Bootstrap copied BFF and local accounts with public Sendico contracts (#34)

backend/pkg/merrors/throttle.go

@@ -0,0 +1,50 @@
+package merrors
+
+import (
+	"errors"
+	"strings"
+	"time"
+)
+
+// ThrottleDetails describes a temporary request limit without coupling callers
+// to a transport-specific response format.
+type ThrottleDetails struct {
+	ScopeKind  string
+	RetryAfter time.Duration
+}
+
+type throttleDetailsError struct {
+	base    error
+	msg     string
+	details ThrottleDetails
+}
+
+func (e throttleDetailsError) Error() string {
+	return Wrap(e.base, e.msg).Error()
+}
+
+func (e throttleDetailsError) Unwrap() error {
+	return e.base
+}
+
+// WithThrottle annotates an error with retry information while preserving its
+// classification for errors.Is and errors.As.
+func WithThrottle(base error, scopeKind string, retryAfter time.Duration, msg string) error {
+	return throttleDetailsError{
+		base: base,
+		msg:  msg,
+		details: ThrottleDetails{
+			ScopeKind:  strings.TrimSpace(scopeKind),
+			RetryAfter: retryAfter,
+		},
+	}
+}
+
+// ThrottleDetailsFrom returns retry information attached by WithThrottle.
+func ThrottleDetailsFrom(err error) (ThrottleDetails, bool) {
+	var throttled throttleDetailsError
+	if !errors.As(err, &throttled) {
+		return ThrottleDetails{}, false
+	}
+	return throttled.details, true
+}