/// <summary>
/// Adds an intersection between two line segments.
/// </summary>
/// <param name="lineSegment1">The first line segment.</param>
/// <param name="lineSegment2">The second line segment.</param>
/// <remarks>
/// <para>Each of the two line segments is added to the other's set of intersecting line
/// segments and the number of intersections in the game level is increased by 1.</para>
/// </remarks>
private void AddIntersection(LineSegment lineSegment1, LineSegment lineSegment2)
{
_intersections[lineSegment1].Add(lineSegment2);
_intersections[lineSegment2].Add(lineSegment1);
IntersectionCount++;
lineSegment1.State = LineSegmentState.Intersected;
lineSegment2.State = LineSegmentState.Intersected;
}
/// <summary>
/// Removes an intersection between two line segments.
/// </summary>
/// <param name="lineSegment1">The first line segment.</param>
/// <param name="lineSegment2">The second line segment.</param>
/// <remarks>
/// <para>Each of the two line segments is removed from the other's set of intersecting
/// line segments and the number of intersections in the game level is decreased by 1.
/// </para>
/// </remarks>
private void RemoveIntersection(LineSegment lineSegment1, LineSegment lineSegment2)
{
HashSet<LineSegment> intersectingSegments1 = _intersections[lineSegment1];
HashSet<LineSegment> intersectingSegments2 = _intersections[lineSegment2];
intersectingSegments1.Remove(lineSegment2);
intersectingSegments2.Remove(lineSegment1);
IntersectionCount--;
lineSegment1.State = (intersectingSegments1.Count > 0
? LineSegmentState.Intersected
: LineSegmentState.Normal);
lineSegment2.State = (intersectingSegments2.Count > 0
? LineSegmentState.Intersected
: LineSegmentState.Normal);
}
/// <summary>
/// Connects the vertex to another vertex with a line segment and returns it.
/// </summary>
/// <param name="otherVertex">The vertex which should be connected to the current one.
/// </param>
/// <returns>The created line segment between the two vertices.</returns>
/// <exception cref="InvalidOperationException">
/// An attempt is made to connect the vertex to itself.
///
/// -or-
/// A line segment between the two vertices already exists.
/// </exception>
public LineSegment ConnectToVertex(Vertex otherVertex)
{
if (this == otherVertex)
throw new InvalidOperationException("A vertex cannot be connected to itself.");
if (_lineSegmentsMap.ContainsKey(otherVertex))
{
throw new InvalidOperationException(
"A line segment between the two vertices already exists.");
}
var lineSegment = new LineSegment(this, otherVertex);
_lineSegmentsMap[otherVertex] = lineSegment;
otherVertex._lineSegmentsMap[this] = lineSegment;
return lineSegment;
}