private IEnumerable <IAction> GetPossibleActions(CaveSearch caveSearch, Cave cave)
{
if (cave.TargetLocation == caveSearch.Location)
{
return(new ChangeEquipment(Torch.Value).RepeatOnce());
}
return(MoveDirections
.Select(d => (destination: caveSearch.Location + d, direction: d))
.Where(m => m.destination.X >= 0 && m.destination.Y >= 0)
.Select(m =>
{
var regionAtDestination = cave[m.destination];
var regionAtCurrent = cave[caveSearch.Location];
if (caveSearch.Equipment.CanEnter(regionAtDestination))
{
return new MoveInDirection(m.direction) as IAction;
}
return Equipments
.Where(e => CanEnterRegionsWithEquipment(e, regionAtCurrent, regionAtDestination))
.Select(e => new ChangeEquipment(e))
.First();
}));
}
public CaveSearch FindQuickestPath(Cave cave)
{
var targetSearch = new CaveSearch(cave.TargetLocation, Torch.Value);
var initialSearch = new CaveSearch(cave.InitialLocation, Torch.Value);
var caveSearchesToExpand = initialSearch.RepeatOnce().ToHashSet(SearchEqualityComparerByEquipmentAndLocation.Value);
var reachedSearches = initialSearch.RepeatOnce().ToHashSet(SearchEqualityComparerByEquipmentAndLocation.Value);
var searchComparer = new CaveSearchComparerByCostAndRemainignPathLength(cave.TargetLocation);
CaveSearch currentSearchToTarget = null;
do
{
// TODO use sorted data structure
var searchToExpand = caveSearchesToExpand.MinBy(searchComparer);
var expandedSearches = ExpandCaveSearch(searchToExpand, cave)
.Where(s => !reachedSearches.TryGetValue(s, out var other) || s.Cost < other.Cost);
caveSearchesToExpand.Remove(searchToExpand);
foreach (var expandedSearch in expandedSearches)
{
caveSearchesToExpand.AddOrUpdate(expandedSearch, (@new, old) => @new.Cost < old.Cost);
reachedSearches.AddOrUpdate(expandedSearch, (@new, old) => @new.Cost < old.Cost);
}
reachedSearches.TryGetValue(targetSearch, out currentSearchToTarget);
} while (currentSearchToTarget == null);
return(currentSearchToTarget);
}
private IEnumerable <CaveSearch> ExpandCaveSearch(CaveSearch caveSearchToExpand, Cave cave)
{
return(GetPossibleActions(caveSearchToExpand, cave)
.Select(a => a.ApplyAction(caveSearchToExpand)));
}
