save first version

internal/config/watcher.go

@@ -0,0 +1,57 @@
+package config
+
+import (
+	"log/slog"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+)
+
+// Watch watches the config file and calls onReload with the new config on change.
+// Debounces Write/Create events by 500ms to avoid multiple triggers on a single save.
+func Watch(path string, provider *Provider, onReload func(*Config)) error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return err
+	}
+	if err := watcher.Add(path); err != nil {
+		watcher.Close()
+		return err
+	}
+
+	go func() {
+		defer watcher.Close()
+		var debounce *time.Timer
+		for {
+			select {
+			case event, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
+				if event.Has(fsnotify.Write) || event.Has(fsnotify.Create) {
+					if debounce != nil {
+						debounce.Stop()
+					}
+					debounce = time.AfterFunc(500*time.Millisecond, func() {
+						cfg, err := Load(path)
+						if err != nil {
+							slog.Error("hot reload: invalid config, keeping old", "err", err)
+							return
+						}
+						provider.Swap(cfg)
+						slog.Info("config reloaded")
+						if onReload != nil {
+							onReload(cfg)
+						}
+					})
+				}
+			case err, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
+				slog.Error("config watcher error", "err", err)
+			}
+		}
+	}()
+	return nil
+}