#include <SDL.h>
#include <SDL_image.h>
#include <SDL_ttf.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include "kiss.h"

char *title = "SDL 24 - Calculating Frame Rate";
SDL_Window *window;
SDL_Renderer *renderer;
TTF_Font *font1;
TTF_Font *font2;
SDL_Texture *text1;
SDL_Texture *text2;
SDL_Texture *text3;
int n_frames;
double fps;

struct timer
{
   uint32_t start;
   uint32_t pause;
};

struct timer _fps_timer = {0, 0};
struct timer *fps_timer = &_fps_timer;

void
timer_start(struct timer *t)
{
   t->start = SDL_GetTicks();
   t->pause = 0;
}

void
timer_stop(struct timer *t)
{
   t->start = 0;
   t->pause = 0;
}

void
timer_pause(struct timer *t)
{
   if (!t->start || t->pause)
     return;
   t->pause = SDL_GetTicks() - t->start;
}

void
timer_unpause(struct timer *t)
{
   if (!t->pause)
     return;
   t->start = SDL_GetTicks() - t->pause;
   t->pause = 0;
}

uint32_t
timer_get(struct timer *t)
{
   if (!t->start)
     return 0;
   if (t->pause)
     return t->pause;
   return SDL_GetTicks() - t->start;
}

bool
timer_is_started(struct timer *t)
{
   return t->start && 1;
}

bool
timer_is_paused(struct timer *t)
{
   return t->pause && 1;
}

int
init_sdl(void)
{
   int status = -1;

   SDL_INIT(SDL_INIT_VIDEO);
   IMG_INIT(IMG_INIT_PNG);
   TTF_INIT();
   window = SDL_CREATEWINDOW(title, 50, 50, 800, 600, SDL_WINDOW_FULLSCREEN_DESKTOP);
   renderer = SDL_CREATERENDERER(window, -1, SDL_RENDERER_ACCELERATED);      // | SDL_RENDERER_PRESENTVSYNC);
   status = 0;
error:
   return status;
}

#define INIT_SDL(...) SDL_ZERO(init_sdl, __VA_ARGS__)

SDL_Texture *
texture_from_text(TTF_Font *font, char *text, SDL_Color colour)
{
   SDL_Texture *texture = NULL;
   SDL_Surface *surface = NULL;
   surface = TTF_RENDERTEXT_BLENDED(font, text, colour);
   texture = SDL_CREATETEXTUREFROMSURFACE(renderer, surface);
error:
   SDL_FreeSurface(surface);
   return texture;
}

#define TEXTURE_FROM_TEXT(...) SDL_CHK(texture_from_text, __VA_ARGS__)

void
close_sdl(void)
{
   SDL_DestroyRenderer(renderer);
   SDL_DestroyWindow(window);
   TTF_Quit();
   IMG_Quit();
   SDL_Quit();
}

int
draw(void)
{
   int status = -1;
   char time_text[20];

   int w, h;
   int tw, th;
   SDL_Rect target;

   snprintf(time_text, sizeof(time_text), "%.4f", fps);

   text2 = TEXTURE_FROM_TEXT(font2, time_text, (SDL_Color){0xFF, 0x7F, 0xCF, 0xFF});

   SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x7F, 0xFF);
   SDL_RENDERCLEAR(renderer);

   SDL_GetWindowSize(window, &w, &h);
   SDL_QUERYTEXTURE(text1, NULL, NULL, &tw, &th);
   target = (SDL_Rect){
      w / 2 - tw / 2, 10, tw, th
   };
   SDL_RENDERCOPY(renderer, text1, NULL, &target);
   SDL_QUERYTEXTURE(text2, NULL, NULL, &tw, &th);
   target = (SDL_Rect){
      w / 2 - tw / 2, h / 2 - th / 2, tw, th
   };
   SDL_RENDERCOPY(renderer, text2, NULL, &target);
   SDL_QUERYTEXTURE(text3, NULL, NULL, &tw, &th);
   target = (SDL_Rect){
      w / 2 - tw / 2, h - th - 10, tw, th
   };
   SDL_RENDERCOPY(renderer, text3, NULL, &target);

   SDL_RenderPresent(renderer);

   SDL_DestroyTexture(text2);

   status = 0;
error:
   return status;
}

#define DRAW(...) SDL_ZERO(draw, __VA_ARGS__)

int
main(void)
{
   int exit_status = EXIT_FAILURE;
   bool quit = 0;
   SDL_Event e;

   INIT_SDL();

   font1 = TTF_OPENFONT("OpenSans-Regular.ttf", 28);
   font2 = TTF_OPENFONT("OpenSans-Regular.ttf", 100);
   text1 = TEXTURE_FROM_TEXT(font1, "Average Frames Per Second:", (SDL_Color){0xFF, 0xFF, 0xFF, 0xFF});
   text3 = TEXTURE_FROM_TEXT(font2, "BOGOMETER", (SDL_Color){0xFF, 0x7F, 0x3F, 0xFF});

   DRAW();

   timer_start(fps_timer);

   while (!quit)
     {
        DRAW();
        n_frames++;
        fps = n_frames / (timer_get(fps_timer) / 1000.0);
        if (SDL_PollEvent(&e))
          {
             if (e.type == SDL_QUIT)
               quit = 1;
          }
     }

   exit_status = EXIT_SUCCESS;
error:
   SDL_DestroyTexture(text1);
   SDL_DestroyTexture(text3);
   TTF_CloseFont(font1);
   TTF_CloseFont(font2);
   close_sdl();
   exit(exit_status);
}