added alternative to EventSource for incompatible browsers

frontend/lightningTip.html

@@ -3,9 +3,9 @@
 
     <link rel="stylesheet" href="lightningTip.css">
 
-    <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>
+    <script async defer src="https://cdn.rawgit.com/kazuhikoarase/qrcode-generator/886a247e/js/qrcode.js"></script>
+    <script async defer src="lightningTip.js"></script>
 </head>
 
 <div id="lightningTip">

frontend/lightningTip.js

@@ -1,7 +1,4 @@
-function resizeInput(element) {
-    element.style.height = "auto";
-    element.style.height = (element.scrollHeight) + "px";
-}
+var requestUrl = window.location.protocol + "//" + window.location.hostname + ":8081/";
 
 // To prohibit multiple requests at the same time
 var running = false;
@@ -13,7 +10,6 @@ var defaultGetInvoice;
 
 // 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) {
@@ -41,7 +37,6 @@ function getInvoice() {
 
                                 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);
@@ -87,7 +82,7 @@ function getInvoice() {
 
                 };
 
-                request.open("POST", "http://localhost:8081/getinvoice", true);
+                request.open("POST", requestUrl + "getinvoice", true);
                 request.send(data);
 
                 var button = document.getElementById("lightningTipGetInvoice");
@@ -114,16 +109,52 @@ function getInvoice() {
 }
 
 function listenInvoiceSettled(hash) {
-    var eventSrc = new EventSource("http://localhost:8081/eventsource");
+    if (EventSource === undefined) {
+        var eventSrc = new EventSource(requestUrl + "eventsource");
 
-    eventSrc.onmessage = function (event) {
-        if (event.data === hash) {
-            var wrapper = document.getElementById("lightningTip");
+        eventSrc.onmessage = function (event) {
+            if (event.data === hash) {
+                eventSrc.close();
 
-            wrapper.innerHTML = "<p id=\"lightningTipLogo\">⚡</p>";
-            wrapper.innerHTML += "<a id='lightningTipThankYou'>Thank you for your tip!</a>";
-        }
-    };
+                showThankYouScreen();
+            }
+
+        };
+
+    } else {
+        console.warn("Your browser does not support EventSource. Sending a request to the server every two second to check if the invoice is settled");
+
+        var interval = setInterval(function () {
+            var request = new XMLHttpRequest();
+
+            request.onreadystatechange = function () {
+                if (request.readyState === 4 && request.status === 200) {
+                    var json = JSON.parse(request.responseText);
+
+                    if (json.Settled) {
+                        clearInterval(interval);
+
+                        showThankYouScreen();
+                    }
+
+                }
+
+            };
+
+            request.open("POST", requestUrl + "invoicesettled", true);
+            request.send(JSON.stringify({"InvoiceHash": hash}))
+
+        }, 2000);
+
+    }
+
+}
+
+function showThankYouScreen() {
+    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) {
@@ -140,6 +171,7 @@ function starTimer(duration, element) {
         }
 
     }, 1000);
+
 }
 
 function showTimer(duration, element) {
@@ -156,6 +188,7 @@ function showTimer(duration, element) {
     } else {
         element.innerHTML = minutes + ":" + seconds;
     }
+
 }
 
 function addLeadingZeros(value) {
@@ -211,6 +244,7 @@ function createQRCode(typeNumber) {
 
         createQRCode(typeNumber + 1);
     }
+
 }
 
 function copyToClipboard(element) {
@@ -238,4 +272,9 @@ function showErrorMessage(message) {
         button.innerHTML = defaultGetInvoice;
     }
 
-}
+}
+
+function resizeInput(element) {
+    element.style.height = "auto";
+    element.style.height = (element.scrollHeight) + "px";
+}

lightningtip.go

@@ -15,6 +15,8 @@ import (
 
 const eventChannel = "invoiceSettled"
 
+const couldNotParseError = "Could not parse values from request"
+
 var eventSrv *eventsource.Server
 
 var pendingInvoices []PendingInvoice
@@ -30,20 +32,29 @@ func (pending PendingInvoice) Id() string    { return "" }
 func (pending PendingInvoice) Event() string { return "" }
 func (pending PendingInvoice) Data() string  { return pending.Hash }
 
+type invoiceRequest struct {
+	Amount  int64
+	Message string
+}
+
 type invoiceResponse struct {
 	Invoice string
 	Expiry  int64
 }
 
-type invoiceRequest struct {
-	Amount  int64
-	Message string
+type invoiceSettledRequest struct {
+	InvoiceHash string
+}
+
+type invoiceSettledResponse struct {
+	Settled bool
 }
 
 type errorResponse struct {
 	Error string
 }
 
+// TODO: write how to build and install in README
 // TODO: add option to show URI of Lightning node
 func main() {
 	initLog()
@@ -61,6 +72,9 @@ func main() {
 		http.HandleFunc("/getinvoice", getInvoiceHandler)
 		http.HandleFunc("/eventsource", eventSrv.Handler(eventChannel))
 
+		// Alternative for browsers which don't support EventSource (Internet Explorer and Edge)
+		http.HandleFunc("/invoicesettled", invoiceSettledHandler)
+
 		log.Info("Subscribing to invoices")
 
 		go func() {
@@ -93,7 +107,7 @@ func main() {
 
 }
 
-// Callbacks when an invoice gets settled
+// Callback for backend
 func publishInvoiceSettled(invoice string, eventSrv *eventsource.Server) {
 	for index, pending := range pendingInvoices {
 		if pending.Invoice == invoice {
@@ -110,8 +124,48 @@ func publishInvoiceSettled(invoice string, eventSrv *eventsource.Server) {
 
 }
 
+func invoiceSettledHandler(writer http.ResponseWriter, request *http.Request) {
+	errorMessage := couldNotParseError
+
+	if request.Method == http.MethodPost {
+		var body invoiceSettledRequest
+
+		data, _ := ioutil.ReadAll(request.Body)
+
+		err := json.Unmarshal(data, &body)
+
+		if err == nil {
+			if body.InvoiceHash != "" {
+				settled := true
+
+				for _, pending := range pendingInvoices {
+					if pending.Hash == body.InvoiceHash {
+						settled = false
+
+						break
+					}
+
+				}
+
+				writer.Write(marshalJson(invoiceSettledResponse{
+					Settled: settled,
+				}))
+
+				return
+
+			}
+
+		}
+
+	}
+
+	log.Error(errorMessage)
+
+	writeError(writer, errorMessage)
+}
+
 func getInvoiceHandler(writer http.ResponseWriter, request *http.Request) {
-	errorMessage := "Could not parse values from request"
+	errorMessage := couldNotParseError
 
 	if request.Method == http.MethodPost {
 		var body invoiceRequest