// 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>
    /// Exception class for <see cref="CoordinateSystemConverter"/>.
    /// </summary>
    public class CoordinateSystemConverterException : Exception
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="CoordinateSystemConverterException"/> class.
        /// </summary>
        /// <param name="message">The message that describes the error.</param>
        public CoordinateSystemConverterException(string message)
            : base(message) {}
    }

    /// <summary>
    /// class for converting object coordinates from global to local system and back.
    /// </summary>
    /// <remarks>Converter assumes all points of the given line are in the same vertical 
    /// 2D plane.</remarks>
    public class CoordinateSystemConverter
    {
        private double cosAlpha = 0;
        private double endX;
        private double endY;
        private bool isGlobalXYZDefined = false;

        private double length;
        private double sinAlpha = 0;
        private double startX = 0.0;
        private double startY = 0.0;

        /// <summary>
        /// cos(alpha) of x-axis of local XYZ system
        /// </summary>
        public double CosAlpha
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return cosAlpha;
            }
        }

        /// <summary>
        /// sin(alpha) of x-axis of local XYZ system
        /// </summary>
        public double SinAlpha
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return sinAlpha;
            }
        }

        /// <summary>
        /// x-coordinate of origin of local XYZ system
        /// </summary>
        public double XStart
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return startX;
            }
        }

        /// <summary>
        /// y-coordinate of origin start point of local XYZ system
        /// </summary>
        public double YStart
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return startY;
            }
        }

        /// <summary>
        /// x-coordinate of origin last point
        /// </summary>
        public double XEnd
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return endX;
            }
        }

        /// <summary>
        /// y-coordinate of origin end point
        /// </summary>
        public double YEnd
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return endY;
            }
        }

        /// <summary>
        /// Gets the length.
        /// </summary>
        /// <value>
        /// The length.
        /// </value>
        public double Length
        {
            get
            {
                ThrowIfGlobalXYZNotDefined();
                return length;
            }
        }

        /// <summary>
        /// Gets a value indicating whether [converted to local].
        /// </summary>
        /// <value>
        ///   <c>true</c> if [converted to local]; otherwise, <c>false</c>.
        /// </value>
        public bool ConvertedToLocal { get; private set; }

        /// <summary>
        /// Define parameters to parameterize the global reference system.
        /// </summary>
        /// <param name="globalLine">Line defined in global coordinates.</param>
        public void DefineGlobalXYZBasedOnLine(GeometryPointString globalLine)
        {
            GeometryPoint firstPoint = globalLine.Points[0];
            GeometryPoint lastPoint = globalLine.Points[globalLine.Points.Count - 1];

            double dX = lastPoint.X - firstPoint.X;
            double dY = lastPoint.Y - firstPoint.Y;

            length = Math.Sqrt(dX*dX + dY*dY);

            cosAlpha = dX/length;
            sinAlpha = dY/length;

            startX = firstPoint.X;
            startY = firstPoint.Y;

            endX = lastPoint.X;
            endY = lastPoint.Y;

            isGlobalXYZDefined = true;
        }

        /// <summary>
        /// Define parameters to define global reference system
        /// </summary>
        [Obsolete]
        public void DefineLocalXZBasedOnSavedProperties(double originalX, double originalY, double angle)
        {
            cosAlpha = Math.Cos(angle);
            sinAlpha = Math.Sin(angle);
            startX = originalX;
            startY = originalY;
            isGlobalXYZDefined = true;
        }

        /// <summary>
        /// Projects a global coordinate to a local XZ reference system.
        /// </summary>
        /// <param name="globalPoint">Global coordinate.</param>
        /// <seealso cref="ConvertGlobalXYZToLocalXZ(GeometryPointString)"/>
        /// <exception cref="CoordinateSystemConverterException">When global parameters haven't
        /// been defined yet with <see cref="DefineGlobalXYZBasedOnLine"/>.</exception>
        public void ConvertGlobalXYZToLocalXZ(GeometryPoint globalPoint)
        {
            ThrowIfGlobalXYZNotDefined();

            globalPoint.X = GetLocalXForGlobalPoint(globalPoint);
            globalPoint.Y = 0.0;
        }

        /// <summary>
        /// Projects a line of global coordinates to a local XZ reference system.
        /// </summary>
        /// <param name="globalLine">Th line in global coordinates.</param>
        /// <seealso cref="ConvertGlobalXYZToLocalXZ(GeometryPoint)"/>
        public void ConvertGlobalXYZToLocalXZ(GeometryPointString globalLine)
        {
            if (!isGlobalXYZDefined)
            {
                DefineGlobalXYZBasedOnLine(globalLine);
            }
            ThrowIfGlobalXYZNotDefined();

            foreach (var point in globalLine.Points)
            {
                ConvertGlobalXYZToLocalXZ(point);
            }
            ConvertedToLocal = true;
        }

        /// <summary>
        /// Projects a local coordinate back to the parameterized global XYZ reference system.
        /// </summary>
        /// <param name="localPoint">Local coordinate.</param>
        /// <seealso cref="ConvertLocalXZToGlobalXYZ(GeometryPointString)"/>
        /// <exception cref="CoordinateSystemConverterException">When global parameters haven't
        /// been defined yet with <see cref="DefineGlobalXYZBasedOnLine"/>.</exception>
        public void ConvertLocalXZToGlobalXYZ(GeometryPoint localPoint)
        {
            ThrowIfGlobalXYZNotDefined();

            double localX = localPoint.X*cosAlpha + startX;
            double localY = localPoint.X*sinAlpha + startY;
            localPoint.X = localX;
            localPoint.Y = localY;
        }

        /// <summary>
        /// Projects a XZ-line local coordinates back to the parameterized global XYZ reference system.
        /// </summary>
        /// <param name="localLine">Line in local coordinates.</param>
        /// <seealso cref="ConvertLocalXZToGlobalXYZ(GeometryPointString)"/>
        /// <exception cref="CoordinateSystemConverterException">When global parameters haven't
        /// been defined yet with <see cref="DefineGlobalXYZBasedOnLine"/>.</exception>
        public void ConvertLocalXZToGlobalXYZ(GeometryPointString localLine)
        {
            ThrowIfGlobalXYZNotDefined();

            foreach (var point in localLine.Points)
            {
                ConvertLocalXZToGlobalXYZ(point);
            }
        }

        private double GetLocalXForGlobalPoint(GeometryPoint globalPoint)
        {
            const double cSinCosThreshold = 0.4;

            double dX = globalPoint.X - startX;
            double dY = globalPoint.Y - startY;

            double localXfromGlobalX = dX/cosAlpha;
            if (Math.Abs(sinAlpha) < cSinCosThreshold)
            {
                // if line tends to be horizontal use local x calculated based on dX
                return localXfromGlobalX;
            }

            double localXfromGlobalY = dY/sinAlpha;
            if (Math.Abs(cosAlpha) < cSinCosThreshold)
            {
                // if line tends to be vertical use local x calculated based on dY
                return localXfromGlobalY;
            }

            // if angle around 45 degrees then use the mean between the 2 values
            return (localXfromGlobalX + localXfromGlobalY)/2;
        }

        /// <summary>
        /// Raise exception if Global XYZ reference system is not defined
        /// </summary>
        private void ThrowIfGlobalXYZNotDefined()
        {
            if (!isGlobalXYZDefined)
            {
                throw new CoordinateSystemConverterException("Global reference coordinate system is not defined");
            }
        }
    }
}