btcpayserver/BTCPayServer/Views/Shared/NFC/CheckoutEnd.cshtml

<template id="lnurl-withdraw-template">
    <div v-if="display" class="mt-4" id="NFC">
        <div v-if="nfcErrorMessage" class="alert alert-danger" v-text="nfcErrorMessage"></div>
        <template v-if="isV2">
            <button class="btn btn-secondary rounded-pill w-100" type="button" id="PayByNFC"
                    :disabled="nfcScanning || submitting" v-on:click="handleClick">{{btnText}}</button>
        </template>
        <template v-else>
            <bp-loading-button>
                <button class="action-button" style="margin: 0 45px;width:calc(100% - 90px) !important" :disabled="nfcScanning || submitting" v-on:click="handleClick" id="PayByNFC"
                        :class="{ 'action-button': nfcSupported, 'btn btn-text w-100': !nfcSupported  }">
                    <span class="button-text">{{btnText}}</span>
                    <div class="loader-wrapper">
                        @await Html.PartialAsync("~/Views/UIInvoice/Checkout-Spinner.cshtml")
                    </div>
                </button>
            </bp-loading-button>
        </template>
    </div>
</template>
<script>
Vue.component("lnurl-withdraw-checkout", {
    template: "#lnurl-withdraw-template",
    props: {
        model: Object,
        isV2: Boolean,
        nfcSupported: Boolean,
        nfcScanning: Boolean,
        nfcErrorMessage: String
    },
    computed: {
        display () {
            const {
                onChainWithLnInvoiceFallback: isUnified,
                paymentMethodId: activePaymentMethodId,
                availableCryptos: availablePaymentMethods,
                invoiceBitcoinUrl: paymentUrl
            } = this.model
            const lnurlwAvailable = 
                // Either we have LN or LNURL available directly
                !!availablePaymentMethods.find(pm => ['BTC_LNURLPAY', 'BTC_LightningLike'].includes(pm.paymentMethodId)) ||
                // Or the BIP21 payment URL flags Lightning support
                !!paymentUrl.match(/lightning=ln/i)
            const isAvailable = activePaymentMethodId === 'BTC_LNURLPAY' || (
                // Unified QR/BIP21 case
                (activePaymentMethodId === 'BTC' && isUnified && lnurlwAvailable) ||
                // Lightning with LNURL available
                (activePaymentMethodId === 'BTC_LightningLike' && lnurlwAvailable))
            return isAvailable && (this.nfcSupported || this.testFallback)
        },
        testFallback () {
            return !this.nfcSupported && window.location.search.match('lnurlwtest=(1|true)')
        },
        btnText () {
            if (this.nfcSupported) {
                if (this.submitting) {
                    return this.isV2 ? this.$t('submitting_nfc') : 'Submitting NFC …'
                } else if (this.nfcScanning) {
                    return this.isV2 ? this.$t('scanning_nfc') : 'Scanning NFC …'
                } else {
                    return this.isV2 ? this.$t('pay_by_nfc') : 'Pay by NFC'
                }
            } else {
                return this.isV2 ? this.$t('pay_by_lnurl') : 'Pay by LNURL-Withdraw'
            }
        }
    },
    data () {
        return {
            url: @Safe.Json(Context.Request.GetAbsoluteUri(Url.Action("SubmitLNURLWithdrawForInvoice", "NFC"))),
            amount: 0,
            submitting: false
        }
    },
    beforeMount () {
        this.$root.$on('read-nfc-data', this.sendData)
    },
    beforeDestroy () {
        this.$root.$off('read-nfc-data')
    },
    methods: {
        async handleClick () {
            if (this.nfcSupported) {
                this.$emit('start-nfc-scan')
            } else {
                if (this.model.isUnsetTopUp) {
                    this.handleUnsetTopUp()
                    if (!this.amount) {
                        return;
                    }
                }
                const lnurl = prompt("Enter LNURL-Withdraw")
                if (lnurl) {
                    await this.sendData(lnurl)
                }
            }
        },
        handleUnsetTopUp () {
            const amountStr = prompt("How many sats do you want to pay?")
            if (amountStr) {
                try {
                    this.amount = parseInt(amountStr)
                } catch {
                    alert("Please provide a valid number amount in sats")
                }
            }
            return false
        },
        async sendData (data) {
            this.submitting = true
            this.$emit('handle-nfc-data')
            
            // Post LNURL-Withdraw data to server
            const body = JSON.stringify({ lnurl: data, invoiceId: this.model.invoiceId, amount: this.amount })
            const opts = { method: 'POST', headers: { 'Content-Type': 'application/json' }, body }
            const response = await fetch(this.url, opts)
            
            // Handle response
            try {
                const result = await response.text()
                const action = response.ok ? 'handle-nfc-result' : 'handle-nfc-error'
                this.$emit(action, result)
            } catch (error) {
                this.$emit('handle-nfc-error', error)
            }
            this.submitting = false
        }
    }
});
</script>