public ITradeResult ExecuteTrade(string symbol, uint volumeRequested, ILockManager lockManager, IQuoteStorageService <T> quoteStorageService) { var response = new TradeResult { Id = Guid.NewGuid(), Symbol = symbol, VolumeRequested = volumeRequested }; double weightedSum = 0; var originalQuotes = new List <T>(); // Intent write is essentially a single writer/many readers lock mode - only one thread can enter intent-write at a time, but readers // are not blocked at all (which is the functionality we're looking for here). Note that we never actually enter a write-lock mode, which // would allow a single writer and nothing else to occur... lockManager.EnterIntentWrite(symbol); try { var quotes = quoteStorageService.GetQuotesByPrice(symbol); if (quotes == null || quotes.Count == 0) { return(response); } foreach (var quote in quotes) { // Candidate quote, has to pass validation predicates to be considered if (!_quoteValidationPredicates.All(p => p(quote))) { continue; } var volumeTaken = quote.AvailableVolume >= (response.VolumeRequested - response.VolumeExecuted) ? (response.VolumeRequested - response.VolumeExecuted) : quote.AvailableVolume; originalQuotes.Add((T)quote.Clone()); quote.AvailableVolume -= volumeTaken; // Mostly here to mimic what would be needed if a non-reference based storage service were to be used... quoteStorageService.Update(quote); weightedSum += volumeTaken * quote.Price; response.VolumeExecuted += volumeTaken; if (response.VolumeExecuted >= response.VolumeRequested) { break; } } } catch when(RevertQuotesAndReturnFalse(originalQuotes, quoteStorageService)) { // Unreachable throw - the above when filter will revert any modified quotes and return false, just rethrowing like an unhandled exception // without unwinding the call stack throw; } finally { lockManager.ExitIntentWrite(symbol); } if (response.VolumeExecuted > 0) { response.VolumeWeightedAveragePrice = weightedSum / response.VolumeExecuted; } return(response); }
public IList <T> GetQuotesByPrice(string symbol) => _quoteStorageService.GetQuotesByPrice(symbol);