feat: implement ndebit QR code display for cash-in flow

Replace LNURL-withdraw with CLINK ndebit for cash-in transactions:
- Add ndebit.ts with TLV-based bech32 encoding/decoding
- Generate clink:ndebit1...?amount=<sats> URIs
- Display QR code with copyable URI in CashInView
- Update state machine flow: generatingNdebit → displayingQR
- Fix shadcn-vue Input binding with :model-value prop

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lamassu-next/apps/machine/src/services/lightning.ts

@@ -19,7 +19,14 @@ import {
   type MachineIdentity,
 } from '@lamassu/nostr-client'
 import { LightningPubClient } from '@lamassu/lightning'
-import { CLINKClient, createOfferSuccess, createOfferError, CLINKErrorCode } from '@lamassu/clink'
+import {
+  CLINKClient,
+  createOfferSuccess,
+  createOfferError,
+  CLINKErrorCode,
+  encodeNdebit,
+  formatNdebitUri,
+} from '@lamassu/clink'
 import type { OfferRequest } from '@lamassu/clink'
 import type { ATMServices, ATMContext } from '@lamassu/state-machine'
 
@@ -186,6 +193,28 @@ function createATMServices(
   _onPaymentSuccess: (preimage: string) => void
 ): ATMServices {
   return {
+    /**
+     * Generate an ndebit URI for cash-in
+     *
+     * The ndebit encodes the ATM's pubkey and relay, with amount as query param.
+     * Format: clink:ndebit1<bech32>?amount=<sats>
+     */
+    generateNdebit: async (context: ATMContext): Promise<string> => {
+      console.log('[ATM Service] Generating ndebit for', context.satsAmount, 'sats')
+
+      // Create ndebit with ATM's pubkey and relay
+      const ndebit = encodeNdebit({
+        pubkey: _identity.publicKey,
+        relay: DEV_CONFIG.relayUrl,
+      })
+
+      // Format as full URI with amount
+      const uri = formatNdebitUri(ndebit, context.satsAmount)
+
+      console.log('[ATM Service] Generated ndebit URI:', uri.slice(0, 60) + '...')
+      return uri
+    },
+
     /**
      * Generate a CLINK offer (noffer) for receiving payment
      *

lamassu-next/apps/machine/src/stores/atm.ts

@@ -20,6 +20,12 @@ const mockServices: ATMServices = {
     return `noffer1mock${Date.now().toString(36)}`
   },
 
+  generateNdebit: async (context) => {
+    console.log('[Mock] Generating ndebit for', context.satsAmount, 'sats')
+    // Mock ndebit URI with amount
+    return `clink:ndebit1mock${Date.now().toString(36)}?amount=${context.satsAmount}`
+  },
+
   generateLnurlWithdraw: async (context) => {
     console.log('[Mock] Generating LNURL-withdraw for', context.satsAmount, 'sats')
     // This is a mock LNURL - in reality it would be a bech32 encoded URL

lamassu-next/apps/machine/src/views/CashInView.vue

@@ -13,16 +13,31 @@ import QRCode from '@/components/QRCode.vue'
 const router = useRouter()
 const atmStore = useAtmStore()
 
-// Input modes
-type PaymentMode = 'clink' | 'invoice'
-const paymentMode = ref<PaymentMode>('clink')
-
 // CLINK Debit: customer's npub/pubkey
 const pubkeyInput = ref('')
 
 // Invoice input for manual payment
 const invoiceInput = ref('')
 
+// Copy state for ndebit URI
+const copied = ref(false)
+
+// Copy ndebit URI to clipboard
+async function copyNdebit() {
+  const uri = atmStore.context?.ndebitUri
+  if (!uri) return
+
+  try {
+    await navigator.clipboard.writeText(uri)
+    copied.value = true
+    setTimeout(() => {
+      copied.value = false
+    }, 2000)
+  } catch (err) {
+    console.error('[CashIn] Failed to copy:', err)
+  }
+}
+
 // Navigate back to idle when transaction completes
 watch(
   () => atmStore.isIdle,
@@ -180,54 +195,71 @@ const isProcessing = computed(() => atmStore.isPayingInvoice || atmStore.isReque
         </CardContent>
       </Card>
 
