// Copyright (C) Stichting Deltares 2018. All rights reserved.
//
// This file is part of the Dam Engine.
//
// The Dam Engine is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// All names, logos, and references to "Deltares" are registered trademarks of
// Stichting Deltares and remain full property of Stichting Deltares at all times.
// All rights reserved.

using System;

namespace Deltares.DamEngine.Data.Geometry
{
    /// <summary>
    /// Geometry Line, connecting begin point to end point with a straight line.
    /// </summary>
    public class Line
    {
        private readonly Line<Point2D> line = new Line<Point2D>();

        /// <summary>
        /// Initializes a new instance of the <see cref="Line"/> class.
        /// </summary>
        public Line() : this(null, null) {}

        /// <summary>
        /// Initializes a new instance of the <see cref="Line"/> class.
        /// </summary>
        /// <param name="beginPoint">The begin point.</param>
        /// <param name="endPoint">The end point.</param>
        public Line(Point2D beginPoint, Point2D endPoint)
        {
            BeginPoint = beginPoint;
            EndPoint = endPoint;
        }

        /// <summary>
        /// Gets or sets the begin point.
        /// </summary>
        /// <value>
        /// The begin point.
        /// </value>
        public Point2D BeginPoint
        {
            get
            {
                return line.Start;
            }
            set
            {
                line.Start = value;
            }
        }

        /// <summary>
        /// Gets or sets the end point.
        /// </summary>
        /// <value>
        /// The end point.
        /// </value>
        public Point2D EndPoint
        {
            get
            {
                return line.End;
            }
            set
            {
                line.End = value;
            }
        }

        /// <summary>
        /// Creates the horizontal z line.
        /// </summary>
        /// <param name="x1">The x1.</param>
        /// <param name="x2">The x2.</param>
        /// <param name="z">The z.</param>
        public void CreateHorizontalZLine(double x1, double x2, double z)
        {
            SetBeginAndEndPoints(new Point2D{ X = x1, Z = z}, new Point2D{ X = x2, Z = z});
        }

        /// <summary>
        /// Sets the begin and end points.
        /// </summary>
        /// <param name="beginPoint">The begin point.</param>
        /// <param name="endPoint">The end point.</param>
        public void SetBeginAndEndPoints(Point2D beginPoint, Point2D endPoint)
        {
            BeginPoint = beginPoint;
            EndPoint = endPoint;
        }

        /// <summary>
        ///     Calculate intersection with another <see cref="Line" /> projected to the XZ plane.
        /// </summary>
        /// <param name="other">The other line segment.</param>
        /// <returns>An intersection point in the XZ-plane, or null in case no intersection.</returns>
        public Point2D GetIntersectPointXz(Line other)
        {
            Point2D intersectionPoint;
            var isIntersecting = line.IntersectsZ(other.line, out intersectionPoint);

            return isIntersecting ? intersectionPoint : null;
        }
    }

    /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class Line<T> where T : Point2D, new()
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="Line{T}"/> class.
        /// </summary>
        public Line() : this(null, null) {}

        /// <summary>
        /// Initializes a new instance of the <see cref="Line{T}"/> class.
        /// </summary>
        /// <param name="start">The start.</param>
        /// <param name="end">The end.</param>
        public Line(T start, T end)
        {
            Start = start;
            End = end;
        }

        /// <summary>
        /// Gets or sets the start.
        /// </summary>
        /// <value>
        /// The start.
        /// </value>
        public T Start { get; set; }

        /// <summary>
        /// Gets or sets the end.
        /// </summary>
        /// <value>
        /// The end.
        /// </value>
        public T End { get; set; }

        /// <summary>
        /// Intersectses the z.
        /// </summary>
        /// <param name="line">The line.</param>
        /// <param name="intersectionPoint">The intersection point.</param>
        /// <returns></returns>
        public bool IntersectsZ(Line<T> line, out T intersectionPoint)
        {
            return Intersects(line, out intersectionPoint);
        }

        private bool Intersects(Line<T> line, out T intersectionPoint)
        {
            intersectionPoint = null;

            var dx1 = End.X - Start.X;
            var dx2 = line.End.X - line.Start.X;

            var dyz1 = End.Z - Start.Z;
            var dyz2 = line.End.Z - line.Start.Z;
            var yz = Start.Z;
            var yzLine = line.Start.Z;
            
            var noem = dx1*dyz2 - dyz1*dx2;
            if (Math.Abs(noem) > 0.0)
            {
                var u = (dx2*(yz - yzLine) - dyz2*(Start.X - line.Start.X))/noem;
                if ((u >= 0.0) && (u <= 1.0))
                {
                    var v = (dx1*(yz - yzLine) - dyz1*(Start.X - line.Start.X))/noem;

                    if ((v >= 0.0) && (v <= 1.0))
                    {
                        intersectionPoint = new T
                        {
                            X = Start.X + u * dx1,
                            Z = yz + u * dyz1
                        };
                        return true;
                    }
                }
            }
            return false;
        }
    }
}