// wait_for_files - Efficiently sleeps until the files specified on the
// command line exist (or have existed during execution).
// Linux 2.6.13, GNU C only.  Use gcc -std=c99
// glibc 2.4 or define PRIVATE_INOTIFY_HEADER

// #define PRIVATE_INOTIFY_HEADER "inotifytools/inotify.h"

#include <errno.h>
#include <error.h>
#include <libgen.h>
#include <stdbool.h>
#include <string.h>
#ifdef PRIVATE_INOTIFY_HEADER
#include PRIVATE_INOTIFY_HEADER
#else
#include <sys/inotify.h>
#endif
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>

char *strdup(const char *s); // wtf?

int main(int argc, char **argv)
{
  if (argc == 1) return 0;
  --argc; ++argv;

  int notify = inotify_init();
  if (notify < 0)
    error(-1, errno, "inotify_init error");

  struct wdtab_t {
    char *basename;
    int wd;		// set to 0 when found
  } wdtab[argc];

  bool done = true;
  for (int i = 0; i < argc; ++i) {
    struct wdtab_t *p = &wdtab[i];

    char *dirname_mem;
    if (!(dirname_mem = strdup(argv[i])) ||
	!(p->basename = strdup(argv[i])))
      error(-1, errno, "strdup error");
    char *dirname_val = dirname(dirname_mem);
    p->basename = basename(p->basename);

    p->wd = inotify_add_watch(notify, dirname_val, IN_CREATE|IN_MASK_ADD);
    if (p->wd < 0)
      error(-1, errno, "inotify_add_watch error (file: %s)", argv[i]);
    free(dirname_mem);

    struct stat dummy; 
    if (stat(argv[i], &dummy) == 0)
      p->wd = 0;
    else
      done = false;
  }
  if (done) return 0;

  for (;;) {
    fd_set rfds;
    FD_ZERO(&rfds);
    FD_SET(notify, &rfds);
    switch (select(notify+1, &rfds, NULL, NULL, NULL)) {
      case -1: error(-1, errno, "select error");
      case 0: continue; // this should never happen
    }

    // is ioctl FIONREAD even documented?
    int bytes_ready = 0;
    if (ioctl(notify, FIONREAD, &bytes_ready) < 0)
      error(-1, errno, "ioctl FIONREAD (inotify) error");
    if (bytes_ready % sizeof(struct inotify_event) != 0)
      // this should never ever ever happen, evar
      error(-1, 0, "ioctl FIONREAD (inotify) returned bizarre result (%i)",
	    bytes_ready);
    if (bytes_ready < sizeof(struct inotify_event))
      continue; // bytes_ready <= 0.  this should never happen

    struct inotify_event evs[bytes_ready / sizeof(struct inotify_event)];

    ssize_t r;
    if ((r = read(notify, evs, sizeof(evs))) != sizeof(evs)) {
      if (r < 0)
	error(-1, errno, "read error (inotify)");
      else
	error(1, 0, "short read (inotify, got %i, expected %i)",
	      (int) r, (int) sizeof(evs));
    }

    done = true;
    for (int j = 0; j < sizeof(evs) / sizeof(evs[0]); ++j) {
      struct inotify_event *ev = &evs[j];
      for (int i = 0; i < argc; ++i) {
	struct wdtab_t *p = &wdtab[i];
	if (!p->wd)
	  continue;
	else if ((ev->wd == p->wd) &&
		 (ev->mask|IN_CREATE) &&
		 !strcmp(ev->name, p->basename))
        {
	  p->wd = 0;
	} else
	  done = false;
      }
    }
    if (done) return 0;
  }
}