// Copyright (C) Stichting Deltares 2019. 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;
using System.Collections.Generic;
using System.Linq;

namespace Deltares.DamEngine.Data.Geometry
{
    /// <summary>
    /// Dataclass for the geometryloop.
    /// </summary>
    /// <seealso cref="Deltares.DamEngine.Data.Geometry.GeometryPointString" />
    public class GeometryLoop : GeometryPointString
    {
        private readonly List<GeometryCurve> curveList = new List<GeometryCurve>();

        /// <summary>
        /// Gets the List of all Curves.
        /// </summary>
        public List<GeometryCurve> CurveList
        {
            get
            {
                return curveList;
            }
        }

        /// <summary>
        /// List of points that describe the physical surface line or surface.
        /// </summary>
        /// <remarks>This property is not serialized. If you want to add point definitions,
        /// do so by adding/inserting a new element to <see cref="CurveList"/>.</remarks>
        public override List<Point2D> CalcPoints
        {
            get
            {
                // explicit use of protected field to prevent stack overflow due to recursive call
                if (calcPoints.Count == 0)
                {
                    PopulateLoopPointList();
                    SyncPoints();
                }

                return calcPoints;
            }
        }

        /// <summary>
        /// Determines whether this instance is loop.
        /// </summary>
        /// <returns></returns>
        public bool IsLoop()
        {
            if (CurveList.Count <= 2)
            {
                return false;
            }

            GeometryCurve beginCurve = curveList[0];
            GeometryCurve endCurve = curveList[curveList.Count - 1];

            if (beginCurve.HeadPoint == endCurve.HeadPoint ||
                beginCurve.HeadPoint == endCurve.EndPoint ||
                beginCurve.EndPoint == endCurve.HeadPoint ||
                beginCurve.EndPoint == endCurve.EndPoint)
            {
                return true;
            }

            return false;
        }

        /// <summary>
        /// Determines whether this instance has area.
        /// </summary>
        /// <returns></returns>
        public bool HasArea()
        {
            if (CurveList.Count < 3)
            {
                return false;
            }

            var points = new List<GeometryPoint>();
            points.AddRange(Points);
            points.Add(points[0]);

            // Calculate area of polygon using Shoelace algorithm:
            var sum = 0.0;
            for (int i = 1; i < points.Count; i++)
            {
                sum += points[i - 1].X * points[i].Z - points[i - 1].Z * points[i].X;
            }

            return Math.Abs(sum) > 1e-6;
        }

        /// <summary>
        /// Determines whether [is clock wise].
        /// </summary>
        /// <returns></returns>
        /// <exception cref="NotEnoughUniquePointsException"></exception>
        /// <exception cref="System.InvalidOperationException">Cannot determine if loop is clockwise if checked location forms a straight line with its neighboring vectors.</exception>
        public bool IsClockWise()
        {
            var polyGon = GetLocalPoint2DList();
            var isClockWise = Routines2D.IsClockWise(polyGon);
            if (isClockWise == Clockwise.NotEnoughUniquePoints)
            {
                throw new NotEnoughUniquePointsException();
            }
            if (isClockWise == Clockwise.PointsOnLine)
            {
                throw new InvalidOperationException("Cannot determine if loop is clockwise if checked location forms a straight line with its neighboring vectors.");
            }
            return isClockWise == Clockwise.IsClockwise;
        }

        /// <summary>
        /// See if a point lies in a closed surface
        /// </summary>
        /// <param name="aPoint"></param>
        /// <returns></returns>
        public bool IsPointInLoopArea(Point2D aPoint)
        {
            return Routines2D.CheckIfPointIsInPolygon(this, aPoint.X, aPoint.Z) != PointInPolygon.OutsidePolygon;
        }

        /// <summary>
        /// Gets the local 2D Points List.
        /// </summary>
        /// <returns></returns>
        private List<Point2D> GetLocalPoint2DList()
        {
            return CalcPoints;//Points.Select(loopPoint => new Point2D(loopPoint.X, loopPoint.Z)).ToList();
        }

        /// <summary>
        /// Populates the loop's GeometryPoint list.
        /// </summary>
        private void PopulateLoopPointList()
        {
            // explicit use of protected field to prevent stack overflow due to recursive call
            if (calcPoints.Count > 0)
            {
                return;
            }
            for (int index = 0; index < curveList.Count; index++)
            {
                if (index == 0)
                {
                    calcPoints.Add(curveList[index].HeadPoint);
                    calcPoints.Add(curveList[index].EndPoint);
                }
                else
                {
                    // TODO why not compare by value instead of reference
                    if (curveList[index].HeadPoint == calcPoints[calcPoints.Count - 1])
                    {
                        calcPoints.Add(curveList[index].EndPoint);
                    }
                    else if (curveList[index].EndPoint == calcPoints[calcPoints.Count - 1])
                    {
                        calcPoints.Add(curveList[index].HeadPoint);
                    }
                    else
                    {
                        if (calcPoints.Count == 2)
                        {
                            calcPoints.Reverse();
                        }
                        if (curveList[index].HeadPoint == calcPoints[calcPoints.Count - 1])
                        {
                            calcPoints.Add(curveList[index].EndPoint);
                        }
                        else if (curveList[index].EndPoint == calcPoints[calcPoints.Count - 1])
                        {
                            calcPoints.Add(curveList[index].HeadPoint);
                        }
                    }
                }
            }

            if (calcPoints.Count > 0)
            {
                if (calcPoints[0] == calcPoints[calcPoints.Count - 1])
                {
                    calcPoints.RemoveAt(calcPoints.Count - 1);
                }
            }
        }

        /// <summary>
        /// Helper class NotEnoughUniquePointsException
        /// </summary>
        public class NotEnoughUniquePointsException : InvalidOperationException
        {
            /// <summary>
            /// Initializes a new instance of the <see cref="NotEnoughUniquePointsException"/> class.
            /// </summary>
            public NotEnoughUniquePointsException()
                : base("At least 3 unique points are required to determine if the loop is running clockwise.") { }
        }
    }
}