feat: edge gateway service

gateway/internal/replay/replay.go

@@ -0,0 +1,24 @@
+// Package replay defines the authenticated replay-reservation contract used by
+// the gateway transport pipeline.
+package replay
+
+import (
+	"context"
+	"errors"
+	"time"
+)
+
+var (
+	// ErrDuplicate reports that the request identifier has already been
+	// reserved for the same device session within the active replay window.
+	ErrDuplicate = errors.New("replay reservation already exists")
+)
+
+// Store reserves authenticated transport request identifiers for a bounded
+// replay window.
+type Store interface {
+	// Reserve marks the deviceSessionID and requestID pair as seen for ttl.
+	// Implementations must wrap ErrDuplicate when the same pair is reserved
+	// again before ttl expires.
+	Reserve(ctx context.Context, deviceSessionID string, requestID string, ttl time.Duration) error
+}