added EventSource to show a thank you message

backends/backend.go

@@ -1,5 +1,10 @@
 package backends
 
+import "github.com/donovanhide/eventsource"
+
+// For callbacks when an invoice gets settled
+type PublishInvoiceSettled func(invoice string, eventSrv *eventsource.Server)
+
 type Backend interface {
 	Connect() error
 

backends/lnd.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"encoding/hex"
 	"errors"
-	"fmt"
+	"github.com/donovanhide/eventsource"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
@@ -90,7 +90,7 @@ func (lnd *LND) GetInvoice(message string, amount int64, expiry int64) (invoice
 	return response.PaymentRequest, err
 }
 
-func (lnd *LND) SubscribeInvoices() error {
+func (lnd *LND) SubscribeInvoices(callback PublishInvoiceSettled, eventSrv *eventsource.Server) error {
 	stream, err := lnd.client.SubscribeInvoices(lnd.ctx, &lnrpc.InvoiceSubscription{})
 
 	if err != nil {
@@ -101,7 +101,7 @@ func (lnd *LND) SubscribeInvoices() error {
 
 	go func() {
 		for {
-			in, streamErr := stream.Recv()
+			invoice, streamErr := stream.Recv()
 
 			if streamErr == io.EOF {
 				err = errors.New("lost connection to LND gRPC")
@@ -119,8 +119,12 @@ func (lnd *LND) SubscribeInvoices() error {
 				return
 			}
 
-			fmt.Println(in)
+			if invoice.Settled {
+				callback(invoice.PaymentRequest, eventSrv)
+			}
+
 		}
+
 	}()
 
 	<-wait

frontend/lightningTip.css

@@ -115,6 +115,12 @@
     float: right;
 }
 
+#lightningTipThankYou {
+    margin-bottom: 0.2em;
+
+    display: block;
+}
+
 .spinner {
     width: 12px;
     height: 12px;

frontend/lightningTip.html

@@ -5,6 +5,7 @@
 
     <script async defer src="lightningTip.js"></script>
     <script async defer src="https://cdn.rawgit.com/kazuhikoarase/qrcode-generator/886a247e/js/qrcode.js"></script>
+    <script async defer src="https://cdn.rawgit.com/emn178/js-sha256/189bb9b0/build/sha256.min.js"></script>
 </head>
 
 <div id="lightningTip">

frontend/lightningTip.js

@@ -11,7 +11,10 @@ var qrCode;
 
 var defaultGetInvoice;
 
-// TODO: listen to eventsource and show tank you when invoice settled
+// TODO: show error when invoice expires
+// TODO: maybe don't show full invoice
+// TODO: proper url handling window.location.protocol + window.location.hostname + ":8081/getinvoice"
+// TODO: show price in dollar?
 function getInvoice() {
     if (running === false) {
         running = true;
@@ -34,6 +37,16 @@ function getInvoice() {
                                 console.log("Got invoice: " + json.Invoice);
                                 console.log("Invoice expires in: " + json.Expiry);
 
+                                var hash = sha256(json.Invoice);
+
+                                console.log("Got hash of invoice: " + hash);
+
+                                // TODO: find alternative for Edge and IE
+                                console.log("Starting listening for invoice to get settled");
+
+                                listenInvoiceSettled(hash);
+
+                                // Update UI
                                 invoice = json.Invoice;
 
                                 var wrapper = document.getElementById("lightningTip");
@@ -65,6 +78,8 @@ function getInvoice() {
                             }
 
                         } catch (exception) {
+                            console.error(exception);
+
                             showErrorMessage("Failed to reach backend");
                         }
 
@@ -72,7 +87,6 @@ function getInvoice() {
 
                 };
 
-                // TODO: proper url handling window.location.protocol + window.location.hostname + ":8081/getinvoice"
                 request.open("POST", "http://localhost:8081/getinvoice", true);
                 request.send(data);
 
