#include <stdio.h>
#include <stdlib.h>
#include "timer.h"

#define SEC_TO_US 1000000

void timer_init(Timer *t) {
	t->start_rusage = (struct rusage*)malloc(sizeof(struct rusage));
	t->end_rusage = (struct rusage*)malloc(sizeof(struct rusage));
	t->result_rusage = (struct rusage*)malloc(sizeof(struct rusage));
}

void timer_start(Timer* t) { 
	getrusage(RUSAGE_SELF, t->start_rusage);
}

void timer_end(Timer* t) { 
	getrusage(RUSAGE_SELF, t->end_rusage); 
	// Calculate the result
	if (t->result_rusage == NULL) { 
		t->result_rusage = (struct rusage*)malloc(sizeof(struct rusage)); 
	}

	diff_timeval(&(t->end_rusage->ru_utime), &t->start_rusage->ru_utime, &t->result_rusage->ru_utime);
	diff_timeval(&t->end_rusage->ru_stime, &t->start_rusage->ru_stime, &t->result_rusage->ru_stime); 
}

void diff_timeval(struct timeval* t1, struct timeval* t2, struct timeval* dst) {
	dst->tv_sec = t1->tv_sec - t2->tv_sec;
	if (t1->tv_usec < t2->tv_usec) { // Do a carry-ish operation
		dst->tv_sec--;
		dst->tv_usec = (t1->tv_usec + SEC_TO_US) - t2->tv_usec;
	} else	dst->tv_usec = t1->tv_usec - t2->tv_usec;
}

void display_statistics(Timer* t) {
	if (t->result_rusage == NULL) {
		printf("No statistics captured.\n");
		return;
	}

	printf("User time used: %lfs\n", (t->result_rusage->ru_utime.tv_sec + ((double)t->result_rusage->ru_utime.tv_usec / SEC_TO_US)));
	printf("Sys time used: %lfs\n", (t->result_rusage->ru_stime.tv_sec + ((double)t->result_rusage->ru_stime.tv_usec / SEC_TO_US)));
}