order sagas

pkg/order/hooks.go

@@ -0,0 +1,58 @@
+package order
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/flow"
+)
+
+// Publisher is the minimal seam the amqp_emit hook needs. cmd/order supplies a
+// RabbitMQ-backed implementation; tests pass a fake. Keeping it an interface
+// keeps pkg/order free of an AMQP dependency.
+type Publisher interface {
+	Publish(exchange, routingKey string, body []byte) error
+}
+
+// RegisterEmitHook registers the "amqp_emit" flow hook, which publishes a flow
+// event to a message broker — the bridge from a saga step to other services
+// (loyalty, ERP sync, notifications) without coupling the flow to them. It is
+// the commerce analogue of the CMS event listeners. Params (optional):
+//
+//	{"exchange": "", "routingKey": "order-events"}
+//
+// The body is {step, phase, id, error, vars}. With a nil publisher the hook is
+// still registered (so the editor lists it) but errors at run time — and since
+// hook errors never abort a flow, that failure is logged, not fatal.
+func RegisterEmitHook(reg *flow.Registry, pub Publisher) {
+	reg.Hook("amqp_emit", func(_ context.Context, st *flow.State, info flow.HookInfo, params json.RawMessage) error {
+		if pub == nil {
+			return fmt.Errorf("amqp_emit: no publisher configured")
+		}
+		var p struct {
+			Exchange   string `json:"exchange"`
+			RoutingKey string `json:"routingKey"`
+		}
+		if len(params) > 0 {
+			if err := json.Unmarshal(params, &p); err != nil {
+				return fmt.Errorf("amqp_emit: bad params: %w", err)
+			}
+		}
+		if p.RoutingKey == "" {
+			p.RoutingKey = "order-events"
+		}
+		errStr := ""
+		if info.Err != nil {
+			errStr = info.Err.Error()
+		}
+		body, _ := json.Marshal(map[string]any{
+			"step":  info.Step,
+			"phase": info.Phase,
+			"id":    st.ID,
+			"error": errStr,
+			"vars":  st.Vars,
+		})
+		return pub.Publish(p.Exchange, p.RoutingKey, body)
+	})
+}