namespace GeometriCS
{
    /// <summary>
    /// A segment of a line going through the R cubed space.
    /// </summary>
    public class LineSegment3d
    {
        /// <summary>
        /// Point at which the line segment starts.
        /// </summary>
        public Vector3d StartPoint {  get; set; }

        /// <summary>
        /// Point at which the line segment ends.
        /// </summary>
        public Vector3d EndPoint { get; set; }

        /// <summary>
        /// A constructor for a segment of a line going throught the R cubed space.
        /// </summary>
        /// <param name="startPoint">Start point of the line.</param>
        /// <param name="endPoint">End point of the line.</param>
        public LineSegment3d(Vector3d startPoint, Vector3d endPoint)
        {
            StartPoint = (Vector3d) startPoint.Clone();
            EndPoint = (Vector3d) endPoint.Clone();
        }

        /// <summary>
        /// String representation of the line segment.
        /// </summary>
        /// <returns>(stPt) -- (endPt)</returns>
        public override string ToString()
        {
            return $"({StartPoint} -- {EndPoint})";
        }

        /// <summary>
        /// Do the two objects represent the same line segment?
        /// </summary>
        /// <param name="obj">Object to compare.</param>
        /// <remarks>
        /// If this lines start point is equal to the other lines end point,
        /// and this lines end point is equal to the other lines start point, the lines will be considered equal.
        /// </remarks>
        /// <returns><c>true</c> if the lines have the same start and end points. Otherwise <c>false</c></returns>
        public override bool Equals(object? obj)
        {
            if (obj is LineSegment3d asLnSgmnt)
            {
                return this == asLnSgmnt;
            }
            else
            {
                return false;
            }
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(StartPoint, EndPoint);
        }

        /// <summary>
        /// Deep copy the line.
        /// </summary>
        /// <returns>Deep copy of the line.</returns>
        public object Clone()
        {
            return new LineSegment3d(StartPoint, EndPoint);
        }

        /// <summary>
        /// Are the line segments equal?
        /// </summary>
        /// <param name="a">First line segment.</param>
        /// <param name="b">Second line segment.</param>
        /// <remarks>
        /// If this lines start point is equal to the other lines end point,
        /// and this lines end point is equal to the other lines start point, the lines will be considered equal.
        /// </remarks>
        /// <returns><c>true</c> if the lines have the same start and end points. Otherwise <c>false</c></returns>
        public static bool operator ==(LineSegment3d a, LineSegment3d b)
        {
            return (a.StartPoint == b.StartPoint && a.EndPoint == b.EndPoint) ||
                   (a.StartPoint == b.EndPoint && a.EndPoint == b.StartPoint);
        }

        /// <summary>
        /// Are the line segments different?
        /// </summary>
        /// <param name="a">First line segment.</param>
        /// <param name="b">Second line segment.</param>
        /// <returns><c>true</c> If the line segments start or end points are different from the other ones. <c>false</c> If both are same, refer to <seealso cref="operator =="/> for details.</returns>
        public static bool operator !=(LineSegment3d a, LineSegment3d b)
        {
            return !(a == b);
        }
    }
}