// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
// Copyright © 2024 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)

using System;
#if WPF
using System.Windows;
#endif

namespace MapControl
{
    public enum MapProjectionType
    {
        WebMercator, // normal cylindrical projection compatible with MapTileLayer
        NormalCylindrical,
        TransverseCylindrical,
        Azimuthal,
        Other
    }

    /// <summary>
    /// Defines a map projection between geographic coordinates and cartesian map coordinates.
    /// </summary>
    public abstract class MapProjection
    {
        public const double Wgs84EquatorialRadius = 6378137d;
        public const double Wgs84MeterPerDegree = Wgs84EquatorialRadius * Math.PI / 180d;
        public const double Wgs84Flattening = 1d / 298.257223563;
        public static readonly double Wgs84Eccentricity = Math.Sqrt((2d - Wgs84Flattening) * Wgs84Flattening);

        /// <summary>
        /// Gets the type of the projection.
        /// </summary>
        public MapProjectionType Type { get; protected set; } = MapProjectionType.Other;

        /// <summary>
        /// Gets the WMS 1.3.0 CRS identifier.
        /// </summary>
        public string CrsId { get; protected set; } = "";

        /// <summary>
        /// Gets or sets an optional projection center.
        /// </summary>
        public virtual Location Center { get; protected internal set; } = new Location();

        /// <summary>
        /// Gets the relative map scale at the specified Location.
        /// </summary>
        public virtual Point GetRelativeScale(Location location) => new Point(1d, 1d);

        /// <summary>
        /// Transforms a Location in geographic coordinates to a Point in projected map coordinates.
        /// Returns null when the Location can not be transformed.
        /// </summary>
        public abstract Point? LocationToMap(Location location);

        /// <summary>
        /// Transforms a Point in projected map coordinates to a Location in geographic coordinates.
        /// Returns null when the Point can not be transformed.
        /// </summary>
        public abstract Location MapToLocation(Point point);

        /// <summary>
        /// Transforms a BoundingBox in geographic coordinates to a Rect in projected map coordinates.
        /// Returns null when the BoundingBox can not be transformed.
        /// </summary>
        public virtual Rect? BoundingBoxToMap(BoundingBox boundingBox)
        {
            Rect? mapRect = null;
            var southWest = LocationToMap(new Location(boundingBox.South, boundingBox.West));
            var northEast = LocationToMap(new Location(boundingBox.North, boundingBox.East));

            if (southWest.HasValue && northEast.HasValue)
            {
                mapRect = new Rect(southWest.Value, northEast.Value);
            }

            return mapRect;
        }

        /// <summary>
        /// Transforms a Rect in projected map coordinates to a BoundingBox in geographic coordinates.
        /// Returns null when the MapRect can not be transformed.
        /// </summary>
        public virtual BoundingBox MapToBoundingBox(Rect mapRect)
        {
            BoundingBox boundingBox = null;
            var southWest = MapToLocation(new Point(mapRect.X, mapRect.Y));
            var northEast = MapToLocation(new Point(mapRect.X + mapRect.Width, mapRect.Y + mapRect.Height));

            if (southWest != null && northEast != null)
            {
                boundingBox = new BoundingBox(southWest, northEast);
            }

            return boundingBox;
        }
    }
}