#region File Description
//-----------------------------------------------------------------------------
// VBScreenHelper.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion

#region Using directives
using System;
using System.Collections.Generic;
using System.Text;
using RacingGame.Graphics;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
#endregion

namespace RacingGame.Shaders
{
    /// <summary>
    /// The VBScreenHelper class helps you to create and use vertex buffers for
    /// on screen rendering used in PreScreen and PostScreen shaders.
    /// You don't have to create a VB for every shader anymore, just call
    /// VBScreenHelper.Render() and everything will be created for you and
    /// reused if same parameters are requested again!
    /// Supports also Grid screen rendering required for radial motion blur.
    /// </summary>
    public static class VBScreenHelper
    {
        #region VBScreen helper class
        /// <summary>
        /// VBScreen holds all data for the vbScreens list to reuse existing
        /// VBScreens. Handles also the VB, creation and rendering.
        /// </summary>
        private class VBScreen
        {
            #region Variables
            /// <summary>
            /// Vertex buffer to render stuff on screen.
            /// </summary>
            private VertexBuffer vbScreen;
            #endregion

            #region Constructor
            /// <summary>
            /// Create VB screen
            /// </summary>
            public VBScreen()
            {
                VertexPositionTexture[] vertices = new VertexPositionTexture[]
                {
                    new VertexPositionTexture(
                        new Vector3(-1.0f, -1.0f, 0.5f),
                        new Vector2(0, 1)),
                    new VertexPositionTexture(
                        new Vector3(-1.0f, 1.0f, 0.5f),
                        new Vector2(0, 0)),
                    new VertexPositionTexture(
                        new Vector3(1.0f, -1.0f, 0.5f),
                        new Vector2(1, 1)),
                    new VertexPositionTexture(
                        new Vector3(1.0f, 1.0f, 0.5f),
                        new Vector2(1, 0)),
                };

                vbScreen = new VertexBuffer(
                    BaseGame.Device,
                    typeof(VertexPositionTexture),
                    vertices.Length,
                    BufferUsage.WriteOnly);

                vbScreen.SetData(vertices);
            }
            #endregion

            #region Render
            /// <summary>
            /// Render
            /// </summary>
            public void Render()
            {
                // Rendering is pretty straight forward (if you know how anyway).
                BaseGame.Device.SetVertexBuffer(vbScreen);
                BaseGame.Device.DrawPrimitives(PrimitiveType.TriangleStrip, 0, 2);
            }
            #endregion
        }
        #endregion

        #region GridScreen helper class
        /// <summary>
        /// Another vertex and index buffer for a screen grid, basically
        /// used for the same purpose as VBScreen, but allows us to create
        /// a grid (e.g. 10x10), very useful for advanced post screen shaders.
        /// </summary>
        private class GridScreen
        {
            #region Variables
            /// <summary>
            /// Grid dimension
            /// </summary>
            int gridWidth, gridHeight;
            /// <summary>
            /// Index buffer
            /// </summary>
            IndexBuffer indexBuffer = null;
            /// <summary>
            /// Vertex buffer
            /// </summary>
            VertexBuffer vertexBuffer = null;

            #endregion

            #region Constructor
            /// <summary>
            /// Create grid screen
            /// </summary>
            /// <param name="setGridDimension">Set grid dimension</param>
            public GridScreen(int setGridWidth, int setGridHeight)
            {
                if (setGridWidth < 2 ||
                    setGridHeight < 2)
                    throw new ArgumentException(
                        "setGridWidth=" + setGridWidth + ", setGridHeight=" + setGridHeight,
                        "Grid size must be at least (2, 2).");
                gridWidth = setGridWidth;
                gridHeight = setGridHeight;

                // Create vertex buffer
                // fix
                //vertexBuffer = new VertexBuffer(
                //    BaseGame.Device,
                //    typeof(VertexPositionTexture),
                //    gridWidth * gridHeight,
                //    ResourceUsage.WriteOnly,
                //    ResourceManagementMode.Automatic);
                vertexBuffer = new VertexBuffer(
                    BaseGame.Device,
                    typeof(VertexPositionTexture),
                    gridWidth * gridHeight,
                    BufferUsage.WriteOnly);

