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// Copyright (c) 2014-2015 The Notify Authors. All rights reserved.
// Use of this source code is governed by the MIT license that can be
// found in the LICENSE file.

// +build darwin,kqueue dragonfly freebsd netbsd openbsd

package notify

import (
    "fmt"
    "os"
    "syscall"
)

// newTrigger returns implementation of trigger.
func newTrigger(pthLkp map[string]*watched) trigger {
    return &kq{
        pthLkp: pthLkp,
        idLkp:  make(map[int]*watched),
    }
}

// kq is a structure implementing trigger for kqueue.
type kq struct {
    // fd is a kqueue file descriptor
    fd int
    // pipefds are file descriptors used to stop `Kevent` call.
    pipefds [2]int
    // idLkp is a data structure mapping file descriptors with data about watching
    // represented by them files/directories.
    idLkp map[int]*watched
    // pthLkp is a structure mapping monitored files/dir with data about them,
    // shared with parent trg structure
    pthLkp map[string]*watched
}

// watched is a data structure representing watched file/directory.
type watched struct {
    // p is a path to watched file/directory.
    p string
    // fd is a file descriptor for watched file/directory.
    fd int
    // fi provides information about watched file/dir.
    fi os.FileInfo
    // eDir represents events watched directly.
    eDir Event
    // eNonDir represents events watched indirectly.
    eNonDir Event
}

// Stop implements trigger.
func (k *kq) Stop() (err error) {
    // trigger event used to interrupt Kevent call.
    _, err = syscall.Write(k.pipefds[1], []byte{0x00})
    return
}

// Close implements trigger.
func (k *kq) Close() error {
    return syscall.Close(k.fd)
}

// NewWatched implements trigger.
func (*kq) NewWatched(p string, fi os.FileInfo) (*watched, error) {
    fd, err := syscall.Open(p, syscall.O_NONBLOCK|syscall.O_RDONLY, 0)
    if err != nil {
        return nil, err
    }
    return &watched{fd: fd, p: p, fi: fi}, nil
}

// Record implements trigger.
func (k *kq) Record(w *watched) {
    k.idLkp[w.fd], k.pthLkp[w.p] = w, w
}

// Del implements trigger.
func (k *kq) Del(w *watched) {
    syscall.Close(w.fd)
    delete(k.idLkp, w.fd)
    delete(k.pthLkp, w.p)
}

func inter2kq(n interface{}) syscall.Kevent_t {
    kq, ok := n.(syscall.Kevent_t)
    if !ok {
        panic(fmt.Sprintf("kqueue: type should be Kevent_t, %T instead", n))
    }
    return kq
}

// Init implements trigger.
func (k *kq) Init() (err error) {
    if k.fd, err = syscall.Kqueue(); err != nil {
        return
    }
    // Creates pipe used to stop `Kevent` call by registering it,
    // watching read end and writing to other end of it.
    if err = syscall.Pipe(k.pipefds[:]); err != nil {
        return nonil(err, k.Close())
    }
    var kevn [1]syscall.Kevent_t
    syscall.SetKevent(&kevn[0], k.pipefds[0], syscall.EVFILT_READ, syscall.EV_ADD)
    if _, err = syscall.Kevent(k.fd, kevn[:], nil, nil); err != nil {
        return nonil(err, k.Close())
    }
    return
}

// Unwatch implements trigger.
func (k *kq) Unwatch(w *watched) (err error) {
    var kevn [1]syscall.Kevent_t
    syscall.SetKevent(&kevn[0], w.fd, syscall.EVFILT_VNODE, syscall.EV_DELETE)

    _, err = syscall.Kevent(k.fd, kevn[:], nil, nil)
    return
}

// Watch implements trigger.
func (k *kq) Watch(fi os.FileInfo, w *watched, e int64) (err error) {
    var kevn [1]syscall.Kevent_t
    syscall.SetKevent(&kevn[0], w.fd, syscall.EVFILT_VNODE,
        syscall.EV_ADD|syscall.EV_CLEAR)
    kevn[0].Fflags = uint32(e)

    _, err = syscall.Kevent(k.fd, kevn[:], nil, nil)
    return
}

// Wait implements trigger.
func (k *kq) Wait() (interface{}, error) {
    var (
        kevn [1]syscall.Kevent_t
        err  error
    )
    kevn[0] = syscall.Kevent_t{}
    _, err = syscall.Kevent(k.fd, nil, kevn[:], nil)

    return kevn[0], err
}

// Watched implements trigger.
func (k *kq) Watched(n interface{}) (*watched, int64, error) {
    kevn, ok := n.(syscall.Kevent_t)
    if !ok {
        panic(fmt.Sprintf("kq: type should be syscall.Kevent_t, %T instead", kevn))
    }
    if _, ok = k.idLkp[int(kevn.Ident)]; !ok {
        return nil, 0, errNotWatched
    }
    return k.idLkp[int(kevn.Ident)], int64(kevn.Fflags), nil
}

// IsStop implements trigger.
func (k *kq) IsStop(n interface{}, err error) bool {
    return int(inter2kq(n).Ident) == k.pipefds[0]
}

func init() {
    encode = func(e Event) (o int64) {
        // Create event is not supported by kqueue. Instead NoteWrite event will
        // be registered. If this event will be reported on dir which is to be
        // monitored for Create, dir will be rescanned and Create events will
        // be generated and returned for new files. In case of files,
        // if not requested NoteRename event is reported, it will be ignored.
        o = int64(e &^ Create)
        if e&Write != 0 {
            o = (o &^ int64(Write)) | int64(NoteWrite)
        }
        if e&Rename != 0 {
            o = (o &^ int64(Rename)) | int64(NoteRename)
        }
        if e&Remove != 0 {
            o = (o &^ int64(Remove)) | int64(NoteDelete)
        }
        return
    }
    nat2not = map[Event]Event{
        NoteWrite:  Write,
        NoteRename: Rename,
        NoteDelete: Remove,
        NoteExtend: Event(0),
        NoteAttrib: Event(0),
        NoteRevoke: Event(0),
        NoteLink:   Event(0),
    }
    not2nat = map[Event]Event{
        Write:  NoteWrite,
        Rename: NoteRename,
        Remove: NoteDelete,
    }
}