feat!: replace msgpack with protobuf for all NATS messages

BREAKING CHANGE: All NATS message serialization now uses Protocol Buffers.
- Added proto/messages/v1/messages.proto with 22 message types
- Generated Go code at gen/messagespb/
- messages/ package now exports type aliases to proto types
- natsutil.Publish/Request/Decode use proto.Marshal/Unmarshal
- Removed legacy MessageHandler, OnMessage, wrapMapHandler
- TypedMessageHandler now returns (proto.Message, error)
- EffectiveQuery is now a free function: messages.EffectiveQuery(req)
- Removed msgpack dependency entirely

natsutil/natsutil.go

@@ -1,70 +1,70 @@
-// Package natsutil provides a NATS/JetStream client with msgpack serialization.
+// Package natsutil provides a NATS/JetStream client with protobuf serialization.
 package natsutil
 
 import (
-	"fmt"
-	"log/slog"
-	"time"
+"fmt"
+"log/slog"
+"time"
 
-	"github.com/nats-io/nats.go"
-	"github.com/vmihailenco/msgpack/v5"
+"github.com/nats-io/nats.go"
+"google.golang.org/protobuf/proto"
 )
 
-// Client wraps a NATS connection with msgpack helpers.
+// Client wraps a NATS connection with protobuf helpers.
 type Client struct {
-	nc   *nats.Conn
-	js   nats.JetStreamContext
-	subs []*nats.Subscription
-	url  string
-	opts []nats.Option
+nc   *nats.Conn
+js   nats.JetStreamContext
+subs []*nats.Subscription
+url  string
+opts []nats.Option
 }
 
 // New creates a NATS client configured to connect to the given URL.
 // Optional NATS options (e.g. credentials) can be appended.
 func New(url string, opts ...nats.Option) *Client {
-	defaults := []nats.Option{
-		nats.ReconnectWait(2 * time.Second),
-		nats.MaxReconnects(-1),
-		nats.DisconnectErrHandler(func(_ *nats.Conn, err error) {
-			slog.Warn("NATS disconnected", "error", err)
-		}),
-		nats.ReconnectHandler(func(_ *nats.Conn) {
-			slog.Info("NATS reconnected")
-		}),
-	}
-	return &Client{
-		url:  url,
-		opts: append(defaults, opts...),
-	}
+defaults := []nats.Option{
+nats.ReconnectWait(2 * time.Second),
+nats.MaxReconnects(-1),
+nats.DisconnectErrHandler(func(_ *nats.Conn, err error) {
+slog.Warn("NATS disconnected", "error", err)
+}),
+nats.ReconnectHandler(func(_ *nats.Conn) {
+slog.Info("NATS reconnected")
+}),
+}
+return &Client{
+url:  url,
+opts: append(defaults, opts...),
+}
 }
 
 // Connect establishes the NATS connection and JetStream context.
 func (c *Client) Connect() error {
-	nc, err := nats.Connect(c.url, c.opts...)
-	if err != nil {
-		return fmt.Errorf("nats connect: %w", err)
-	}
-	js, err := nc.JetStream()
-	if err != nil {
-		nc.Close()
-		return fmt.Errorf("jetstream: %w", err)
-	}
-	c.nc = nc
-	c.js = js
-	slog.Info("connected to NATS", "url", c.url)
-	return nil
+nc, err := nats.Connect(c.url, c.opts...)
+if err != nil {
+return fmt.Errorf("nats connect: %w", err)
+}
+js, err := nc.JetStream()
+if err != nil {
+nc.Close()
+return fmt.Errorf("jetstream: %w", err)
+}
+c.nc = nc
+c.js = js
+slog.Info("connected to NATS", "url", c.url)
+return nil
 }
 
 // Close drains subscriptions and closes the connection.
 func (c *Client) Close() {
-	if c.nc == nil {
-		return
-	}
-	for _, sub := range c.subs {
-		_ = sub.Drain()
-	}
-	c.nc.Close()
-	slog.Info("NATS connection closed")
+if c.nc == nil {
+return
+}
+for _, sub := range c.subs {
+_ = sub.Drain()
+}
+c.nc.Close()
+slog.Info("NATS connection closed")
 }
 
 // Conn returns the underlying *nats.Conn.
@@ -75,68 +75,56 @@ func (c *Client) JS() nats.JetStreamContext { return c.js }
 
