/// <summary>
/// Randomly alter a RoadNetwork to Produce a slightly different RoadNetwork
/// </summary>
/// <param name="source">The RoadNetwork to mutate</param>
/// <returns>The mutated RoadNetwork</returns>
public static RoadNetwork Mutate(RoadNetwork source)
{
Map map = source.Map;
int mapWidth = map.Width;
int mapHeight = map.Height;
int maxXChange = 1 + mapWidth / 10;
int maxYChange = 1 + mapHeight / 10;
source.ClearCopies();
source.SetVisited(false);
source.SetBroken(true);
RoadNetwork destination = new RoadNetwork(map);
int endVertexIndex = -1;
LinkedList<Vertex> vertexStack = new LinkedList<Vertex>();
source.Start.Visited = true;
vertexStack.AddFirst(source.Start);
while (vertexStack.Count > 0)
{
Vertex vertex = vertexStack.First();
vertexStack.RemoveFirst();
List<Vertex> nextVertices = new List<Vertex>();
for (int i = 0; i < vertex.EdgeCount; i++)
{
Edge edge = vertex.GetEdge(i);
Vertex nextVertex = edge.End;
if (!nextVertex.Visited)
{
edge.Broken = false;
nextVertex.Visited = true;
nextVertices.Add(nextVertex);
}
}
//If this vertex is a leaf of the tree and not the end vertex it has a 25% chance of
//begin removed.
if (nextVertices.Count > 0 || vertex == source.End || random.Next(4) > 0)
{
if (vertex == source.End)
{
endVertexIndex = destination.VertexCount;
}
if (vertex == source.Start || vertex == source.End || random.Next(10) > 0)
{
destination.CopyVertex(vertex);
}
else
{
int x = vertex.Coordinates.X + random.Next(2 * maxXChange+1) - maxXChange;
int y = vertex.Coordinates.Y + random.Next(2 * maxYChange + 1) - maxYChange;
x = Math.Max(0, Math.Min(x, map.Width - 1));
y = Math.Max(0, Math.Min(y, map.Height - 1));
vertex.Copy = destination.AddVertex(x, y);
}
}
//Shuffle Vertices
for (int n = nextVertices.Count - 1; n > 0; n--)
{
int m = random.Next(n + 1);
Vertex temp = nextVertices[m];
nextVertices[m] = nextVertices[n];
nextVertices[n] = temp;
}
//Push vertices onto stack in shiffled order.
foreach (Vertex nextVertex in nextVertices)
{
vertexStack.AddFirst(nextVertex);
}
}
for (int i = 0; i < source.EdgeCount; i++)
{
Edge edge = source.GetEdge(i);
if ((!edge.Broken || random.Next(4) > 0) && edge.Start.Copy != null && edge.End.Copy != null)
{
destination.CopyEdge(edge);
}
}
int verticesToAdd = random.Next(10);
for (int i = 0; i < verticesToAdd; i++)
{
Vertex startVertex = destination.GetVertex(random.Next(destination.VertexCount));
Vertex endVertex = destination.AddVertex(random.Next(mapWidth), random.Next(mapHeight));
destination.AddEdge(startVertex, endVertex);
}
int edgesToAdd = random.Next(destination.VertexCount/2);
for (int i = 0; i < edgesToAdd; i++)
{
Vertex startVertex = destination.GetVertex(random.Next(destination.VertexCount));
Vertex endVertex = destination.GetVertex(random.Next(destination.VertexCount));
if (startVertex != endVertex)
{
destination.AddEdge(startVertex, endVertex);
}
}
if (endVertexIndex == -1)
{
throw new Exception("End vertex not found.");
}
else
{
destination.SetEnd(endVertexIndex);
}
return destination;
}