//Every windows application needs to include this
#include "windows.h"

//Every Direct3D application this
#include "d3d9.h"
#include "d3dx9.h"

bool g_bContinue = true;
LPD3DXEFFECT g_lpEffect = NULL;
LPDIRECT3DVERTEXBUFFER9 g_lpVertexBuffer = NULL;
D3DXMATRIX g_ShaderMatrix;

//Definition of the Vertex Format including position and diffuse color
#define D3DFVF_COLOREDVERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE)

struct COLORED_VERTEX
{
    float x, y, z;  //Position
    DWORD color;    //Color
};

//Besides the main function, there must be a message processing function
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    switch( msg )
    {
        case WM_DESTROY:
            PostQuitMessage( 0 );
            g_bContinue = false;
            return 0;
    }
    return DefWindowProc( hWnd, msg, wParam, lParam );
}

//The entry point of a windows application is the WinMain function
INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR, INT )
{
    //Create a window class.
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
                    GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
                    "Direct3D Window", NULL };

    //Register the window class.
    RegisterClassEx( &wc );

    //Create the application's window.
    HWND hWnd = CreateWindow( "Direct3D Window", "DirectXers - D3D9 Tutorial 2",
                            WS_OVERLAPPEDWINDOW, 100, 100, 400, 400,
                            GetDesktopWindow(), NULL, wc.hInstance, NULL );

    ShowWindow(hWnd,SW_SHOW);

    //Create the Direct3D Object
    LPDIRECT3D9 pD3D = NULL;
    if( NULL == (pD3D = Direct3DCreate9(D3D_SDK_VERSION)))
      return E_FAIL;

    //Setup the device presentation parameters
    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory( &d3dpp, sizeof(d3dpp) );
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;

    //The final step is to use the IDirect3D9::CreateDevice method to create the Direct3D device, as illustrated in the
    //following code example.
    LPDIRECT3DDEVICE9 pd3dDevice = NULL;
    if( FAILED( pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
                                    D3DCREATE_HARDWARE_VERTEXPROCESSING,
                                    &d3dpp, &pd3dDevice ) ) )
    {
        MessageBox(hWnd, "No HAL HARDWARE_VERTEXPROCESSING! Sample will exit!", NULL, 0);
        pD3D->Release();
        pD3D = NULL;
        return E_FAIL;
    }

    //set the vertex buffer size 4 vertices * vertex structure size
    UINT uiBufferSize = 4*sizeof(COLORED_VERTEX);

    //create the buffer
    if( FAILED( pd3dDevice->CreateVertexBuffer( uiBufferSize,
            D3DUSAGE_WRITEONLY, D3DFVF_COLOREDVERTEX, D3DPOOL_DEFAULT, &g_lpVertexBuffer, NULL ) ) )
        return E_FAIL;

    COLORED_VERTEX* pVertices;
    //lock the buffer for writing
    if( FAILED( g_lpVertexBuffer->Lock( 0, uiBufferSize, (void**)&pVertices, 0 ) ) )
        return E_FAIL;

    //write the vertices. Here a simple rectangle
    pVertices[0].x =  -1.0f; //left
    pVertices[0].y =  -1.0f; //bottom
    pVertices[0].z =   0.0f;
    pVertices[0].color =  0xffff0000; //red

    pVertices[1].x =  -1.0f; //left
    pVertices[1].y =   1.0f; //top
    pVertices[1].z =   0.0f;
    pVertices[1].color =  0xff0000ff; //blue

    pVertices[2].x =   1.0f; //right
    pVertices[2].y =  -1.0f; //bottom
    pVertices[2].z =   0.0f;
    pVertices[2].color =  0xff00ff00; //green

    pVertices[3].x =  1.0f; //right
    pVertices[3].y =  1.0f; //top
    pVertices[3].z =  0.0f;
    pVertices[3].color =  0xffffffff; //white

    //unlock the buffer
    g_lpVertexBuffer->Unlock();

    //set the Vertex Format
    pd3dDevice->SetFVF( D3DFVF_COLOREDVERTEX );

    //transfer the buffer to the gpu
    pd3dDevice->SetStreamSource( 0, g_lpVertexBuffer, 0, sizeof(COLORED_VERTEX) );

    //create an effect
    if(FAILED(D3DXCreateEffectFromFile( pd3dDevice, "Effect.fx", NULL,
        NULL, D3DXSHADER_ENABLE_BACKWARDS_COMPATIBILITY, NULL, &g_lpEffect, NULL )))
        return E_FAIL;

    D3DXMatrixIdentity(&g_ShaderMatrix);
    g_lpEffect->SetMatrix( "ShaderMatrix", &g_ShaderMatrix );

    MSG msg;
    while( g_bContinue )
    {
        //Clear render region with blue
        pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0,0,255), 1.0f, 0 );

        //before rendering something, you have to call this
        pd3dDevice->BeginScene();

        //rendering of scene objects happens here

        //begin the effect
        UINT uiPasses = 0;
        g_lpEffect->Begin(&uiPasses, 0);
        for (UINT uiPass = 0; uiPass < uiPasses; uiPass++)
        {
            //render an effect pass
            g_lpEffect->BeginPass(uiPass);

            //render the rectangle
            pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 2 );

            g_lpEffect->EndPass();
        }
        g_lpEffect->End();

        //after the scene call
        pd3dDevice->EndScene();

        //update screen = swap front and backbuffer
        pd3dDevice->Present(NULL, NULL, NULL, NULL);

        // A window has to handle its messages.
        TranslateMessage( &msg );
        DispatchMessage( &msg );
        PeekMessage(&msg, 0, 0, 0, PM_REMOVE);
    }

    //Do not forget to clean up here
    pd3dDevice->Release();
    pd3dDevice = NULL;
    pD3D->Release();
    pD3D = NULL;
    g_lpEffect->Release();
    g_lpEffect = NULL;
    g_lpVertexBuffer->Release();
    g_lpVertexBuffer = NULL;
    return 0;
}