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

namespace Chernobyl.Graphics.Xna.Texture
{
    /// <summary>
    /// Implements an XNA 2D render target.
    /// </summary>
    public class XnaRenderTarget2D : Drawable, IRenderTarget2D
    {
        /// <summary>
        /// Constructor.
        /// </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.</param>
        /// <param name="format">The format of the texture (aka, surface).</param>
        public XnaRenderTarget2D(IEventCollection<object> services, uint width, uint height, uint mipmapLevels, TextureFormat format)
        {
            if (Functions.IsPowerOfTwo(width) == false)
                throw new ArgumentException(WidthHeightPowerOfTwoErrorMsg + "width specified: " + width, "width");
            if (Functions.IsPowerOfTwo(height) == false)
                throw new ArgumentException(WidthHeightPowerOfTwoErrorMsg + "height specified: " + height, "height");

            this.GraphicsDevice = services.OfType<GraphicsDevice>().First();
            RenderTarget = new Microsoft.Xna.Framework.Graphics.RenderTarget2D(this.GraphicsDevice, (int)width, (int)height, (int)mipmapLevels, Utility.ToSurfaceFormat(format));
        }

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

            // set this render target
            this.GraphicsDevice.SetRenderTarget(0, RenderTarget);

            // clear this render target
            this.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.
            this.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; private set; }

        /// <summary>
        /// The width of the render target.
        /// </summary>
        public uint Width { get; private set; }

        /// <summary>
        /// The height of the render target.
        /// </summary>
        public uint Height { get; private set; }

        /// <summary>
        /// The XNA render target.
        /// </summary>
        public Microsoft.Xna.Framework.Graphics.RenderTarget2D RenderTarget {get; private set;}

        /// <summary>
        /// Used to hold the previous target when the new target is set.
        /// </summary>
        RenderTarget PreviousTarget { get; set; }

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

        /// <summary>
        /// Error message used when width or height is not a power of two.
        /// </summary>
        static string WidthHeightPowerOfTwoErrorMsg = "The width and height of a IRenderTarget2D must be powers of two (8, 16, 32, 64, 128, 256, 512, 1024, etc).";
    }
}