-      <!-- Generating LNURL-withdraw -->
+      <!-- Generating NDebit -->
-      <Card v-else-if="nestedState === 'generatingLnurlWithdraw'" class="w-80 border-0 bg-white/5">
+      <Card v-else-if="nestedState === 'generatingNdebit'" class="w-80 border-0 bg-white/5">
         <CardContent class="flex flex-col items-center gap-4 p-8">
           <Skeleton class="h-10 w-10 rounded-full" />
-          <p class="text-muted-foreground">Preparing your withdrawal...</p>
+          <p class="text-muted-foreground">Preparing payment code...</p>
         </CardContent>
       </Card>
 
-      <!-- Display Payment Options -->
+      <!-- Display NDebit QR -->
       <Card v-else-if="nestedState === 'displayingQR'" class="w-[480px] border-0 bg-white/5">
         <CardHeader class="text-center">
-          <CardTitle>Receive Your Sats</CardTitle>
+          <CardTitle>Scan to Receive Sats</CardTitle>
           <CardDescription v-if="context">
             <Badge variant="secondary" class="text-lg">
               {{ formatSats(context.satsAmount) }} sats
             </Badge>
           </CardDescription>
         </CardHeader>
-        <CardContent class="space-y-4">
+        <CardContent class="space-y-6">
-          <!-- Payment mode tabs -->
+          <!-- NDebit QR Code (Primary) -->
-          <div class="flex gap-2 rounded-lg bg-white/5 p-1">
+          <div class="flex flex-col items-center">
-            <Button
+            <QRCode v-if="context?.ndebitUri" :value="context.ndebitUri" :size="220" />
-              :variant="paymentMode === 'clink' ? 'default' : 'ghost'"
+            <p class="mt-4 text-center text-sm text-muted-foreground">
-              size="sm"
+              Scan with Shock Wallet or compatible CLINK wallet
-              class="flex-1"
+            </p>
-              @click="paymentMode = 'clink'"
-            >
-              CLINK Debit (Nostr)
-            </Button>
-            <Button
-              :variant="paymentMode === 'invoice' ? 'default' : 'ghost'"
-              size="sm"
-              class="flex-1"
-              @click="paymentMode = 'invoice'"
-            >
-              Paste Invoice
-            </Button>
           </div>
 
