feat(muxterm): wire protocol types and parser

muxterm/protocol.go

@@ -0,0 +1,94 @@
+package main
+
+import "encoding/json"
+
+// --- Client-to-server message types ---
+
+// AttachMsg requests attaching to a named tmux session.
+type AttachMsg struct {
+	Attach string `json:"attach"`
+}
+
+// ResizeMsg requests a PTY resize.
+type ResizeMsg struct {
+	Resize struct {
+		Cols int `json:"cols"`
+		Rows int `json:"rows"`
+	} `json:"resize"`
+}
+
+// DetachMsg requests detaching from the current session.
+type DetachMsg struct {
+	Detach bool `json:"detach"`
+}
+
+// --- Server-to-client message types ---
+
+// AttachedMsg confirms a successful attach.
+type AttachedMsg struct {
+	Attached string `json:"attached"`
+}
+
+// ErrorMsg reports an error to the client.
+type ErrorMsg struct {
+	Error string `json:"error"`
+}
+
+// ExitedMsg reports that a session's process has exited.
+type ExitedMsg struct {
+	Exited string `json:"exited"`
+}
+
+// ParseControlMessage unmarshals a JSON control message and returns the
+// message kind and a pointer to the typed value. Returns ("invalid", nil)
+// for unparseable JSON and ("unknown", nil) for unrecognised keys.
+func ParseControlMessage(data []byte) (string, interface{}) {
+	var raw map[string]json.RawMessage
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return "invalid", nil
+	}
+
+	if _, ok := raw["attach"]; ok {
+		var msg AttachMsg
+		if err := json.Unmarshal(data, &msg); err != nil {
+			return "invalid", nil
+		}
+		return "attach", &msg
+	}
+
+	if _, ok := raw["resize"]; ok {
+		var msg ResizeMsg
+		if err := json.Unmarshal(data, &msg); err != nil {
+			return "invalid", nil
+		}
+		return "resize", &msg
+	}
+
+	if _, ok := raw["detach"]; ok {
+		var msg DetachMsg
+		if err := json.Unmarshal(data, &msg); err != nil {
+			return "invalid", nil
+		}
+		return "detach", &msg
+	}
+
+	return "unknown", nil
+}
+
+// MarshalAttached returns JSON for an AttachedMsg.
+func MarshalAttached(session string) []byte {
+	b, _ := json.Marshal(AttachedMsg{Attached: session})
+	return b
+}
+
+// MarshalError returns JSON for an ErrorMsg.
+func MarshalError(msg string) []byte {
+	b, _ := json.Marshal(ErrorMsg{Error: msg})
+	return b
+}
+
+// MarshalExited returns JSON for an ExitedMsg.
+func MarshalExited(session string) []byte {
+	b, _ := json.Marshal(ExitedMsg{Exited: session})
+	return b
+}