/*-----------------------------------------------------------------------------
 *				HTBLA-Leonding / Class: 2IHIF
 *-----------------------------------------------------------------------------
 * Exercise Number: S05
 * Title:			Stopwatch
 * Author:			Marc Tismonar
 *-----------------------------------------------------------------------------
 * Description:
 * Implementation of a simple stopwatch
 *-----------------------------------------------------------------------------
*/
#include <time.h>
#include <stdbool.h>

#include "stopwatch.h"

/**
 * Implementation hints:
 * 
 * time functions:
 *   are provided by `time.h`
 *   use function `clock()` to get the current `ticks`
 *   `ticks` are of type `clock_t`
 *   use `CLOCKS_PER_SEC` to calculate the time in seconds from ticks
 *     -> seconds = ticks / CLOCK_PER_SEC
 *   microseconds are s * 10^-6
 */

static clock_t start_time = 0;
static clock_t passed_time = 0;
static bool is_active = false;

/**
 * Starts taking the time. This function always starts at 0.
 */
void stopwatch_start()
{
    start_time = clock();
    passed_time = 0;
    is_active = true;
}

/**
 * Stops or pauses taking the time. Time measurement can be resumed 
 * via `stopwatch_resume`.
 */
void stopwatch_stop()
{
    if (!is_active) {
        return;
    }

    passed_time += clock() - start_time;
    is_active = false;
}

/**
 * Resumes taking the time. The previously measured time value is
 * used as start value.
 */
void stopwatch_resume()
{
    if (is_active) {
        return;
    }

    start_time = clock();
    is_active = true;
}

/**
 * Determines whether or not the stopwatch takes the time.
 * @return True if the stopwatch is measuring, false otherwise.
 */
bool stopwatch_is_active()
{
    return is_active;
}

/**
 * The measured time in microseconds.
 * 
 * @return Either the processor time elapsed since start_stopwatch() has been called or
 * the processor time elapsed between the calls of start_stopwatch() and stop_stopwatch().
 */
double stopwatch_get_elapsed_time()
{
    clock_t total_time = passed_time;
    
    if (is_active) {
        total_time += clock() - start_time;
    }
    
    return ((double)total_time / CLOCKS_PER_SEC) * 1000000.0;
}