checkout: show the GoblinPay mark on the QR and the pay page

The hosted checkout page gains the GoblinPay wordmark header, and the QR center logo defaults to a new high-contrast GoblinPay mark (dark P on brand gold) instead of the generic goblin mark. Still overridable via GP_QR_LOGO (url/path/off); the legacy /static/goblin-mark.svg route is kept for operators who pinned it.
checkout: encode amount (and memo) in the invoice QR pay-URI
2026-07-02 17:00:36 -04:00 · 2026-07-02 15:26:14 -04:00 · 2026-07-02 13:20:48 -04:00
8 changed files with 241 additions and 18 deletions
@@ -6,36 +6,33 @@ travels as a gift-wrapped slatepack over Nostr (optionally over the Nym
 mixnet). GoblinPay auto-receives, returns the S2 reply so the payer can
 finalize, confirms the transaction on chain, and signals paid.

-**Status: milestone 6 (invoices, hosted checkout, per-user endpubs,
-notifications).** On top of the milestone 2-4 wallet + transport + confirmation
-path, GoblinPay now carries the full merchant surface:
+Beyond the core wallet + transport + on-chain confirmation path, GoblinPay
+carries the full merchant surface:

- **Invoices + matching (M5):** create an invoice against an order, matched by
+- **Invoices + matching:** create an invoice against an order, matched by
  any of three modes (per-invoice override or the `GP_MATCH_MODE` default):
  the payer's memo, a per-invoice derived Nostr identity (a stateless child of
  the server nsec, recommended for stores), or an exact amount. The matcher
  runs inside the ingest pipeline, so a gift-wrapped payment resolves to its
  invoice automatically.
- **Hosted checkout (M5):** a zero-JS `/pay/<token>` page (server-rendered
+- **Hosted checkout:** a zero-JS `/pay/<token>` page (server-rendered
  Askama + one CSS file + a server-generated QR SVG at ECC level H with an
-  optional Goblin-mark center logo), live status via `<meta http-equiv=refresh>`,
+  optional GoblinPay-mark center logo), live status via `<meta http-equiv=refresh>`,
  and a manual slatepack fallback (paste S1 -> offline `receive_tx` -> copy the
  S2 back) on every page. The same renderer serves embedded and hosted use.
- **Per-user endpubs (M5b):** an admin assigns one receiving identity per user
+- **Per-user endpubs:** an admin assigns one receiving identity per user
  (a derived child keyed by `(user_id, epoch)`; only public keys and the
  rotation clock are stored, never private keys), with optional rolling rotation
  and an overlap window so a just-rotated endpub still lands. All funds still
  land in the one Grin wallet.
- **Notifications (M6, all optional):** an HMAC-signed, idempotent, retried
+- **Notifications (all optional):** an HMAC-signed, idempotent, retried
  HTTP webhook (the WooCommerce contract), an authenticated admin dashboard +
  JSON API, and NIP-17 DMs to the merchant / payer.

 All relay traffic rides an in-process Nym mixnet tunnel (smolmix, auto-selected
 exit, mix-dns; `GP_NYM=off` is a debugging escape hatch only). Encryption
 negotiates NIP-44 v3 (the NIP-17 extension, via the companion `nip44` crate) per
-recipient, with v2 as the mandatory baseline. Store connectors and the
-conversion oracle arrive in later milestones; comprehensive documentation lands
-at milestone 11.
+recipient, with v2 as the mandatory baseline.

