public ExchangeRateResponse ExchangeRate(ExchangeRateRequest request)
{
lock (lockTheEntireGraph)
{
var response = new ExchangeRateResponse();
var spt = new BellmanFord <ExchangeCurrency>(graph, request.Source);
if (spt.HasNegativeCycle())
{
response.IsCycle = true;
var cycle = spt.NegativeCycle();
response.Cycle = EdgesToVertexes(cycle);
return(response); // TODO: cycle ==> arbitrage opportunity
}
if (spt.HasPathTo(request.Destination))
{
response.IsHasPath = true;
var path = spt.PathTo(request.Destination);
var vertexesOnPath = EdgesToVertexes(path);
double rate = 1;
foreach (var edge in path)
{
rate *= Math.Exp(-edge.Weight);
}
response.Source = request.Source;
response.Destination = request.Destination;
response.Rate = rate;
response.Path = vertexesOnPath;
return(response);
}
if (!spt.HasPathTo(request.Destination))
{
response.IsHasPath = false;
return(response);
}
throw new NotImplementedException();
}
}