[Add] SearchStep(void) method now implemented.

-- Yes, there is some code I have held back for now..

src/libUnuk/Engine/Pathfinding.cpp

@@ -2,7 +2,7 @@
 
 template<class UserState>
 AStarSearch<UserState>::AStarSearch(void) :
-		_state(SEARCH_STATE_NOT_INITIALISED),
+		_state(SEARCH_STATE_NOT_INITIALIZED),
 		_currentSolutionNode(NULL),
 		_allocateNodeCount(0),
 		_cancelRequest(false) {}
@@ -21,15 +21,15 @@ void AStarSearch<UserState>::SetStartAndGoalStates(UserState& start, UserState&
 
 	assert((_start != NULL && _goal != NULL));
 
-	_start->_UserState = _start;
-	_goal->_UserState  = _goal;
+	_start->_userState = _start;
+	_goal->_userState  = _goal;
 
 	_state = SEARCH_STATE_SEARCHING;
 
-	// Initialise the AStar specific parts of the start node.
+	// Initialize the AStar specific parts of the start node.
 	// You only need to fill out the state information.
 	_start->g = 0;
-	_start->h = _start->_UserState.GoalDistanceEstimate(_goal->_UserState);
+	_start->h = _start->_userState.GoalDistanceEstimate(_goal->_userState);
 	_start->f = _start->g + _start->h;
 	_start->parent = 0;
 
@@ -39,13 +39,155 @@ void AStarSearch<UserState>::SetStartAndGoalStates(UserState& start, UserState&
 	// Sort back element into the heap.
 	push_heap(_openList.begin(), _openList.end(), HeapCompare_f());
 
-	// Initialise counter for the search steps.
+	// Initialize counter for the search steps.
 	_steps = 0;
 }
 
 template<class UserState>
 unsigned int  AStarSearch<UserState>::SearchStep(void) {
+	// Break if the search has not been initialized.
+	assert((_state > SEARCH_STATE_NOT_INITIALIZED) && ( _state < SEARCH_STATE_INVALID));
 