 // IsConnected returns true if the NATS connection is active.
 func (c *Client) IsConnected() bool {
-	return c.nc != nil && c.nc.IsConnected()
+return c.nc != nil && c.nc.IsConnected()
 }
 
 // Subscribe subscribes to a subject with an optional queue group.
 // The handler receives the raw *nats.Msg.
 func (c *Client) Subscribe(subject string, handler nats.MsgHandler, queue string) error {
-	var sub *nats.Subscription
-	var err error
-	if queue != "" {
-		sub, err = c.nc.QueueSubscribe(subject, queue, handler)
-		slog.Info("subscribed", "subject", subject, "queue", queue)
-	} else {
-		sub, err = c.nc.Subscribe(subject, handler)
-		slog.Info("subscribed", "subject", subject)
-	}
-	if err != nil {
-		return fmt.Errorf("subscribe %s: %w", subject, err)
-	}
-	c.subs = append(c.subs, sub)
-	return nil
+var sub *nats.Subscription
+var err error
+if queue != "" {
+sub, err = c.nc.QueueSubscribe(subject, queue, handler)
+slog.Info("subscribed", "subject", subject, "queue", queue)
+} else {
+sub, err = c.nc.Subscribe(subject, handler)
+slog.Info("subscribed", "subject", subject)
+}
+if err != nil {
+return fmt.Errorf("subscribe %s: %w", subject, err)
+}
+c.subs = append(c.subs, sub)
+return nil
 }
 
-// Publish encodes data as msgpack and publishes to the subject.
-func (c *Client) Publish(subject string, data any) error {
-	payload, err := msgpack.Marshal(data)
-	if err != nil {
-		return fmt.Errorf("msgpack marshal: %w", err)
-	}
-	return c.nc.Publish(subject, payload)
+// Publish encodes data as protobuf and publishes to the subject.
+func (c *Client) Publish(subject string, data proto.Message) error {
+payload, err := proto.Marshal(data)
+if err != nil {
+return fmt.Errorf("proto marshal: %w", err)
+}
+return c.nc.Publish(subject, payload)
 }
 
-// Request sends a msgpack-encoded request and decodes the response into result.
-func (c *Client) Request(subject string, data any, result any, timeout time.Duration) error {
-	payload, err := msgpack.Marshal(data)
-	if err != nil {
-		return fmt.Errorf("msgpack marshal: %w", err)
-	}
-	msg, err := c.nc.Request(subject, payload, timeout)
-	if err != nil {
-		return fmt.Errorf("nats request: %w", err)
-	}
-	return msgpack.Unmarshal(msg.Data, result)
+// PublishRaw publishes pre-encoded bytes to the subject.
+func (c *Client) PublishRaw(subject string, data []byte) error {
+return c.nc.Publish(subject, data)
 }
 
-// DecodeMsgpack decodes msgpack-encoded NATS message data into dest.
-func DecodeMsgpack(msg *nats.Msg, dest any) error {
-	return msgpack.Unmarshal(msg.Data, dest)
+// Request sends a protobuf-encoded request and decodes the response into result.
+func (c *Client) Request(subject string, data proto.Message, result proto.Message, timeout time.Duration) error {
+payload, err := proto.Marshal(data)
+if err != nil {
+return fmt.Errorf("proto marshal: %w", err)
+}
+msg, err := c.nc.Request(subject, payload, timeout)
+if err != nil {
+return fmt.Errorf("nats request: %w", err)
+}
+return proto.Unmarshal(msg.Data, result)
 }
 
-// Decode is a generic helper that unmarshals msgpack bytes into T.
-// Usage:  req, err := natsutil.Decode[messages.ChatRequest](msg.Data)
-func Decode[T any](data []byte) (T, error) {
-	var v T
-	err := msgpack.Unmarshal(data, &v)
-	return v, err
-}
-
-// DecodeMsgpackMap decodes msgpack data into a generic map.
-func DecodeMsgpackMap(data []byte) (map[string]any, error) {
-	var m map[string]any
-	if err := msgpack.Unmarshal(data, &m); err != nil {
-		return nil, err
-	}
-	return m, nil
+// Decode unmarshals protobuf bytes into dest.
+func Decode(data []byte, dest proto.Message) error {
+return proto.Unmarshal(data, dest)
 }