using System;
using ThinkGeo.MapSuite.AndroidEdition;
using ThinkGeo.MapSuite.Core;

namespace ZoomToTest
{
    public static class Extensions
    {
        public static void ZoomTo(this MapView mapView, PointShape center, double scale)
        {
            double mapWidth = mapView.Width;
            double mapHeight = mapView.Height;

            if (Double.IsNaN(mapWidth) || Double.IsNaN(mapHeight))
            {
                return;
            }

            double resolution = GetResolutionFromScale(scale, mapView.MapUnit);
            double widthInDegree = mapWidth * resolution;
            double heightInDegree = mapHeight * resolution;
            double left = center.X - widthInDegree * .5;
            double right = center.X + widthInDegree * .5;
            double top = center.Y + heightInDegree * .5;
            double bottom = center.Y - heightInDegree * .5;

            mapView.ZoomTo(new RectangleShape(left, top, right, bottom));
        }

        #region private
        private const int dotsPerInch = 96;
        private const double feet = 12.0;
        private const double meter = 39.3701;
        private const double decimalDegree = 4374754;

        private static double GetResolutionFromScale(double scale, GeographyUnit unit)
        {
            return scale / (GetInchesByUnit(unit) * dotsPerInch);
        }

        private static double GetInchesByUnit(GeographyUnit unit)
        {
            switch (unit)
            {
                case GeographyUnit.Feet: return feet;
                case GeographyUnit.Meter: return meter;
                case GeographyUnit.DecimalDegree: return decimalDegree;
                default: return double.NaN;
            }
        }
        #endregion
    }
}