Second checkpoint

internal/messaging/rabbitmq/example_consumer.go

@@ -0,0 +1,74 @@
+package rabbitmq
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"time"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+const (
+	// ExampleRoutingKey is the routing key used by the generic example flow.
+	ExampleRoutingKey = "example.created"
+	// ExampleBindingKey binds the example queue to example.* routing keys.
+	ExampleBindingKey = "example.#"
+)
+
+// EventRecorder persists a received event. It is the seam between the messaging
+// layer and storage for the example flow; a real domain would call its own
+// service instead.
+type EventRecorder interface {
+	Record(ctx context.Context, kind string, payload json.RawMessage) error
+}
+
+// ExampleMessage is the payload published and consumed by the scaffold.
+type ExampleMessage struct {
+	Kind      string    `json:"kind"`
+	Message   string    `json:"message"`
+	EmittedAt time.Time `json:"emitted_at"`
+}
+
+// ExampleHandler is a generic consumer that records every delivery into the
+// events table. It demonstrates the messaging -> storage path; delete it when a
+// real async use case replaces the scaffold.
+type ExampleHandler struct {
+	recorder EventRecorder
+	log      *slog.Logger
+}
+
+// NewExampleHandler returns an ExampleHandler.
+func NewExampleHandler(recorder EventRecorder, log *slog.Logger) *ExampleHandler {
+	return &ExampleHandler{recorder: recorder, log: log}
+}
+
+// Handle decodes the delivery (best-effort) and records it.
+func (h *ExampleHandler) Handle(ctx context.Context, d amqp.Delivery) error {
+	var msg ExampleMessage
+	if err := json.Unmarshal(d.Body, &msg); err != nil {
+		return fmt.Errorf("decode example message: %w", err)
+	}
+
+	h.log.Info("received example message",
+		"routing_key", d.RoutingKey, "kind", msg.Kind, "message", msg.Message)
+
+	if err := h.recorder.Record(ctx, "example", d.Body); err != nil {
+		return fmt.Errorf("record event: %w", err)
+	}
+	return nil
+}
+
+// PublishExample emits a single example message; used by `gis worker --publish-example`.
+func PublishExample(ctx context.Context, pub *Publisher) error {
+	body, err := json.Marshal(ExampleMessage{
+		Kind:      "example",
+		Message:   "hello from gis worker",
+		EmittedAt: time.Now().UTC(),
+	})
+	if err != nil {
+		return err
+	}
+	return pub.Publish(ctx, ExampleRoutingKey, body)
+}