@@ -99,6 +113,19 @@ function getInvoice() {
 
 }
 
+function listenInvoiceSettled(hash) {
+    var eventSrc = new EventSource("http://localhost:8081/eventsource");
+
+    eventSrc.onmessage = function (event) {
+        if (event.data === hash) {
+            var wrapper = document.getElementById("lightningTip");
+
+            wrapper.innerHTML = "<p id=\"lightningTipLogo\">⚡</p>";
+            wrapper.innerHTML += "<a id='lightningTipThankYou'>Thank you for your tip!</a>";
+        }
+    };
+}
+
 function starTimer(duration, element) {
     showTimer(duration, element);
 

lightningtip.go

@@ -1,14 +1,35 @@
 package main
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"github.com/donovanhide/eventsource"
 	"io/ioutil"
 	"net/http"
 	"os"
 	"strconv"
+	"time"
 )
 
+const eventChannel = "invoiceSettled"
+
+var eventSrv *eventsource.Server
+
+var pendingInvoices []PendingInvoice
+
+type PendingInvoice struct {
+	Invoice string
+	Hash    string
+	Expiry  time.Time
+}
+
+// To use the pendingInvoice type as event for the EventSource stream
+func (pending PendingInvoice) Id() string    { return "" }
+func (pending PendingInvoice) Event() string { return "" }
+func (pending PendingInvoice) Data() string  { return pending.Hash }
+
 type invoiceResponse struct {
 	Invoice string
 	Expiry  int64
@@ -32,14 +53,18 @@ func main() {
 	err := backend.Connect()
 
 	if err == nil {
+		log.Info("Starting EventSource stream")
+
+		eventSrv = eventsource.NewServer()
+
 		http.HandleFunc("/", notFoundHandler)
 		http.HandleFunc("/getinvoice", getInvoiceHandler)
+		http.HandleFunc("/eventsource", eventSrv.Handler(eventChannel))
 
 		log.Info("Subscribing to invoices")
 
 		go func() {
-			// TODO: let clients listen if their invoice was paid (eventsource)
-			err = cfg.LND.SubscribeInvoices()
+			err = cfg.LND.SubscribeInvoices(publishInvoiceSettled, eventSrv)
 
 			if err != nil {
 				log.Error("Failed to subscribe to invoices: " + fmt.Sprint(err))
@@ -68,6 +93,23 @@ func main() {
 
 }
 
+// Callbacks when an invoice gets settled
+func publishInvoiceSettled(invoice string, eventSrv *eventsource.Server) {
+	for index, pending := range pendingInvoices {
+		if pending.Invoice == invoice {
+			log.Info("Invoice settled: " + invoice)
+
+			eventSrv.Publish([]string{eventChannel}, pending)
+
+			pendingInvoices = append(pendingInvoices[:index], pendingInvoices[index+1:]...)
+
+			break
+		}
+
+	}
+
+}
+
 func getInvoiceHandler(writer http.ResponseWriter, request *http.Request) {
 	errorMessage := "Could not parse values from request"
 
@@ -89,8 +131,22 @@ func getInvoiceHandler(writer http.ResponseWriter, request *http.Request) {
 						logMessage += " with message \"" + body.Message + "\""
 					}
 
+					sha := sha256.New()
+					sha.Write([]byte(invoice))
+
+					hash := hex.EncodeToString(sha.Sum(nil))
+
+					expiryDuration := time.Duration(cfg.TipExpiry) * time.Second
+
 					log.Info(logMessage)
 
+					// TODO: check every minute or so if expired
+					pendingInvoices = append(pendingInvoices, PendingInvoice{
+						Invoice: invoice,
+						Hash:    hash,
+						Expiry:  time.Now().Add(expiryDuration),
+					})
+
 					writer.Write(marshalJson(invoiceResponse{
 						Invoice: invoice,
 						Expiry:  cfg.TipExpiry,