#include <stddef.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>

/* cherche l'entree to_find dans le répertoire dirname */
void find_file(const char*dirname, const char* to_find) {
  DIR *curdir=opendir(dirname);
  assert(curdir);
  struct dirent *dir_entry = readdir(curdir);
  assert(dir_entry);

  /* on parcoure la liste des fichiers du repertoire */
  while(dir_entry) {

    if(strcmp(dir_entry->d_name, to_find) == 0) {
      /* fichier trouvé ! */
      printf("%s/%s\n", dirname, to_find);
    }

    if((strcmp(dir_entry->d_name, ".") != 0) &&
       (strcmp(dir_entry->d_name, "..") != 0)) {
      struct stat buf;

      int new_dirname_len = strlen(dirname) + strlen("/") + strlen(dir_entry->d_name) + 1;
      char* new_dirname = malloc(sizeof(char) * new_dirname_len);
      snprintf(new_dirname, new_dirname_len, "%s/%s", dirname, dir_entry->d_name);

      int ret = stat(new_dirname, &buf);
      assert(ret == 0);

      /* on cherche le fichier dans le sous-repertoire */
      if(S_ISDIR(buf.st_mode)) {
	find_file(new_dirname, to_find);
      }

      free(new_dirname);
    }
    dir_entry = readdir(curdir);
  }
}


/* Version reentrante de find_file
 * cherche l'entree to_find dans le répertoire dirname
 *
 */
void find_file_r(const char*dirname, const char* to_find) {
  DIR *curdir=opendir(dirname);
  assert(curdir);

  /* on suppose qu'il n'y a pas de nom de fichier > 255 caracteres
   * voir man readdir_r pour un exemple plus robuste
   */
  int name_max = 255;
  int len = offsetof(struct dirent, d_name) + name_max + 1;
  struct dirent *buffer = malloc(len);
  struct dirent *dir_entry = NULL;

  int ret = readdir_r(curdir, buffer, &dir_entry);
  assert(ret == 0);
  /* on parcoure la liste des fichiers du repertoire */
  while(dir_entry) {

    if(strcmp(dir_entry->d_name, to_find) == 0) {
      /* fichier trouvé ! */
      printf("%s/%s\n", dirname, to_find);
    }

    if((strcmp(dir_entry->d_name, ".") != 0) &&
       (strcmp(dir_entry->d_name, "..") != 0)) {
      struct stat buf;

      int new_dirname_len = strlen(dirname) + strlen("/") + strlen(dir_entry->d_name) + 1;
      char* new_dirname = malloc(sizeof(char) * new_dirname_len);
      snprintf(new_dirname, new_dirname_len, "%s/%s", dirname, dir_entry->d_name);

      int ret = stat(new_dirname, &buf);
      assert(ret == 0);

      /* on cherche le fichier dans le sous-repertoire */
      if(S_ISDIR(buf.st_mode)) {
	find_file_r(new_dirname, to_find);
      }

      free(new_dirname);
    }
    ret = readdir_r(curdir, buffer, &dir_entry);
  }
}

int main(int argc, char**argv) {
  if(argc<2){
    fprintf(stderr, "usage: %s <file>\n", argv[0]);
    return EXIT_FAILURE;
  }

  char* to_find=argv[1];

  find_file(".", to_find);

  return EXIT_SUCCESS;
}