-          <!-- CLINK Debit Mode -->
+          <!-- Copyable NDebit URI -->
-          <div v-if="paymentMode === 'clink'" class="space-y-4">
+          <div v-if="context?.ndebitUri" class="space-y-2">
-            <Alert class="border-blue-500/50 bg-blue-500/10">
+            <div class="flex gap-2">
-              <AlertDescription>
+              <Input :model-value="context.ndebitUri" readonly class="flex-1 font-mono text-xs" />
-                <p class="mb-2 text-sm font-medium text-blue-400">CLINK Debit (Nostr-Native)</p>
+              <Button variant="outline" size="sm" @click="copyNdebit">
-                <p class="mb-3 text-xs text-muted-foreground">
+                {{ copied ? '✓ Copied' : 'Copy' }}
-                  Enter your Shock Wallet's npub or pubkey. We'll send a debit request and your
+              </Button>
-                  wallet will automatically pay.
+            </div>
-                </p>
+            <p class="text-center text-xs text-muted-foreground">
+              Or copy and paste into your wallet
+            </p>
+          </div>
+
+          <!-- Instructions -->
+          <Alert class="border-green-500/50 bg-green-500/10">
+            <AlertDescription>
+              <p class="mb-2 text-sm font-medium text-green-400">How it works:</p>
+              <ol class="space-y-1 text-xs text-muted-foreground">
+                <li>1. Scan the QR code with your Lightning wallet</li>
+                <li>
+                  2. Your wallet creates an invoice for
+                  {{ formatSats(context?.satsAmount || 0) }} sats
+                </li>
+                <li>3. Confirm the claim in your wallet</li>
+                <li>4. Receive your sats instantly!</li>
+              </ol>
+            </AlertDescription>
+          </Alert>
+
+          <!-- Alternative: Manual Options (collapsed) -->
+          <details class="rounded-lg bg-white/5 p-3">
+            <summary class="cursor-pointer text-sm text-muted-foreground">
+              Alternative: Manual payment options
+            </summary>
+            <div class="mt-4 space-y-4">
+              <!-- CLINK Debit by pubkey -->
+              <div class="space-y-2">
+                <p class="text-xs font-medium text-blue-400">Enter your npub/pubkey:</p>
                 <div class="flex gap-2">
                   <Input
                     v-model="pubkeyInput"
@@ -236,33 +268,19 @@ const isProcessing = computed(() => atmStore.isPayingInvoice || atmStore.isReque
                     :disabled="isProcessing"
                   />
                   <Button
-                    variant="default"
+                    variant="outline"
                     size="sm"
                     :disabled="!pubkeyInput.trim() || isProcessing"
                     @click="submitDebitRequest"
                   >
-                    {{ atmStore.isRequestingDebit ? 'Requesting...' : 'Request' }}
+                    {{ atmStore.isRequestingDebit ? '...' : 'Send' }}
                   </Button>
                 </div>
-                <p v-if="atmStore.paymentError" class="mt-2 text-xs text-red-400">
+              </div>
-                  Error: {{ atmStore.paymentError }}
-                </p>
-              </AlertDescription>
-            </Alert>
-            <p class="text-center text-xs text-muted-foreground">
-              Your Shock Wallet must be connected to relay: ws://192.168.1.122:7777
-            </p>
-          </div>
 
-          <!-- Invoice Paste Mode -->
+              <!-- Invoice paste -->
-          <div v-if="paymentMode === 'invoice'" class="space-y-4">
+              <div class="space-y-2">
-            <Alert class="border-orange-500/50 bg-orange-500/10">
+                <p class="text-xs font-medium text-orange-400">Or paste your invoice:</p>
-              <AlertDescription>
-                <p class="mb-2 text-sm font-medium text-orange-400">Manual Invoice Payment</p>
-                <p class="mb-3 text-xs text-muted-foreground">
-                  Create a {{ formatSats(context?.satsAmount || 0) }} sat invoice in your wallet and
-                  paste it below. We'll pay it instantly.
-                </p>
                 <div class="flex gap-2">
                   <Input
                     v-model="invoiceInput"
@@ -271,41 +289,21 @@ const isProcessing = computed(() => atmStore.isPayingInvoice || atmStore.isReque
                     :disabled="isProcessing"
                   />
                   <Button
-                    variant="default"
+                    variant="outline"
                     size="sm"
                     :disabled="!invoiceInput.trim() || isProcessing"
                     @click="submitInvoice"
                   >
-                    {{ atmStore.isPayingInvoice ? 'Paying...' : 'Pay' }}
+                    {{ atmStore.isPayingInvoice ? '...' : 'Pay' }}
                   </Button>
                 </div>
-                <p v-if="atmStore.paymentError" class="mt-2 text-xs text-red-400">
+              </div>
-                  Error: {{ atmStore.paymentError }}
-                </p>
-              </AlertDescription>
-            </Alert>
-            <p class="text-center text-xs text-muted-foreground">
-              Note: Invoice must be on same network (regtest for dev)
-            </p>
-          </div>
 
-          <!-- Divider -->
+              <p v-if="atmStore.paymentError" class="text-xs text-red-400">
-          <div class="relative flex items-center justify-center py-2">
+                Error: {{ atmStore.paymentError }}
-            <div class="absolute inset-0 flex items-center">
+              </p>
-              <span class="w-full border-t border-white/20" />
             </div>
-            <span class="relative bg-background px-3 text-xs text-muted-foreground">
+          </details>
-              or scan QR
-            </span>
-          </div>
-
-          <!-- LNURL QR (for wallet scanning - mock in browser) -->
-          <div class="flex flex-col items-center">
-            <QRCode v-if="context?.lnurlWithdraw" :value="context.lnurlWithdraw" :size="150" />
-            <p class="mt-2 text-center text-xs text-muted-foreground">
-              LNURL-withdraw (mock in browser dev)
-            </p>
-          </div>
 
