// Copyright (C) Stichting Deltares 2024. 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 Deltares.DamEngine.Data.Standard;

namespace Deltares.DamEngine.Data.Geometry;

/// <summary>
/// Dataclass for the geometryloop.
/// </summary>
/// <seealso cref="Deltares.DamEngine.Data.Geometry.GeometryPointString" />
public class GeometryLoop : GeometryPointString
{
    /// <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>
    /// Gets the List of all Curves.
    /// </summary>
    public List<GeometryCurve> CurveList { get; } = new List<GeometryCurve>();

    /// <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[^1];
        // Just check that the first and last curve are connected
        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;
        }

        // Make sure points from curves are also exist as points
        if (CalcPoints.Count > 0)
        {
            SyncPoints();
        }

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

        // Calculate area of polygon using Shoelace algorithm:
        var sum = 0.0;
        for (var 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()
    {
        List<Point2D> polyGon = GetLocalPoint2DList();
        Clockwise 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>
    /// Determines whether this loop is continuous (i.e. the end point of a curve is the start point of the next curve).
    /// </summary>
    /// <returns>True if continuous, false if not</returns>
    public bool IsContinuous()
    {
        for (var i = 0; i < CurveList.Count - 1; i++)
        {
            if ((CurveList[i].EndPoint != CurveList[i + 1].HeadPoint) &&
                (CurveList[i].EndPoint != CurveList[i + 1].EndPoint) &&
                (CurveList[i].HeadPoint != CurveList[i + 1].HeadPoint) &&
                (CurveList[i].HeadPoint != CurveList[i + 1].EndPoint))
            {
                return false;
            }
        }

        return true;
    }

    /// <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>
    /// Creates a clone of the geometry loop
    /// </summary>
    /// <returns>The cloned GeometryLoop</returns>
    public override GeometryLoop Clone()
    {
        // Note: explicit use of CalcPoints to ensure calcPoints are populated 
        List<Point2D> p = CalcPoints;
        if (p.Count > 0)
        {
            SyncPoints();
        }

        GeometryPointString clonedGeometryPointString = base.Clone();
        var clonedGeometryLoop = new GeometryLoop();
        clonedGeometryLoop.Points.AddRange(clonedGeometryPointString.Points);
        clonedGeometryLoop.SyncCalcPoints();
        foreach (GeometryCurve curve in CurveList)
        {
            clonedGeometryLoop.CurveList.Add(curve.Clone(clonedGeometryLoop.CalcPoints));
        }

        return clonedGeometryLoop;
    }

    /// <summary>
    /// Gets the local 2D Points List.
    /// </summary>
    /// <returns></returns>
    private List<Point2D> GetLocalPoint2DList()
    {
        return CalcPoints;
    }

    /// <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 (var index = 0; index < CurveList.Count; index++)
        {
            if (index == 0)
            {
                calcPoints.Add(CurveList[index].HeadPoint);
                calcPoints.Add(CurveList[index].EndPoint);
            }
            else
            {
                if (!AddEitherHeadOrEndPointOfCurveToCalcPoints(index))
                {
                    if (calcPoints.Count == 2)
                    {
                        calcPoints.Reverse();
                    }

                    AddEitherHeadOrEndPointOfCurveToCalcPoints(index);
                }
            }
        }

        RemoveDoubleClosingPointWhenNeeded();
    }

    private bool AddEitherHeadOrEndPointOfCurveToCalcPoints(int index)
    {
        // Compare by reference (is faster then by value)
        if (CurveList[index].HeadPoint == calcPoints[calcPoints.Count - 1])
        {
            calcPoints.Add(CurveList[index].EndPoint);
            return true;
        }

        if (CurveList[index].EndPoint != calcPoints[calcPoints.Count - 1])
        {
            return false;
        }

        calcPoints.Add(CurveList[index].HeadPoint);
        return true;
    }

    private void RemoveDoubleClosingPointWhenNeeded()
    {
        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.") {}
    }
}