add(l.interval)
+	if now.Before(nextAllowed) {
+		timer := time.NewTimer(nextAllowed.Sub(now))
+		defer timer.Stop()
+
+		select {
+		case <-timer.C:
+		case <-ctx.Done():
+			return fmt.Errorf("request canceled while waiting for rate limit: %w", ctx.Err())
+		}
+		l.lastReqTime = time.Now()
+		return nil
+	}
+
+	l.lastReqTime = now
+	return nil
+}