 ## Workspace

@@ -78,7 +75,7 @@ Everything is environment variables, defaults are safe for local use.
 | `GP_ADMIN_TOKEN` | unset | Bearer token for the admin dashboard + endpub/webhook API |
 | `GP_WEBHOOK_URL` | unset | Webhook endpoint for payment events (requires `GP_WEBHOOK_SECRET`) |
 | `GP_WEBHOOK_SECRET` | unset | HMAC-SHA256 secret for signing webhooks |
-| `GP_QR_LOGO` | Goblin mark | Checkout QR center logo: unset = Goblin mark, `off`/`none` = plain, else a URL/path |
+| `GP_QR_LOGO` | GoblinPay mark | Checkout QR center logo: unset = GoblinPay mark, `off`/`none` = plain, else a URL/path |
 | `GP_MERCHANT_NPUB` | unset | Merchant npub for the NIP-17 confirmed-payment DM |
 | `GP_NOTIFY_MERCHANT_DM` | `off` | Send a NIP-17 DM to the merchant on a received payment |
 | `GP_NOTIFY_PAYER_RECEIPT` | `off` | Send a NIP-17 receipt DM to the payer |
@@ -133,7 +130,7 @@ variant works for `GP_API_TOKEN`, `GP_ADMIN_TOKEN`, and `GP_WEBHOOK_SECRET` too.
 | GET | `/pay/{token}/status` | token | Invoice status JSON (for polling) |
 | POST | `/pay/{token}/slatepack` | token | Manual fallback: paste S1, returns the S2 page |
 | GET | `/payment/{id}` | token | Payment status JSON |
-| GET | `/payment/{id}/receipt` | token | Server-signed verifiable receipt (M4) |
+| GET | `/payment/{id}/receipt` | token | Server-signed verifiable receipt |
 | GET | `/admin` | admin | Dashboard (payments, balances, config) |
 | GET | `/admin/payments` | admin | Recent payments JSON |
 | GET/POST | `/admin/users` | admin | List users / create a user + endpub |
@@ -171,7 +171,7 @@ pub struct Config {
    #[serde(skip)]
    pub webhook_secret: Option<Secret>,
    /// Center-logo source for checkout QR codes (`GP_QR_LOGO`): unset = the
-    /// bundled Goblin mark, `off`/`none` = no logo, else a URL or static path.
+    /// bundled GoblinPay mark, `off`/`none` = no logo, else a URL or static path.
    pub qr_logo: Option<String>,
    /// Merchant npub for confirmed-payment DMs (`GP_MERCHANT_NPUB`).
    pub merchant_npub: Option<String>,
@@ -213,7 +213,7 @@ pub const DEFAULT_RATE_CACHE_TTL: i64 = 60;
 pub const DEFAULT_QUOTE_TTL: i64 = 900;

 /// Default center-logo path served by gp-server when `GP_QR_LOGO` is unset.
-pub const DEFAULT_QR_LOGO: &str = "/static/goblin-mark.svg";
+pub const DEFAULT_QR_LOGO: &str = "/static/goblinpay-mark.svg";

 impl Default for Config {
    fn default() -> Self {
@@ -48,7 +48,16 @@ pub fn build_info(inv: &Invoice, cfg: &Config) -> CheckoutInfo {
        Ok(pk) => (gp_nostr::npub_of(pk), gp_nostr::nprofile(pk, &relays)),
        Err(_) => (String::new(), String::new()),
    };
-    let qr_svg = qr::svg(&nprofile, cfg.qr_logo_href()).unwrap_or_default();
+    // The QR carries a pay-URI so a scanning wallet can auto-fill the amount
+    // (and memo). The human-readable nprofile/npub strings on the page are
+    // unchanged — only the QR payload gains the query. An invalid pubkey yields
+    // an empty nprofile; keep that empty (no useless `nostr:` QR).
+    let qr_payload = if nprofile.is_empty() {
+        nprofile.clone()
+    } else {
+        pay_uri(&nprofile, inv)
+    };
+    let qr_svg = qr::svg(&qr_payload, cfg.qr_logo_href()).unwrap_or_default();
    let amount_display = amount_display(inv);
    let token = inv.token.clone().unwrap_or_default();
    CheckoutInfo {
@@ -86,6 +95,53 @@ fn amount_display(inv: &Invoice) -> String {
    }
 }

