/*
 * This file is part of fwm-sysdaemon
 *  fwatch.c - watch single file for updates
 *
 * Copyright (c) 2022 firk (firk@cantconnect.ru)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The origin of this software must not be misrepresented; you must
 *    not claim that you wrote the original software.
 * 4. Altered versions in any form must be plainly marked as such, and
 *    must not be misinterpreted as being the original software.
 *
 * This software is provided by the author and contributors `as is'
 * without any express or implied warranty.
 */

#include <unistd.h>
#include <errno.h>
#include <poll.h>
#include <sys/types.h>
#include <sys/inotify.h>
#include "fwatch.h"

static int qfd = -2;
static int err;

extern int fwatch_add(char const *fn) {
  int wd;
  if(qfd==-2 && (qfd = inotify_init1(IN_NONBLOCK))<0) { err=errno; qfd = -1; }
  if(qfd<0) { errno=err; return -1; }
  return inotify_add_watch(qfd, fn, IN_MODIFY);
}

extern int fwatch_check(void) {
  struct inotify_event e[3];
  ssize_t len;
  int r;
  
  if(qfd==-2) return 0;
  if(qfd<0) { errno=EBADF; return -1; }
  r = 0;
  while(1) {
    if((len = read(qfd, e, sizeof(e)))<0) {
      if(errno==EAGAIN) return r;
      return -1;
    }
    if(!r) { errno=-1; return -1; }
    r = 1;
  }
}

extern int fwatch_wait(int ms) {
  struct pollfd pfd;
  int r;

  if(qfd==-2) { usleep(ms*1000); return 0; }
  if(qfd<0) { errno=EBADF; return -1; }
  pfd.fd = qfd;
  pfd.events = POLLIN;
  pfd.revents = 0;
  r = poll(&pfd, 1, ms);
  /* ret. -1/EINTR or -1/errno or 0(timeout) or 1(have) */
  return fwatch_check();
}