Add handler for AccountLinking process

actions.go

@@ -20,4 +20,7 @@ const (
 	OptInAction
 	// ReferralAction represents ?ref parameter in m.me URLs
 	ReferralAction
+	// AccountLinkingAction means that the event concerns changes in account linking
+	// status.
+	AccountLinkingAction
 )

message.go

@@ -60,6 +60,19 @@ type PostBack struct {
 	Referral Referral `json:"referral"`
 }
 
+type AccountLinking struct {
+	// Sender is who the message was sent from.
+	Sender Sender `json:"-"`
+	// Recipient is who the message was sent to.
+	Recipient Recipient `json:"-"`
+	// Time is when the message was sent.
+	Time time.Time `json:"-"`
+	// Status represents the new account linking status.
+	Status string `json:"status"`
+	// AuthorizationCode is a pass-through code set during the linking process.
+	AuthorizationCode string `json:"authorization_code"`
+}
+
 // Watermark is the RawWatermark timestamp rendered as a time.Time.
 func (d Delivery) Watermark() time.Time {
 	return time.Unix(d.RawWatermark/int64(time.Microsecond), 0)

messenger.go

@@ -59,6 +59,10 @@ type OptInHandler func(OptIn, *Response)
 // ReferralHandler is a handler used postback callbacks.
 type ReferralHandler func(ReferralMessage, *Response)
 
+// AccountLinkingHandler is a handler used to react to an account
+// being linked or unlinked.
+type AccountLinkingHandler func(AccountLinking, *Response)
+
 // Messenger is the client which manages communication with the Messenger Platform API.
 type Messenger struct {
 	mux                    *http.ServeMux
@@ -68,6 +72,7 @@ type Messenger struct {
 	postBackHandlers       []PostBackHandler
 	optInHandlers          []OptInHandler
 	referralHandlers       []ReferralHandler
+	accountLinkingHandlers []AccountLinkingHandler
 	token                  string
 	verifyHandler          func(http.ResponseWriter, *http.Request)
 	verify                 bool
@@ -131,6 +136,11 @@ func (m *Messenger) HandleReferral(f ReferralHandler) {
 	m.referralHandlers = append(m.referralHandlers, f)
 }
 
+// HandleAccountLinking adds a new AccountLinkingHandler to the Messenger
+func (m *Messenger) HandleAccountLinking(f AccountLinkingHandler) {
+	m.accountLinkingHandlers = append(m.accountLinkingHandlers, f)
+}
+
 // Handler returns the Messenger in HTTP client form.
 func (m *Messenger) Handler() http.Handler {
 	return m.mux
@@ -370,6 +380,14 @@ func (m *Messenger) dispatch(r Receive) {
 					message.Time = time.Unix(info.Timestamp/int64(time.Microsecond), 0)
 					f(message, resp)
 				}
+			case AccountLinkingAction:
+				for _, f := range m.accountLinkingHandlers {
+					message := *info.AccountLinking
+					message.Sender = info.Sender
+					message.Recipient = info.Recipient
+					message.Time = time.Unix(info.Timestamp/int64(time.Microsecond), 0)
+					f(message, resp)
+				}
 			}
 		}
 	}
@@ -431,6 +449,8 @@ func (m *Messenger) classify(info MessageInfo, e Entry) Action {
 		return OptInAction
 	} else if info.ReferralMessage != nil {
 		return ReferralAction
+	} else if info.AccountLinking != nil {
+		return AccountLinkingAction
 	}
 	return UnknownAction
 }

receiving.go

@@ -43,6 +43,8 @@ type MessageInfo struct {
 	OptIn *OptIn `json:"optin"`
 
 	ReferralMessage *ReferralMessage `json:"referral"`
+
+	AccountLinking *AccountLinking `json:"account_linking"`
 }
 
 type OptIn struct {