/// <summary>
/// The SimulationTimerEventHandler method is called when the simulation timer expires.
/// It updates the current state of the simulation.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void SimulationTimerEventHandler(object sender, EventArgs e)
{
try
{
if (SimulationState == SimulationState.Running)
{
MazeCell robotLocation = MazeCells.First(x => x.ContainsRobot); // Retrieve the current location of the robot.
int cellIndex = MazeCells.IndexOf(robotLocation); // Retrieve the index of the cell.
// Determine the indexes for the cell's neighbours.
int northNeighbourIndex = cellIndex - MazeWidthHeightCells;
int eastNeighbourIndex = cellIndex + 1;
int southNeighbourIndex = cellIndex + MazeWidthHeightCells;
int westNeighbourIndex = cellIndex - 1;
// Determine if the cell is on the north/east/south/west edge of the maze - certain neighbours must be ignored if the current cell is on an edge.
bool northEdge = cellIndex < MazeWidthHeightCells ? true : false;
bool eastEdge = ((cellIndex + 1) % MazeWidthHeightCells) == 0 ? true : false;
bool westEdge = (cellIndex % MazeWidthHeightCells) == 0 ? true : false;
bool southEdge = (cellIndex + MazeWidthHeightCells) >= (MazeWidthHeightCells * MazeWidthHeightCells) ? true : false;
// Retrieve the cell's neighbours.
MazeCell northCell = null;
MazeCell eastCell = null;
MazeCell southCell = null;
MazeCell westCell = null;
// North cell.
if (!northEdge && IsCellIndexValid(northNeighbourIndex))
{
northCell = MazeCells[northNeighbourIndex];
}
// East cell.
if (!eastEdge && IsCellIndexValid(eastNeighbourIndex))
{
eastCell = MazeCells[eastNeighbourIndex];
}
// South cell.
if (!southEdge && IsCellIndexValid(southNeighbourIndex))
{
southCell = MazeCells[southNeighbourIndex];
}
// West cell.
if (!westEdge && IsCellIndexValid(westNeighbourIndex))
{
westCell = MazeCells[westNeighbourIndex];
}
// Create a maze segment at the robot's current location.
MazeSegment mazeSegment = new MazeSegment(robotLocation, northCell, eastCell, southCell, westCell);
_robot.Move(mazeSegment); // Move the robot.
SimulationTime = SimulationTime.Add(TimeSpan.FromMilliseconds(Constants.DefaultStepIntervalMilliSeconds));
}
}
catch (Exception ex)
{
throw new Exception("Maze.SimulationTimerEventHandler(object sender, EventArgs e): " + ex.ToString());
}
}
/// <summary>
/// The RetrieveNeighbours method is called to retrieve the neighbour cells for the provided cell.
/// The neighbour cells are "offset" cells from the provided cell, in all 4 directions.
/// </summary>
/// <param name="cell"></param>
/// <returns></returns>
private List <MazeCell> RetrieveNeighbours(MazeCell cell, int offset = 1)
{
try
{
if (cell == null)
{
throw new Exception("cell can not be null.");
}
if (offset < 1)
{
throw new Exception("offset must be greater than or equal to 1.");
}
int cellIndex = MazeCells.IndexOf(cell); // Retrieve the index of the cell.
// Determine the indexes for the current cell's neighbours.
int northNeighbourIndex = cellIndex - offset * MazeWidthHeightCells;
int eastNeighbourIndex = cellIndex + offset;
int southNeighbourIndex = cellIndex + offset * MazeWidthHeightCells;
int westNeighbourIndex = cellIndex - offset;
// Determine if the current cell is on the north/east/south/west edge of the maze - certain neighbours must be ignored if the current cell is on an edge.
bool northEdge = cellIndex < MazeWidthHeightCells ? true : false;
bool eastEdge = ((cellIndex + 1) % MazeWidthHeightCells) == 0 ? true : false;
bool westEdge = (cellIndex % MazeWidthHeightCells) == 0 ? true : false;
bool southEdge = (cellIndex + MazeWidthHeightCells) >= (MazeWidthHeightCells * MazeWidthHeightCells) ? true : false;
// Retrieve the current cell's neighbours.
