protected override async Task <Queue <TileRef> > Process()
{
// VERY similar to A*; main difference is with the neighbor tiles you look for jump nodes instead
if (_startNode == null ||
_endNode == null)
{
return(null);
}
// If we couldn't get a nearby node that's good enough
if (!PathfindingHelpers.TryEndNode(ref _endNode, _pathfindingArgs))
{
return(null);
}
var openTiles = new PriorityQueue <ValueTuple <float, PathfindingNode> >(new PathfindingComparer());
var gScores = new Dictionary <PathfindingNode, float>();
var cameFrom = new Dictionary <PathfindingNode, PathfindingNode>();
var closedTiles = new HashSet <PathfindingNode>();
#if DEBUG
var jumpNodes = new HashSet <PathfindingNode>();
#endif
PathfindingNode currentNode = null;
openTiles.Add((0, _startNode));
gScores[_startNode] = 0.0f;
var routeFound = false;
var count = 0;
while (openTiles.Count > 0)
{
count++;
// JPS probably getting a lot fewer nodes than A* is
if (count % 5 == 0 && count > 0)
{
await SuspendIfOutOfTime();
}
(_, currentNode) = openTiles.Take();
if (currentNode.Equals(_endNode))
{
routeFound = true;
break;
}
foreach (var node in currentNode.GetNeighbors())
{
var direction = PathfindingHelpers.RelativeDirection(node, currentNode);
var jumpNode = GetJumpPoint(currentNode, direction, _endNode);
if (jumpNode != null && !closedTiles.Contains(jumpNode))
{
closedTiles.Add(jumpNode);
#if DEBUG
jumpNodes.Add(jumpNode);
#endif
// GetJumpPoint should already check if we can traverse to the node
var tileCost = PathfindingHelpers.GetTileCost(_pathfindingArgs, currentNode, jumpNode);
if (tileCost == null)
{
throw new InvalidOperationException();
}
var gScore = gScores[currentNode] + tileCost.Value;
if (gScores.TryGetValue(jumpNode, out var nextValue) && gScore >= nextValue)
{
continue;
}
cameFrom[jumpNode] = currentNode;
gScores[jumpNode] = gScore;
// pFactor is tie-breaker where the fscore is otherwise equal.
// See http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html#breaking-ties
// There's other ways to do it but future consideration
var fScore = gScores[jumpNode] + PathfindingHelpers.OctileDistance(_endNode, jumpNode) * (1.0f + 1.0f / 1000.0f);
openTiles.Add((fScore, jumpNode));
}
}
}
if (!routeFound)
{
return(null);
}
var route = PathfindingHelpers.ReconstructJumpPath(cameFrom, currentNode);
if (route.Count == 1)
{
return(null);
}
#if DEBUG
// Need to get data into an easier format to send to the relevant clients
if (DebugRoute != null && route.Count > 0)
{
var debugJumpNodes = new HashSet <TileRef>(jumpNodes.Count);
foreach (var node in jumpNodes)
{
debugJumpNodes.Add(node.TileRef);
}
var debugRoute = new SharedAiDebug.JpsRouteDebug(
_pathfindingArgs.Uid,
route,
debugJumpNodes,
DebugTime);
DebugRoute.Invoke(debugRoute);
}
#endif
return(route);
}