/// <summary>
/// Expands the current coverage area with all neighbors of the specified <see
/// cref="Graph"/> node that can be reached by the current <see cref="Agent"/>.</summary>
/// <param name="node">
/// The <see cref="Graph"/> node whose neighbors to examine.</param>
/// <param name="cost">
/// The total path cost to reach <paramref name="node"/>, measured as the sum of all <see
/// cref="IGraphAgent{T}.GetStepCost"/> results for each movement step between neighboring
/// nodes.</param>
/// <remarks><para>
/// <b>ExpandArea</b> recursively computes all possible movement paths for the current <see
/// cref="Agent"/>, adding all valid nodes in any affordable path to the <see cref="Nodes"/>
/// collection.
/// </para><para>
/// <b>ExpandArea</b> never revisits nodes that were already reached by a better path. The
/// source node specified in the <see cref="FindReachable"/> call is never added to the
/// <b>Nodes</b> collection.</para></remarks>
private void ExpandArea(T node, double cost)
{
// get valid neighbors of current node
IList <T> neighbors = Graph.GetNeighbors(node);
// recurse into all valid neighbors
for (int i = 0; i < neighbors.Count; i++)
{
T neighbor = neighbors[i];
double minCost;
// skip nodes with better path
_pathCosts.TryGetValue(neighbor, out minCost);
if (minCost != 0 && minCost <= cost)
{
continue;
}
// skip unreachable nodes
if (!_agent.CanMakeStep(node, neighbor))
{
continue;
}
// get cost for next movement step
double stepCost = _agent.GetStepCost(node, neighbor);
Debug.Assert(stepCost > 0);
// skip unaffordable nodes
if (!_agent.RelaxedRange && cost + stepCost > _maxCost)
{
continue;
}
// skip nodes with better path
if (minCost != 0 && minCost <= cost + stepCost)
{
continue;
}
// add newly reached neighbor if possible
if (minCost == 0 && _agent.CanOccupy(neighbor))
{
_nodes.Add(neighbor);
}
// store new minimum path cost
_pathCosts[neighbor] = cost + stepCost;
// visit neighbors if still affordable
if (cost + stepCost < _maxCost)
{
ExpandArea(neighbor, cost + stepCost);
}
}
}
/// <summary>
/// Adds all valid neighbors as children to the specified parent node.</summary>
/// <param name="parent">
/// The <see cref="PathNode{T}"/> whose neighbors to examine.</param>
private void CreateChildren(PathNode <T> parent)
{
T source = parent.Node;
// compute direct neighbors of parent node
IList <T> neighbors = Graph.GetNeighbors(source);
// link all children that can be reached
for (int i = 0; i < neighbors.Count; i++)
{
T neighbor = neighbors[i];
if (_agent.CanMakeStep(source, neighbor))
{
LinkChild(parent, neighbor);
}
}
}
