#include <SDL.h>
#include "clock.h"

#define TICK_SECS 0.001

Clock::Clock()
: time_factor(1),
  frame_delta(0), real_frame_delta(0),
  step_delta(0), real_step_delta(0),
  time_left(0), pause_mode(false),
  initialized(false)
{
}

void Clock::setTimeFactor(double tf) {
    double ratio = tf / time_factor;
    time_factor = tf;
    frame_delta *= ratio;
    step_delta *= ratio;
    time_left *= ratio;
}

void Clock::update() {
    int new_ticks = measureTicks();
    if (!initialized) {
        ticks = new_ticks;
        initialized = true;
    }
    
    // will be incremented with each catchup, cause we can't guarantee that
    // the whole time span that has passed will be caught up.
    frame_delta = 0;
    
    real_frame_delta = (double)(new_ticks - ticks) * TICK_SECS;
    
    if (pause_mode) {
        step_delta = real_step_delta = 0;
    } else {
        time_left = real_frame_delta * time_factor;
    }
    ticks = new_ticks;
}

bool Clock::catchup(double time) {
    if (pause_mode) return false;
    if (time_left <= 0.0) {
        time_left = step_delta = real_step_delta = 0;
        return false;
    }
    if (time_left < time) time = time_left;
    time_left -= time;
    step_delta = time;
    real_step_delta = time / time_factor;
    frame_delta += time;
    return true;
}

void Clock::skip() {
    if (pause_mode) return;
    time_left = 0;
}

int Clock::measureTicks() {
    return SDL_GetTicks();
}