✨ Add repository guidelines and enhance documentation for project structure, build commands, coding standards, and testing practices. Introduce AGENTS.md for contributor guidance, update README.md to reference new guidelines, and improve configuration documentation for NATS modes. Update Makefile and Taskfile with clearer run commands and requirements for development and production modes. Add production deployment guide and improve logging configuration for better observability.

internal/infra/nats/message_handler_test.go

@@ -0,0 +1,62 @@
+package nats
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	"github.com/nats-io/nats.go"
+	"go.uber.org/zap/zaptest"
+)
+
+var _ = Describe("MessageHandler", func() {
+	var (
+		c *Consumer
+	)
+
+	BeforeEach(func() {
+		c = &Consumer{
+			mode:         "jetstream",
+			streamName:   "TEST_STREAM",
+			consumerName: "test-consumer",
+			logger:       zaptest.NewLogger(GinkgoT()),
+		}
+	})
+
+	Describe("resolveMsgID", func() {
+		It("extracts message ID from header", func() {
+			msg := &nats.Msg{
+				Header: nats.Header{},
+			}
+			msg.Header.Set("Nats-Msg-Id", "msg-123")
+
+			id, source, err := c.resolveMsgID(msg)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(id).To(Equal("msg-123"))
+			Expect(source).To(Equal("header"))
+		})
+
+		It("generates UUID for core mode when header is missing", func() {
+			c.mode = "core"
+			msg := &nats.Msg{
+				Header: nats.Header{},
+			}
+
+			id, source, err := c.resolveMsgID(msg)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(id).NotTo(BeEmpty())
+			Expect(source).To(Equal("generated"))
+		})
+
+		It("returns error for JetStream mode when header and metadata are missing", func() {
+			c.mode = "jetstream"
+			msg := &nats.Msg{
+				Header: nats.Header{},
+			}
+
+			// Without metadata, this should return an error
+			_, _, err := c.resolveMsgID(msg)
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("fetch metadata"))
+		})
+	})
+})
+