Inject Config as dependency for database, routing table, and snapshotter

- Remove old database Config struct and related functions
- Update database.New() to accept config.Config parameter
- Update routingtable.New() to accept config.Config parameter
- Update snapshotter.New() to accept config.Config parameter
- Simplify fx module providers in app.go
- Fix truthiness check for environment variables
- Handle empty state directory gracefully in routing table and snapshotter
- Update all tests to use empty state directory for testing

internal/snapshotter/snapshotter.go

@@ -10,16 +10,16 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
-	"runtime"
 	"sync"
 	"time"
 
+	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/routingtable"
 )
 
 const (
 	snapshotInterval = 10 * time.Minute
-	snapshotFilename = "routewatch-snapshot.json.gz"
+	snapshotFilename = "routingtable.json.gz"
 	tempFileSuffix   = ".tmp"
 )
 
@@ -36,16 +36,15 @@ type Snapshotter struct {
 }
 
 // New creates a new Snapshotter instance
-func New(rt *routingtable.RoutingTable, logger *slog.Logger) (*Snapshotter, error) {
-	stateDir, err := getStateDirectory()
-	if err != nil {
-		return nil, fmt.Errorf("failed to determine state directory: %w", err)
-	}
+func New(rt *routingtable.RoutingTable, cfg *config.Config, logger *slog.Logger) (*Snapshotter, error) {
+	stateDir := cfg.GetStateDir()
 
-	// Ensure state directory exists
-	const stateDirPerms = 0750
-	if err := os.MkdirAll(stateDir, stateDirPerms); err != nil {
-		return nil, fmt.Errorf("failed to create state directory: %w", err)
+	// If state directory is specified, ensure it exists
+	if stateDir != "" {
+		const stateDirPerms = 0750
+		if err := os.MkdirAll(stateDir, stateDirPerms); err != nil {
+			return nil, fmt.Errorf("failed to create snapshot directory: %w", err)
+		}
 	}
 
 	s := &Snapshotter{
@@ -76,38 +75,6 @@ func (s *Snapshotter) Start(ctx context.Context) {
 	go s.periodicSnapshot()
 }
 
-// getStateDirectory returns the appropriate state directory based on the OS
-func getStateDirectory() (string, error) {
-	switch runtime.GOOS {
-	case "darwin":
-		// macOS: Use ~/Library/Application Support/routewatch
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return "", err
-		}
-
-		return filepath.Join(home, "Library", "Application Support", "routewatch"), nil
-	case "linux", "freebsd", "openbsd", "netbsd":
-		// Unix-like: Use /var/lib/routewatch if running as root, otherwise use XDG_STATE_HOME
-		if os.Geteuid() == 0 {
-			return "/var/lib/routewatch", nil
-		}
-		// Check XDG_STATE_HOME first
-		if xdgState := os.Getenv("XDG_STATE_HOME"); xdgState != "" {
-			return filepath.Join(xdgState, "routewatch"), nil
-		}
-		// Fall back to ~/.local/state/routewatch
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return "", err
-		}
-
-		return filepath.Join(home, ".local", "state", "routewatch"), nil
-	default:
-		return "", fmt.Errorf("unsupported operating system: %s", runtime.GOOS)
-	}
-}
-
 // periodicSnapshot runs periodic snapshots
 func (s *Snapshotter) periodicSnapshot() {
 	defer s.wg.Done()
@@ -130,6 +97,11 @@ func (s *Snapshotter) periodicSnapshot() {
 
 // TakeSnapshot creates a snapshot of the current routing table state
 func (s *Snapshotter) TakeSnapshot() error {
+	// Can't take snapshot without a state directory
+	if s.stateDir == "" {
+		return nil
+	}
+
 	// Ensure only one snapshot runs at a time
 	s.mu.Lock()
 	defer s.mu.Unlock()