From a618f901fc020025e9d2e5bbaa91b475e2f33a57 Mon Sep 17 00:00:00 2001
From: Kukks <evilkukka@gmail.com>
Date: Fri, 2 Jun 2023 11:21:21 +0200
Subject: [PATCH] Support NFC on modal

---
 .../Views/Shared/NFC/CheckoutEnd.cshtml       | 37 ++++++++++++++--
 BTCPayServer/wwwroot/modal/btcpay.js          | 44 ++++++++++++++++++-
 2 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/BTCPayServer/Views/Shared/NFC/CheckoutEnd.cshtml b/BTCPayServer/Views/Shared/NFC/CheckoutEnd.cshtml
index 2b1892157..368ec900c 100644
--- a/BTCPayServer/Views/Shared/NFC/CheckoutEnd.cshtml
+++ b/BTCPayServer/Views/Shared/NFC/CheckoutEnd.cshtml
@@ -22,7 +22,38 @@
     </template>
 </template>
 <script type="text/javascript">
-// https://developer.chrome.com/articles/nfc/
+class NDEFReaderWrapper {
+    constructor() {
+        this.onreading = null;
+        this.onreadingerror = null;
+    }
+
+    async scan( opts) {
+        
+        if (opts && opts.signal){
+            opts.signal.addEventListener("abort", () => {
+                window.parent.postMessage("abortNfc", "*");
+            });
+        }
+        window.parent.postMessage("startNfcScan", "*");
+    }
+}
+
+window.addEventListener("message", (event) => {
+    const { action, data } = event.data;
+    if (action === "nfcData") {
+        if (ndef.onreading) {
+            ndef.onreading({ message: { records: [{ data }] } });
+        }
+    } else if (action === "nfcError") {
+        if (ndef.onreadingerror) {
+            ndef.onreadingerror();
+        }
+    }
+});
+
+
+
 Vue.component("lnurl-withdraw-checkout", {
     template: "#lnurl-withdraw-template",
     props: {
@@ -69,7 +100,7 @@ Vue.component("lnurl-withdraw-checkout", {
     data () {
         return {
             url: @Safe.Json(Context.Request.GetAbsoluteUri(Url.Action("SubmitLNURLWithdrawForInvoice", "NFC"))),
-            supported: 'NDEFReader' in window && window.self === window.top,
+            supported: 'NDEFReader' in window ,
             scanning: false,
             submitting: false,
             permissionGranted: false,
@@ -135,7 +166,7 @@ Vue.component("lnurl-withdraw-checkout", {
             this.submitting = false;
             this.scanning = true;
             try {
-                const ndef = new NDEFReader()
+                const ndef = window.self === window.top?  new NDEFReader() : new NDEFReaderWrapper();
                 this.readerAbortController = new AbortController()
                 this.readerAbortController.signal.onabort = () => {
                     this.scanning = false;
diff --git a/BTCPayServer/wwwroot/modal/btcpay.js b/BTCPayServer/wwwroot/modal/btcpay.js
index c1b313375..63310d9a3 100644
--- a/BTCPayServer/wwwroot/modal/btcpay.js
+++ b/BTCPayServer/wwwroot/modal/btcpay.js
@@ -48,7 +48,7 @@
     var scriptMatch = thisScript.match(scriptSrcRegex)
     if (scriptMatch) {
         // We can't just take the domain as btcpay can run under a sub path with RootPath
-        origin = thisScript.substr(0, thisScript.length - scriptMatch[0].length);
+        origin = thisScript.slice(0, thisScript.length - scriptMatch[0].length);
     }
     // urlPrefix should be site root without trailing slash
     function setApiUrlPrefix(urlPrefix) {
@@ -62,6 +62,7 @@
     var onModalWillLeaveMethod = function () { };
     var onModalReceiveMessageMethod = function (event) { };
 
+    var nfcSupportAvailable = "NDEFReader" in window;
     function showFrame() {
         if (window.document.getElementsByName('btcpay').length === 0) {
             window.document.body.appendChild(iframe);
@@ -88,7 +89,40 @@
     function onModalReceiveMessage(customOnModalReceiveMessage) {
         onModalReceiveMessageMethod = customOnModalReceiveMessage;
     }
+    var readerAbortController = null;
 
+    function startNfcScan() {
+        const ndef = new NDEFReader();
+        readerAbortController = new AbortController()
+        readerAbortController.signal.onabort = () => {
+            this.scanning = false;
+        };
+        ndef.scan({signal:readerAbortController.signal}).then(() => {
+            console.log("> Scan started successfully.");
+            ndef.onreading = (event) => {
+                const message = event.message;
+                const record = message.records[0];
+                const textDecoder = new TextDecoder('utf-8');
+                const lnurl = textDecoder.decode(record.data);
+
+                // Send NFC data back to the iframe
+                if (iframe) {
+                    iframe.contentWindow.postMessage({ action: "nfcData", data: lnurl }, "*");
+                }
+            };
+            ndef.onerror = () => {
+                console.log("Error! Cannot read data from the NFC tag. Try another one.");
+
+                // Send error message back to the iframe
+                if (iframe) {
+                    iframe.contentWindow.postMessage({ action: "nfcError" }, "*");
+                }
+            };
+        }).catch(error => {
+            console.log(`Argh! ${error}`);
+        });
+    }
+    
     function receiveMessage(event) {
         var uri;
 
@@ -99,6 +133,14 @@
             hideFrame();
         } else if (event.data === 'loaded') {
             showFrame();
+        }
+        else if(event.data === "startNfcScan") {
+            startNfcScan();
+        }
+        else if(event.data === "abortNfc") {
+            if (readerAbortController) {
+                readerAbortController.abort()
+            }
         } else if (event.data && event.data.open) {
             uri = event.data.open;
             if (uri.indexOf('bitcoin:') === 0) {