3 files changed, 200 insertions, 0 deletions
diff --git a/lib/watchers/fsevents.go b/lib/watchers/fsevents.go
new file mode 100644
index 00000000..905db2af
--- /dev/null
+++ b/lib/watchers/fsevents.go
@@ -0,0 +1,82 @@
+//go:build darwin
+// +build darwin
+
+package watchers
+
+import (
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/log"
+	"github.com/fsnotify/fsevents"
+)
+
+func init() {
+	RegisterWatcherFactory(newDarwinWatcher)
+}
+
+type darwinWatcher struct {
+	ch        chan *FSEvent
+	w         *fsevents.EventStream
+	watcherCh chan []fsevents.Event
+}
+
+func newDarwinWatcher() (FSWatcher, error) {
+	watcher := &darwinWatcher{
+		watcherCh: make(chan []fsevents.Event),
+		ch:        make(chan *FSEvent),
+		w: &fsevents.EventStream{
+			Flags:   fsevents.FileEvents | fsevents.WatchRoot,
+			Latency: 500 * time.Millisecond,
+		},
+	}
+	return watcher, nil
+}
+
+func (w *darwinWatcher) watch() {
+	defer log.PanicHandler()
+	for events := range w.w.Events {
+		for _, ev := range events {
+			switch {
+			case ev.Flags&fsevents.ItemCreated > 0:
+				w.ch <- &FSEvent{
+					Operation: FSCreate,
+					Path:      ev.Path,
+				}
+			case ev.Flags&fsevents.ItemRenamed > 0:
+				w.ch <- &FSEvent{
+					Operation: FSRename,
+					Path:      ev.Path,
+				}
+			case ev.Flags&fsevents.ItemRemoved > 0:
+				w.ch <- &FSEvent{
+					Operation: FSRemove,
+					Path:      ev.Path,
+				}
+			}
+		}
+	}
+}
+
+func (w *darwinWatcher) Configure(root string) error {
+	dev, err := fsevents.DeviceForPath(root)
+	if err != nil {
+		return err
+	}
+	w.w.Device = dev
+	w.w.Paths = []string{root}
+	w.w.Start()
+	go w.watch()
+	return nil
+}
+
+func (w *darwinWatcher) Events() chan *FSEvent {
+	return w.ch
+}
+
+func (w *darwinWatcher) Add(p string) error {
+	return nil
+}
+
+func (w *darwinWatcher) Remove(p string) error {
+	return nil
+}
diff --git a/lib/watchers/inotify.go b/lib/watchers/inotify.go
new file mode 100644
index 00000000..22290307
--- /dev/null
+++ b/lib/watchers/inotify.go
@@ -0,0 +1,74 @@
+//go:build !darwin
+// +build !darwin
+
+package watchers
+
+import (
+	"git.sr.ht/~rjarry/aerc/log"
+	"github.com/fsnotify/fsnotify"
+)
+
+func init() {
+	RegisterWatcherFactory(newInotifyWatcher)
+}
+
+type inotifyWatcher struct {
+	w  *fsnotify.Watcher
+	ch chan *FSEvent
+}
+
+func newInotifyWatcher() (FSWatcher, error) {
+	watcher := &inotifyWatcher{
+		ch: make(chan *FSEvent),
+	}
+	w, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, err
+	}
+	watcher.w = w
+
+	go watcher.watch()
+	return watcher, nil
+}
+
+func (w *inotifyWatcher) watch() {
+	defer log.PanicHandler()
+	for ev := range w.w.Events {
+		// we only care about files being created, removed or renamed
+		switch ev.Op {
+		case fsnotify.Create:
+			w.ch <- &FSEvent{
+				Operation: FSCreate,
+				Path:      ev.Name,
+			}
+		case fsnotify.Remove:
+			w.ch <- &FSEvent{
+				Operation: FSRemove,
+				Path:      ev.Name,
+			}
+		case fsnotify.Rename:
+			w.ch <- &FSEvent{
+				Operation: FSRename,
+				Path:      ev.Name,
+			}
+		default:
+			continue
+		}
+	}
+}
+
+func (w *inotifyWatcher) Configure(root string) error {
+	return w.w.Add(root)
+}
+
+func (w *inotifyWatcher) Events() chan *FSEvent {
+	return w.ch
+}
+
+func (w *inotifyWatcher) Add(p string) error {
+	return w.w.Add(p)
+}
+
+func (w *inotifyWatcher) Remove(p string) error {
+	return w.w.Remove(p)
+}
diff --git a/lib/watchers/watchers.go b/lib/watchers/watchers.go
new file mode 100644
index 00000000..06ef985c
--- /dev/null
+++ b/lib/watchers/watchers.go
@@ -0,0 +1,44 @@
+package watchers
+
+import (
+	"fmt"
+	"runtime"
+)
+
+// FSWatcher is a file system watcher
+type FSWatcher interface {
+	Configure(string) error
+	Events() chan *FSEvent
+	// Adds a directory or file to the watcher
+	Add(string) error
+	// Removes a directory or file from the watcher
+	Remove(string) error
+}
+
+type FSOperation int
+
+const (
+	FSCreate FSOperation = iota
+	FSRemove
+	FSRename
+)
+
+type FSEvent struct {
+	Operation FSOperation
+	Path      string
+}
+
+type WatcherFactoryFunc func() (FSWatcher, error)
+
+var watcherFactory WatcherFactoryFunc
+
+func RegisterWatcherFactory(fn WatcherFactoryFunc) {
+	watcherFactory = fn
+}
+
+func NewWatcher() (FSWatcher, error) {
+	if watcherFactory == nil {
+		return nil, fmt.Errorf("Unsupported OS: %s", runtime.GOOS)
+	}
+	return watcherFactory()
+}