           <!-- Debug: Simulate payment button -->
           <div v-if="atmStore.debugMode" class="pt-2 text-center">

lamassu-next/packages/clink/src/index.ts

@@ -70,6 +70,9 @@ export {
   type CLINKOffer,
   type PriceType,
   NofferTLV,
+  // Ndebit types
+  type DebitPointer,
+  NdebitTLV,
   // Function types
   type GenerateInvoice,
   type PayInvoice,
@@ -82,6 +85,15 @@ export {
 // Noffer encoding/decoding
 export { encodeNoffer, decodeNoffer, isValidNoffer, npubToHex, hexToNpub } from './noffer.js'
 
+// Ndebit encoding/decoding
+export {
+  encodeNdebit,
+  decodeNdebit,
+  isValidNdebit,
+  formatNdebitUri,
+  parseNdebitAmount,
+} from './ndebit.js'
+
 // Client
 export {
   CLINKClient,

lamassu-next/packages/clink/src/ndebit.ts

@@ -0,0 +1,206 @@
+/**
+ * ndebit encoding/decoding
+ *
+ * ndebits are bech32-encoded debit pointers that contain
+ * pubkey, relay, and optional pointer information.
+ *
+ * Format: ndebit1<bech32-encoded-tlv-data>
+ *
+ * For ATM cash-in flow, the URI format includes amount:
+ * clink:ndebit1<bech32data>?amount=<sats>
+ */
+
+import { bech32 } from '@scure/base'
+import { nip19 } from 'nostr-tools'
+import type { DebitPointer } from './types.js'
+import { NdebitTLV } from './types.js'
+
+const NDEBIT_PREFIX = 'ndebit'
+const BECH32_LIMIT = 2000
+
+/**
+ * Encode a debit pointer as an ndebit string
+ */
+export function encodeNdebit(pointer: DebitPointer): string {
+  const tlvData: number[] = []
+
+  // Pubkey (TLV 0) - convert npub to hex if needed
+  const hexPubkey = npubToHex(pointer.pubkey)
+  const pubkeyBytes = hexToBytes(hexPubkey)
+  writeTLV(tlvData, NdebitTLV.Pubkey, pubkeyBytes)
+
+  // Relay (TLV 1)
+  const relayBytes = new TextEncoder().encode(pointer.relay)
+  writeTLV(tlvData, NdebitTLV.Relay, relayBytes)
+
+  // Pointer (TLV 2) - if present
+  if (pointer.pointer) {
+    const pointerBytes = new TextEncoder().encode(pointer.pointer)
+    writeTLV(tlvData, NdebitTLV.Pointer, pointerBytes)
+  }
+
+  // Convert to Uint8Array and bech32 encode
+  const bytes = new Uint8Array(tlvData)
+  const words = bech32.toWords(bytes)
+
+  return bech32.encode(NDEBIT_PREFIX, words, BECH32_LIMIT)
+}
+
+/**
+ * Decode an ndebit string to a debit pointer
+ */
+export function decodeNdebit(ndebit: string): DebitPointer {
+  // Remove clink: prefix if present
+  let cleaned = ndebit
+  if (cleaned.toLowerCase().startsWith('clink:')) {
+    cleaned = cleaned.slice(6)
+  }
+  if (cleaned.toLowerCase().startsWith('lightning:')) {
+    cleaned = cleaned.slice(10)
+  }
+
+  // Remove query parameters if present
+  const queryIndex = cleaned.indexOf('?')
+  if (queryIndex !== -1) {
+    cleaned = cleaned.slice(0, queryIndex)
+  }
+
+  // Decode bech32 - cast to expected type (contains "1" separator)
+  const { prefix, words } = bech32.decode(cleaned as `${string}1${string}`, BECH32_LIMIT)
+
+  if (prefix !== NDEBIT_PREFIX) {
+    throw new Error(`Invalid ndebit prefix: ${prefix}`)
+  }
+
+  const bytes = bech32.fromWords(words)
+  const data = new Uint8Array(bytes)
