1 files changed, 73 insertions, 0 deletions
diff --git a/pkg/hooks/monitor.go b/pkg/hooks/monitor.go
new file mode 100644
index 000000000..ba5e0f246
--- /dev/null
+++ b/pkg/hooks/monitor.go
@@ -0,0 +1,73 @@
+package hooks
+
+import (
+	"context"
+	"path/filepath"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/sirupsen/logrus"
+)
+
+// Monitor dynamically monitors hook directories for additions,
+// updates, and removals.
+//
+// This function write two empty structs to the sync channel: the
+// first is written after the watchers are established and the second
+// when this function exits.  The expected usage is:
+//
+//   ctx, cancel := context.WithCancel(context.Background())
+//   sync := make(chan error, 2)
+//   go m.Monitor(ctx, sync)
+//   err := <-sync // block until writers are established
+//   if err != nil {
+//     return err // failed to establish watchers
+//   }
+//   // do stuff
+//   cancel()
+//   err = <-sync // block until monitor finishes
+func (m *Manager) Monitor(ctx context.Context, sync chan<- error) {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		sync <- err
+		return
+	}
+	defer watcher.Close()
+
+	for _, dir := range m.directories {
+		err = watcher.Add(dir)
+		if err != nil {
+			logrus.Errorf("failed to watch %q for hooks", dir)
+			sync <- err
+			return
+		}
+		logrus.Debugf("monitoring %q for hooks", dir)
+	}
+
+	sync <- nil
+
+	for {
+		select {
+		case event := <-watcher.Events:
+			if event.Op&fsnotify.Remove == fsnotify.Remove {
+				ok := m.remove(filepath.Base(event.Name))
+				if ok {
+					logrus.Debugf("removed hook %s", event.Name)
+				}
+			}
+			if event.Op&fsnotify.Create == fsnotify.Create || event.Op&fsnotify.Write == fsnotify.Write {
+				err = m.add(event.Name)
+				if err == nil {
+					logrus.Debugf("added hook %s", event.Name)
+				} else if err != ErrNoJSONSuffix {
+					logrus.Errorf("failed to add hook %s: %v", event.Name, err)
+				}
+			}
+		case <-ctx.Done():
+			err = ctx.Err()
+			logrus.Debugf("hook monitoring canceled: %v", err)
+			sync <- err
+			close(sync)
+			return
+		}
+	}
+}