Add CoinGecko price API

Author: Coding-Enthusiast

WatchOnlyBitcoinWallet/Services/ApiBase.cs

@@ -15,6 +15,7 @@ public enum PriceServiceNames
         MempoolSpace,
         Bitfinex,
         Coindesk,
+        CoinGecko,
     }
     public enum BalanceServiceNames
     {

WatchOnlyBitcoinWallet/Services/PriceServices/CoinGecko.cs

@@ -0,0 +1,37 @@
+// WatchOnlyBitcoinWallet
+// Copyright (c) 2016 Coding Enthusiast
+// Distributed under the MIT software license, see the accompanying
+// file LICENCE or http://www.opensource.org/licenses/mit-license.php.
+
+using Newtonsoft.Json.Linq;
+using System.Diagnostics;
+using System.Threading.Tasks;
+
+namespace WatchOnlyBitcoinWallet.Services.PriceServices
+{
+    public class CoinGecko : ApiBase, IPriceApi
+    {
+        public async Task<Response<decimal>> UpdatePriceAsync()
+        {
+            Response<decimal> resp = new();
+            Response<JObject> apiResp = await SendApiRequestAsync("https://api.coingecko.com/api/v3/exchange_rates");
+            if (!apiResp.IsSuccess)
+            {
+                resp.Error = apiResp.Error;
+                return resp;
+            }
+            Debug.Assert(apiResp.Result is not null);
+
+            JToken? x = apiResp.Result["rates"]?["usd"]?["value"];
+            if (x is null)
+            {
+                resp.Error = "JSON in API response doesn't include the params " +
+                             "(API may have changed, please report this as a bug).";
+                return resp;
+            }
+
+            resp.Result = (decimal)x; 
+            return resp;
+        }
+    }
+}

WatchOnlyBitcoinWallet/ViewModels/SettingsViewModel.cs

@@ -65,6 +65,7 @@ private async void UpdatePrice()
                 PriceServiceNames.MempoolSpace => new MempoolSpace(),
                 PriceServiceNames.Bitfinex => new Bitfinex(),
                 PriceServiceNames.Coindesk => new Coindesk(),
+                PriceServiceNames.CoinGecko => new CoinGecko(),
                 _ => throw new NotImplementedException(),
             };