namespace GeometriCS
{
    /// <summary>
    /// Intersection between two two-dimensional lines.
    /// </summary>
    public class IntersectionLine2ToLine2d
    {
        /// <summary>
        /// Possible statuses the intersection can be.
        /// </summary>
        public enum Statuses
        {
            /// <summary>
            /// Intersection is valid.
            /// </summary>
            SUCCESS,
            /// <summary>
            /// The two lines are parallel.
            /// </summary>
            PARALLEL,
            /// <summary>
            /// The two lines are colinear and intersect on their whole length.
            /// </summary>
            COLINEAR,
        }

        /// <summary>
        /// First of the intersecting lines.
        /// </summary>
        public Line2d Line1 { get; }

        /// <summary>
        /// The second intersecting line.
        /// </summary>
        public Line2d Line2 { get; }

        /// <summary>
        /// Status of the intersection.
        /// </summary>
        public Statuses Status { get; }

        /// <summary>
        /// The point of the intersection between the two lines.
        /// </summary>
        public Vector2d? Result { get; }

        /// <summary>
        /// Constructor for Line2d to Line2d intersection.
        /// </summary>
        /// <param name="line1">First of the intersecting lines.</param>
        /// <param name="line1">Second of the intersecting lines.</param>
        public IntersectionLine2ToLine2d(Line2d line1, Line2d line2)
        {
            // Set the intersector references
            Line1 = line1;
            Line2 = line2;

            // Check if lines are parallel
            // TODO: Check what happens if coeff_B == 0
            if(Utils.DoubleEquals(line1.Coeff_A / line1.Coeff_B, line2.Coeff_A / line2.Coeff_B))
            {
                // Null result
                Result = null;

                // Check if lines are coincidental
                if (Utils.DoubleEquals(line1.Coeff_A / line2.Coeff_A, line1.Coeff_B / line2.Coeff_B) && 
                    Utils.DoubleEquals(line1.Coeff_A / line2.Coeff_A, line1.Coeff_C / line2.Coeff_C))
                {
                    Status = Statuses.COLINEAR;
                }
                else
                {
                    Status = Statuses.PARALLEL;
                }

                return;
            }

            // Perform the intersection calculation
            double divisor = line1.Coeff_A * line2.Coeff_B - line2.Coeff_A * line1.Coeff_B;
            double x0 = (line1.Coeff_B * line2.Coeff_C - line2.Coeff_B * line1.Coeff_C) / divisor;
            double y0 = (line1.Coeff_C * line2.Coeff_A - line2.Coeff_C * line1.Coeff_A) / divisor;
            Result = new Vector2d(x0, y0);
            Status = Statuses.SUCCESS;
        }
    }
}