+
+  // Parse TLV entries
+  let pubkey: string | undefined
+  let relay: string | undefined
+  let pointer: string | undefined
+
+  let offset = 0
+  while (offset < data.length) {
+    const type = data[offset]
+    offset++
+
+    if (offset >= data.length) break
+
+    const length = data[offset]
+    offset++
+
+    if (offset + (length ?? 0) > data.length) {
+      throw new Error('Invalid TLV: data truncated')
+    }
+
+    const value = data.slice(offset, offset + (length ?? 0))
+    offset += length ?? 0
+
+    switch (type) {
+      case NdebitTLV.Pubkey:
+        pubkey = bytesToHex(value)
+        break
+      case NdebitTLV.Relay:
+        relay = new TextDecoder().decode(value)
+        break
+      case NdebitTLV.Pointer:
+        pointer = new TextDecoder().decode(value)
+        break
+      // Ignore unknown TLV types for forward compatibility
+    }
+  }
+
+  if (!pubkey) {
+    throw new Error('Invalid ndebit: missing pubkey')
+  }
+
+  if (!relay) {
+    throw new Error('Invalid ndebit: missing relay')
+  }
+
+  return {
+    pubkey,
+    relay,
+    pointer,
+  }
+}
+
+/**
+ * Validate an ndebit string without fully decoding
+ */
+export function isValidNdebit(ndebit: string): boolean {
+  try {
+    decodeNdebit(ndebit)
+    return true
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Format an ndebit as a full clink: URI with amount
+ */
+export function formatNdebitUri(ndebit: string, amountSats: number): string {
+  // Ensure ndebit doesn't already have clink: prefix
+  let cleaned = ndebit
+  if (cleaned.toLowerCase().startsWith('clink:')) {
+    cleaned = cleaned.slice(6)
+  }
+  if (cleaned.toLowerCase().startsWith('lightning:')) {
+    cleaned = cleaned.slice(10)
+  }
+
+  return `clink:${cleaned}?amount=${amountSats}`
+}
+
+/**
+ * Parse amount from ndebit URI query parameters
+ */
+export function parseNdebitAmount(uri: string): number | undefined {
+  const match = uri.match(/[?&]amount=(\d+)/)
+  if (match && match[1]) {
+    return parseInt(match[1], 10)
+  }
+  return undefined
+}
+
+// TLV helpers
+
+function writeTLV(data: number[], type: number, value: number[] | Uint8Array): void {
+  data.push(type)
+  data.push(value.length)
+  for (const byte of value) {
+    data.push(byte)
+  }
+}
+
+function hexToBytes(hex: string): Uint8Array {
+  const bytes = new Uint8Array(hex.length / 2)
+  for (let i = 0; i < hex.length; i += 2) {
+    bytes[i / 2] = parseInt(hex.slice(i, i + 2), 16)
+  }
+  return bytes
+}
+
+function bytesToHex(bytes: Uint8Array): string {
+  return Array.from(bytes)
+    .map((b) => b.toString(16).padStart(2, '0'))
+    .join('')
+}
+
+/**
+ * Convert npub to hex pubkey
+ * Accepts either npub1... or hex format, returns hex
+ */
+function npubToHex(pubkey: string): string {
+  if (pubkey.startsWith('npub1')) {
+    const decoded = nip19.decode(pubkey)
+    if (decoded.type !== 'npub') {
+      throw new Error(`Invalid npub: expected npub type, got ${decoded.type}`)
+    }
+    return decoded.data
+  }
+  // Already hex
+  return pubkey
+}

