Retrieves rates from CNB API and converts it

jobs/Backend/Task/ExchangeRateProvider.cs

@@ -1,5 +1,11 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Linq;
+using System.Net.Http.Headers;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+using ExchangeRateUpdater.Models;
 
 namespace ExchangeRateUpdater
 {
@@ -11,9 +17,77 @@ public class ExchangeRateProvider
         /// do not return exchange rate "USD/CZK" with value calculated as 1 / "CZK/USD". If the source does not provide
         /// some of the currencies, ignore them.
         /// </summary>
-        public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies)
+        public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies, Currency baseCurrency)
         {
-            return Enumerable.Empty<ExchangeRate>();
+            var exchangeRates = new List<ExchangeRate>();
+
+            // Created two different calls to exemplify how API can change individually, despite being right now, returning the data in the same format
+            var ratesDaily = GetExchangeRatesDailyAsync(currencies).Result;
+            var ratesForex = GetExchangeRatesForexAsync(currencies).Result;
+
+            // Conversion should be one or two different depending on what is done with the API calls. In this case, for simplicity, I've done one single converter
+            exchangeRates.AddRange(RateConverter.ConvertApiToExchangeRate(ratesDaily, baseCurrency));
+            exchangeRates.AddRange(RateConverter.ConvertApiToExchangeRate(ratesForex, baseCurrency));
+
+            return exchangeRates;
+        }
+
+        private async Task<IEnumerable<ExchangeRateApi>> GetExchangeRatesDailyAsync(IEnumerable<Currency> currencies)
+        {
+            var exchangeRates = new List<ExchangeRateApi>();
+
+            var dayDate = DateTime.Now.ToString("yyyy-MM-dd");
+
+            var urlApi = $"https://api.cnb.cz/cnbapi/exrates/daily";
+            var parametersApi = $"?date={dayDate}";
+
+            HttpClient client = new HttpClient();
+            client.BaseAddress = new Uri(urlApi);
+            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
+
+            HttpResponseMessage response = await client.GetAsync(parametersApi).ConfigureAwait(false);
+
+            if (response.IsSuccessStatusCode)
+            {
+                var jsonString = await response.Content.ReadAsStringAsync();
+                var ratesList = JsonConvert.DeserializeObject<ExchangeRatesList>(jsonString);
+
+                if (ratesList != null)
+                {
+                    exchangeRates.AddRange(ratesList.Rates.Where(e => currencies.Any(c => c.Code == e.CurrencyCode)));
+                }
+            }
+
+            return exchangeRates;
+        }
+
+        private async Task<IEnumerable<ExchangeRateApi>> GetExchangeRatesForexAsync(IEnumerable<Currency> currencies)
+        {
+            var exchangeRates = new List<ExchangeRateApi>();
+
+            var monthDate = DateTime.Now.AddMonths(-1).ToString("yyyy-MM");
+
+            var urlApi = $"https://api.cnb.cz/cnbapi/fxrates/daily-month";
+            var parametersApi = $"?yearMonth={monthDate}";
+
+            HttpClient client = new HttpClient();
+            client.BaseAddress = new Uri(urlApi);
+            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
+
+            HttpResponseMessage response = await client.GetAsync(parametersApi).ConfigureAwait(false);
+
+            if (response.IsSuccessStatusCode)
+            {
+                var jsonString = await response.Content.ReadAsStringAsync();
+                var ratesList = JsonConvert.DeserializeObject<ExchangeRatesList>(jsonString);
+
+                if (ratesList != null)
+                {
+                    exchangeRates.AddRange(ratesList.Rates.Where(e => currencies.Any(c => c.Code == e.CurrencyCode)));
+                }
+            }
+
+            return exchangeRates;
         }
     }
 }

jobs/Backend/Task/ExchangeRateUpdater.csproj

@@ -5,4 +5,8 @@
     <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
 </Project>

jobs/Backend/Task/Models/ExchangeRateApi.cs

@@ -0,0 +1,22 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ExchangeRateUpdater.Models
+{
+    [Serializable]
+    public class ExchangeRateApi
+    {
+        [JsonProperty("currencyCode")]
+        public string CurrencyCode { get; set; }
+
+        [JsonProperty("rate")]
+        public decimal Rate { get; set; }
+
+        [JsonProperty("amount")]
+        public decimal Amount { get; set; }
+    }
+}

jobs/Backend/Task/Models/ExchangeRatesList.cs

@@ -0,0 +1,16 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ExchangeRateUpdater.Models
+{
+    [Serializable]
+    public class ExchangeRatesList
+    {
+        [JsonProperty("rates")]
+        public IEnumerable<ExchangeRateApi> Rates { get; set; }
+    }
+}

jobs/Backend/Task/Program.cs

@@ -19,12 +19,14 @@ public static class Program
             new Currency("XYZ")
         };
 
+        public static Currency baseCurrency = new Currency("CZK");
+
         public static void Main(string[] args)
         {
             try
             {
                 var provider = new ExchangeRateProvider();
-                var rates = provider.GetExchangeRates(currencies);
+                var rates = provider.GetExchangeRates(currencies, baseCurrency);
 
                 Console.WriteLine($"Successfully retrieved {rates.Count()} exchange rates:");
                 foreach (var rate in rates)

jobs/Backend/Task/RateConverter.cs

@@ -0,0 +1,15 @@
+using ExchangeRateUpdater.Models;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace ExchangeRateUpdater
+{
+    internal static class RateConverter
+    {
+        // Convert from ExchangeRateApi to ExchangeRate
+        public static IEnumerable<ExchangeRate> ConvertApiToExchangeRate(IEnumerable<ExchangeRateApi> ratesApi, Currency baseCurrency)
+        {
+            return ratesApi.Select(c => new ExchangeRate(new Currency(c.CurrencyCode), baseCurrency, c.Rate / c.Amount));
+        }
+    }
+}