omaha: split request and response structures

Despite having common names between the request and response XML
structures the actual values which may appear in them are completely
disjoint. Splitting the types up makes the protocol easier to understand
when reading the code. When applicable, required fields like status are
passed to Add* methods.

omaha/protocol.go

@@ -28,18 +28,19 @@ import (
 	"github.com/coreos/mantle/version"
 )
 
+// Request sent by the Omaha client
 type Request struct {
 	XMLName        xml.Name      `xml:"request" json:"-"`
 	OS             *OS           `xml:"os"`
-	Apps           []*App   `xml:"app"`
+	Apps           []*AppRequest `xml:"app"`
 	Protocol       string        `xml:"protocol,attr"`
 	Version        string        `xml:"version,attr,omitempty"`
 	IsMachine      string        `xml:"ismachine,attr,omitempty"`
+	RequestId      string        `xml:"requestid,attr,omitempty"`
 	SessionId      string        `xml:"sessionid,attr,omitempty"`
 	UserId         string        `xml:"userid,attr,omitempty"`
 	InstallSource  string        `xml:"installsource,attr,omitempty"`
 	TestSource     string        `xml:"testsource,attr,omitempty"`
-	RequestId      string   `xml:"requestid,attr,omitempty"`
 	UpdaterVersion string        `xml:"updaterversion,attr,omitempty"`
 }
 
@@ -55,16 +56,69 @@ func NewRequest() *Request {
 	}
 }
 
-func (r *Request) AddApp(id, version string) *App {
+func (r *Request) AddApp(id, version string) *AppRequest {
-	a := &App{Id: id, Version: version}
+	a := &AppRequest{Id: id, Version: version}
 	r.Apps = append(r.Apps, a)
 	return a
 }
 
+type AppRequest struct {
+	Ping        *PingRequest    `xml:"ping"`
+	UpdateCheck *UpdateRequest  `xml:"updatecheck"`
+	Events      []*EventRequest `xml:"event" json:",omitempty"`
+	Id          string          `xml:"appid,attr,omitempty"`
+	Version     string          `xml:"version,attr,omitempty"`
+	NextVersion string          `xml:"nextversion,attr,omitempty"`
+	Lang        string          `xml:"lang,attr,omitempty"`
+	Client      string          `xml:"client,attr,omitempty"`
+	InstallAge  string          `xml:"installage,attr,omitempty"`
+
+	// update engine extensions
+	Track     string `xml:"track,attr,omitempty"`
+	FromTrack string `xml:"from_track,attr,omitempty"`
+
+	// coreos update engine extensions
+	BootId    string `xml:"bootid,attr,omitempty"`
+	MachineID string `xml:"machineid,attr,omitempty"`
+	OEM       string `xml:"oem,attr,omitempty"`
+}
+
+func (a *AppRequest) AddUpdateCheck() *UpdateRequest {
+	a.UpdateCheck = &UpdateRequest{}
+	return a.UpdateCheck
+}
+
+func (a *AppRequest) AddPing() *PingRequest {
+	a.Ping = new(PingRequest)
+	return a.Ping
+}
+
+func (a *AppRequest) AddEvent() *EventRequest {
+	event := &EventRequest{}
+	a.Events = append(a.Events, event)
+	return event
+}
+
+type UpdateRequest struct {
+	TargetVersionPrefix string `xml:"targetversionprefix,attr,omitempty"`
+}
+
+type PingRequest struct {
+	LastReportDays string `xml:"r,attr,omitempty"`
+}
+
+type EventRequest struct {
+	Type            EventType   `xml:"eventtype,attr"`
+	Result          EventResult `xml:"eventresult,attr"`
+	PreviousVersion string      `xml:"previousversion,attr,omitempty"`
+	ErrorCode       string      `xml:"errorcode,attr,omitempty"`
+}
+
+// Response sent by the Omaha server
 type Response struct {
 	XMLName  xml.Name       `xml:"response" json:"-"`
 	DayStart DayStart       `xml:"daystart"`
-	Apps     []*App   `xml:"app"`
+	Apps     []*AppResponse `xml:"app"`
 	Protocol string         `xml:"protocol,attr"`
 	Server   string         `xml:"server,attr"`
 }
@@ -81,58 +135,43 @@ type DayStart struct {
 	ElapsedSeconds string `xml:"elapsed_seconds,attr"`
 }
 
