/// <summary>
/// Return the distance from me to another face. Distances are computed
/// by the backend and stored by the UI
/// </summary>
/// <param name="otherFace">Other face</param>
/// <returns>Distance</returns>
public double GetDistanceToFace(Face otherFace)
{
if (DistanceVector.ContainsKey(otherFace))
{
return(DistanceVector[otherFace]);
}
return(_mainCanvas.OptionDialog.DefaultMaxDistance);
}
/// <summary>
/// Finds the shortest route to a target.
///
/// To start with can be in one of two states:
/// A: No route known
/// B: There is a route known
///
/// Can finish in one of four states
/// 1. There was no route originally and one has been found
/// 2. There is a new, shorter route along a different link
/// 3. The target can no longer be reached but used to be reachable
/// 4. The original route is still shortest but is now a different length
/// 5. The original route is no longer available but a new route was found
/// 6. The original route is still shortest and has not changed
/// 7. The target was not reachable before and is still not reachable
///
/// 1 = Update distance vector, broadcast update, trigger routing table changed event
/// 2 = Update distance vector, broadcast update, trigger routing table changed event
/// 3 = Update distance vector, broadcast update, trigger routing table changed event
/// 4 = Update distance vector, broadcast update, trigger routing table changed event
/// 5 = Update distance vector, broadcast update, trigger routing table changed event
/// 6 = No events triggered
/// 7 = No events triggered
/// </summary>
/// <param name="targetNode"></param>
/// <returns></returns>
private bool findShortestPath(IMNodeInternal targetNode, List <string> changes)
{
UUID target = targetNode.ID;
//oldDist == null indicates initial state A, otherwise initial state B.
Distance oldDist;
lock (distanceVector)
oldDist = distanceVector.ContainsKey(target) ? distanceVector[target].copy() : null;
IKeyTable <DistanceVector> tmpNeighbours = neighbourVectors.Copy();
IMLink link = null;
float dist = float.MaxValue;
if (oldDist != null && oldDist.Link.OtherEnd(ID).Equals(target) && Links.ContainsKey(target))
{
//If there was an old route and target is a neighbour and the link was the link between them use the weight of that link as the starting weight
link = Links[target];
dist = link.Weight;
}
else if (oldDist != null && tmpNeighbours.ContainsKey(oldDist.Hop.ID) && tmpNeighbours[oldDist.Hop.ID].ContainsKey(target) && tmpNeighbours[oldDist.Hop.ID][target].Dist > 0f)
{
//If there was an old route and it involved routing via a neighbour and that neighbour can still route then take the starting weight as the distance to the neighbour + the distance from the neighbour to the target
link = Links[oldDist.Hop.ID];
dist = tmpNeighbours[oldDist.Hop.ID][target].Dist + link.Weight;
}
//Check every neighbour to see if the weight of the link to that neighbour + the distance the neighbour can achieve to the target is shorter .
foreach (var neighbour in Neighbours)
{
var neighbourLink = Links[neighbour.ID];
var neighbourVector = tmpNeighbours.ContainsKey(neighbour.ID) && tmpNeighbours[neighbour.ID].ContainsKey(target) ? tmpNeighbours[neighbour.ID][target] : null;
var neighbourDist = neighbourVector != null ? neighbourLink.Weight + neighbourVector.Dist : float.MaxValue;
//Neighbour vector distance of 0 or less indicates poison reverse or a link to itself
//Also checks to see if the link at the other end is the neighbour and whether the weight of the link is less than the current distance
if ((neighbourVector != null && neighbourVector.Dist > 0 && neighbourDist < dist) ||
neighbour.Equals(targetNode) && neighbourLink.Weight < dist)
{
link = neighbourLink;
dist = neighbour.Equals(targetNode) ? link.Weight : neighbourDist;
}
}
if (link == null && oldDist == null)
{
//Case 5 + 6
return(false);
}
if (link != null && oldDist == null)
{
//1. There was no route originally and one has been found
UpdateRoutes(targetNode, link.OtherEnd(Node), link, dist);
changes.Add("Distance Vector added route to " + targetNode.Name + " via " + link.OtherEnd(Node).Name + " with distance " + Math.Round(dist, 2) + ".");
}
else if (link == null && oldDist != null)
{
//3. The target can no longer be reached but used to be reachable
lock (distanceVector) {
distanceVector.Remove(target);
RemoveRoute(DV.DV_NAME, target);
changes.Add("Distance Vector removed route to " + targetNode.Name + ". " + oldDist.Hop.Name + " is no longer a valid first hop and no other route was found.");
}
}
else if (oldDist != null && !link.Equals(oldDist.Link))
{
//2. There is a new, shorter route along a different link
UpdateRoutes(targetNode, link.OtherEnd(Node), link, dist);
changes.Add("Distance Vector changed route to " + targetNode.Name + " from " + oldDist.Hop.Name + " to " + link.OtherEnd(Node).Name + " with distance " + Math.Round(dist, 2) + ".");
}
else if (oldDist != null && link.Equals(oldDist.Link) && dist != oldDist.Dist)
{
//4. The original route is still shortest but is now a different length
UpdateRoutes(targetNode, link.OtherEnd(Node), link, dist);
changes.Add("Distance Vector changed weight of route to " + targetNode.Name + " from " + Math.Round(oldDist.Dist, 2) + " to " + Math.Round(dist, 2) + ".");
}
else
{
return(false);
}
return(true);
}