lamassu-next/packages/clink/src/types.ts

@@ -269,6 +269,30 @@ export enum NofferTLV {
   Description = 4,
 }
 
+// ============================================================================
+// Ndebit (Debit Pointer) encoding
+// ============================================================================
+
+/** Debit pointer for ndebit encoding */
+export interface DebitPointer {
+  /** Public key of the service that will pay (hex) */
+  pubkey: string
+  /** Relay URL for communication */
+  relay: string
+  /** Optional session/voucher identifier */
+  pointer?: string
+}
+
+/** ndebit TLV types */
+export enum NdebitTLV {
+  /** Public key (32 bytes) */
+  Pubkey = 0,
+  /** Relay URL (variable length string) */
+  Relay = 1,
+  /** Pointer/session identifier (variable length string) */
+  Pointer = 2,
+}
+
 // ============================================================================
 // Function types for service injection
 // ============================================================================

lamassu-next/packages/state-machine/src/machine.ts

@@ -30,6 +30,12 @@ export function createATMMachine(services: Partial<ATMServices> = {}) {
         }
         return services.generateClinkOffer(input)
       }),
+      generateNdebit: fromPromise(async ({ input }: { input: ATMContext }) => {
+        if (!services.generateNdebit) {
+          throw new Error('generateNdebit service not provided')
+        }
+        return services.generateNdebit(input)
+      }),
       generateLnurlWithdraw: fromPromise(async ({ input }: { input: ATMContext }) => {
         if (!services.generateLnurlWithdraw) {
           throw new Error('generateLnurlWithdraw service not provided')
@@ -288,21 +294,21 @@ export function createATMMachine(services: Partial<ATMServices> = {}) {
               },
               FINISH_INSERTING: {
                 guard: 'hasInsertedBills',
-                target: 'generatingLnurlWithdraw',
+                target: 'generatingNdebit',
               },
               CANCEL: '#atm.idle',
               TIMEOUT: '#atm.idle',
             },
           },
-          generatingLnurlWithdraw: {
+          generatingNdebit: {
             invoke: {
-              src: 'generateLnurlWithdraw',
+              src: 'generateNdebit',
               input: ({ context }) => context,
               onDone: {
                 target: 'displayingQR',
                 actions: assign({
-                  lnurlWithdraw: ({ event }) => event.output,
+                  ndebitUri: ({ event }) => event.output,
-                  paymentMethod: () => 'lnurl_withdraw' as const,
+                  paymentMethod: () => 'clink_offer' as const,
                 }),
               },
               onError: {

lamassu-next/packages/state-machine/src/types.ts

@@ -41,7 +41,9 @@ export interface ATMContext {
   clinkOffer: string | null
   /** noffer string displayed to user for cash-out */
   nofferString: string | null
-  /** LNURL-withdraw string - for cash-in (customer receives sats) */
+  /** ndebit URI for cash-in (clink:ndebit1...?amount=X) */
+  ndebitUri: string | null
+  /** LNURL-withdraw string - for cash-in (customer receives sats) - legacy */
   lnurlWithdraw: string | null
   /** Current payment status */
   paymentStatus: PaymentStatus
@@ -116,6 +118,7 @@ export const initialContext: ATMContext = {
   invoice: null,
   clinkOffer: null,
   nofferString: null,
+  ndebitUri: null,
   lnurlWithdraw: null,
   paymentStatus: null,
   preimage: null,
@@ -135,7 +138,9 @@ export const initialContext: ATMContext = {
 export interface ATMServices {
   /** Generate a CLINK offer (for cash-out) */
   generateClinkOffer: (context: ATMContext) => Promise<string>
-  /** Generate an LNURL-withdraw link (for cash-in - customer receives sats) */
+  /** Generate an ndebit URI for cash-in (clink:ndebit1...?amount=X) */
+  generateNdebit: (context: ATMContext) => Promise<string>
+  /** Generate an LNURL-withdraw link (for cash-in - customer receives sats) - legacy */
   generateLnurlWithdraw: (context: ATMContext) => Promise<string>
   /** Generate a Lightning invoice */
   generateInvoice: (amountMsat: number) => Promise<string>