#include "fps_counter.h"

#include <SDL2/SDL_timer.h>

#include "log.h"

void fps_counter_init(struct fps_counter *counter) {
    counter->started = SDL_FALSE;
    // no need to initialize the other fields, they are meaningful only when
    // started is true
}

void fps_counter_start(struct fps_counter *counter) {
    counter->started = SDL_TRUE;
    counter->slice_start = SDL_GetTicks();
    counter->nr_rendered = 0;
#ifdef SKIP_FRAMES
    counter->nr_skipped = 0;
#endif
}

void fps_counter_stop(struct fps_counter *counter) {
    counter->started = SDL_FALSE;
}

static void display_fps(struct fps_counter *counter) {
#ifdef SKIP_FRAMES
    if (counter->nr_skipped) {
        LOGI("%d fps (+%d frames skipped)", counter->nr_rendered, counter->nr_skipped);
    } else {
#endif
    LOGI("%d fps", counter->nr_rendered);
#ifdef SKIP_FRAMES
    }
#endif
}

static void check_expired(struct fps_counter *counter) {
    Uint32 now = SDL_GetTicks();
    if (now - counter->slice_start >= 1000) {
        display_fps(counter);
        // add a multiple of one second
        Uint32 elapsed_slices = (now - counter->slice_start) / 1000;
        counter->slice_start += 1000 * elapsed_slices;
        counter->nr_rendered = 0;
#ifdef SKIP_FRAMES
        counter->nr_skipped = 0;
#endif
    }
}

void fps_counter_add_rendered_frame(struct fps_counter *counter) {
    check_expired(counter);
    ++counter->nr_rendered;
}

#ifdef SKIP_FRAMES
void fps_counter_add_skipped_frame(struct fps_counter *counter) {
    check_expired(counter);
    ++counter->nr_skipped;
}
#endif