#include "gl3w.h"
#include "Window.h"

#define INITIAL_WIDTH   500
#define INITIAL_HEIGHT  500

/**
 * Initialize SDL.
 *
 * @retval true SDL was loaded successfully.
 * @retval false Loading SDL failed.
 */
static bool Initialize_SDL()
{
    static bool initialized = false;

    if (initialized)
    {
        return true;
    }

    if (SDL_Init(SDL_INIT_VIDEO) != 0)
    {
        return false;
    }

    atexit(SDL_Quit);

    initialized = true;
    return true;
}

/**
 * Initialize OpenGL.
 *
 * @retval true OpenGL was loaded successfully.
 * @retval false Loading OpenGL failed.
 */
static bool Initialize_OpenGL()
{
    if (gl3wInit() != 0)
    {
        /* Failed to gl3wInit() */
        return false;
    }

    if (!gl3wIsSupported(3, 0))
    {
        /* OpenGL 3.0 is not supported */
        return false;
    }

    glEnable(GL_SCISSOR_TEST);
    glActiveTexture(GL_TEXTURE0);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    return true;
}

/**
 * Create a Window.
 *
 * @retval true The Window was created successfully.
 * @retval false There was an error while creating the Window.
 */
bool Window::create()
{
    if (!Initialize_SDL())
    {
        return false;
    }

    m_window = SDL_CreateWindow(
            "jes",
            SDL_WINDOWPOS_UNDEFINED,
            SDL_WINDOWPOS_UNDEFINED,
            INITIAL_WIDTH,
            INITIAL_HEIGHT,
            SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
    if (m_window == NULL)
    {
        return false;
    }

    (void)SDL_GL_CreateContext(m_window);

    if (!Initialize_OpenGL())
    {
        return false;
    }

    m_exit_requested = false;

    resize();

    return true;
}

/**
 * Run the Window event loop.
 *
 * TODO: make this a static method to support multiple GUI windows.
 */
void Window::run_event_loop()
{
    SDL_Event event;

    while ((!m_exit_requested) && SDL_WaitEvent(&event))
    {
        handle_event(event);
    }
}

/**
 * Handle a SDL event.
 *
 * @retval true E
 */
void Window::handle_event(SDL_Event & event)
{
    switch (event.type)
    {
    case SDL_QUIT:
        m_exit_requested = true;
        break;

    case SDL_KEYDOWN:
        switch (event.key.keysym.sym)
        {
        case SDLK_ESCAPE:
            m_exit_requested = true;
            break;
        }
        break;

    case SDL_WINDOWEVENT:
        switch (event.window.event)
        {
        case SDL_WINDOWEVENT_EXPOSED:
            redraw();
            break;
        case SDL_WINDOWEVENT_RESIZED:
            resize();
            redraw();
            break;
        }
        break;
    }
}

void Window::resize()
{
    int width;
    int height;
    SDL_GetWindowSize(m_window, &width, &height);
    glViewport(0, 0, width, height);
}

void Window::redraw()
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    SDL_GL_SwapWindow(m_window);
}