feat(messaging): define core messaging interfaces, types, and config

messaging/config.go

@@ -1 +1,19 @@
 package messaging
+
+import "time"
+
+// Config holds library-wide options for producers and consumers.
+type Config struct {
+	RetryCount int
+	RetryDelay time.Duration
+	Timeout    time.Duration
+}
+
+// DefaultConfig returns a reasonable default configuration
+func DefaultConfig() Config {
+	return Config{
+		RetryCount: 3,
+		RetryDelay: 500 * time.Millisecond,
+		Timeout:    5 * time.Second,
+	}
+}

messaging/consumer.go

@@ -1 +1,9 @@
 package messaging
+
+import "context"
+
+// Consumer defines the interface for consuming messages.
+type Consumer interface {
+	Subscribe(ctx context.Context, topic string, handler HandlerFunc) error
+	Close() error
+}

messaging/error.go

@@ -1 +1,8 @@
 package messaging
+
+import "errors"
+
+var (
+	ErrPublishFailed   = errors.New("failed to publish message")
+	ErrSubscriptionErr = errors.New("failed to subscribe to topic")
+)

messaging/handler.go

@@ -1 +1,6 @@
 package messaging
+
+import "context"
+
+// HandlerFunc defines the function signature for consuming messages.
+type HandlerFunc func(ctx context.Context, msg Message) error

messaging/message.go

@@ -1 +1,9 @@
 package messaging
+
+// Message represents a single message in the system.
+type Message struct {
+	ID        string
+	Payload   []byte
+	Headers   map[string]string
+	Timestamp int64
+}

messaging/producer.go

@@ -1 +1,9 @@
 package messaging
+
+import "context"
+
+// Producer defines the interface for publishing messages.
+type Producer interface {
+	Publish(ctx context.Context, topic string, msg Message) error
+	Close() error
+}