public static async Task <StopDistanceResult> GetNearestStop(GeoCoordinate center)
{
await nearestStopLock.WaitAsync();
if (nearestStopTime < DateTime.Now - TimeSpan.FromMinutes(1))
{
LastNearestStop = await calculateNearestStop(center);
nearestStopTime = DateTime.Now;
}
nearestStopLock.Release();
return(LastNearestStop);
}
public static async Task <IEnumerable <StopDistanceResult> > WalkDistances(Stop sourceStop, IEnumerable <Stop> targetStops)
{
var unknownStops = new List <Stop>();
var result = new List <StopDistanceResult>();
double walkingSpeed = WalkingSpeed();
var sourceTransfers = sourceStop.Transfers.ToArray();
foreach (Stop currentStop in targetStops)
{
if (currentStop.Coordinate == sourceStop.Coordinate)
{
result.Add(new StopDistanceResult
{
Stop = currentStop,
EstimatedDuration = TimeSpan.Zero,
DistanceInMeters = 0.0
});
}
else
{
Transfer matchingTransfer = sourceTransfers.FirstOrDefault(t => t.Target.Coordinate == currentStop.Coordinate);
if (matchingTransfer != null)
{
var entry = new StopDistanceResult
{
Stop = currentStop,
EstimatedDuration = TimeSpan.FromSeconds(matchingTransfer.Distance / walkingSpeed),
DistanceInMeters = (double)matchingTransfer.Distance
};
result.Add(entry);
AddToCache(sourceStop.Coordinate, currentStop.Coordinate, new Direction {
EstimatedDuration = entry.EstimatedDuration, DistanceInMeters = entry.DistanceInMeters
});
}
else
{
unknownStops.Add(currentStop);
}
}
}
result.AddRange(await WalkDistances(sourceStop.Coordinate, unknownStops));
return(result);
}
private static async Task <StopDistanceResult> calculateNearestStop(GeoCoordinate center)
{
StopDistanceResult result = null;
if (center != null)
{
var stops = TransitBaseComponent.Current.Stops
.Where(s => s.StraightLineDistanceTo(center.Latitude, center.Longitude) < 2000)
.Select(s => new { Stop = s, Distance = s.StraightLineDistanceTo(center.Latitude, center.Longitude) })
.OrderBy(x => x.Distance)
.ToList();
StopDistanceResult prevResult = new StopDistanceResult {
DistanceInMeters = double.MaxValue
};
while (stops.Count > 0)
{
var minDistance = stops.First().Distance;
var nextStops = stops.TakeWhile(s => s.Distance < minDistance + 200.0).ToList();
stops.RemoveRange(0, nextStops.Count);
var results = await WalkDistances(center, nextStops.Select(x => x.Stop));
var minResult = results.Concat(new StopDistanceResult[] { prevResult }).MinBy(r => r.DistanceInMeters);
if (stops.Count == 0 || minResult.DistanceInMeters <= stops.First().Distance)
{
result = minResult;
break;
}
else
{
prevResult = minResult;
}
}
}
return(result);
}