/// <summary>
/// Calculates a path for the actor from multiple possible sources to target.
/// Returned path is *reversed* and given target to source.
/// The shortest path between a source and the target is returned.
/// </summary>
/// <remarks>
/// Searches that provide a multiple source cells are slower than those than provide only a single source cell,
/// as optimizations are possible for the single source case. Use searches from multiple source cells
/// sparingly.
/// </remarks>
public List <CPos> FindUnitPathToTargetCell(
Actor self, IEnumerable <CPos> sources, CPos target, BlockedByActor check,
Func <CPos, int> customCost = null,
Actor ignoreActor = null,
bool laneBias = true)
{
var sourcesList = sources.ToList();
if (sourcesList.Count == 0)
{
return(NoPath);
}
var locomotor = GetLocomotor(self);
// If the target cell is inaccessible, bail early.
var inaccessible =
!locomotor.CanMoveFreelyInto(self, target, check, ignoreActor) ||
(!(customCost is null) && customCost(target) == PathGraph.PathCostForInvalidPath);
if (inaccessible)
{
return(NoPath);
}
// When searching from only one source cell, some optimizations are possible.
if (sourcesList.Count == 1)
{
var source = sourcesList[0];
// For adjacent cells on the same layer, we can return the path without invoking a full search.
if (source.Layer == target.Layer && (source - target).LengthSquared < 3)
{
return new List <CPos>(2)
{
target, source
}
}
;
// With one starting point, we can use a bidirectional search.
using (var fromTarget = PathSearch.ToTargetCell(
world, locomotor, self, new[] { target }, source, check, ignoreActor: ignoreActor))
using (var fromSource = PathSearch.ToTargetCell(
world, locomotor, self, new[] { source }, target, check, ignoreActor: ignoreActor, inReverse: true))
return(PathSearch.FindBidiPath(fromTarget, fromSource));
}
// With multiple starting points, we can only use a unidirectional search.
using (var search = PathSearch.ToTargetCell(
world, locomotor, self, sourcesList, target, check, customCost, ignoreActor, laneBias))
return(search.FindPath());
}