Implement watching crontab file

crontabd/go.mod

@@ -2,4 +2,9 @@ module crontabd
 
 go 1.23.6
 
-require git.site.quack-lab.dev/dave/cylogger v1.2.3
+require (
+	git.site.quack-lab.dev/dave/cylogger v1.2.3
+	github.com/fsnotify/fsnotify v1.9.0
+)
+
+require golang.org/x/sys v0.13.0 // indirect

crontabd/go.sum

@@ -1,2 +1,6 @@
 git.site.quack-lab.dev/dave/cylogger v1.2.3 h1:g6fwgrd3HvGsxljvKbjcFaMynTO2AZFWjC2ZvCi1raQ=
 git.site.quack-lab.dev/dave/cylogger v1.2.3/go.mod h1:sf16Zs5ZRncn0ySgwxRJShkge1M10CM2RAUkKn8Bel8=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

crontabd/main.go

@@ -2,9 +2,12 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"os"
 	"path/filepath"
 
+	"github.com/fsnotify/fsnotify"
+
 	logger "git.site.quack-lab.dev/dave/cylogger"
 )
 
@@ -14,13 +17,65 @@ func main() {
 	flag.Parse()
 	logger.InitFlag()
 
-	homeDir, err := os.UserHomeDir()
+	var err error
+	crontabFile, err = resolveCrontabPath()
 	if err != nil {
-		logger.Error("Failed to get user home directory: %v", err)
+		logger.Error("Failed to resolve crontab file path: %v", err)
 		return
 	}
 
+	err = ensureExists(crontabFile)
+	if err != nil {
+		logger.Error("Failed to ensure crontab file exists: %v", err)
+		return
+	}
+	logger.Info("Crontab file resolved as: %s", crontabFile)
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		logger.Error("Failed to create watcher: %v", err)
+		return
+	}
+
+	err = watcher.Add(crontabFile)
+	if err != nil {
+		logger.Error("Failed to add crontab file to watcher: %v", err)
+		return
+	}
+	logger.Info("Watching crontab file: %s", crontabFile)
+}
+
+func resolveCrontabPath() (string, error) {
+	// Resolve crontab file location
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get user home directory: %v", err)
+	}
 	userName := os.Getenv("USERNAME")
 	crontabFile = filepath.Join(homeDir, "crontab", userName+".cron")
-	logger.Info("Crontab file: %s", crontabFile)
+	crontabFile, err = filepath.Abs(crontabFile)
+	if err != nil {
+		return "", fmt.Errorf("failed to get absolute path: %v", err)
+	}
+	crontabFile = filepath.Clean(crontabFile)
+	return crontabFile, nil
+}
+
+func ensureExists(path string) error {
+	// Make sure it exists
+	err := os.MkdirAll(filepath.Dir(path), 0755)
+	if err != nil {
+		return fmt.Errorf("failed to create directory: %v", err)
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			os.WriteFile(path, []byte(""), 0644)
+		} else {
+			return fmt.Errorf("failed to open crontab file: %v", err)
+		}
+	}
+	defer file.Close()
+	return nil
 }