btcpayserver/BTCPayServer.Rating/CurrencyNameTable.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using NBitcoin;
using Newtonsoft.Json;

namespace BTCPayServer.Services.Rates
{
    public class CurrencyData
    {
        public string Name { get; set; }
        public string Code { get; set; }
        public int Divisibility { get; set; }
        public string Symbol { get; set; }
        public bool Crypto { get; set; }
    }
    public interface CurrencyDataProvider
    {
        Task<CurrencyData[]> LoadCurrencyData(CancellationToken cancellationToken);
    }
    public class InMemoryCurrencyDataProvider : CurrencyDataProvider
    {
        private readonly CurrencyData[] _currencyData;

        public InMemoryCurrencyDataProvider(CurrencyData[] currencyData)
        {
            _currencyData = currencyData;
        }

        public Task<CurrencyData[]> LoadCurrencyData(CancellationToken cancellationToken) => Task.FromResult(_currencyData);
    }
    public class AssemblyCurrencyDataProvider : CurrencyDataProvider
    {
        private readonly Assembly _assembly;
        private readonly string _manifestResourceStream;

        public AssemblyCurrencyDataProvider(Assembly assembly, string manifestResourceStream)
        {
            _assembly = assembly;
            _manifestResourceStream = manifestResourceStream;
        }
        public Task<CurrencyData[]> LoadCurrencyData(CancellationToken cancellationToken)
        {
            var stream = _assembly.GetManifestResourceStream(_manifestResourceStream);
            if (stream is null)
                throw new InvalidOperationException("Unknown manifestResourceStream");
            string content = null;
            using (var reader = new StreamReader(stream, Encoding.UTF8))
            {
                content = reader.ReadToEnd();
            }

            var currencies = JsonConvert.DeserializeObject<CurrencyData[]>(content);
            return Task.FromResult(currencies.ToArray());
        }
    }
    public class CurrencyNameTable
    {
        public CurrencyNameTable(IEnumerable<CurrencyDataProvider> currencyDataProviders, ILogger<CurrencyNameTable> logger)
        {
            _currencyDataProviders = currencyDataProviders;
            _logger = logger;
        }

        public async Task ReloadCurrencyData(CancellationToken cancellationToken)
        {
            var currencies = new Dictionary<string, CurrencyData>(StringComparer.InvariantCultureIgnoreCase);
            var loadings = _currencyDataProviders.Select(c => (Task: c.LoadCurrencyData(cancellationToken), Prov: c)).ToList();
            foreach (var loading in loadings)
            {
                try
                {
                    foreach (var curr in await loading.Task)
                    {
                        currencies.TryAdd(curr.Code, curr);
                    }
                }
                catch (Exception ex)
                {
                    _logger.LogWarning(ex, "Error loading currency data for " + loading.Prov.GetType().FullName);
                }
            }
            _Currencies = currencies;
        }
        static readonly Dictionary<string, IFormatProvider> _CurrencyProviders = new();

        public NumberFormatInfo GetNumberFormatInfo(string currency, bool useFallback)
        {
            var data = GetCurrencyProvider(currency);
            if (data is NumberFormatInfo nfi)
                return nfi;
            if (data is CultureInfo ci)
                return ci.NumberFormat;
            if (!useFallback)
                return null;
            return CreateFallbackCurrencyFormatInfo(currency);
        }

        private NumberFormatInfo CreateFallbackCurrencyFormatInfo(string currency)
        {
            var usd = GetNumberFormatInfo("USD", false);
            var currencyInfo = (NumberFormatInfo)usd.Clone();
            currencyInfo.CurrencySymbol = currency;
            return currencyInfo;
        }

        public NumberFormatInfo GetNumberFormatInfo(string currency)
        {
            var curr = GetCurrencyProvider(currency);
            if (curr is CultureInfo cu)
                return cu.NumberFormat;
            if (curr is NumberFormatInfo ni)
                return ni;
            return null;
        }

        public IFormatProvider GetCurrencyProvider(string currency)
        {
            lock (_CurrencyProviders)
            {
                if (_CurrencyProviders.Count == 0)
                {
                    foreach (var culture in CultureInfo.GetCultures(CultureTypes.AllCultures))
                    {
                        // This avoid storms of exception throwing slowing up
                        // startup and debugging sessions
                        if (culture switch
                        {
                            { LCID: 0x007F or 0x0000 or 0x0c00 or 0x1000 } => true,
                            { IsNeutralCulture : true } => true,
                            _ => false
                        })
                            continue;
                        try
                        {
                            var symbol = new RegionInfo(culture.LCID).ISOCurrencySymbol;
                            var c = symbol switch
                            {
                                // ARS and COP are officially 2 digits, but due to depreciation,
                                // nobody really use those anymore. (See https://github.com/btcpayserver/btcpayserver/issues/5708)
                                "ARS" or "COP" => ModifyCurrencyDecimalDigit(culture, 0),
                                _ => culture
                            };
                            _CurrencyProviders.TryAdd(symbol, c);
                        }
                        catch { }
                    }

                    foreach (var curr in _Currencies.Where(pair => pair.Value.Crypto))
                    {
                        AddCurrency(_CurrencyProviders, curr.Key, curr.Value.Divisibility, curr.Value.Symbol ?? curr.Value.Code);
                    }
                }
                return _CurrencyProviders.TryGet(currency.ToUpperInvariant());
            }
        }

        private CultureInfo ModifyCurrencyDecimalDigit(CultureInfo culture, int decimals)
        {
            var modifiedCulture = new CultureInfo(culture.Name);
            NumberFormatInfo modifiedNumberFormat = (NumberFormatInfo)modifiedCulture.NumberFormat.Clone();
            modifiedNumberFormat.CurrencyDecimalDigits = decimals;
            modifiedCulture.NumberFormat = modifiedNumberFormat;
            return modifiedCulture;
        }

        private void AddCurrency(Dictionary<string, IFormatProvider> currencyProviders, string code, int divisibility, string symbol)
        {
            var culture = new CultureInfo("en-US");
            var number = new NumberFormatInfo();
            number.CurrencyDecimalDigits = divisibility;
            number.CurrencySymbol = symbol;
            number.CurrencyDecimalSeparator = culture.NumberFormat.CurrencyDecimalSeparator;
            number.CurrencyGroupSeparator = culture.NumberFormat.CurrencyGroupSeparator;
            number.CurrencyGroupSizes = culture.NumberFormat.CurrencyGroupSizes;
            number.CurrencyNegativePattern = 8;
            number.CurrencyPositivePattern = 3;
            number.NegativeSign = culture.NumberFormat.NegativeSign;
            currencyProviders.TryAdd(code, number);
        }

        Dictionary<string, CurrencyData> _Currencies = new();
        private readonly IEnumerable<CurrencyDataProvider> _currencyDataProviders;
        private readonly ILogger<CurrencyNameTable> _logger;

        public IEnumerable<CurrencyData> Currencies => _Currencies.Values;

        public CurrencyData GetCurrencyData(string currency, bool useFallback)
        {
            ArgumentNullException.ThrowIfNull(currency);
            CurrencyData result;
            if (!_Currencies.TryGetValue(currency.ToUpperInvariant(), out result))
            {
                if (useFallback)
                {
                    var usd = GetCurrencyData("USD", false);
                    result = new CurrencyData()
                    {
                        Code = currency,
                        Crypto = true,
                        Name = currency,
                        Divisibility = usd.Divisibility
                    };
                }
            }
            return result;
        }

    }
}