List <MazeCell> cellNeightbours = new List <MazeCell>();
// North cell.
if (!northEdge && IsCellIndexValid(northNeighbourIndex))
{
cellNeightbours.Add(MazeCells[northNeighbourIndex]);
}
// East cell.
if (!eastEdge && IsCellIndexValid(eastNeighbourIndex))
{
cellNeightbours.Add(MazeCells[eastNeighbourIndex]);
}
// South cell.
if (!southEdge && IsCellIndexValid(southNeighbourIndex))
{
cellNeightbours.Add(MazeCells[southNeighbourIndex]);
}
// West cell.
if (!westEdge && IsCellIndexValid(westNeighbourIndex))
{
cellNeightbours.Add(MazeCells[westNeighbourIndex]);
}
return(cellNeightbours);
}
catch (Exception ex)
{
throw new Exception("Maze.RetrieveNeighbours(MazeCell cell): " + ex.ToString());
}
}
/// <summary>
/// The ConnectCells method is called to connect two cells.
/// The wall cell that exists between the two cells becomes a passage.
/// </summary>
/// <param name="cellOne"></param>
/// <param name="cellTwo"></param>
private void ConnectCells(MazeCell cellOne, MazeCell cellTwo)
{
try
{
if (cellOne == null)
{
throw new Exception("cellOne can not be null.");
}
if (cellTwo == null)
{
throw new Exception("cellTwo can not be null.");
}
int indexOne = MazeCells.IndexOf(cellOne);
int indexTwo = MazeCells.IndexOf(cellTwo);
if (!IsCellIndexValid(indexOne))
{
throw new Exception("can not determine index for cellOne.");
}
if (!IsCellIndexValid(indexTwo))
{
throw new Exception("can not determine index for cellTwo.");
}
int offset = indexOne - indexTwo;
int wallIndex = indexOne - (offset / 2);
if (IsCellIndexValid(wallIndex))
{
MazeCell wallCell = MazeCells[wallIndex];
wallCell.CellType = CellType.Passage;
}
else
{
throw new Exception("unable to retireve cell between cellOne and cellTwo.");
}
}
catch (Exception ex)
{
throw new Exception("Maze.ConnectCells(MazeCell cellOne, MazeCell cellTwo): " + ex.ToString());
}
}
/// <summary>
/// The IsCellOnTheEdge method is called to determine if the provided cell is on the edge of the maze grid.
/// </summary>
/// <param name="cell"></param>
/// <returns></returns>
private bool IsCellOnTheEdge(MazeCell cell)
{
try
{
if (cell == null)
{
throw new Exception("cell can not be null.");
}
int cellIndex = MazeCells.IndexOf(cell); // Retrieve the index of the cell.
// Determine if the current cell is on the north/east/south/west edge of the maze.
bool northEdge = cellIndex < MazeWidthHeightCells ? true : false;
bool eastEdge = ((cellIndex + 1) % MazeWidthHeightCells) == 0 ? true : false;
bool westEdge = (cellIndex % MazeWidthHeightCells) == 0 ? true : false;
bool southEdge = (cellIndex + MazeWidthHeightCells) >= (MazeWidthHeightCells * MazeWidthHeightCells) ? true : false;
return(northEdge || eastEdge || westEdge || southEdge);
}
catch (Exception ex)
{
throw new Exception("Maze.IsCellOnTheEdge(MazeCell cell): " + ex.ToString());
}
}
/// <summary>
/// The GenerateNewMaze method is called to generate a new maze.
/// The Recursive Backtracker algorithm is used to generate the maze.
/// http://weblog.jamisbuck.org/2010/12/27/maze-generation-recursive-backtracking
/// https://en.wikipedia.org/wiki/Maze_generation_algorithm#Recursive_backtracker
/// </summary>
private async Task GenerateNewMaze(MazeCell currentCell)
{
try
{
await Task.Delay(Constants.MazeGenerationDelayMilliSeconds);
if (MazeCells.Any(x => x.CellState == CellState.Default) || _mazeGeneratorStack.Count > 0) // The maze contains unvisited cells or the stack is not empty.
