feat: refactor relative path function for filesystem walker

Signed-off-by: Brian McGee <brian@bmcgee.ie>

walk/filesystem.go

@@ -8,35 +8,35 @@ import (
 )
 
 type filesystemWalker struct {
-	root    string
-	pathsCh chan string
+	root          string
+	pathsCh       chan string
+	relPathOffset int
 }
 
 func (f filesystemWalker) Root() string {
 	return f.root
 }
 
-func (f filesystemWalker) Walk(_ context.Context, fn WalkFunc) error {
-	relPathOffset := len(f.root) + 1
-
-	relPathFn := func(path string) (string, error) {
-		// quick optimization for the majority of use cases
-		if len(path) >= relPathOffset && path[:len(f.root)] == f.root {
-			return path[relPathOffset:], nil
-		}
-		// fallback to proper relative path resolution
-		return filepath.Rel(f.root, path)
+func (f filesystemWalker) relPath(path string) (string, error) {
+	// quick optimization for the majority of use cases
+	if len(path) >= f.relPathOffset && path[:len(f.root)] == f.root {
+		return path[f.relPathOffset:], nil
 	}
+	// fallback to proper relative path resolution
+	return filepath.Rel(f.root, path)
+}
 
+func (f filesystemWalker) Walk(_ context.Context, fn WalkFunc) error {
 	walkFn := func(path string, info fs.FileInfo, _ error) error {
 		if info == nil {
 			return fmt.Errorf("no such file or directory '%s'", path)
 		}
 
-		relPath, err := relPathFn(path)
+		relPath, err := f.relPath(path)
 		if err != nil {
 			return fmt.Errorf("failed to determine a relative path for %s: %w", path, err)
 		}
+
 		file := File{
 			Path:    path,
 			RelPath: relPath,
@@ -55,5 +55,9 @@ func (f filesystemWalker) Walk(_ context.Context, fn WalkFunc) error {
 }
 
 func NewFilesystem(root string, paths chan string) (Walker, error) {
-	return filesystemWalker{root, paths}, nil
+	return filesystemWalker{
+		root:          root,
+		pathsCh:       paths,
+		relPathOffset: len(root) + 1,
+	}, nil
 }