feat: 基本广播服务

- 由Hub接收/push/{topic}的请求并解析信息体广播到对应的Client

interval/protocol/message.go

@@ -0,0 +1,39 @@
+package protocol
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type ControlMessage struct {
+	Type   MessageType `json:"type"`
+	Topic  Topic       `json:"topic,omitempty"`
+	Topics []Topic     `json:"topics,omitempty"`
+}
+
+type BroadcastMessage struct {
+	Type    MessageType     `json:"type"`
+	Topic   Topic           `json:"topic"`
+	Payload json.RawMessage `json:"payload"`
+}
+
+func (m ControlMessage) Validate() error {
+	switch m.Type {
+	case MsgInit:
+		if len(m.Topics) == 0 {
+			return errors.New("init requires topics")
+		}
+	case MsgSubscribe:
+		if m.Topic == "" {
+			return errors.New("subscribe requires topic")
+		}
+	default:
+		return errors.New("unknown message type")
+	}
+	return nil
+}
+
+var (
+	ErrInvalidMessage  = errors.New("invalid message")
+	ErrPolicyViolation = errors.New("policy violation")
+)

interval/protocol/subscription.go

@@ -0,0 +1,6 @@
+package protocol
+
+type Subscription struct {
+	ClientID string
+	Topic    Topic
+}

interval/protocol/types.go

@@ -0,0 +1,17 @@
+package protocol
+
+type MessageType string
+
+const (
+	MsgInit        MessageType = "init"
+	MsgSubscribe   MessageType = "subscribe"
+	MsgUnsubscribe MessageType = "unsubscribe"
+	MsgBroadcast   MessageType = "broadcast"
+	MsgError       MessageType = "error"
+)
+
+type Topic string
+
+func (t Topic) Valid() bool {
+	return t != ""
+}