Avoid spammy payment DMs

backend/migrations/0001_init.sql

@@ -55,6 +55,7 @@ CREATE TABLE IF NOT EXISTS invoice (
   created_at INTEGER NOT NULL,
   paid_at INTEGER,
   voided_at INTEGER,
+  notified_at INTEGER,
   FOREIGN KEY (tenant_pubkey) REFERENCES tenant(pubkey)
 );
 

backend/src/billing.rs

@@ -18,6 +18,7 @@ const GRACE_PERIOD_SECS: i64 = 7 * 24 * 60 * 60;
 /// issued invoice is surfaced to the tenant in-app first (e.g. right after they
 /// create a relay), so we don't also nag by DM on the first dunning cycles.
 const FRESH_INVOICE_DM_GRACE_SECS: i64 = 24 * 60 * 60;
+const MANUAL_PAYMENT_DM_INTERVAL_SECS: i64 = 12 * 24 * 60 * 60;
 const MANUAL_PAYMENT_DM: &str = "Payment is due for your relay subscription. Open the link below to review the invoice and pay by Lightning or card:";
 const CHURN_DM: &str = "Your relay subscription is past due, so your relays have been paused. You can restore service any time by adding a payment method or paying an invoice from your dashboard:";
 
@@ -424,12 +425,19 @@ impl Billing {
         invoice: &Invoice,
         error: Option<String>,
     ) -> Result<()> {
-        // If the invoice was just generated, give the user a chance to check the dashboard before nagging them.
         let now = chrono::Utc::now().timestamp();
+
+        // If the invoice was just generated, give the user a chance to check the dashboard before nagging them.
         if now - invoice.created_at < FRESH_INVOICE_DM_GRACE_SECS {
             return Ok(());
         }
 
+        // The dunning poll runs hourly; avoid excessive reminder DMs.
+        if invoice.notified_at.is_some_and(|t| now - t < MANUAL_PAYMENT_DM_INTERVAL_SECS) {
+            return Ok(());
+        }
+
+        // Build the message
         let invoice_id = &invoice.id;
         let url_base = &env::get().app_url;
         let payment_url = format!("{url_base}/account?invoice={invoice_id}");
@@ -443,7 +451,11 @@ impl Billing {
             _ => base,
         };
 
-        self.robot.send_dm(&tenant.pubkey, &dm_message).await
+        // Send via NIP 17
+        self.robot.send_dm(&tenant.pubkey, &dm_message).await?;
+
+        // Record the send to avoid spammy notifications.
+        command::mark_invoice_notified(invoice_id).await
     }
 
     // --- Bolt11 utils ---

backend/src/command.rs

@@ -422,6 +422,19 @@ pub async fn settle_invoice_via_stripe(
     .await
 }
 
+/// Stamp an invoice with the time its manual-payment reminder DM was sent, so
+/// dunning sends that DM once instead of on every hourly poll.
+pub async fn mark_invoice_notified(invoice_id: &str) -> Result<()> {
+    let notified_at = chrono::Utc::now().timestamp();
+
+    sqlx::query("UPDATE invoice SET notified_at = ? WHERE id = ?")
+        .bind(notified_at)
+        .bind(invoice_id)
+        .execute(pool())
+        .await?;
+    Ok(())
+}
+
 // --- Bolt11 records ---
 
 pub async fn insert_bolt11(

backend/src/models.rs

@@ -133,6 +133,9 @@ pub struct Invoice {
     pub created_at: i64,
     pub paid_at: Option<i64>,
     pub voided_at: Option<i64>,
+    /// When the manual-payment reminder DM was sent for this invoice, or `None` if
+    /// it hasn't been sent in order to avoid duplicate reminders for the same invoice.
+    pub notified_at: Option<i64>,
     /// How the invoice was paid — `nwc`, `stripe`, or `oob` (out-of-band
     /// Lightning) — set when it is marked paid; `None` while open or void.
     pub method: Option<String>,