{
int cellIndex = MazeCells.IndexOf(currentCell); // Retrieve the index of the current cell.
// Determine the indexes for the current cell's neighbours.
int northNeighbourIndex = cellIndex - Constants.MazeWidth;
int eastNeighbourIndex = cellIndex + 1;
int southNeighbourIndex = cellIndex + Constants.MazeHeight;
int westNeighbourIndex = cellIndex - 1;
// Determine if the current cell is on the north/east/south/west edge of the maze - certain neighbours must be ignored if the current cell is on an edge.
bool northEdge = cellIndex < Constants.MazeWidth ? true : false;
bool eastEdge = ((cellIndex + 1) % Constants.MazeWidth) == 0 ? true : false;
bool westEdge = (cellIndex % Constants.MazeWidth) == 0 ? true : false;
bool southEdge = (cellIndex + Constants.MazeWidth) >= (Constants.MazeWidth * Constants.MazeHeight) ? true : false;
// Retrieve the current cell's unvisited neighbours.
List <MazeCell> unvisitedNeighbours = new List <MazeCell>();
// North cell.
if (!northEdge && IsCellIndexValid(northNeighbourIndex) && MazeCells[northNeighbourIndex].CellState == CellState.Default)
{
unvisitedNeighbours.Add(MazeCells[northNeighbourIndex]);
}
// East cell.
if (!eastEdge && IsCellIndexValid(eastNeighbourIndex) && MazeCells[eastNeighbourIndex].CellState == CellState.Default)
{
unvisitedNeighbours.Add(MazeCells[eastNeighbourIndex]);
}
// South cell.
if (!southEdge && IsCellIndexValid(southNeighbourIndex) && MazeCells[southNeighbourIndex].CellState == CellState.Default)
{
unvisitedNeighbours.Add(MazeCells[southNeighbourIndex]);
}
// West cell.
if (!westEdge && IsCellIndexValid(westNeighbourIndex) && MazeCells[westNeighbourIndex].CellState == CellState.Default)
{
unvisitedNeighbours.Add(MazeCells[westNeighbourIndex]);
}
if (unvisitedNeighbours.Count > 0)
{
// The current cell has unvisited neighbours - select a random unvisited neighbour.
MazeCell selectedNeighbour = unvisitedNeighbours.ElementAt(_randomNumberGenerator.Next(unvisitedNeighbours.Count));
// Remove the wall between the current cell and the selected neighbour.
int selectedNeightbourIndex = MazeCells.IndexOf(selectedNeighbour);
if (selectedNeightbourIndex == northNeighbourIndex)
{
currentCell.RemoveWall(Direction.North);
selectedNeighbour.RemoveWall(Direction.South);
}
else if (selectedNeightbourIndex == eastNeighbourIndex)
{
currentCell.RemoveWall(Direction.East);
selectedNeighbour.RemoveWall(Direction.West);
}
else if (selectedNeightbourIndex == southNeighbourIndex)
{
currentCell.RemoveWall(Direction.South);
selectedNeighbour.RemoveWall(Direction.North);
}
else if (selectedNeightbourIndex == westNeighbourIndex)
{
currentCell.RemoveWall(Direction.West);
selectedNeighbour.RemoveWall(Direction.East);
}
// Put the current cell on the stack.
_mazeGeneratorStack.Push(currentCell);
// Set the selected neighbour as visited.
selectedNeighbour.CellState = CellState.Visited;
// Repeat the process with the selected neighbour as the new current cell.
await GenerateNewMaze(selectedNeighbour);
}
else
{
// Set the current cell to empty - it is now part of the maze.
currentCell.CellState = CellState.Empty;
// The current cell has no unvisited neighbours - pop a cell from the stack.
MazeCell previousCell = _mazeGeneratorStack.Pop();
previousCell.CellState = CellState.Empty; // Set the popped cell to empty - it is now part of the maze.
// Repeat the process with the popped cell as the new current cell.
await GenerateNewMaze(previousCell);
}
}
}
catch (Exception ex)
{
throw new Exception("Maze.GenerateNewMaze(MazeCell currentCell): " + ex.ToString());
}
}
