/// <summary>
/// converts currencies from one type to another
/// </summary>
/// <param name="fromCurrency">code of source currency</param>
/// <param name="toCurrency">code of destination currency</param>
/// <returns>returns the ratio SRC/DST </returns>
public async Task <double> ConvertAsync(string fromCurrency, string toCurrency)
{
HistoricalCurrencyEntity currentInfo = (await new Dal().GetTimeSpanCurrency(1)).FirstOrDefault(); //Gilad - was get by day
double from = 1 / currentInfo.GetValue(fromCurrency); // 1/(USD/from) = from/USD
double to = currentInfo.GetValue(toCurrency); //USD/to
return(from * to); // from/USD * USD/to = from/to
}
/// <summary>
/// another async layer to make sure nothing gets stuck <see cref="UpdateDataBaseAsync"/>
/// </summary>
private async Task _updateDataBaseAsync(DateTime start, DateTime finish, bool force)
{
using (var ctx = new CurrencyContext()) {
DateTime checkStart = start.Date; //make sure requested date is not later than the latest downloaded because
//it is assumed that everything is updated until the latest date available
if (!force) //if we should only update what is necessary
{
checkStart = DateTime.Parse((from hc in ctx.HistoricalCurrency select hc.date).ToList().LastOrDefault()).AddDays(1); //latest update to the database
}
if (start < checkStart)
{
start = checkStart; //make sure everything is updated until latest available
}
Task <string>[] taskList = new Task <string> [(finish - start).Days + 1];
for (int i = 0; start <= finish; i++, start = start.AddDays(1)) //each day in date range
{
string parsedDate = ParseDate(start);
taskList[i] = Task <string> .Factory.StartNew(() => {//real concurrency!
string jsonData = "";
using (var wc = new WebClient()) {
for (int j = 0; j < 4; j++) //try 4 times
{
try { //we calculate url here so we get a new key each time
string url = @"http://apilayer.net/api/historical?access_key=" + GetKey() + "&date=" +
parsedDate + @"¤cies=EUR,GBP,ILS,BTC,JMD&format=1";
jsonData = wc.DownloadString(url);
if (jsonData.Contains("success\":true"))//CurrencyClayer's way of saying good
{
break;
}
}
catch (Exception e) {
Console.WriteLine(e.Message);
}
}
}
return(jsonData);
});
}
Task.WaitAll(taskList);//wait for all of the threads to finish
foreach (var item in taskList)
{
if (item.Result == "")
{
continue; //something went wrong
}
HistoricalCurrencyEntity entity =
JsonConvert.DeserializeObject <HistoricalCurrencyEntity>(item.Result);
if (!ctx.HistoricalCurrency.Any(e => e.date == entity.date)) //only add if it's not saved already
{
ctx.HistoricalCurrency.Add(entity);
}
}
await ctx.SaveChangesAsync();
}
}
