/// <summary>
/// Read an external file and convert currency
/// </summary>
/// <param name="FullFilePath"></param>
public decimal ConvertCurrencyFromExternalFile(string FullFilePath)
{
var TargetCurrencyToConvert = new CurrencyToConvert();
var CurrencyRates = new List <CurrencyRate>();
//Read Te file and get all the rows from file
var rows = fileManager.ReadExternalCurrencyExchageFile(FullFilePath);
//Mapping of the rows to TargetCurrencyToConvert and CurrencyRates information
foreach (var item in rows)
{
if (typeof(CurrencyToConvert) == item.GetType())
{
TargetCurrencyToConvert = (CurrencyToConvert)item;
}
else
{
CurrencyRates.Add((CurrencyRate)item);
}
}
//Calculate the exchange rate
var result = ExchageCalculator(TargetCurrencyToConvert, CurrencyRates);
//Show the result in the console and return its value.
Console.WriteLine(result);
return(result);
}
/// <summary>
/// Calculate Currency exchange From/To and amount by using a list of currency rates
/// </summary>
/// <param name="currencyToConvert"></param>
/// <param name="currencyRates"></param>
/// <returns></returns>
private decimal ExchageCalculator(CurrencyToConvert currencyToConvert, List <CurrencyRate> currencyRates)
{
//The intermediate result from evaluating all currencies one to one, starting from the InputCurrencyFrom
var currenciesUsed = new Dictionary <string, decimal>(StringComparer.CurrentCultureIgnoreCase);
currenciesUsed.Add(currencyToConvert.InputCurrencyFrom, currencyToConvert.InputAmountToExchage);
try
{
//Create a list of all the currencies from the currencyRates (information)
var allCurrencies = GetAllCurrenciesInList(currencyRates);
//Check if the list of currency rate (information) has any error
CheckError(allCurrencies, currencyToConvert, currencyRates);
//Loop finish when the InputCurrencyTo is in the list of currenciesUsed - It means i already have the result from evaluation
while (currenciesUsed.Any() && !currenciesUsed.Any(m => m.Key == currencyToConvert.InputCurrencyTo) && allCurrencies.Any())
{
//CurrencyInUse is the currency in evaluation
var CurrencyInUse = currenciesUsed.First();
allCurrencies.Remove(CurrencyInUse.Key);
//Next currencies to be evaluated linked to CurrencyInUse.
var NextCurrenciesInUse = currencyRates.Where(m => m.CurrencyFrom == CurrencyInUse.Key || m.CurrencyTo == CurrencyInUse.Key);
foreach (var NextCurrency in NextCurrenciesInUse)
{
if (NextCurrency.CurrencyTo == CurrencyInUse.Key)
{
NextCurrency.CurrencyTo = NextCurrency.CurrencyFrom;
NextCurrency.CurrencyFrom = CurrencyInUse.Key;
NextCurrency.Rate = Math.Round(1 / NextCurrency.Rate, 4);
}
if (allCurrencies.Contains(NextCurrency.CurrencyTo))
{
currenciesUsed.Add(NextCurrency.CurrencyTo, Math.Round(NextCurrency.Rate * CurrencyInUse.Value, 4));
}
}
//Remove the currency already evaluated
currenciesUsed.Remove(CurrencyInUse.Key);
}
if (!currenciesUsed.Any())
{
throw new Exception("Error : List of currency rates incomplete - No match was found");
}
return(Math.Round(currenciesUsed.FirstOrDefault(m => m.Key == currencyToConvert.InputCurrencyTo).Value, 0));
}
catch (Exception e)
{
throw new Exception(e.Message);
}
}
private void CheckError(List <string> allCurrencies, CurrencyToConvert currencyToConvert, List <CurrencyRate> currencyRates)
{
if (!allCurrencies.Contains(currencyToConvert.InputCurrencyFrom))
{
throw new Exception($"Error : Currency rate list doesn't contain the Input Currency : <{currencyToConvert.InputCurrencyFrom}>");
}
if (!allCurrencies.Contains(currencyToConvert.InputCurrencyTo))
{
throw new Exception($"Error : Currency rate list doesn't contain the Input Currency : <{currencyToConvert.InputCurrencyTo}>");
}
if (currencyRates.Any(m => m.Rate < 0) || currencyToConvert.InputAmountToExchage < 0)
{
throw new Exception("Error : Currency rate cannot be negative !");
}
}
