#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdlib.h>
#include <sys/time.h>
#include "thread.h"

/* Somme divide and conquer
 *
 * la durée doit être proportionnel à la valeur du résultat.
 * valgrind doit être content.
 * jusqu'à quelle valeur cela fonctionne-t-il ?
 *
 * support nécessaire:
 * - thread_create()
 * - thread_join() avec récupération de la valeur de retour
 * - retour sans thread_exit()
 */

struct dac_in_t {
    unsigned long* arr;
    int st;
    int end;
};

static void* s_dac_sum(void* _value)
{
  thread_t th, th2;
  int err;
  void *res = NULL, *res2 = NULL;
  struct dac_in_t* in = (struct dac_in_t*) _value;

  /* on passe un peu la main aux autres pour eviter de faire uniquement la partie gauche de l'arbre */
  thread_yield();

  if (in->end <= in->st + 1)
    return (void*)in->arr[in->st];

  size_t mid = (in->end + in->st) / 2;
  struct dac_in_t in1 = {in->arr, in->st, mid};
  struct dac_in_t in2 = {in->arr, mid, in->end};

  err = thread_create(&th, s_dac_sum, (void*)&in1);
  assert(!err);
  err = thread_create(&th2, s_dac_sum, (void*)&in2);
  assert(!err);

  err = thread_join(th, &res);
  assert(!err);
  err = thread_join(th2, &res2);
  assert(!err);

  return (void*)((unsigned long) res + (unsigned long) res2);
}

int main(int argc, char *argv[])
{
  unsigned long res;
  size_t n;
  struct timeval tv1, tv2;
  double s;

  if (argc < 2) {
    printf("argument manquant: entier n pour lequel dac_sum(n)\n");
    return EXIT_FAILURE;
  }

  n = atoi(argv[1]);
  unsigned long arr[n];
  for (size_t i = 0 ; i < n ; ++i)
      arr[i] = i + 1;

  struct dac_in_t in = { arr, .st=0, .end=n };
  gettimeofday(&tv1, NULL);
  res = (unsigned long)s_dac_sum((void *)&in);
  gettimeofday(&tv2, NULL);
  s = (tv2.tv_sec-tv1.tv_sec) + (tv2.tv_usec-tv1.tv_usec) * 1e-6;

  unsigned long expected = (n * (n + 1)) / 2;
  if (res != expected) {
    printf("dac(%lu) != %lu (FAILED)\n", res, expected);
    printf("GRAPH;%lu;%lu;%e;%s\n", n, res, s, "FAILED" );
    return EXIT_FAILURE;
  } else {
    printf("fibo(%lu) = %lu en %e s\n", n, res, s );
    printf("GRAPH;%lu;%lu;%e;%s\n", n, res, s, "SUCCESS" );
    return EXIT_SUCCESS;
  }
}