/// <summary>
/// We first traverse to the root, then apply tasks from there to get them in the right order
/// such that the last task on the queue is the task of our leaf node that we started with.
/// </summary>
/// <param name="node"></param>
private void GeneratePlan(IContext ctx, GOAPNode node)
{
if (node != null && node.Task != null)
{
GeneratePlan(ctx, node.Parent);
node.Task.ApplyEffects(ctx);
Plan.Enqueue(node.Task);
}
}
private void FreeNode(IContext ctx, GOAPNode node)
{
var nextNode = node.Parent;
ctx.Factory.Free(ref node);
if (nextNode != null)
{
FreeNode(ctx, nextNode);
}
}
private GOAPNode GetCheapestLeaf(List <GOAPNode> leaves)
{
GOAPNode cheapestLeaf = null;
foreach (var leaf in leaves)
{
if (cheapestLeaf != null)
{
if (leaf.RunningCost < cheapestLeaf.RunningCost)
{
cheapestLeaf = leaf;
}
}
else
{
cheapestLeaf = leaf;
}
}
return(cheapestLeaf);
}
private bool TryBuildGraph(IContext ctx, GOAPNode parent, List <GOAPNode> leaves, List <ITask> openSubtasks)
{
var foundLeaf = false;
for (var taskIndex = 0; taskIndex < openSubtasks.Count; taskIndex++)
{
var task = openSubtasks[taskIndex];
if (task.IsValid(ctx) == false)
{
continue;
}
if (task is IGOAPTask goapTask)
{
// Due to branching permutations of state, and multiple possible solutions
// to the goal, where we want to end up with the shortest path, we need to
// reset the state stack for every task we operate on.
var oldStackDepth = ctx.GetWorldStateChangeDepth(ctx.Factory);
goapTask.ApplyEffects(ctx);
var node = ctx.Factory.Create <GOAPNode>();
{
node.Parent = parent;
node.RunningCost = parent.RunningCost + goapTask.Cost(ctx);
node.Task = goapTask;
}
if (ValidatesGoal(ctx))
{
leaves.Add(node);
foundLeaf = true;
}
else
{
var subset = GetSubset(ctx, task, openSubtasks);
if (TryBuildGraph(ctx, node, leaves, subset))
{
foundLeaf = true;
}
else
{
// If we failed to find a valid branch for this node,
// then it will no longer be referenced after this point.
// Otherwise its still used as a parent reference in the
// leaves list, and we can't return it to the factory yet.
ctx.Factory.Free(ref node);
}
ctx.Factory.FreeList(ref subset);
}
// Because of the branching permutations of state with GOAP,
// we must always reset the state stack back to the state it
// was in previous to the changes applied by this particular
// permutation.
ctx.TrimToStackDepth(oldStackDepth);
}
}
return(foundLeaf);
}
