using System.Linq;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Graphics.Drawing;
using Chernobyl.Graphics.Texture;
using Microsoft.Xna.Framework.Graphics;

namespace Chernobyl.Graphics.Xna.Texture
{
    /// <summary>
    /// Allows access to the XNA back buffer.
    /// </summary>
    public class XnaBackBuffer : Drawable, IBackBuffer
    {
        /// <summary>
        /// Configures this render target.
        /// </summary>
        /// <param name="services">The object that holds the services.</param>
        /// <param name="width">The width of the render target. This must be a 
        /// power of two.</param>
        /// <param name="height">The height of the render target.This must be a 
        /// power of two.</param>
        /// <param name="mipmapLevels">The number of mipmap levels to generate.  
        /// See http://en.wikipedia.org/wiki/Mipmap for more information
        /// about mipmaps. Set this to 0 to generate all mipmaps down to 1x1 pixels.</param>
        /// <param name="format">The format of the texture (aka, surface).</param>
        public void Configure(IEventCollection<object> services, uint width, uint height, uint mipmapLevels, TextureFormat format)
        {
            if(IsConfigured == false)
            {
                GraphicsDevice = services.OfType<GraphicsDevice>().First();
                IsConfigured = true;
            }
        }

        /// <summary>
        /// Called before the "Draw" method to apply any states
        /// or preconditions.
        /// </summary>
        public override void PreDraw()
        {
            // grab the current render target
            PreviousTarget = GraphicsDevice.GetRenderTarget(0);

            // set the back buffer
            GraphicsDevice.SetRenderTarget(0, null);

            // clear this render target
            GraphicsDevice.Clear(ClearOptions.Target, Microsoft.Xna.Framework.Graphics.Color.CornflowerBlue, 0, 0);
        }

        /// <summary>
        /// Called after the "Draw" method to remove any states
        /// or preconditions.
        /// </summary>
        public override void PostDraw()
        {
            // switch back to the previous device.
            GraphicsDevice.SetRenderTarget(0, PreviousTarget as Microsoft.Xna.Framework.Graphics.RenderTarget2D);
        }

        /// <summary>
        /// The number of mipmaps generated for this render target.
        /// </summary>
        public uint MipmapLevelsCount { get { return 1; } }

        /// <summary>
        /// The width of the render target.
        /// </summary>
        public uint Width { get { return (uint)GraphicsDevice.PresentationParameters.BackBufferWidth; } }

        /// <summary>
        /// The height of the render target.
        /// </summary>
        public uint Height { get { return (uint)GraphicsDevice.PresentationParameters.BackBufferHeight; } }

        /// <summary>
        /// True if the render target has been configured, false if
        /// otherwise.
        /// </summary>
        bool IsConfigured { get; set; }

        /// <summary>
        /// The XNA graphics device.
        /// </summary>
        GraphicsDevice GraphicsDevice { get; set; }

        /// <summary>
        /// Holds the past render target when PreDraw is called.
        /// </summary>
        RenderTarget PreviousTarget { get; set; }
    }
}