// Headers
#include <windows.h>
#include "GLee.h"

// Globals
bool g_WindowOpen = true;

// Window event handler
LRESULT CALLBACK windowEvent( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    if ( msg == WM_DESTROY ) g_WindowOpen = false;

    return DefWindowProc( hWnd, msg, wParam, lParam );
}

// Application entry point
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
{
    // Create the window
    WNDCLASSEX windowClass;
    ZeroMemory( &windowClass, sizeof( windowClass ) );
    windowClass.cbSize = sizeof( WNDCLASSEX );
    windowClass.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
    windowClass.lpfnWndProc = windowEvent;
    windowClass.hIcon =  LoadIcon( NULL, IDI_APPLICATION );
    windowClass.hIconSm = LoadIcon( NULL, IDI_APPLICATION );
    windowClass.hCursor = LoadCursor( NULL, IDC_ARROW );
    windowClass.hbrBackground = (HBRUSH)GetStockObject( WHITE_BRUSH );
    windowClass.lpszClassName = L"OpenGLWindow";
    RegisterClassEx( &windowClass );

    RECT windowSize;
    windowSize.left = 0;
    windowSize.top = 0;
    windowSize.right = 800;
    windowSize.bottom = 600;
    AdjustWindowRect( &windowSize, WS_POPUPWINDOW | WS_CAPTION, false );

    HWND window = CreateWindowEx( WS_EX_OVERLAPPEDWINDOW, L"OpenGLWindow", L"OpenGL", WS_POPUPWINDOW | WS_CAPTION, 250, 50, windowSize.right - windowSize.left, windowSize.bottom - windowSize.top, NULL, NULL, NULL, NULL );
    HDC dc = GetDC( window );
    ShowWindow( window, SW_SHOWNORMAL );
    UpdateWindow( window );

    // Choose appropriate pixel format
    PIXELFORMATDESCRIPTOR pfd;
    ZeroMemory( &pfd, sizeof( pfd ) );
    pfd.nSize = sizeof( pfd );
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DOUBLEBUFFER | PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;
    pfd.cDepthBits = 32;
    pfd.iLayerType = PFD_MAIN_PLANE;
    int pixelFormat = ChoosePixelFormat( dc, &pfd );
    SetPixelFormat( dc, pixelFormat, &pfd );

    // Create OpenGL context
    HGLRC context = wglCreateContext( dc );
    wglMakeCurrent( dc, context );

    // Set viewport and clear color
    glViewport( 0, 0, 800, 600 );
    glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );

    // Load shaders and specify input sources
    const char* vertexShaderSource = "in vec2 in_Position;\
    in vec3 in_Color;\
    varying vec3 ex_Color;\
    \
    void main()\
    {\
        gl_Position = vec4( ( in_Position.x - 400.0 ) / 400.0, ( 300.0 - in_Position.y ) / 300.0, 0.0, 1.0 );\
        ex_Color = in_Color;\
    }";
    const char* fragmentShaderSource = "varying vec3 ex_Color;\
    \
    void main()\
    {\
        gl_FragColor = vec4( ex_Color, 1.0 );\
    }";

    int vertexShader = glCreateShader( GL_VERTEX_SHADER );
    glShaderSource( vertexShader, 1, &vertexShaderSource, 0 );
    glCompileShader( vertexShader );

    int fragmentShader = glCreateShader( GL_FRAGMENT_SHADER );
    glShaderSource( fragmentShader, 1, &fragmentShaderSource, 0 );
    glCompileShader( fragmentShader );

    int shaderProgram = glCreateProgram();
    glAttachShader( shaderProgram, vertexShader );
    glAttachShader( shaderProgram, fragmentShader );
    glBindAttribLocation( shaderProgram, 0, "in_Position" );
    glBindAttribLocation( shaderProgram, 1, "in_Color" );
    glLinkProgram( shaderProgram );
    glUseProgram( shaderProgram );

    // Put vertex data in a VBO and set the position and color pointers
    float vertices[] = {
        50.0f, 50.0f, 1.0f, 0.0f, 0.0f,
        750.0f, 50.0f, 0.0f, 1.0f, 0.0f,
        750.0f, 550.0f, 0.0f, 0.0f, 1.0f,

        750.0f, 550.0f, 0.0f, 0.0f, 1.0f,
        50.0f, 550.0f, 1.0f, 0.0f, 1.0f,
        50.0f, 50.0f, 1.0f, 0.0f, 0.0f,
    };
    unsigned int vbo;
    glGenBuffers( 1, &vbo );
    glBindBuffer( GL_ARRAY_BUFFER, vbo );
    glBufferData( GL_ARRAY_BUFFER, sizeof( vertices ), vertices, GL_STATIC_DRAW );

    glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, sizeof( float ) * 5, 0 );
    glEnableVertexAttribArray( 0 );
    glVertexAttribPointer( 1, 3, GL_FLOAT, GL_FALSE, sizeof( float ) * 5, (void*)( 2 * sizeof( float ) ) );
    glEnableVertexAttribArray( 1 );

    // Main loop
    MSG msg;
    while ( g_WindowOpen )
    {
        while ( PeekMessage( &msg, window, 0, 0, PM_REMOVE ) )
        {
            TranslateMessage( &msg );
            DispatchMessage( &msg );
        }

        // Clear and draw
        glClear( GL_COLOR_BUFFER_BIT );

        glDrawArrays( GL_TRIANGLES, 0, 6 );

        // Present
        SwapBuffers( dc );
    }
}