+/// Build the QR pay-URI for an invoice: `nostr:<nprofile>`, plus `?amount=`
+/// when the invoice has an exact expected amount, plus `&memo=` when it carries
+/// a human memo. A scanning Goblin wallet auto-fills the amount (and note) from
+/// this; open-amount invoices stay a bare `nostr:<nprofile>`.
+///
+/// The URI never carries the invoice token or any key — only the already-public
+/// recipient nprofile, relay hints, the amount, and the human memo shown on the
+/// page. `expected_amount` is a locked nanogrin quote (i64 in the DB, always
+/// non-negative here); only strictly positive amounts are emitted.
+fn pay_uri(nprofile: &str, inv: &Invoice) -> String {
+    let mut uri = format!("nostr:{nprofile}");
+    let mut sep = '?';
+    if let Some(nano) = inv.expected_amount {
+        if nano > 0 {
+            uri.push(sep);
+            uri.push_str("amount=");
+            uri.push_str(&nanogrin_to_grin(nano as u64));
+            sep = '&';
+        }
+    }
+    if let Some(memo) = inv.memo.as_deref() {
+        let memo = memo.trim();
+        if !memo.is_empty() {
+            uri.push(sep);
+            uri.push_str("memo=");
+            uri.push_str(&percent_encode(memo));
+        }
+    }
+    uri
+}
+
+/// Minimal RFC-3986 percent-encoding for a query value: keep the unreserved set
+/// (`A-Z a-z 0-9 - . _ ~`), percent-escape every other byte. Small and
+/// dependency-free (gp-core has no percent-encoding crate).
+fn percent_encode(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    for &b in s.as_bytes() {
+        match b {
+            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'.' | b'_' | b'~' => {
+                out.push(b as char)
+            }
+            _ => out.push_str(&format!("%{b:02X}")),
+        }
+    }
+    out
+}
+
 /// The checkout page template.
 #[derive(Template)]
 #[template(path = "pay.html")]
@@ -243,3 +299,93 @@ fn render<T: Template>(page: T) -> HttpResponse {
        }
    }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// A minimal invoice fixture: only the fields the QR pay-URI reads matter.
+    fn invoice(expected_amount: Option<i64>, memo: Option<&str>) -> Invoice {
+        Invoice {
+            id: "inv_1".into(),
+            order_ref: None,
+            expected_amount,
+            expiry: None,
+            status: "open".into(),
+            created_at: "2026-01-01T00:00:00Z".into(),
+            token: Some("secret-token-should-never-leak".into()),
+            memo: memo.map(str::to_string),
+            recipient_pubkey: Some("aa".repeat(32)),
+            fiat_amount: None,
+            fiat_currency: None,
+            match_mode: None,
+            paid_payment_id: None,
+            paid_at: None,
+            quote_rate: None,
+            quote_source: None,
+        }
+    }
+
+    #[test]
+    fn amount_invoice_encodes_amount() {
+        // 1.5 GRIN → nostr:<nprofile>?amount=1.5
+        let inv = invoice(Some(1_500_000_000), None);
+        assert_eq!(
+            pay_uri("nprofile1abc", &inv),
+            "nostr:nprofile1abc?amount=1.5"
+        );
+    }
+
+    #[test]
+    fn open_amount_invoice_stays_bare() {
+        // Open amount (no expected_amount, no memo) → bare nostr:<nprofile>.
+        let inv = invoice(None, None);
+        assert_eq!(pay_uri("nprofile1abc", &inv), "nostr:nprofile1abc");
+    }
+
+    #[test]
+    fn amount_and_memo_encoded() {
+        let inv = invoice(Some(1_000_000_000), Some("Coffee & cake"));
+        assert_eq!(
+            pay_uri("nprofile1abc", &inv),
+            "nostr:nprofile1abc?amount=1&memo=Coffee%20%26%20cake"
+        );
+    }
+
+    #[test]
+    fn memo_only_uses_question_mark() {
+        // No amount but a memo → the memo is the first (and only) query param.
+        let inv = invoice(None, Some("hi"));
+        assert_eq!(pay_uri("nprofile1abc", &inv), "nostr:nprofile1abc?memo=hi");
+    }
+
+    #[test]
+    fn zero_and_blank_are_treated_as_open() {
+        assert_eq!(
+            pay_uri("nprofile1abc", &invoice(Some(0), None)),
+            "nostr:nprofile1abc"
+        );
+        // A whitespace-only memo is dropped.
+        assert_eq!(
+            pay_uri("nprofile1abc", &invoice(None, Some("   "))),
+            "nostr:nprofile1abc"
+        );
+    }
+
+    #[test]
+    fn uri_never_leaks_token_or_key() {
+        // The token and recipient private material must never appear in the QR.
+        let inv = invoice(Some(2_000_000_000), Some("order 42"));
+        let uri = pay_uri("nprofile1abc", &inv);
+        assert!(!uri.contains("secret-token-should-never-leak"));
+        assert!(!uri.contains("token"));
+    }
+
+    #[test]
+    fn percent_encode_covers_reserved_and_unicode() {
+        assert_eq!(percent_encode("a-b_c.d~e"), "a-b_c.d~e");
+        assert_eq!(percent_encode("a b&c=d"), "a%20b%26c%3Dd");
+        // Multi-byte UTF-8 is percent-encoded byte-by-byte.
+        assert_eq!(percent_encode("é"), "%C3%A9");
+    }
+}
@@ -44,19 +44,40 @@ async fn style() -> impl Responder {
        .body(include_str!("../../../static/style.css"))
 }