-func (r *Response) AddApp(id string, status AppStatus) *App {
+func (r *Response) AddApp(id string, status AppStatus) *AppResponse {
-	a := &App{Id: id, Status: status}
+	a := &AppResponse{Id: id, Status: status}
 	r.Apps = append(r.Apps, a)
 	return a
 }
 
-type App struct {
+type AppResponse struct {
-	Ping        *Ping        `xml:"ping"`
+	Ping        *PingResponse    `xml:"ping"`
-	UpdateCheck *UpdateCheck `xml:"updatecheck"`
+	UpdateCheck *UpdateResponse  `xml:"updatecheck"`
-	Events      []*Event     `xml:"event" json:",omitempty"`
+	Events      []*EventResponse `xml:"event" json:",omitempty"`
 	Id          string           `xml:"appid,attr,omitempty"`
-	Version     string       `xml:"version,attr,omitempty"`
-	NextVersion string       `xml:"nextversion,attr,omitempty"`
-	Lang        string       `xml:"lang,attr,omitempty"`
-	Client      string       `xml:"client,attr,omitempty"`
-	InstallAge  string       `xml:"installage,attr,omitempty"`
 	Status      AppStatus        `xml:"status,attr,omitempty"`
-
-	// update engine extensions
-	Track     string `xml:"track,attr,omitempty"`
-	FromTrack string `xml:"from_track,attr,omitempty"`
-
-	// coreos update engine extensions
-	BootId    string `xml:"bootid,attr,omitempty"`
-	MachineID string `xml:"machineid,attr,omitempty"`
-	OEM       string `xml:"oem,attr,omitempty"`
 }
 
-func (a *App) AddUpdateCheck() *UpdateCheck {
+func (a *AppResponse) AddUpdateCheck(status UpdateStatus) *UpdateResponse {
-	a.UpdateCheck = new(UpdateCheck)
+	a.UpdateCheck = &UpdateResponse{Status: status}
 	return a.UpdateCheck
 }
 
-func (a *App) AddPing() *Ping {
+func (a *AppResponse) AddPing() *PingResponse {
-	a.Ping = new(Ping)
+	a.Ping = &PingResponse{"ok"}
 	return a.Ping
 }
 
-func (a *App) AddEvent() *Event {
+func (a *AppResponse) AddEvent() *EventResponse {
-	event := new(Event)
+	event := &EventResponse{"ok"}
 	a.Events = append(a.Events, event)
 	return event
 }
 
-type UpdateCheck struct {
+type UpdateResponse struct {
 	URLs     *URLs        `xml:"urls"`
 	Manifest *Manifest    `xml:"manifest"`
-	TargetVersionPrefix string       `xml:"targetversionprefix,attr,omitempty"`
 	Status   UpdateStatus `xml:"status,attr,omitempty"`
 }
 
-func (u *UpdateCheck) AddURL(codebase string) *URL {
+func (u *UpdateResponse) AddURL(codebase string) *URL {
 	// An intermediate struct is used instead of a "urls>url" tag simply
 	// to keep Go from generating <urls></urls> if the list is empty.
 	if u.URLs == nil {
@@ -143,14 +182,17 @@ func (u *UpdateCheck) AddURL(codebase string) *URL {
 	return url
 }
 
-func (u *UpdateCheck) AddManifest(version string) *Manifest {
+func (u *UpdateResponse) AddManifest(version string) *Manifest {
 	u.Manifest = &Manifest{Version: version}
 	return u.Manifest
 }
 
-type Ping struct {
+type PingResponse struct {
-	LastReportDays string `xml:"r,attr,omitempty"`
+	Status string `xml:"status,attr"` // Always "ok".
-	Status         string `xml:"status,attr,omitempty"`
+}
+
+type EventResponse struct {
+	Status string `xml:"status,attr"` // Always "ok".
 }
 
 type OS struct {

omaha/protocol_test.go

@@ -83,10 +83,8 @@ func TestOmahaRequestUpdateCheck(t *testing.T) {
 func ExampleNewResponse() {
 	response := NewResponse()
 	app := response.AddApp("{52F1B9BC-D31A-4D86-9276-CBC256AADF9A}", "ok")
-	p := app.AddPing()
+	app.AddPing()
-	p.Status = "ok"
+	u := app.AddUpdateCheck(UpdateOK)
-	u := app.AddUpdateCheck()
-	u.Status = "ok"
 	u.AddURL("http://localhost/updates")
 	m := u.AddManifest("9999.0.0")
 	k := m.AddPackage()