//This method is supposed to provide any character with coordinates to the next step
//The method is based on Breath First Search method
//In short: it puts a node into the queue and starts a loop. It then dequeues a node from the queue, check it's neighbours and puts it into the queue. Then it marks the node as visited, to ignore it in the future.
//The node that followed the node is added to list of previous nodes. Each node on the grid has its entry on that list.
//In following loop iterations it then dequeues subsequent nodes and repeats the steps.
//Once node that's supposed to be the end of the path is reached, the loop is stopped.
//Then, based on the previous list, the path is recreated, from the end
//Last node of the path is then provided back to the asking character.
public static GridField GetNextStep(GridField startField, GridField targetField, GridScript grid)
{
#region properties
Queue <GridField> queue = new Queue <GridField>(); //The queue that's the base of the first part of the method.
List <GridField> visited = new List <GridField>(); //List of nodes that were already handled.
List <GridField> previous = new List <GridField>(); //List in which a node prior for each node can be found. For example node previous to node "1,0" can be found in this list's index 10.
List <GridField> path = new List <GridField>(); //This is the path to the final node. Since it's always writen backwards, ending node is already added to it. Subsequent nodes are separated with a ;. It's important that after split(), last element will be empty, so the actual first step is 2nd to last.
GridScript gameGrid = grid; //Grid is necessary to calculate surrounding nodes and to get field information.
float stime = Time.realtimeSinceStartup;
queue.Enqueue(startField); //Enqueueing the 1st node - start - to kickstart the loop.
visited.Add(startField); //s node is immediately marked as visited.
#endregion
//This loop adds initially empty strings to 'previous' list, for each node on the grid.
#region fill 'previous' list with empty strings
for (int i = 0; i < (gameGrid.rows * gameGrid.columns); i++)
{
previous.Add(null);
}
#endregion
//This loop is ultimately responssible for filling the 'previous' list with proper data, up to the end node.
#region 1st loop filling in previous list
int loop1c = 0; //This is just a safety check. If loop takes too many iterations, we break out of it, based on this value.
while (queue.Count > 0)
{
loop1c++;
bool foundEnd = false; //This is set to true when found neighbour turns out to be the ending node.
GridField field = queue.Dequeue(); //Dequeueing node from queue. Initially it's the 's' node.
List <string> nodesNeighbours = GetSurroundingNodes(field, gameGrid); //Getting surrounding nodes for currently processed node.
foreach (string z in nodesNeighbours) //Loop within a loop could be dangerous. Luckily, it's 4 iterations at most, in theory.
{
if (z == targetField.stringRepresentation) //Handling case in which found neighbour turns out to bbe the ending node
{
string[] split = z.Split(','); //Temprorary solution since node handling is a mix of processing a string and two ints. To be changed to a unified format.
int x = int.Parse(split[0]); int y = int.Parse(split[1]);
previous[int.Parse(x.ToString() + y.ToString())] = field; //Replacing empty string in 'previous' for the found NEIGHBOUR list with currently handled (dequeued) node.
foundEnd = true; //Finding the ending node ends the loop.
break;
}
if (!grid.isFieldWalkable(z)) //If field is not walkable, we simply don't process it.
{
visited.Add(grid.GetFieldByCoord(z));
}
if (!visited.Contains(grid.GetFieldByCoord(z))) //This part of the loop only executes if found neighbour wasn't already processed.
{
queue.Enqueue(grid.GetFieldByCoord(z)); //Each found neighbour is put to the queue.
visited.Add(grid.GetFieldByCoord(z)); //It's also marked as visited, to not revisit it in the future.
string[] split = z.Split(',');
int x = int.Parse(split[0]); int y = int.Parse(split[1]); //Temprorary solution since node handling is a mix of processing a string and two ints. To be changed to a unified format.
previous[int.Parse(x.ToString() + y.ToString())] = field; //Replacing empty string in 'previous' for the found NEIGHBOUR list with currently handled (dequeued) node.
}
}
if (foundEnd) //If we've found the end node, not only foreach (inner) loop is ended, but the whole while (outer) loop as well.
{
break;
}
if (loop1c > 100) //If the loop has reached 100 iterations we crash.
{
throw new Exception("Breaking out of 1st loop of GetNextStep() method as it reached more than 100 iterations, suggesting an infinite loop.");
break; //Probably unnecessary.
}
}
#endregion
//This loop recreates the path based on 'previous' list and puts it to a string.
#region 2nd loop creating path string
GridField previousField = previous[int.Parse(targetField.intRepresentationX.ToString() + targetField.intRepresentationY.ToString())]; //previousNode represents the previous node of currently handled node. Since we have to start somewhere, we're initially assigning it to the end node.
int loop2c = 0; //As with the first loop, we also break out of this one if it reaches 100 iterations.
while (true)
{
loop2c++;
if (previous[int.Parse(previousField.intRepresentationX.ToString() + previousField.intRepresentationY.ToString())] != startField) //Unless the previousNode is the starting node, we process it.
{
path.Add(previous[int.Parse(previousField.intRepresentationX.ToString() + previousField.intRepresentationY.ToString())]); //We add the the node that's in the 'previous' list in the index reserved for previousNode, so we add previous node of previousNode. Previousception.
previousField = previous[int.Parse(previousField.intRepresentationX.ToString() + previousField.intRepresentationY.ToString())]; //Then we replace previousNode with previous node of current previousNode. Names are stupid.
}
else //If previous node turns out to be starting node, we break out of the loop.
{
break;
}
if (loop2c > 100) //If the loop has reached 100 iterations, we crash.
{
throw new Exception("Breaking out of 2nd loop of GetNextStep() method as it reached more than 100 iterations, suggesting an infinite loop.");
break;
}
}
#endregion
float etime = Time.realtimeSinceStartup;
Debug.Log("Calculating path fromm " + startField.stringRepresentation + " to " + targetField.stringRepresentation + " took " + ((etime - stime) * 1000).ToString() + "ms.");
return(path[path.Count - 1]); //
}
