btcpayserver/BTCPayServer/Payments/Bitcoin/BitcoinPaymentModelExtension.cs

#nullable enable
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using BTCPayServer.Models.InvoicingModels;
using BTCPayServer.Services;
using BTCPayServer.Services.Invoices;
using Microsoft.AspNetCore.Mvc;
using NBitcoin;
using NBitcoin.DataEncoders;

namespace BTCPayServer.Payments.Bitcoin
{
    public class BitcoinPaymentModelExtension : IPaymentModelExtension
    {
        private readonly PaymentMethodHandlerDictionary _handlers;
        private readonly BTCPayNetwork _Network;
        private readonly DisplayFormatter _displayFormatter;
        private readonly IPaymentLinkExtension paymentLinkExtension;
        private readonly IPaymentLinkExtension? lnPaymentLinkExtension;
        private readonly IPaymentLinkExtension? lnurlPaymentLinkExtension;
        private readonly string? _bech32Prefix;

        public BitcoinPaymentModelExtension(
            PaymentMethodId paymentMethodId,
            BTCPayNetwork network,
            IEnumerable<IPaymentLinkExtension> paymentLinkExtensions,
            DisplayFormatter displayFormatter,
            PaymentMethodHandlerDictionary handlers)
        {
            PaymentMethodId = paymentMethodId;
            _handlers = handlers;
            _Network = network;
            _displayFormatter = displayFormatter;
            paymentLinkExtension = paymentLinkExtensions.Single(p => p.PaymentMethodId == PaymentMethodId);
            var lnPmi = PaymentTypes.LN.GetPaymentMethodId(network.CryptoCode);
            lnPaymentLinkExtension = paymentLinkExtensions.SingleOrDefault(p => p.PaymentMethodId == lnPmi);
            var lnurlPmi = PaymentTypes.LNURL.GetPaymentMethodId(network.CryptoCode);
            lnurlPaymentLinkExtension = paymentLinkExtensions.SingleOrDefault(p => p.PaymentMethodId == lnurlPmi);
            _bech32Prefix = network.NBitcoinNetwork.GetBech32Encoder(Bech32Type.WITNESS_PUBKEY_ADDRESS, false) is { } enc ? Encoders.ASCII.EncodeData(enc.HumanReadablePart) : null;
        }
        public string DisplayName => _Network.DisplayName;
        public string Image => _Network.CryptoImagePath;
        public string Badge => "";
        public PaymentMethodId PaymentMethodId { get; }
        public void ModifyPaymentModel(PaymentModelContext context)
        {
            var prompt = context.Prompt;
            if (!_handlers.TryGetValue(PaymentMethodId, out var o) || o is not BitcoinLikePaymentHandler handler)
                return;
            var details = handler.ParsePaymentPromptDetails(prompt.Details);
            context.Model.ShowRecommendedFee = context.StoreBlob.ShowRecommendedFee;
            context.Model.FeeRate = details.RecommendedFeeRate.SatoshiPerByte;

            
            var bip21Case = _Network.SupportLightning && context.StoreBlob.OnChainWithLnInvoiceFallback;
            var amountInSats = bip21Case && context.StoreBlob.LightningAmountInSatoshi && context.Model.CryptoCode == "BTC";
            string? lightningFallback = null;
            if (context.Model.Activated && bip21Case)
            {
                var lnPmi = PaymentTypes.LN.GetPaymentMethodId(handler.Network.CryptoCode);
                var lnPrompt = context.InvoiceEntity.GetPaymentPrompt(lnPmi);
                if (lnPrompt is { Destination: not null })
                {
                    var lnUrl = lnPaymentLinkExtension?.GetPaymentLink(lnPrompt, context.UrlHelper);
                    if (lnUrl is not null)
                        lightningFallback = lnUrl;
                }
                else
                {
                    var lnurlPmi = PaymentTypes.LNURL.GetPaymentMethodId(handler.Network.CryptoCode);
                    var lnurlPrompt = context.InvoiceEntity.GetPaymentPrompt(lnurlPmi);
                    var lnUrl = lnurlPrompt is null ? null : lnurlPaymentLinkExtension?.GetPaymentLink(lnurlPrompt, context.UrlHelper);
                    if (lnUrl is not null)
                        lightningFallback = lnUrl;

                }
                if (!string.IsNullOrEmpty(lightningFallback))
                {
                    lightningFallback = lightningFallback
                        .Replace("lightning:", "lightning=", StringComparison.OrdinalIgnoreCase);
                }
            }

            if (context.Model.Activated)
            {
                // We're leading the way in Bitcoin community with adding UPPERCASE Bech32 addresses in QR Code
                //
                // Correct casing: Addresses in payment URI need to be …
                // - lowercase in link version
                // - uppercase in QR version
                //
                // The keys (e.g. "bitcoin:" or "lightning=" should be lowercase!

