feat:drinkkaart

packages/api/src/lib/drinkkaart-utils.ts

@@ -0,0 +1,120 @@
+// QR token utilities for Drinkkaart using Web Crypto API
+// Compatible with Cloudflare Workers (no node:crypto dependency).
+
+const QR_TOKEN_TTL_MS = 5 * 60 * 1000; // 5 minutes
+
+interface QrPayload {
+	drinkkaartId: string;
+	userId: string;
+	iat: number;
+	exp: number;
+}
+
+function toBase64Url(buffer: ArrayBuffer): string {
+	return btoa(String.fromCharCode(...new Uint8Array(buffer)))
+		.replace(/\+/g, "-")
+		.replace(/\//g, "_")
+		.replace(/=/g, "");
+}
+
+function base64UrlToBuffer(str: string): Uint8Array<ArrayBuffer> {
+	const base64 = str.replace(/-/g, "+").replace(/_/g, "/");
+	const bytes = Uint8Array.from(atob(base64), (c) => c.charCodeAt(0));
+	// Ensure the underlying buffer is a plain ArrayBuffer (required by crypto.subtle)
+	return new Uint8Array(bytes.buffer.slice(0));
+}
+
+/** Generate a cryptographically secure 32-byte hex secret for a new Drinkkaart. */
+export function generateQrSecret(): string {
+	const bytes = new Uint8Array(32);
+	crypto.getRandomValues(bytes);
+	return Array.from(bytes)
+		.map((b) => b.toString(16).padStart(2, "0"))
+		.join("");
+}
+
+/**
+ * Sign a QR token for the given drinkkaart / user.
+ * Returns the compact token string and the expiry date.
+ */
+export async function signQrToken(
+	payload: Omit<QrPayload, "iat" | "exp">,
+	qrSecret: string,
+	authSecret: string,
+): Promise<{ token: string; expiresAt: Date }> {
+	const now = Date.now();
+	const exp = now + QR_TOKEN_TTL_MS;
+	const full: QrPayload = { ...payload, iat: now, exp };
+
+	const encodedPayload = btoa(JSON.stringify(full))
+		.replace(/\+/g, "-")
+		.replace(/\//g, "_")
+		.replace(/=/g, "");
+
+	const keyData = new TextEncoder().encode(qrSecret + authSecret);
+	const key = await crypto.subtle.importKey(
+		"raw",
+		keyData,
+		{ name: "HMAC", hash: "SHA-256" },
+		false,
+		["sign"],
+	);
+
+	const sigBuffer = await crypto.subtle.sign(
+		"HMAC",
+		key,
+		new TextEncoder().encode(encodedPayload),
+	);
+	const sig = toBase64Url(sigBuffer);
+
+	return { token: `${encodedPayload}.${sig}`, expiresAt: new Date(exp) };
+}
+
+/**
+ * Verify a QR token. Throws if the signature is invalid or the token is expired.
+ * Returns the decoded payload.
+ */
+export async function verifyQrToken(
+	token: string,
+	qrSecret: string,
+	authSecret: string,
+): Promise<QrPayload> {
+	const parts = token.split(".");
+	if (parts.length !== 2) throw new Error("MALFORMED");
+
+	const [encodedPayload, providedSig] = parts as [string, string];
+
+	const keyData = new TextEncoder().encode(qrSecret + authSecret);
+	const key = await crypto.subtle.importKey(
+		"raw",
+		keyData,
+		{ name: "HMAC", hash: "SHA-256" },
+		false,
+		["verify"],
+	);
+
+	const sigBytes = base64UrlToBuffer(providedSig);
+	const valid = await crypto.subtle.verify(
+		"HMAC",
+		key,
+		sigBytes,
+		new TextEncoder().encode(encodedPayload),
+	);
+	if (!valid) throw new Error("INVALID_SIGNATURE");
+
+	const payload: QrPayload = JSON.parse(
+		atob(encodedPayload.replace(/-/g, "+").replace(/_/g, "/")),
+	);
+
+	if (Date.now() > payload.exp) throw new Error("EXPIRED");
+
+	return payload;
+}
+
+/** Format a cents integer as a Belgian euro string, e.g. 1250 → "€ 12,50". */
+export function formatCents(cents: number): string {
+	return new Intl.NumberFormat("nl-BE", {
+		style: "currency",
+		currency: "EUR",
+	}).format(cents / 100);
+}