/* firedemo with SDL2, from http://www.hanshq.net/fire.html */

#include <SDL.h>
#include <stdbool.h>
#include <stdio.h>

#define WIDTH 80
#define HEIGHT 50
#define WIN_WIDTH 640
#define WIN_HEIGHT 400
#define FPS 30

static const uint32_t palette[256] = {
/* Jare's original FirePal. */
#define C(r,g,b) ((((r) * 4) << 16) | ((g) * 4 << 8) | ((b) * 4))
C( 0,   0,   0), C( 0,   1,   1), C( 0,   4,   5), C( 0,   7,   9),
C( 0,   8,  11), C( 0,   9,  12), C(15,   6,   8), C(25,   4,   4),
C(33,   3,   3), C(40,   2,   2), C(48,   2,   2), C(55,   1,   1),
C(63,   0,   0), C(63,   0,   0), C(63,   3,   0), C(63,   7,   0),
C(63,  10,   0), C(63,  13,   0), C(63,  16,   0), C(63,  20,   0),
C(63,  23,   0), C(63,  26,   0), C(63,  29,   0), C(63,  33,   0),
C(63,  36,   0), C(63,  39,   0), C(63,  39,   0), C(63,  40,   0),
C(63,  40,   0), C(63,  41,   0), C(63,  42,   0), C(63,  42,   0),
C(63,  43,   0), C(63,  44,   0), C(63,  44,   0), C(63,  45,   0),
C(63,  45,   0), C(63,  46,   0), C(63,  47,   0), C(63,  47,   0),
C(63,  48,   0), C(63,  49,   0), C(63,  49,   0), C(63,  50,   0),
C(63,  51,   0), C(63,  51,   0), C(63,  52,   0), C(63,  53,   0),
C(63,  53,   0), C(63,  54,   0), C(63,  55,   0), C(63,  55,   0),
C(63,  56,   0), C(63,  57,   0), C(63,  57,   0), C(63,  58,   0),
C(63,  58,   0), C(63,  59,   0), C(63,  60,   0), C(63,  60,   0),
C(63,  61,   0), C(63,  62,   0), C(63,  62,   0), C(63,  63,   0),
/* Followed by "white heat". */
#define W C(63,63,63)
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W,
W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W, W
#undef W
#undef C
};

static uint8_t fire[WIDTH * HEIGHT];
static uint8_t prev_fire[WIDTH * HEIGHT];
static uint32_t framebuf[WIDTH * HEIGHT];

int main()
{
        SDL_Window *window;
        SDL_Renderer *renderer;
        SDL_Texture *texture;
        SDL_Event event;
        int i;
        uint32_t sum;
        uint8_t avg;
        bool full_screen = false;
        bool keep_running = true;

        if (SDL_Init(SDL_INIT_VIDEO) < 0) {
                fprintf(stderr, "Failed SDL_Init: %s\n", SDL_GetError());
                return 1;
        }

        window = SDL_CreateWindow("SDL2 firedemo (www.hanshq.net/fire.html)",
                        SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
                        WIN_WIDTH, WIN_HEIGHT,
                        SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
        if (window == NULL) {
                fprintf(stderr, "Failed CreateWindow: %s\n", SDL_GetError());
                return 1;
        }

        renderer = SDL_CreateRenderer(window, -1, 0);
        if (renderer == NULL) {
                fprintf(stderr, "Failed CreateRenderer: %s\n", SDL_GetError());
                return 1;
        }

        texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
                        SDL_TEXTUREACCESS_STREAMING, WIDTH, HEIGHT);
        if (texture == NULL) {
                fprintf(stderr, "Failed CreateTexture: %s\n", SDL_GetError());
                return 1;
        }


        while (keep_running) {
                while (SDL_PollEvent(&event)) {
                        if (event.type == SDL_QUIT) {
                                keep_running = false;
                        } else if (event.type == SDL_KEYDOWN) {
                                if (event.key.keysym.sym == SDLK_f) {
                                        full_screen = !full_screen;
                                        SDL_SetWindowFullscreen(window,
                                                full_screen ?
                                                SDL_WINDOW_FULLSCREEN_DESKTOP :
                                                0);
                                } else if (event.key.keysym.sym == SDLK_q) {
                                        keep_running = false;
                                }
                        }
                }

                for (i = WIDTH + 1; i < (HEIGHT - 1) * WIDTH - 1; i++) {
                        /* Average the eight neighbours. */
                        sum = prev_fire[i - WIDTH - 1] +
                              prev_fire[i - WIDTH    ] +
                              prev_fire[i - WIDTH + 1] +
                              prev_fire[i - 1] +
                              prev_fire[i + 1] +
                              prev_fire[i + WIDTH - 1] +
                              prev_fire[i + WIDTH    ] +
                              prev_fire[i + WIDTH + 1];
                        avg = (uint8_t)(sum / 8);

                        /* "Cool" the pixel if the two bottom bits of the
                           sum are clear (somewhat random). For the bottom
                           rows, cooling can overflow, causing "sparks". */
                        if (!(sum & 3) &&
                            (avg > 0 || i >= (HEIGHT - 4) * WIDTH)) {
                                avg--;
                        }
                        fire[i] = avg;
                }

                /* Copy back and scroll up one row.
                   The bottom row is all zeros, so it can be skipped. */
                for (i = 0; i < (HEIGHT - 2) * WIDTH; i++) {
                        prev_fire[i] = fire[i + WIDTH];
                }

                /* Remove dark pixels from the bottom rows (except again the
                   bottom row which is all zeros). */
                for (i = (HEIGHT - 7) * WIDTH; i < (HEIGHT - 1) * WIDTH; i++) {
                        if (fire[i] < 15) {
                                fire[i] = 22 - fire[i];
                        }
                }

                /* Copy to framebuffer and map to RGBA, scrolling up one row. */
                for (i = 0; i < (HEIGHT - 2) * WIDTH; i++) {
                        framebuf[i] = palette[fire[i + WIDTH]];
                }

                /* Update the texture and render it. */
                SDL_UpdateTexture(texture, NULL, framebuf,
                                WIDTH * sizeof(framebuf[0]));
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, texture, NULL, NULL);
                SDL_RenderPresent(renderer);

                SDL_Delay(1000 / FPS);
        }

        SDL_DestroyTexture(texture);
        SDL_DestroyRenderer(renderer);
        SDL_DestroyWindow(window);

        SDL_Quit();

        return 0;
}