/// <summary>
/// Finds, provided it exists, the intersection point with the specified <see cref="LineSegment"/>.
/// </summary>
///
/// <param name="other"><see cref="LineSegment"/> to find intersection with.</param>
///
/// <returns>Returns intersection point with the specified <see cref="LineSegment"/>, or <see langword="null"/>,
/// if this line does not intersect with the segment.</returns>
///
/// <remarks><para>If the line and segment do not intersect, the method returns <see langword="null"/>.
/// If the line and segment share multiple points, the method throws an <see cref="InvalidOperationException"/>.
/// </para></remarks>
///
/// <exception cref="InvalidOperationException">Thrown if <paramref name="other"/> is a portion
/// of this line.</exception>
///
public Point? GetIntersectionWith( LineSegment other )
{
return other.GetIntersectionWith( this );
}
/// <summary>
/// Finds, provided it exists, the intersection point with the specified <see cref="LineSegment"/>.
/// </summary>
///
/// <param name="other"><see cref="LineSegment"/> to find intersection with.</param>
///
/// <returns>Returns intersection point with the specified <see cref="LineSegment"/>, or <see langword="null"/>, if
/// the two segments do not intersect.</returns>
///
/// <remarks><para>If the two segments do not intersect, the method returns <see langword="null"/>. If the two
/// segments share multiple points, this throws an <see cref="InvalidOperationException"/>.
/// </para></remarks>
///
/// <exception cref="InvalidOperationException">Thrown if the segments overlap - if they have
/// multiple points in common.</exception>
///
public Point? GetIntersectionWith( LineSegment other )
{
Point? result = null;
if ( ( line.Slope == other.line.Slope ) || ( line.IsVertical && other.line.IsVertical ) )
{
if ( line.Intercept == other.line.Intercept )
{
// Collinear segments. Inspect and handle.
// Consider this segment AB and other as CD. (start/end in both cases)
// There are three cases:
// 0 shared points: C and D both project onto the same ray of AB
// 1 shared point: One of A or B equals one of C or D, and the other of C/D
// projects on the correct ray.
// Many shared points.
ProjectionLocation projC = LocateProjection( other.start ), projD = LocateProjection( other.end );
if ( ( projC != ProjectionLocation.SegmentAB ) && ( projC == projD ) )
{
// no shared points
result = null;
}
else if ( ( ( start == other.start ) && ( projD == ProjectionLocation.RayA ) ) ||
( ( start == other.end ) && ( projC == ProjectionLocation.RayA ) ) )
{
// shared start point
result = start;
}
else if ( ( ( end == other.start ) && ( projD == ProjectionLocation.RayB ) ) ||
( ( end == other.end ) && ( projC == ProjectionLocation.RayB ) ) )
{
// shared end point
result = end;
}
else
{
// overlapping
throw new InvalidOperationException( "Overlapping segments do not have a single intersection point." );
}
}
}
else
{
result = GetIntersectionWith( other.line );
if ( ( result.HasValue ) && ( other.LocateProjection( result.Value ) != ProjectionLocation.SegmentAB ) )
{
// the intersection is on the extended line of this segment
result = null;
}
}
return result;
}
/// <summary>
/// Finds, provided it exists, the intersection point with the specified <see cref="LineSegment"/>.
/// </summary>
///
/// <param name="other"><see cref="LineSegment"/> to find intersection with.</param>
///
/// <returns>Returns intersection point with the specified <see cref="LineSegment"/>, or <see langword="null"/>,
/// if this line does not intersect with the segment.</returns>
///
/// <remarks><para>If the line and segment do not intersect, the method returns <see langword="null"/>.
/// If the line and segment share multiple points, the method throws an <see cref="InvalidOperationException"/>.
/// </para></remarks>
///
/// <exception cref="InvalidOperationException">Thrown if <paramref name="other"/> is a portion
/// of this line.</exception>
///
public Point?GetIntersectionWith(LineSegment other)
{
return(other.GetIntersectionWith(this));
}
