Can send max invoice value for lightning payments

BTCPayServer/CurrencyValue.cs

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+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using BTCPayServer.Services.Rates;
+
+namespace BTCPayServer
+{
+    public class CurrencyValue
+    {
+        static Regex _Regex = new Regex("^([0-9]+(\\.[0-9]+)?)\\s*([a-zA-Z]+)$");
+        static CurrencyNameTable _CurrencyTable = new CurrencyNameTable();
+        public static bool TryParse(string str, out CurrencyValue value)
+        {
+            value = null;
+            var match = _Regex.Match(str);
+            if (!match.Success ||
+                !decimal.TryParse(match.Groups[1].Value, out var v))
+                return false;
+
+            var currency = match.Groups.Last().Value.ToUpperInvariant();
+            var currencyData = _CurrencyTable.GetCurrencyData(currency);
+            if (currencyData == null)
+                return false;
+            v = Math.Round(v, currencyData.Divisibility);
+            value = new CurrencyValue()
+            {
+                Value = v,
+                Currency = currency
+            };
+            return true;
+        }
+
+        public decimal Value { get; set; }
+        public string Currency { get; set; }
+
+        public override string ToString()
+        {
+            return Value.ToString(CultureInfo.InvariantCulture) + " " + Currency;
+        }
+    }
+}