From c042141bf548ce380eb18e9b50e21b78ba4ca77a Mon Sep 17 00:00:00 2001
From: 2ro <17595647+2ro@users.noreply.github.com>
Date: Sun, 7 Jun 2026 13:29:20 -0400
Subject: [PATCH] fix: emit a consistent webhook payload from both dispatch
 paths

The two webhook dispatch paths drifted in payload shape:

- GrinService.DispatchWebhook (checkout / broadcast -> InvoiceProcessing)
  sent top-level `invoiceId` + `storeId`, `invoice.confirmations`, and
  `metadata.order_id`.
- GrinPaymentMonitorService.DispatchWebhookAsync (settled / invalid /
  expired) omitted `invoiceId`, `storeId` and `confirmations`, and used
  `metadata.medusa_cart_id` instead of `metadata.order_id`.

So a webhook consumer that handles both broadcast and settlement events
sees two different shapes, and any consumer keyed on `metadata.order_id`
silently drops every settlement/expiry (the broadcast arrives, but the
order never advances or cancels). The in-code comments claiming the two
paths are kept "bit-for-bit identical" only ever applied to the signature
encoding, not the payload.

Extract a single GrinWebhookPayload.Build() used by both paths so they
can't drift. To stay backward compatible the order reference is emitted
under BOTH `order_id` and `medusa_cart_id` (same value), and the monitor
path now also includes `invoiceId`, `storeId` and `confirmations`.

No signature-format change (WebhookSignatureTests still pass).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../Services/GrinPaymentMonitorService.cs     | 17 +-------
 .../Services/GrinService.cs                   | 19 +--------
 .../Services/GrinWebhookPayload.cs            | 40 +++++++++++++++++++
 3 files changed, 42 insertions(+), 34 deletions(-)
 create mode 100644 BTCPayServer.Plugins.Grin/Services/GrinWebhookPayload.cs

diff --git a/BTCPayServer.Plugins.Grin/Services/GrinPaymentMonitorService.cs b/BTCPayServer.Plugins.Grin/Services/GrinPaymentMonitorService.cs
index e61ec25..94ae159 100644
--- a/BTCPayServer.Plugins.Grin/Services/GrinPaymentMonitorService.cs
+++ b/BTCPayServer.Plugins.Grin/Services/GrinPaymentMonitorService.cs
@@ -261,22 +261,7 @@ private async Task DispatchWebhookAsync(GrinInvoice invoice, GrinStoreSettings s
 
         try
         {
-            var amountGrin = invoice.AmountNanogrin / 1_000_000_000m;
-            var payload = new
-            {
-                @event = eventType,
-                invoice = new
-                {
-                    id = invoice.Id,
-                    status = invoice.Status.ToString(),
-                    amount = amountGrin,
-                    metadata = new
-                    {
-                        session_id = invoice.SessionId ?? "",
-                        medusa_cart_id = invoice.OrderId ?? "",
-                    }
-                }
-            };
+            var payload = GrinWebhookPayload.Build(invoice, eventType);
 
             var json = JsonSerializer.Serialize(payload);
             var content = new StringContent(json, Encoding.UTF8, "application/json");
diff --git a/BTCPayServer.Plugins.Grin/Services/GrinService.cs b/BTCPayServer.Plugins.Grin/Services/GrinService.cs
index 3f758ab..ee0dddb 100644
--- a/BTCPayServer.Plugins.Grin/Services/GrinService.cs
+++ b/BTCPayServer.Plugins.Grin/Services/GrinService.cs
@@ -204,24 +204,7 @@ public async Task DispatchWebhook(GrinStoreSettings settings, GrinInvoice invoic
 
         try
         {
-            var payload = new
-            {
-                @event = eventType,
-                invoiceId = invoice.Id,
-                storeId = invoice.StoreId,
-                invoice = new
-                {
-                    id = invoice.Id,
-                    status = invoice.Status.ToString(),
-                    amount = invoice.AmountNanogrin / 1_000_000_000m,
-                    confirmations = invoice.Confirmations,
-                    metadata = new
-                    {
-                        session_id = invoice.SessionId ?? "",
-                        order_id = invoice.OrderId ?? "",
-                    },
-                },
-            };
+            var payload = GrinWebhookPayload.Build(invoice, eventType);
 
             var json = System.Text.Json.JsonSerializer.Serialize(payload);
             var body = System.Text.Encoding.UTF8.GetBytes(json);
diff --git a/BTCPayServer.Plugins.Grin/Services/GrinWebhookPayload.cs b/BTCPayServer.Plugins.Grin/Services/GrinWebhookPayload.cs
new file mode 100644
index 0000000..6227ad8
--- /dev/null
+++ b/BTCPayServer.Plugins.Grin/Services/GrinWebhookPayload.cs
@@ -0,0 +1,40 @@
+using BTCPayServer.Plugins.Grin.Data;
+
+namespace BTCPayServer.Plugins.Grin.Services;
+
+/// <summary>
+/// Single source of truth for the webhook JSON payload, shared by both dispatch
+/// paths — <see cref="GrinService.DispatchWebhook"/> (checkout / broadcast →
+/// InvoiceProcessing) and <see cref="GrinPaymentMonitorService"/> (settled /
+/// invalid / expired). Previously each path built its own anonymous object and
+/// they had drifted: the monitor omitted the top-level <c>invoiceId</c>/
+/// <c>storeId</c> and <c>confirmations</c>, and used <c>metadata.medusa_cart_id</c>
+/// while the checkout path used <c>metadata.order_id</c>. Consumers that handle
+/// both broadcast and settlement events therefore had to special-case two
+/// shapes (and any keyed only on <c>order_id</c> silently missed settlements).
+///
+/// To stay backward compatible, the order reference is emitted under BOTH
+/// <c>order_id</c> and <c>medusa_cart_id</c> (same value).
+/// </summary>
+public static class GrinWebhookPayload
+{
+    public static object Build(GrinInvoice invoice, string eventType) => new
+    {
+        @event = eventType,
+        invoiceId = invoice.Id,
+        storeId = invoice.StoreId,
+        invoice = new
+        {
+            id = invoice.Id,
+            status = invoice.Status.ToString(),
+            amount = invoice.AmountNanogrin / 1_000_000_000m,
+            confirmations = invoice.Confirmations,
+            metadata = new
+            {
+                session_id = invoice.SessionId ?? "",
+                order_id = invoice.OrderId ?? "",
+                medusa_cart_id = invoice.OrderId ?? "",
+            }
+        }
+    };
+}