+	// Ensure it is safe to do a seach step once the seach has succeeded.
+	if((_state == SEARCH_STATE_SUCCEEDED) || (_state == SEARCH_STATE_FAILED)) { return false; }
+
+	if(_openList.empty() || _cancelRequest) {
+		// Then there is nothing left to search, so fail.
+		FreeAllNodes();
+		_state = SEARCH_STATE_FAILED;
+		return _state;
+	}
+
+	_steps++;
+
+	// Pop the best node. -- The one with the lowest f.
+	Node* n = _openList.front(); // Get pointer to the node.
+	pop_heap(_openList.begin(), _openList.end(), HeapCompare_f());
+	_openList.pop_back();
+
+	// Check for the goal, once we pop that, we are done.
+	if(n->_userState.IsGoal(_goal->_userState)) {
+		// Copy the parent pointer of n, as we will use the passed in goal node.
+		_goal->parent = n->parent;
+
+		// If the goal was passed in at the start..
+		if(false == n->_userState.IsSameState(_start->_userState)) {
+			FreeNode(n);
+
+			// Set the child pointers in each node, apart from goal, as it has no child.
+			Node* nodeChild = _goal;
+			Node* nodeParent = _goal->parent;
+
+			while(nodeChild != _start) {
+				// Start is always the first node by definition.
+				nodeParent->child = nodeChild;
+
+				nodeChild = nodeParent;
+				nodeParent = nodeParent->parent;
+			}
+		}
+		// Delete nodes that are not needed for the solution.
+		FreeUnusedNodes();
+		_state = SEARCH_STATE_SUCCEEDED;
+
+		return _state;
+	} else {
+		// Not goal.
+
+		/*
+		 * Generate the successors of this node.
+		 * The user helps us to do this, and we keep
+		 * the new nodes in _successors.
+		 */
+		_successors.clear(); // empty the vector of successor nodes to n.
+
+		// The user provides this functions and uses AddSuccessor to add each
+		// successor of node 'n' to _successors.
+		bool ret = n->_userState.GetSuccessors(this, n->parent ? &n->parent->_userState : NULL);
+
+		if(!ret) {
+			typename vector<Node*>::iterator successor;
+
+			// Free the nodes that may have previously been added.
+			for(successor = _successors.begin(); successor != _successors.end(); successor++) {
+				FreeNode((*successor));
+			}
+			// Empty vector of successor nodes nodes to n.
+			_successors.clear();
+
+			// Free up everything else we allocated along the way.
+			FreeAllNodes();
+
+			_state = SEARCH_STATE_OUT_OF_MEMORY;
+			return _state;
+		}
+		// Now handle each successor to the current node..
+		for(typename vector<Node*>::iterator successor = _successors.begin(); successor != _successors.end(); successor++) {
+			// The g value for this successor.
+			float newg = n->g + n->_userState.GetCost((*successor)->_userState);
+
+			/*
+			 * We need to see whether the node is on the open or closed
+			 * list. If it is, but the node that is already on them is better
+			 * (lower g) then we can forget about this successor.
+			 *
+			 * First linear search of open list to find node.
+			 */
+			typename vector<Node*>::iterator openlist_result;
+			for(openlist_result = _openList.begin(); openlist_result != _openList.end(); openlist_result++) {
+				if((*openlist_result)->_userState.IsSameState((*successor)->_userState)) {
+					break;
+				}
+			}
+			if(openlist_result != _openList.end()) {
+				// We found this state open.
+				if((*openlist_result)->g <= newg) {
+					FreeNode((*successor));
+					// The one on the open list is cheaper than this one.
+					continue;
+				}
+			}
+			typename vector<Node*>::iterator closedlist_result;
+			for(closedlist_result = _closedList.begin(); closedlist_result != _closedList.end(); closedlist_result++) {
+				if((*closedlist_result)->_userState.IsSameState((*successor)->_userState)) {
+					break;
+				}
+			}
+			if(closedlist_result != _closedList.end()) {
+				// We found this state closed.
+				if((*closedlist_result)->g <= newg) {
+					// The one on the closed list is cheaper than this one.
+					FreeNode((*successor));
+					continue;
+				}
+			}
+			// This node is the best node so fat with this particular state.
+			// So lets keep it, and set up its AStar specific data..
+			(*successor)->parent = n;
+			(*successor)->g = newg;
+			(*successor)->h = (*successor)->_userState.GoalDistanceEstimate(_goal->_userState);
+			(*successor)->f = (*successor)->g + (*successor)->h;
+
+			// Remove successor from closed if it was on it.
+			if(closedlist_result != _closedList.end()) {
+				// Remove it from the closed list.
+				FreeNode((*closedlist_result));
+				_closedList.erase(closedlist_result);
+
+				// Now remake the heap!!
+				make_heap(_openList.begin(), _openList.end(), HeapCompare_f());
+			}
+
+			// The heap is now unsorted.
+			_openList.push_back((*successor));
+
+			// Sort back elements into the heap.
+			push_heap(_openList.begin(), _openList.end(), HeapCompare_f());
+		}
+		// push n onto the closed list as it has now been expanded.
+		_closedList.push_back(n);
+	} // (Not goal, so expand)
+	return _state; // Succeeded bool should be false at this point.
 }
 
 template<class UserState>

src/libUnuk/Engine/Pathfinding.h

@@ -16,7 +16,7 @@ using namespace std;
 template<class UserState> class AStarSearch {
 public:
 	enum {
-		SEARCH_STATE_NOT_INITIALISED,
+		SEARCH_STATE_NOT_INITIALIZED,
 		SEARCH_STATE_SEARCHING,
 		SEARCH_STATE_SUCCEEDED,
 		SEARCH_STATE_FAILED,
@@ -39,7 +39,7 @@ public:
 
 		Node(void) : parent(0), child(0), g(0.0f), h(0.0f), f(0.0) {}
 
-		UserState _UserState;
+		UserState _userState;
 	};
 
 	// Compare the f values of the two nodes.