public PathfinderNode(T location, int cost, PathfinderNode <T> previousNode, int minRemaining = 0)
{
Location = location;
Cost = cost;
PreviousNode = previousNode;
MinimumCostRemaining = minRemaining;
}
public static IEnumerable <PathfinderNode <T> > CreateDijkstraMap <T>(T start, T end, ConnectivityGraph <T> graph)
{
// pathfind!
// step 1: empty priority queue with cost to reach each node
var queue = new List <PathfinderNode <T> >();
// step 2: empty set of previously visited nodes, along with costs and previous-node references
var visited = new SafeDictionary <T, PathfinderNode <T> >();
// step 3: add start node and cost
queue.Add(new PathfinderNode <T>(start, 0, null));
// step 4: quit if there are no nodes (all paths exhausted without finding goal)
bool success = false;
while (queue.Any() && !success)
{
// step 5: take lowest cost node out of queue
// also prefer straight line movement to diagonal
var minCost = queue.Min(n => n.Cost);
var node = queue.Where(n => n.Cost == minCost).First();
queue.Remove(node);
// step 6: if node is the goal, stop - success!
if (node.Location.Equals(end))
{
success = true;
}
// step 7: check possible moves
var moves = graph.GetExits(node.Location);
// step 7a: remove blocked points (aka calculate cost)
// nothing to do here
// step 7b: update priority queue
foreach (var move in moves)
{
if (!visited.ContainsKey(move))
{
// didn't visit yet
var newnode = new PathfinderNode <T>(move, node.Cost + 1, node);
queue.Add(newnode);
visited.Add(move, newnode);
}
else
{
// already visited - but is it by a longer path?
var items = queue.Where(n => n.Location.Equals(move) && n.Cost > node.Cost + 1);
if (items.Any())
{
foreach (var old in items.ToArray())
{
queue.Remove(old);
}
var newnode = new PathfinderNode <T>(move, node.Cost + 1, node);
queue.Add(newnode);
visited.Add(move, newnode);
}
}
}
}
return(visited.Values);
}
public static IDictionary <PathfinderNode <Sector>, ISet <PathfinderNode <Sector> > > CreateDijkstraMap(IMobileSpaceObject me, Sector start, Sector end, bool avoidEnemies, bool avoidDamagingSectors)
{
// step 2a (do it here so we can return map if start or end is null): empty map with nodes, their costs, and previous-node references
var map = new Dictionary <PathfinderNode <Sector>, ISet <PathfinderNode <Sector> > >();
// if we are nowhere or we're going nowhere, that's impossible!
if (start == null || end == null)
{
return(map);
}
var startSys = start.StarSystem;
// pathfind!
// step 1: empty priority queue with cost to reach each node
var queue = new Dictionary <int, ISet <PathfinderNode <Sector> > >();
// step 2b: empty set of previously visited nodes
var visited = new HashSet <Sector>();
// step 3: add start node and cost
queue.Add(0, new HashSet <PathfinderNode <Sector> >());
queue[0].Add(new PathfinderNode <Sector>(start, 0, null, EstimateDistance(start, end, me == null ? null : me.Owner)));
// step 4: quit if there are no nodes (all paths exhausted without finding goal)
bool success = false;
while (queue.SelectMany(kvp => kvp.Value).Any() && !success)
{
// step 5: take lowest cost node out of queue
// TODO - also prefer straight line movement to diagonal?
var minCost = queue.Keys.Min();
while (!queue[minCost].Any())
{
queue.Remove(minCost);
minCost = queue.Keys.Min();
}
var node = queue[minCost].First();
queue[minCost].Remove(node);
map.Add(node, new HashSet <PathfinderNode <Sector> >());
// step 6: if node is the goal, stop after it's done - success!
if (node.Location == end)
{
success = true;
}
// step 7: check possible moves
var moves = GetPossibleMoves(node.Location, me == null ? true : me.CanWarp, me == null ? null : me.Owner);
// step 7a: remove blocked points (aka calculate cost)
if (avoidEnemies)
{
// avoid enemies, except at the destination
moves = moves.Where(m => m == null || m == end || !m.SpaceObjects.Where(sobj => sobj.CheckVisibility(me.Owner) >= Visibility.Visible || sobj.FindMemory(me.Owner)?.Sector == m).OfType <ICombatant>().Any(sobj => sobj.IsHostileTo(me == null ? null : me.Owner)));
}
if (avoidDamagingSectors)
{
// don't avoid the destination, even if it is a damaging sector
moves = moves.Where(m => m == end || m == null || !m.SpaceObjects.Where(sobj => sobj.CheckVisibility(me.Owner) >= Visibility.Visible || sobj.FindMemory(me.Owner)?.Sector == m).Any(sobj => sobj.GetAbilityValue("Sector - Damage").ToInt() > 0));
}
// step 7b: update priority queue
Action <Sector> f = move =>
{
// When we lock the queue, we do so because it is being checked and modified by other threads,
// and we don't want them stepping on each other's toes.
// e.g. thread 1 is checking for the existence of an item in the queue
// while thread 2 is busy adding that same item!
if (!visited.Contains(move))
{
// didn't visit yet
var newnode = new PathfinderNode <Sector>(move, node.Cost + 1, node, EstimateDistance(move, end, me == null ? null : me.Owner));
lock (queue)
{
if (!queue.ContainsKey(newnode.Cost))
{
queue.Add(newnode.Cost, new HashSet <PathfinderNode <Sector> >());
}
queue[newnode.Cost].Add(newnode);
}
if (!map.ContainsKey(node)) // don't need to lock map, we're only adding a node which should only get added once per run
{
map.Add(node, new HashSet <PathfinderNode <Sector> >());
}
map[node].Add(newnode);
visited.Add(move);
}
else
{
// already visited - but is it by a longer path?
var moreCost = queue.Where(kvp => kvp.Key > node.Cost + 1).SelectMany(kvp => kvp.Value);
var items = moreCost.Where(n => n.Location == move && n.Cost > node.Cost + 1);
if (items.Any())
{
PathfinderNode <Sector> newnode;
foreach (var old in items.ToArray())
{
lock (queue[old.Cost]) queue[old.Cost].Remove(old);
map.Remove(old);
}
newnode = new PathfinderNode <Sector>(move, node.Cost + 1, node);
lock (queue[newnode.Cost]) queue[newnode.Cost].Add(newnode);
if (!map.ContainsKey(node)) // don't need to lock map, we're only adding a node which should only get added once per run
{
map.Add(node, new HashSet <PathfinderNode <Sector> >());
}
map[node].Add(newnode);
}
}
};
moves.SafeForeach(f);
}
return(map);
}
