Build a Dual-Chain Mini App with Nimiq Pay

npm create vite@latest my-mini-app -- --template vue-ts
cd my-mini-app
npm install

import vue from '@vitejs/plugin-vue'
import { defineConfig } from 'vite'

export default defineConfig({
  plugins: [vue()],
  server: {
    port: 5173,
    host: true,
  },
})

<script setup lang="ts">
import { init } from '@nimiq/mini-app-sdk'
import { onMounted, ref } from 'vue'

interface EthereumProvider {
  request: (args: { method: string, params?: unknown[] | Record<string, unknown> }) => Promise<any>
}

declare global {
  interface Window {
    ethereum?: EthereumProvider
  }
}

let nimiqPromise: ReturnType<typeof init> | null = null

const loading = ref(false)
const isNimiqConnecting = ref(true)
const status = ref<string | null>(null)
const errorMessage = ref<string | null>(null)

const nimiqAccounts = ref<string[] | null>(null)
const nimiqSignature = ref<string | null>(null)
const ethAccounts = ref<string[] | null>(null)
const ethSignature = ref<string | null>(null)

// Convert a UTF-8 string to hex for personal_sign.
function toHexUtf8(input: string) {
  return `0x${Array.from(new TextEncoder().encode(input))
    .map(byte => byte.toString(16).padStart(2, '0'))
    .join('')}`
}

function resetFeedback() {
  errorMessage.value = null
  status.value = null
}

onMounted(async () => {
  try {
    nimiqPromise = init({ timeout: 10_000 })
    await nimiqPromise
  }
  catch (error) {
    errorMessage.value = error instanceof Error ? error.message : String(error)
  }
  finally {
    isNimiqConnecting.value = false
  }
})

async function runNimiqFlow() {
  resetFeedback()
  nimiqAccounts.value = null
  nimiqSignature.value = null

  if (!nimiqPromise) {
    errorMessage.value = 'Nimiq provider not ready. Open this app inside Nimiq Pay.'
    status.value = 'Nimiq flow failed.'
    return
  }

  loading.value = true

  try {
    const nimiq = await nimiqPromise

    // Request account sharing if the provider has no cached accounts.
    status.value = 'Requesting Nimiq accounts...'
    const accounts = await nimiq.listAccounts()
    nimiqAccounts.value = accounts
    if (!accounts.length)
      throw new Error('No Nimiq accounts returned.')

    // Request signing confirmation.
    status.value = 'Requesting Nimiq signing confirmation...'
    const signatureResult = await nimiq.sign('Nimiq Pay dual-chain tutorial')
    nimiqSignature.value = JSON.stringify(signatureResult, null, 2)
    status.value = 'Nimiq flow completed.'
  }
  catch (error) {
    errorMessage.value = error instanceof Error ? error.message : String(error)
    status.value = 'Nimiq flow failed.'
  }
  finally {
    loading.value = false
  }
}

async function runEthereumFlow() {
  resetFeedback()
  ethAccounts.value = null
  ethSignature.value = null

  if (!window.ethereum) {
    errorMessage.value = 'Ethereum provider not found. Open this app inside Nimiq Pay.'
    status.value = 'Ethereum flow failed.'
    return
  }

  loading.value = true

  try {
    // Prompt 1: wallet connection confirmation.
    status.value = 'Requesting Ethereum accounts...'
    const accounts = await window.ethereum.request({
      method: 'eth_requestAccounts',
    }) as string[]
    ethAccounts.value = accounts
    if (!accounts.length)
      throw new Error('No Ethereum accounts returned.')

    // Request signing confirmation.
    const message = toHexUtf8('Nimiq Pay dual-chain tutorial')
    status.value = 'Requesting Ethereum signing confirmation...'
    const signature = await window.ethereum.request({
      method: 'personal_sign',
      params: [message, accounts[0]],
    }) as string
    ethSignature.value = signature
    status.value = 'Ethereum flow completed.'
  }
  catch (error) {
    errorMessage.value = error instanceof Error ? error.message : String(error)
    status.value = 'Ethereum flow failed.'
  }
  finally {
    loading.value = false
  }
}
</script>

<template>
  <div class="app">
    <h1>Dual-Chain Mini App</h1>

    <div class="actions">
      <button :disabled="loading || isNimiqConnecting" @click="runNimiqFlow">
        Run Nimiq flow
      </button>
      <button :disabled="loading" @click="runEthereumFlow">
        Run Ethereum flow
      </button>
    </div>

    <p v-if="isNimiqConnecting">
      Waiting for the Nimiq provider to initialize...
    </p>

    <p v-if="status">
      <strong>Status:</strong> {{ status }}
    </p>
    <p v-if="errorMessage" class="error">
      <strong>Error:</strong> {{ errorMessage }}
    </p>

    <h2>Nimiq Output</h2>
    <pre v-if="nimiqAccounts" class="result">Accounts: {{ JSON.stringify(nimiqAccounts, null, 2) }}</pre>
    <pre v-if="nimiqSignature" class="result">Signature: {{ nimiqSignature }}</pre>

    <h2>Ethereum Output</h2>
    <pre v-if="ethAccounts" class="result">Accounts: {{ JSON.stringify(ethAccounts, null, 2) }}</pre>
    <pre v-if="ethSignature" class="result">Signature: {{ ethSignature }}</pre>
  </div>
</template>

<style scoped>
.app {
  max-width: 42rem;
  margin: 0 auto;
  padding: 1rem;
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  color: #1f3553;
}

h1 {
  margin: 0 0 1rem;
  font-size: clamp(1.75rem, 7vw, 2.4rem);
  line-height: 1.2;
}

h2 {
  margin: 1rem 0 0.5rem;
}

.actions {
  display: grid;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

button {
  width: 100%;
  min-height: 44px;
  border: none;
  border-radius: 0.625rem;
  padding: 0.625rem 0.875rem;
  font-weight: 600;
  background: #1f3553;
  color: #fff;
}

button:disabled {
  opacity: 0.55;
}

.error {
  color: #b31b1b;
}

.result {
  margin: 0 0 0.625rem;
  padding: 0.625rem;
  border-radius: 0.5rem;
  background: #f5f8fc;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  word-break: break-word;
}

@media (min-width: 640px) {
  .actions {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}
</style>

const language = window.nimiqPay?.language
  || navigator.language.split('-')[0]
  || 'en'

npm run dev -- --host

http://192.168.1.42:5173