// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
//
// This is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of
// the License, or (at your option) any later version.
//
// This software is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this manual; if not, see
// <http://www.gnu.org/licenses/>.

package inotify

import (
	"os"

	"golang.org/x/sys/unix"
)

func newPathError(op string, path string, err error) error {
	if err == nil {
		return nil
	}
	return &os.PathError{Op: op, Path: path, Err: err}
}

// Create and initialize inotify instance.
func sys_inotify_init() (inFd, error) {
	fd, err := unix.InotifyInit()
	return inFd(fd), os.NewSyscallError("inotify_init", err)
}

// Create and initialize inotify instance.
func sys_inotify_init1(flags int) (inFd, error) {
	fd, err := unix.InotifyInit1(flags)
	return inFd(fd), os.NewSyscallError("inotify_init1", err)
}

// Add watch of object NAME to inotify instance FD.  Notify about
// events specified by MASK.
func sys_inotify_add_watch(fd inFd, name string, mask Mask) (Wd, error) {
	wd, err := unix.InotifyAddWatch(int(fd), name, uint32(mask))
	return Wd(wd), newPathError("inotify_add_watch", name, err)
}

// Remove the watch specified by WD from the inotify instance FD.
func sys_inotify_rm_watch(fd inFd, wd Wd) error {
	success, err := unix.InotifyRmWatch(int(fd), uint32(wd))
	switch success {
	case -1:
		if err == nil {
			panic("should never happen")
		}
		os.NewSyscallError("inotify_rm_watch", err)
	case 0:
		if err != nil {
			panic("should never happen")
		}
		return nil
	}
	panic("should never happen")
}

func sys_close(fd inFd) error {
	return os.NewSyscallError("close", unix.Close(int(fd)))
}

func sys_read(fd inFd, p []byte) (int, error) {
	n, err := unix.Read(int(fd), p)
	return n, os.NewSyscallError("read", err)
}

func sys_dupfd_cloexec(fd inFd) (inFd, error) {
	n, _, errno := unix.Syscall(unix.SYS_FCNTL, uintptr(fd), unix.F_DUPFD_CLOEXEC, 0)
	if errno != 0 {
		return -1, os.NewSyscallError("dupfd_cloexec", errno)
	}
	return inFd(n), nil
}

func sys_setnonblock(fd inFd, nonblocking bool) error {
	err := unix.SetNonblock(int(fd), nonblocking)
	return os.NewSyscallError("setnonblock", err)
}

func sys_getnonblock(fd inFd) (bool, error) {
	flag, _, errno := unix.Syscall(unix.SYS_FCNTL, uintptr(fd), unix.F_GETFL, 0)
	if errno != 0 {
		return false, os.NewSyscallError("getnonblock", errno)
	}
	return flag&unix.O_NONBLOCK != 0, nil
}