public ScanNode Scan(ScanContext context, IReadOnlyDictionary <Resource, double> initialPositions)
{
// Initialise our scan with a terminal node
ScanNode terminator = new ScanNode(new Task("terminator", context.desires, Empty(), Empty()), 0, Empty());
SortedSet <ScanNode> nodes = new SortedSet <ScanNode>(new ScanNode.ScanNodeComparer());
nodes.Add(terminator);
while (nodes.Count > 0)
{
ScanNode successor = nodes.Last();
nodes.Remove(successor);
if (successor.task.needs.Count == 0)
{
// This is it -- we found a worthy task
return(successor);
}
foreach (var needEntry in successor.task.needs)
{
if (needEntry.Value <= 0)
{
continue;
}
Resource successorNeed = needEntry.Key;
foreach (var task in context.tasks.Where(task => task.outcomes.ContainsKey(successorNeed)))
{
ScanNode candidate = new ScanNode(task, context.profitOfTask(task, successor) + successor.profit, successor.updatePositions(task.positions));
if (candidate.task.needs.Count == 0)
{
// finally, the candidate will also be considered with the cost to get back to the scanner's initial position
candidate.profit -= context.repositioningCost(initialPositions, candidate.positions);
}
nodes.Add(candidate);
}
}
}
return(null);
}
public double profitOfTask(Task task, ScanNode successor)
{
return(outcomeProfits(task.outcomes) - repositioningCost(successor.positions, task.positions));
}