-/// The bundled Goblin mark, the default QR center logo.
+/// The bundled Goblin mark (legacy default QR center logo; still served so an
+/// operator can keep `GP_QR_LOGO=/static/goblin-mark.svg`).
 async fn goblin_mark() -> impl Responder {
    HttpResponse::Ok()
        .content_type("image/svg+xml")
        .body(include_str!("../../../static/goblin-mark.svg"))
 }

+/// The GoblinPay mark, the default QR center logo (dark "P" on the brand gold,
+/// sized for contrast on the QR's white backing).
+async fn goblinpay_mark() -> impl Responder {
+    HttpResponse::Ok()
+        .content_type("image/svg+xml")
+        .body(include_str!("../../../static/goblinpay-mark.svg"))
+}
+
+/// The GoblinPay wordmark (white), shown as the checkout page header logo.
+async fn goblinpay_wordmark() -> impl Responder {
+    HttpResponse::Ok()
+        .content_type("image/svg+xml")
+        .body(include_str!("../../../static/goblinpay-wordmark.svg"))
+}
+
 /// Route table, shared by `main` and the tests.
 fn routes(cfg: &mut web::ServiceConfig) {
    cfg.route("/", web::get().to(index))
        .route("/health", web::get().to(health))
        .route("/static/style.css", web::get().to(style))
-        .route("/static/goblin-mark.svg", web::get().to(goblin_mark));
+        .route("/static/goblin-mark.svg", web::get().to(goblin_mark))
+        .route("/static/goblinpay-mark.svg", web::get().to(goblinpay_mark))
+        .route(
+            "/static/goblinpay-wordmark.svg",
+            web::get().to(goblinpay_wordmark),
+        );
    // Payment status + signed-receipt reads (public-by-token, M4).
    payments::configure(cfg);
    // Hosted checkout + manual slatepack (public-by-token, M5).
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" role="img" aria-label="GoblinPay">
+  <rect width="64" height="64" rx="14" fill="#e9c542"/>
+  <path fill="#201d09" fill-rule="evenodd" d="M22 14H35a12 12 0 0 1 0 24H30V50H22ZM30 21H34a6 6 0 0 1 0 12H30Z"/>
+</svg>
@@ -0,0 +1,51 @@
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
+ "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
+<svg version="1.0" xmlns="http://www.w3.org/2000/svg"
+ width="600.000000pt" height="232.000000pt" viewBox="0 0 600.000000 232.000000"
+ preserveAspectRatio="xMidYMid meet">
+<g transform="translate(0.000000,232.000000) scale(0.050000,-0.050000)"
+fill="#ffffff" stroke="none">
+<path d="M52 4522 c-131 -444 37 -874 416 -1064 l122 -61 -95 11 c-111 13
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+</g>
+</svg>
@@ -31,6 +31,9 @@ main {

 main.admin { max-width: 60rem; }

+.brand { display: block; }
+.brandmark { height: 30px; width: auto; display: block; margin: 0 0 1.25rem; }
+
 h1 { font-size: 1.5rem; margin: 0 0 0.5rem; }
 h2 { font-size: 1.05rem; margin: 1.75rem 0 0.5rem; color: var(--dim); text-transform: uppercase; letter-spacing: 0.04em; }

@@ -9,6 +9,7 @@
 </head>
 <body>
 <main class="checkout">
+  <a class="brand" href="/"><img class="brandmark" src="/static/goblinpay-wordmark.svg" alt="GoblinPay"></a>
  <h1>Pay with Goblin</h1>
  <p class="amount">{{ info.amount_display }}</p>