feat(fs): add file watching function

add the fs.watch function which takes a path and a callback.
it will notify of any file events for the given path.

this function also returns a "watcher" object which
has start and stop functions.

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/chuckpreslar/emission v0.0.0-20170206194824-a7ddd980baf9
 	github.com/maxlandon/readline v0.1.0-beta.0.20211027085530-2b76cabb8036
 	github.com/pborman/getopt v1.1.0
+	github.com/rjeczalik/notify v0.9.3
 	github.com/sahilm/fuzzy v0.1.0
 	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a
 	golang.org/x/term v0.0.0-20220411215600-e5f449aeb171

go.sum

@@ -46,6 +46,8 @@ github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsK
 github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rjeczalik/notify v0.9.3 h1:6rJAzHTGKXGj76sbRgDiDcYj/HniypXmSJo1SWakZeY=
+github.com/rjeczalik/notify v0.9.3/go.mod h1:gF3zSOrafR9DQEWSE8TjfI9NkooDxbyT4UgRGKZA0lc=
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/rogpeppe/go-internal v1.8.1-0.20210923151022-86f73c517451 h1:d1PiN4RxzIFXCJTvRkvSkKqwtRAl5ZV4lATKtQI0B7I=
 github.com/rogpeppe/go-internal v1.8.1-0.20210923151022-86f73c517451/go.mod h1:JeRgkft04UBgHMgCIwADu4Pn6Mtm5d4nPKWu0nJ5d+o=
@@ -55,6 +57,7 @@ golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cO
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220513210516-0976fa681c29 h1:w8s32wxx3sY+OjLlv9qltkLU5yvJzxjjgiHWLjdIcw4=
 golang.org/x/sync v0.0.0-20220513210516-0976fa681c29/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20180926160741-c2ed4eda69e7/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210320140829-1e4c9ba3b0c4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

golibs/fs/fs.go

@@ -17,12 +17,39 @@ import (
 	"github.com/arnodel/golua/lib/packagelib"
 )
 
+var rtmm *rt.Runtime
+var watcherMetaKey = rt.StringValue("hshwatcher")
 var Loader = packagelib.Loader{
 	Load: loaderFunc,
 	Name: "fs",
 }
 
 func loaderFunc(rtm *rt.Runtime) (rt.Value, func()) {
+	rtmm = rtm
+	watcherMethods := rt.NewTable()
+	watcherFuncs := map[string]util.LuaExport{
+		"start": {watcherStart, 1, false},
+		"stop": {watcherStop, 1, false},
+	}
+	util.SetExports(rtm, watcherMethods, watcherFuncs)
+
+	watcherMeta := rt.NewTable()
+	watcherIndex := func(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+		//ti, _ := watcherArg(c, 0)
+
+		arg := c.Arg(1)
+		val := watcherMethods.Get(arg)
+
+		if val != rt.NilValue {
+			return c.PushingNext1(t.Runtime, val), nil
+		}
+
+		return c.PushingNext1(t.Runtime, val), nil
+	}
+
+	watcherMeta.Set(rt.StringValue("__index"), rt.FunctionValue(rt.NewGoFunction(watcherIndex, "__index", 2, false)))
+	rtm.SetRegistry(watcherMetaKey, rt.TableValue(watcherMeta))
+
 	exports := map[string]util.LuaExport{
 		"cd": util.LuaExport{fcd, 1, false},
 		"mkdir": util.LuaExport{fmkdir, 2, false},
@@ -33,6 +60,7 @@ func loaderFunc(rtm *rt.Runtime) (rt.Value, func()) {
 		"dir": util.LuaExport{fdir, 1, false},
 		"glob": util.LuaExport{fglob, 1, false},
 		"join": util.LuaExport{fjoin, 0, true},
+		"watch": util.LuaExport{fwatch, 2, false},
 	}
 	mod := rt.NewTable()
 	util.SetExports(rtm, mod, exports)
@@ -250,3 +278,23 @@ func fjoin(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
 
 	return c.PushingNext(t.Runtime, rt.StringValue(res)), nil
 }
+
+func fwatch(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+	if err := c.CheckNArgs(2); err != nil {
+		return nil, err
+	}
+
+	dir, err := c.StringArg(0)
+	if err != nil {
+		return nil, err
+	}
+
+	watcher, err := c.ClosureArg(1)
+	if err != nil {
+		return nil, err
+	}
+
+	dw := newWatcher(dir, watcher)
+
+	return c.PushingNext1(t.Runtime, rt.UserDataValue(dw.ud)), nil
+}

golibs/fs/watcher.go

@@ -0,0 +1,101 @@
+package fs
+
+import (
+	"fmt"
+
+	"github.com/rjeczalik/notify"
+	rt "github.com/arnodel/golua/runtime"
+)
+
+type pathWatcher struct{
+	path string
+	callback *rt.Closure
+	paused bool
+	started bool
+	ud *rt.UserData
+	notifyChan chan notify.EventInfo
+}
+
+func (w *pathWatcher) start() {
+	if w.callback == nil || w.started {
+		return
+	}
+
+	w.started = true
+	w.notifyChan = make(chan notify.EventInfo)
+	notify.Watch(w.path, w.notifyChan, notify.All)
+
+	go func() {
+		for notif := range w.notifyChan {
+			ev := notif.Event().String()
+			path := notif.Path()
+
+			_, err := rt.Call1(rtmm.MainThread(), rt.FunctionValue(w.callback), rt.StringValue(ev), rt.StringValue(path))
+			if err != nil {
+				// TODO: throw error
+			}
+		}
+	}()
+}
+
+func (w *pathWatcher) stop() {
+	w.started = false
+	notify.Stop(w.notifyChan)
+}
+
+func watcherStart(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+	pw, err := watcherArg(c, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	pw.start()
+
+	return c.Next(), nil
+}
+
+func watcherStop(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+	pw, err := watcherArg(c, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	pw.stop()
+
+	return c.Next(), nil
+}
+
+func newWatcher(path string, callback *rt.Closure) *pathWatcher {
+	pw := &pathWatcher{
+		path: path,
+		callback: callback,
+	}
+	pw.ud = watcherUserData(pw)
+	pw.start()
+
+	return pw
+}
+
+func watcherArg(c *rt.GoCont, arg int) (*pathWatcher, error) {
+	j, ok := valueToWatcher(c.Arg(arg))
+	if !ok {
+		return nil, fmt.Errorf("#%d must be a watcher", arg + 1)
+	}
+
+	return j, nil
+}
+
+func valueToWatcher(val rt.Value) (*pathWatcher, bool) {
+	u, ok := val.TryUserData()
+	if !ok {
+		return nil, false
+	}
+
+	j, ok := u.Value().(*pathWatcher)
+	return j, ok
+}
+
+func watcherUserData(j *pathWatcher) *rt.UserData {
+	watcherMeta := rtmm.Registry(watcherMetaKey)
+	return rt.NewUserData(j, watcherMeta.AsTable())
+}