#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <GL/glew.h>
#include <SDL3/SDL.h>
#include <SDL3/SDL_opengl.h>
#include <SDL3/SDL_main.h> // only include this one in the source file with main()!
#include "opengl.h"

#define INITIAL_FPS 60

static double FPS = INITIAL_FPS;
static double FrameTime = 1.0 / INITIAL_FPS;

static double PerformancePeriod;

static double GetTime( void )
{
    return PerformancePeriod * SDL_GetPerformanceCounter();
}

static void SetTitle ( SDL_Window *window )
{
    char title[48] = {0};
    SDL_snprintf(title, sizeof(title), "Hello Triangles! Framelimit: %6.3f Hz", FPS);
    SDL_SetWindowTitle(window, title);
}

int main( int argc, char* argv[] )
{
    _glWindows_t glW;
    const int WIDTH = 640;
    const int HEIGHT = 480;
    int delayThreshold = 2;
    int r, g, b, alpha_s, depth_s, stencil_s, dbuffer, glVersionMa, glVersionMi, glAccel, glProfile = 0;
    double sleepTime = 0;
    double timeCounter = 0;
    bool loopShouldStop = false;

    SDL_SetHint(SDL_HINT_RENDER_VSYNC, 0);
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "SDL_Init failed: %s", SDL_GetError());
        exit(EXIT_FAILURE);
    }

    if (!SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY)) {
        SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "Set atrribute SDL_GL_CONTEXT_PROFILE_MASK: %s", SDL_GetError());
        exit(EXIT_FAILURE);
    }

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

    PerformancePeriod = 1.0 / SDL_GetPerformanceFrequency();
    timeCounter = GetTime();

    glW.window = SDL_CreateWindow("Hello SDL", WIDTH, HEIGHT, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
    if (!glW.window) {
        SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "SDL_CreateWindow: %s", SDL_GetError());
        exit(EXIT_FAILURE);
    }

    glW.glcontext = SDL_GL_CreateContext(glW.window);
    if (!glW.glcontext) {
        SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "SDL_GL_CreateContext: %s", SDL_GetError());
        exit(EXIT_FAILURE);
    }

    SetTitle(glW.window);

    SDL_HideCursor();

    glewExperimental = GL_TRUE;
    GLenum err = glewInit();
    if (err != GLEW_OK) {
        SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "glewInit: %s", glewGetErrorString(err));
        exit(EXIT_FAILURE);
    }

    SDL_LogVerbose(SDL_LOG_CATEGORY_RENDER, "Status: Using GLEW %s\n", glewGetString(GLEW_VERSION));
    SDL_GL_GetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, &glProfile);
    SDL_GL_GetAttribute(SDL_GL_ACCELERATED_VISUAL, &glAccel);
    SDL_GL_GetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, &glVersionMa);
    SDL_GL_GetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, &glVersionMi);
    SDL_GL_GetAttribute(SDL_GL_RED_SIZE, &r);
    SDL_GL_GetAttribute(SDL_GL_GREEN_SIZE, &g);
    SDL_GL_GetAttribute(SDL_GL_BLUE_SIZE, &b);
    SDL_GL_GetAttribute(SDL_GL_ALPHA_SIZE, &alpha_s);
    SDL_GL_GetAttribute(SDL_GL_DEPTH_SIZE, &depth_s);
    SDL_GL_GetAttribute(SDL_GL_STENCIL_SIZE, &stencil_s);
    SDL_GL_GetAttribute(SDL_GL_DOUBLEBUFFER, &dbuffer);

    SDL_LogVerbose(SDL_LOG_CATEGORY_RENDER, "OpenGL Version: %d.%d, OpenGL Accelerated: %d, OpenGL Profile Mask: %d",
                   glVersionMa, glVersionMi, glAccel, glProfile);
    SDL_LogVerbose(SDL_LOG_CATEGORY_RENDER, "Red size: %d, Green size: %d, Blue size: %d, Alpha size: %d, Depth size: %d, Stencil size: %d, DoubleBuffer: %d",
                   r, g, b, alpha_s, depth_s, stencil_s, dbuffer);

    SDL_GL_SetSwapInterval(0);
    startShaderProg();

    while (!loopShouldStop) {
        SDL_Event e;
        SDL_zero(e);
        while (SDL_PollEvent(&e)) {
            if (e.type == SDL_EVENT_QUIT)
                loopShouldStop = true;
            else if (e.type == SDL_EVENT_WINDOW_RESIZED) {
                resizeWindow(e.window.data1, e.window.data2);
            }
            else if (e.type == SDL_EVENT_KEY_DOWN) {
                if (e.key.key == SDLK_X) {
                    FPS -= 0.1;
                    if (FPS < 1) {
                        FPS = 1;
                    }
                    FrameTime = 1.0 / FPS;
                    SetTitle(glW.window);
                } else if (e.key.key == SDLK_C) {
                    FPS += 0.1;
                    FrameTime = 1.0 / FPS;
                    SetTitle(glW.window);
                }
                if (e.key.key == SDLK_ESCAPE)
                    loopShouldStop = true;
            }
        }

        _GLBuffer();
        if (!SDL_GL_SwapWindow(glW.window)) {
            SDL_LogCritical(SDL_LOG_CATEGORY_ASSERT, "SDL_GL_SwapWwindow: %s", SDL_GetError());
            exit(EXIT_FAILURE);
        }

        sleepTime = timeCounter - GetTime();
        if (sleepTime * 1000 > delayThreshold) {
            Uint32 ms = (Uint32)(sleepTime * 1000) - delayThreshold;
            SDL_Delay(ms);
            if (timeCounter < GetTime()) {
                delayThreshold++;
                SDL_Log("Slept too long. Increased threshold to %u ms", delayThreshold);
            }
        }

        while (timeCounter > GetTime()) {
        /* Waiting for the right moment. */
        }
        timeCounter += FrameTime;
    }

    SDL_DestroyWindow(glW.window);
    SDL_GL_DestroyContext(glW.glcontext);
    SDL_Quit();
    exit(EXIT_SUCCESS);
}