using Blacklight.Core;
using System.IO;
using System.Reflection;

namespace Glass.Blacklight
{
    /// <summary>
    /// A cursor backed by one cell of a registered sprite sheet.
    /// </summary>
    public sealed class SpriteCursor : Cursor
    {
        public SpriteMaterial Sprite { get; }

        /// <summary>
        /// Where the pointer's reported position sits within Sprite's cell, unscaled.
        /// </summary>
        public Point Hotspot { get; }

        public SpriteCursor(SpriteMaterial sprite, Point hotspot)
        {
            Sprite = sprite;
            Hotspot = hotspot;
        }

        /// <summary>
        /// Crops <paramref name="sprite"/>'s cell out of its sheet and returns cursor pixels, enlarged by <paramref
        /// name="scale"/>, for a host to hand to the OS.
        /// </summary>
        /// <param name="artAssembly">The assembly that embeds the sheet's image.</param>
        public static CursorImage ImageFor(SpriteMaterial sprite, Point hotspot, int scale, Assembly artAssembly)
        {
            SpriteSheetAttribute sheet = sprite.SpriteSheet;

            var cell = new System.Drawing.Rectangle(
                sheet.GridOriginX + sprite.CellLocation.X * (sheet.SpriteSize.X + sheet.BorderSize),
                sheet.GridOriginY + sprite.CellLocation.Y * (sheet.SpriteSize.Y + sheet.BorderSize),
                sheet.SpriteSize.X,
                sheet.SpriteSize.Y);

            using (Stream art = artAssembly.GetManifestResourceStream(sheet.SpriteSheetSource))
            {
                return CursorImage.FromImageStream(art, cell, hotspot, scale);
            }
        }

        /// <summary>
        /// Returns this cursor's pixels, enlarged by <paramref name="scale"/>.
        /// </summary>
        /// <param name="artAssembly">The assembly that embeds the sheet's image.</param>
        public CursorImage ImageFor(int scale, Assembly artAssembly)
        {
            return ImageFor(Sprite, Hotspot, scale, artAssembly);
        }
    }
}