Technical Assesment MEWS Gabriel Cebrian

jobs/Backend/Task/ExchangeRateProvider.cs

@@ -1,5 +1,10 @@
 using System.Collections.Generic;
 using System.Linq;
+//Add new libraries for the implementation
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+using System.Globalization;
 
 namespace ExchangeRateUpdater
 {
@@ -11,9 +16,75 @@ 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>
+
+        private static readonly HttpClient _httpClient = new HttpClient(); //client for making the request
+        private const string CNB_URL = "https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/daily.txt";//url for retrieving the info
+
+
         public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies)
         {
-            return Enumerable.Empty<ExchangeRate>();
+            try 
+            {
+                var  cnbData  = DownloadCnbData();
+                var  exchangeRates  = ParseCnbData(cnbData);
+                var  requestedCodes  = currencies.Select(c  => c.Code).ToHashSet();
+                var  results  = new  List<ExchangeRate>();
+
+                foreach  (var  rate  in  exchangeRates)
+                {
+                    if  (requestedCodes.Contains(rate.CurrencyCode))
+                    {
+                        var  czk  = new  Currency("CZK");
+                        var  target  = new  Currency(rate.CurrencyCode);
+                        var  exchRate  = new  ExchangeRate(czk,  target,  rate.Rate);
+                        results.Add(exchRate);
+                    }
+                }
+
+                return  results;
+            }
+            catch  (Exception  ex)
+            {
+                Console.WriteLine($"Error:  {ex.Message}");
+                return  Enumerable.Empty<ExchangeRate>();
+            }
+        }
+
+private  List<(string  CurrencyCode,  decimal  Rate)>  ParseCnbData(string  cnbData)
+        {
+            var  rates  = new  List<(string  CurrencyCode,  decimal  Rate)>();
+            var  lines  = cnbData.Split('\n',  StringSplitOptions.RemoveEmptyEntries);
+
+            for  (int  i  = 2;  i  < lines.Length;  i++)
+            {
+                var  parts  = lines[i].Split('|');
+                if  (parts.Length  >= 5)
+                {
+                    try
+                    {
+                        var  currencyCode  = parts[3].Trim();
+                        var  amount  = decimal.Parse(parts[2].Trim());
+                        var  rate  = decimal.Parse(parts[4].Trim(),  CultureInfo.InvariantCulture);
+
+                        var  normalizedRate  = rate  / amount;
+                        rates.Add((currencyCode,  normalizedRate));
+
+                        Console.WriteLine($"Parsed:  {currencyCode}  =  {normalizedRate}");
+                    }
+                    catch  (Exception  ex)
+                    {
+                        Console.WriteLine($"Error  parsing  line:  {lines[i]}  -  {ex.Message}");
+                    }
+                }
+            }
+
+            return  rates;
+        }
+
+        private  string  DownloadCnbData()
+        {
+            var  task  =  _httpClient.GetStringAsync(CNB_URL);
+            return  task.Result;
         }
     }
 }