#include <unistd.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <assert.h>
#include <string.h>

#include "lib.h"

struct backup_streamer backup_streamer_init(char *cwd) {
  struct backup_streamer output;
  output.cwd_length = strnlen(cwd, PATH_MAX);
  char *end = stpncpy(output.to_prefix, cwd, PATH_MAX - 3);
  *(end++) = '.';
  *(end++) = 'b';
  *(end++) = 'k';
  *(end++) = 0;
  return output;
}

void get_backup_destination(struct backup_streamer *streamer, char* from) {
  char *cursor = stpncpy(streamer->cursor, streamer->to_prefix, PATH_MAX);
  from += streamer->cwd_length;
  int n = (cursor - streamer->cursor) - 2;
  strncpy(cursor, from, PATH_MAX - n);
}

int is_dir(char *path) {
  struct stat info;
  if (stat(path, &info) != 0) return -1;
  return S_ISDIR(info.st_mode);
}

void backup_file(char *from, char *to) {
  ensure_parents_exist(to);
  pid_t pid;
  if ((pid = fork()) == 0) {
    char *argv[] = {"/usr/bin/cp", from, to, NULL};
    execv(argv[0], argv);
  }
  assert(waitpid(pid, NULL, 0) != -1);
}

void ensure_parents_exist(char *path) {
  int n = strnlen(path, PATH_MAX);
  for (int i = 1; i < n; i++) {
    if (path[i] != '/') continue;
    path[i] = 0;
    if (is_dir(path) == -1) {
      debugf("mkdir %s\n", path);
      assert(mkdir(path, 0755) != -1);
    }
    path[i] = '/';
  }
}