                // cryptoInfo.PaymentUrls?.BIP21: bitcoin:bcrt1qxp2qa5?amount=0.00044007
                var bip21 = paymentLinkExtension.GetPaymentLink(prompt, context.UrlHelper);
                context.Model.InvoiceBitcoinUrl = context.Model.InvoiceBitcoinUrlQR = bip21 ?? "";
                // model.InvoiceBitcoinUrl: bitcoin:bcrt1qxp2qa5?amount=0.00044007
                // model.InvoiceBitcoinUrlQR: bitcoin:bcrt1qxp2qa5?amount=0.00044007

                if (!string.IsNullOrEmpty(lightningFallback))
                {
                    var delimiterUrl = context.Model.InvoiceBitcoinUrl.Contains("?") ? "&" : "?";
                    context.Model.InvoiceBitcoinUrl += $"{delimiterUrl}{lightningFallback}";
                    // model.InvoiceBitcoinUrl: bitcoin:bcrt1qxp2qa5dhn7?amount=0.00044007&lightning=lnbcrt440070n1...

                    var delimiterUrlQR = context.Model.InvoiceBitcoinUrlQR.Contains("?") ? "&" : "?";
                    context.Model.InvoiceBitcoinUrlQR += $"{delimiterUrlQR}{lightningFallback.ToUpperInvariant().Replace("LIGHTNING=", "lightning=", StringComparison.OrdinalIgnoreCase)}";
                    // model.InvoiceBitcoinUrlQR: bitcoin:bcrt1qxp2qa5dhn7?amount=0.00044007&lightning=LNBCRT4400...
                }

                if (_Network.CryptoCode.Equals("BTC", StringComparison.InvariantCultureIgnoreCase) && _bech32Prefix is not null && context.Model.BtcAddress.StartsWith(_bech32Prefix, StringComparison.OrdinalIgnoreCase))
                {
                    context.Model.InvoiceBitcoinUrlQR = context.Model.InvoiceBitcoinUrlQR.Replace(
                        $"{_Network.NBitcoinNetwork.UriScheme}:{context.Model.BtcAddress}", $"{_Network.NBitcoinNetwork.UriScheme}:{context.Model.BtcAddress.ToUpperInvariant()}",
                        StringComparison.OrdinalIgnoreCase);
                    // model.InvoiceBitcoinUrlQR: bitcoin:BCRT1QXP2QA5DHN...?amount=0.00044007&lightning=LNBCRT4400...
                }
            }
            else
            {
                context.Model.InvoiceBitcoinUrl = context.Model.InvoiceBitcoinUrlQR = string.Empty;
            }

            if (context.Model.Activated && amountInSats)
            {
                PreparePaymentModelForAmountInSats(context.Model, context.Prompt.Rate, _displayFormatter);
            }
        }

        public static void PreparePaymentModelForAmountInSats(PaymentModel model, decimal rate, DisplayFormatter displayFormatter)
        {
            var satoshiCulture = new CultureInfo(CultureInfo.InvariantCulture.Name)
            {
                NumberFormat = { NumberGroupSeparator = " " }
            };
            model.CryptoCode = "sats";
            model.BtcDue = Money.Parse(model.BtcDue).ToUnit(MoneyUnit.Satoshi).ToString("N0", satoshiCulture);
            model.BtcPaid = Money.Parse(model.BtcPaid).ToUnit(MoneyUnit.Satoshi).ToString("N0", satoshiCulture);
            model.OrderAmount = Money.Parse(model.OrderAmount).ToUnit(MoneyUnit.Satoshi).ToString("N0", satoshiCulture);
            model.NetworkFee = new Money(model.NetworkFee, MoneyUnit.BTC).ToUnit(MoneyUnit.Satoshi);
            model.Rate = model.InvoiceCurrency is "BTC" or "SATS"
                ? null
                : displayFormatter.Currency(rate / 100_000_000, model.InvoiceCurrency, DisplayFormatter.CurrencyFormat.Symbol);
        }

    }
}