/// <summary>
/// This function returns an object of the class <see cref="Route"/> if
/// a route exists bewteen the provided locations. Otherwise, NULL is returned.
/// </summary>
/// <returns>A <see cref="Route"/> An object describing the shortest path from the start to end location</returns>
/// <param name="startLoc">The start location in the desired route.</param>
/// <param name="endLoc">The destination location of the desired route.</param>
/// <para>
/// This function uses and A* search to find the shortest route between the two given locations
/// on the network.
/// </para>
protected Route CalculateRoute(Location startLoc, Location endLoc)
{
if (startLoc == null || endLoc == null)
{
return(null);
}
// Already at the location
Route retRoute;
if (startLoc.LocID == endLoc.LocID)
{
retRoute = new Route();
return(retRoute);
}
Location start;
Location goal;
netLocs.TryGetValue(startLoc.LocID, out start);
netLocs.TryGetValue(endLoc.LocID, out goal);
if (start == null || goal == null)
{
return(null);
}
// Make Lists for search
List <SearchNode> openList = new List <SearchNode>();
List <SearchNode> closedList = new List <SearchNode>();
// Place starting node in open list list
openList.Add(new SearchNode(start, null, 0, calculateDistance(start, goal)));
SearchNode curSearchNode;
SearchNode goalSearchNode = null;
while (true)
{
//Exit upon empty openList
if (openList.Count == 0)
{
break;
}
// Sort openList and choose lowest F
openList.Sort();
// Take lowest F in openList and move to closedList
curSearchNode = openList[0];
openList.RemoveAt(0);
closedList.Add(curSearchNode);
// Check for goal node
if (curSearchNode.Equals(goal))
{
goalSearchNode = curSearchNode;
break;
}
// Add connected nodes to open list if not already listed in closedList, update if on openList
foreach (Location location in curSearchNode.location)
{
bool found = false;
// Ignore node if on closed list
foreach (SearchNode searchNode in closedList)
{
if (searchNode.Equals(location))
{
found = true;
break;
}
}
if (found)
{
continue;
}
// Potentially update SearchNode if it is on the openList and the costToNode is less
foreach (SearchNode searchNode in openList)
{
if (searchNode.Equals(location))
{
// Compare costToNode, update parent if node has lower cost
float newCostToNode = curSearchNode.costToNode + calculateDistance(curSearchNode.location, location);
if (newCostToNode < searchNode.costToNode)
{
searchNode.parentSearchNode = curSearchNode;
searchNode.costToNode = newCostToNode;
}
found = true;
break;
}
}
if (found)
{
continue;
}
openList.Add(new SearchNode(location, curSearchNode, curSearchNode.costToNode + calculateDistance(curSearchNode.location, location), calculateDistance(location, goal)));
}
}
if (goalSearchNode == null)
{
return(null);
}
// Make a route if the final NodeWrap, a route from start to goal, was found
retRoute = new Route();
SearchNode parent = goalSearchNode;
// Create route from goal to start
while (parent != null)
{
retRoute.AddLocation(parent.location);
parent = parent.parentSearchNode;
}
// Reverse route becuase it was created from goal to start then lock it
retRoute.Reverse();
retRoute.Lock();
return(retRoute);
}
