feat: Handle error when requesting a hodl invoice

If we can't receive a hodl invoice the app gracefully handles that scenario and shows an according message instead of the invoice.

mobile/lib/features/trade/application/order_service.dart

@@ -7,9 +7,9 @@ import 'package:get_10101/ffi.dart' as rust;
 
 class ExternalFunding {
   final String bitcoinAddress;
-  final String paymentRequest;
+  final String? paymentRequest;
 
-  const ExternalFunding({required this.bitcoinAddress, required this.paymentRequest});
+  const ExternalFunding({required this.bitcoinAddress, this.paymentRequest});
 
   static ExternalFunding fromApi(rust.ExternalFunding funding) {
     return ExternalFunding(

mobile/lib/features/trade/channel_creation_flow/channel_funding_screen.dart

@@ -67,8 +67,12 @@ class _ChannelFunding extends State<ChannelFunding> {
 
     final qrCode = switch (selectedBox) {
       FundingType.lightning => CustomQrCode(
-          data: widget.funding.paymentRequest,
-          embeddedImage: const AssetImage("assets/10101_logo_icon_white_background.png"),
+          data: widget.funding.paymentRequest ?? "https://x.com/get10101",
+          embeddedImage: widget.funding.paymentRequest != null
+              ? const AssetImage("assets/10101_logo_icon_white_background.png")
+              : const AssetImage("assets/coming_soon.png"),
+          embeddedImageSizeHeight: widget.funding.paymentRequest != null ? 50 : 350,
+          embeddedImageSizeWidth: widget.funding.paymentRequest != null ? 50 : 350,
           dimension: 300,
         ),
       FundingType.onchain => CustomQrCode(
@@ -87,9 +91,10 @@ class _ChannelFunding extends State<ChannelFunding> {
     };
 
     final qrCodeSubTitle = switch (selectedBox) {
-      FundingType.lightning => widget.funding.paymentRequest,
+      FundingType.lightning =>
+        widget.funding.paymentRequest ?? "Currently not available. Try again later.",
       FundingType.onchain => widget.funding.bitcoinAddress,
-      FundingType.unified || FundingType.external => "Follow us on social media for updates",
+      FundingType.unified || FundingType.external => "Follow us on social media for updates.",
     };
 
     return Scaffold(

mobile/native/src/hodl_invoice.rs

@@ -7,6 +7,7 @@ use bitcoin::Amount;
 use reqwest::Url;
 use xxi_node::commons;
 
+#[derive(Clone)]
 pub struct HodlInvoice {
     pub payment_request: String,
     pub pre_image: String,

mobile/native/src/unfunded_channel_opening_order.rs

@@ -12,7 +12,8 @@ use xxi_node::commons::ChannelOpeningParams;
 
 pub struct ExternalFunding {
     pub bitcoin_address: String,
-    pub payment_request: String,
+    /// The payment request of the hodl invoice. Could be none if the lnd node is down.
+    pub payment_request: Option<String>,
 }
 
 /// handles orders which would open a channel where the user does not have funds in his wallets
@@ -39,15 +40,20 @@ pub async fn submit_unfunded_channel_opening_order(
         + crate::dlc::estimated_funding_tx_fee()?;
 
     let funding_amount = Amount::from_sat(estimated_margin + trader_reserve) + fees;
-    let hodl_invoice = hodl_invoice::get_hodl_invoice_from_coordinator(funding_amount).await?;
-    let pre_image = hodl_invoice.pre_image;
+    let hodl_invoice = hodl_invoice::get_hodl_invoice_from_coordinator(funding_amount)
+        .await
+        .inspect_err(|e| tracing::error!("Failed to get hodl invoice. Error: {e:#}"))
+        .ok();
+
+    let payment_request = hodl_invoice.clone().map(|invoice| invoice.payment_request);
 
     // abort previous watcher before starting new task.
     abort_watcher().await?;
 
     let runtime = crate::state::get_or_create_tokio_runtime()?;
     let watch_handle = runtime.spawn({
         let bitcoin_address = bitcoin_address.clone();
+        let pre_image = hodl_invoice.map(|invoice| invoice.pre_image);
         async move {
             event::publish(&EventInternal::FundingChannelNotification(
                 FundingChannelTask::Pending,
@@ -63,7 +69,7 @@ pub async fn submit_unfunded_channel_opening_order(
                 _ = watcher::watch_lightning_payment() => {
                     // received lightning payment.
                     tracing::info!(%funding_amount, "Found lighting payment.");
-                    Some(pre_image)
+                    pre_image
                 }
             };
 
@@ -109,7 +115,7 @@ pub async fn submit_unfunded_channel_opening_order(
 
     Ok(ExternalFunding {
         bitcoin_address: bitcoin_address.to_string(),
-        payment_request: hodl_invoice.payment_request,
+        payment_request,
     })
 }