Merge pull request #9 from Teamwork/webhooks

Extract and expose webhook handler logic as http.Handler

webhook.go

@@ -12,31 +12,21 @@ import (
 	"net/http"
 )
 
-// WebhookListener receives requests from a Nylas webhook.
-// See: https://docs.nylas.com/reference#webhooks
-type WebhookListener struct {
-	clientSecret string
-}
-
-// NewWebhookListener returns a new WebhookListener..
-func NewWebhookListener(clientSecret string) *WebhookListener {
-	return &WebhookListener{clientSecret}
-}
-
-// Listen for webhooks on the given address.
-// The callback will be called for each webhook and a non-nil error will respond
-// with a 500 including the error message.
+// WebhookHandler returns a new http.Handler for handling Nylas webhooks.
 //
-// Note: the callback is handled synchronously, so if you need to do slow work
-// in response to a webhook return nil and handle it in another routine.
+// The X-Nylas-Signature will be verified and any non-nil error returned from fn
+// will result in a 500 response with the error message.
+//
+// When mounting this route it should be called for both GET and POST requests
+// to handle the initial webhook setup.
 //
 // See: https://docs.nylas.com/reference#receiving-notifications
-func (l *WebhookListener) Listen(addr string, fn func(WebhookDelta) error) error {
-	mux := http.NewServeMux()
-	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+func WebhookHandler(clientSecret string, fn func(WebhookDelta) error) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			challenge := r.URL.Query().Get("challenge")
 			if r.Method == http.MethodGet && challenge != "" {
+				w.Header().Add("Content-Type", "text/plain")
 				_, _ = io.WriteString(w, challenge)
 				return
 			}
@@ -52,7 +42,7 @@ func (l *WebhookListener) Listen(addr string, fn func(WebhookDelta) error) error
 		}
 
 		signature := r.Header.Get("X-Nylas-Signature")
-		if err := checkSignature(l.clientSecret, signature, data); err != nil {
+		if err := checkSignature(clientSecret, signature, data); err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
@@ -73,6 +63,30 @@ func (l *WebhookListener) Listen(addr string, fn func(WebhookDelta) error) error
 			}
 		}
 	})
+}
+
+// WebhookListener receives requests from a Nylas webhook.
+// See: https://docs.nylas.com/reference#webhooks
+type WebhookListener struct {
+	clientSecret string
+}
+
+// NewWebhookListener returns a new WebhookListener..
+func NewWebhookListener(clientSecret string) *WebhookListener {
+	return &WebhookListener{clientSecret}
+}
+
+// Listen for webhooks on the given address.
+// The callback will be called for each webhook and a non-nil error will respond
+// with a 500 including the error message.
+//
+// Note: the callback is handled synchronously, so if you need to do slow work
+// in response to a webhook return nil and handle it in another routine.
+//
+// See: https://docs.nylas.com/reference#receiving-notifications
+func (l *WebhookListener) Listen(addr string, fn func(WebhookDelta) error) error {
+	mux := http.NewServeMux()
+	mux.Handle("/", WebhookHandler(l.clientSecret, fn))
 	return http.ListenAndServe(addr, mux)
 }