using Blacklight.Core;
using System.Reflection;

namespace Glass.Blacklight
{
    /// <summary>
    /// Keeps a host's cursor showing whichever one the UI asks for under the pointer.
    /// </summary>
    public class CursorSync
    {
        private readonly ICursorSurface surface;
        private readonly int scale;
        private readonly Assembly artAssembly;

        // The cursor last handed to the surface, so a pointer resting on a control doesn't decode its art every frame.
        private SpriteCursor applied = null;

        /// <param name="surface">The host's cursor.</param>
        /// <param name="scale">How many times larger than its art a cursor is drawn.</param>
        /// <param name="artAssembly">The assembly that embeds the cursors' sprite sheet.</param>
        public CursorSync(ICursorSurface surface, int scale, Assembly artAssembly)
        {
            this.surface = surface;
            this.scale = scale;
            this.artAssembly = artAssembly;
        }

        /// <summary>
        /// Shows <paramref name="wanted"/>, or hands the cursor back to the host when it isn't a sprite cursor.
        /// </summary>
        public void Apply(Cursor wanted)
        {
            var sprite = wanted as SpriteCursor;

            if (ReferenceEquals(sprite, applied))
            {
                return;
            }

            applied = sprite;

            if (sprite == null)
            {
                surface.ClearCursor();
            }
            else
            {
                surface.TrySetCursor(sprite.ImageFor(scale, artAssembly));
            }
        }
    }
}