Initial commit: Lightning Lottery - Bitcoin Lightning Network powered lottery

Features:
- Lightning Network payments via LNbits integration
- Provably fair draws using CSPRNG
- Random ticket number generation
- Automatic payouts with retry/redraw logic
- Nostr authentication (NIP-07)
- Multiple draw cycles (hourly, daily, weekly, monthly)
- PostgreSQL and SQLite database support
- Real-time countdown and payment animations
- Swagger API documentation
- Docker support

Stack:
- Backend: Node.js, TypeScript, Express
- Frontend: Next.js, React, TailwindCSS, Redux
- Payments: LNbits

back_end/src/utils/validation.ts

@@ -0,0 +1,70 @@
+/**
+ * Validates a Lightning Address format
+ */
+export function validateLightningAddress(address: string): boolean {
+  if (!address || typeof address !== 'string') {
+    return false;
+  }
+
+  // Must contain @ symbol
+  if (!address.includes('@')) {
+    return false;
+  }
+
+  // Basic email-like format check
+  const parts = address.split('@');
+  if (parts.length !== 2) {
+    return false;
+  }
+
+  const [username, domain] = parts;
+
+  // Username and domain must not be empty
+  if (!username || !domain) {
+    return false;
+  }
+
+  // Length check
+  if (address.length > 255) {
+    return false;
+  }
+
+  return true;
+}
+
+/**
+ * Validates Nostr public key (hex or npub format)
+ */
+export function validateNostrPubkey(pubkey: string): boolean {
+  if (!pubkey || typeof pubkey !== 'string') {
+    return false;
+  }
+
+  // Hex format: 64 characters
+  if (/^[0-9a-f]{64}$/i.test(pubkey)) {
+    return true;
+  }
+
+  // npub format (bech32)
+  if (pubkey.startsWith('npub1') && pubkey.length === 63) {
+    return true;
+  }
+
+  return false;
+}
+
+/**
+ * Validates number of tickets
+ */
+export function validateTicketCount(count: number, max: number = 100): boolean {
+  return Number.isInteger(count) && count > 0 && count <= max;
+}
+
+/**
+ * Sanitizes input string
+ */
+export function sanitizeString(input: string, maxLength: number = 255): string {
+  if (!input) return '';
+  return input.trim().substring(0, maxLength);
+}
+