                // Create all vertices
                VertexPositionTexture[] vertices =
                    new VertexPositionTexture[gridWidth * gridHeight];
                // Just simply create all vertices of the grid
                for (int x = 0; x < gridWidth; x++)
                    for (int y = 0; y < gridHeight; y++)
                    {
                        vertices[x + y * gridWidth] =
                            new VertexPositionTexture(new Vector3(
                            -1.0f + 2.0f * (float)x / (float)(gridWidth - 1),
                            -1.0f + 2.0f * (float)y / (float)(gridHeight - 1),
                            0.5f),
                            new Vector2((float)x / (float)(gridWidth - 1),
                            // XNA expect bottom up for the screen rendering.
                            1.0f - ((float)y / (float)(gridHeight - 1))));
                    }
                vertexBuffer.SetData(vertices);

                // Index buffer
                // fix
                //indexBuffer = new IndexBuffer(
                //    BaseGame.Device,
                //    typeof(ushort),
                //    (gridWidth - 1) * (gridHeight - 1) * 2 * 3,
                //    ResourceUsage.WriteOnly,
                //    ResourceManagementMode.Automatic);
                indexBuffer = new IndexBuffer(
                    BaseGame.Device,
                    typeof(ushort),
                    (gridWidth - 1) * (gridHeight - 1) * 2 * 3,
                    BufferUsage.WriteOnly);

                ushort[] indices = new ushort[
                    (gridWidth - 1) * (gridHeight - 1) * 3 * 2];
                // Just simply create all indices of the grid
                int num = 0;
                for (int x = 0; x < gridWidth - 1; x++)
                    for (int y = 0; y < gridHeight - 1; y++)
                    {
                        ushort index1 = (ushort)(x + y * gridWidth);
                        ushort index2 = (ushort)((x + 1) + y * gridWidth);
                        ushort index3 = (ushort)((x + 1) + (y + 1) * gridWidth);
                        ushort index4 = (ushort)(x + (y + 1) * gridWidth);

                        indices[num] = index1;
                        indices[num + 1] = index3;
                        indices[num + 2] = index2;
                        indices[num + 3] = index1;
                        indices[num + 4] = index4;
                        indices[num + 5] = index3;

                        num += 6;
                    }
                indexBuffer.SetData(indices);
            }
            #endregion

            #region Render
            /// <summary>
            /// Render
            /// </summary>
            public void Render()
            {
                // Rendering is pretty straight forward (if you know how anyway).
                BaseGame.Device.SetVertexBuffer(vertexBuffer);
                BaseGame.Device.Indices = indexBuffer;
                BaseGame.Device.DrawIndexedPrimitives(PrimitiveType.TriangleList,
                    0, 0, gridWidth * gridHeight,
                    0, (gridWidth - 1) * (gridHeight - 1) * 2);
            }
            #endregion
        }
        #endregion

        #region Render
        /// <summary>
        /// Vb screen instance
        /// </summary>
        static VBScreen vbScreenInstance = null;
        /// <summary>
        /// Just render a vertex buffer with the screen coordinates.
        /// No subTexelSize stuff is performed, do that in the fx file.
        /// </summary>
        public static void Render()
        {
            if (vbScreenInstance == null)
                vbScreenInstance = new VBScreen();

            vbScreenInstance.Render();
        }
        #endregion

        #region Render 10x10 screen grid
        /// <summary>
        /// Grid screen 1 0x 10 instance
        /// </summary>
        static GridScreen gridScreen10x10Instance = null;
        /// <summary>
        /// Just render a 10x10 grid with help of GridScreen on the screen.
        /// No subTexelSize stuff is performed, do that in the fx file.
        /// </summary>
        public static void Render10x10Grid()
        {
            if (gridScreen10x10Instance == null)
                gridScreen10x10Instance = new GridScreen(10, 10);

            gridScreen10x10Instance.Render();
        }
        #endregion
    }
}