diff --git a/internal/fs/fs.go b/internal/fs/fs.go
new file mode 100644
index 0000000..b34d020
--- /dev/null
+++ b/internal/fs/fs.go
@@ -0,0 +1,80 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package fs
+
+import (
+	"io/fs"
+	"log/slog"
+	"path/filepath"
+	"fmt"
+)
+
+type DirEntry fs.DirEntry
+type FS fs.FS
+type Selector[Item comparable] func(r Item) bool
+ 
+type WalkFunc func(fsys FS, path string, file DirEntry) (err error)
+
+type WalkDir struct {
+	root *WorkingDir
+	subDirsStack []*WorkingDir `yaml:"-" json:"-"`
+	fn WalkFunc
+}
+
+type WorkingDir struct {
+	path string
+	fsys FS
+}
+
+func NewWalkDir(fsys FS, path string, fn WalkFunc) *WalkDir {
+	w := &WalkDir{
+		subDirsStack: make([]*WorkingDir, 0, 100),
+		fn: fn,
+	}
+	
+	w.root = &WorkingDir{ path: path, fsys: fsys }
+	w.subDirsStack = append(w.subDirsStack, w.root)
+	return w
+}
+
+func (w *WalkDir) WalkDirectory(fsys FS, path string, filter Selector[DirEntry]) (err error) {
+	var files []fs.DirEntry
+
+	if files, err = fs.ReadDir(fsys, "."); err == nil {
+		for _,file := range files {
+			if filter != nil && filter(file) {
+				continue
+			}
+			slog.Info("fs.WalkDir.WalkDirectory()", "file", file, "path", path, "file", file.Name())
+			entryPath := filepath.Join(path, file.Name())
+			if err = w.fn(fsys, entryPath, file); err != nil {
+				slog.Info("fs.WalkDir.WalkDirectory() ERROR", "file", entryPath, "error", err)
+				return
+			}
+			if file.IsDir() {
+				var dir FS
+				if dir, err = fs.Sub(fsys, file.Name()); err != nil {
+					slog.Info("fs.WalkDir.WalkDirectory() SubDir ERROR", "dir", dir, "error", err)
+					return
+				} else {
+					w.subDirsStack = append(w.subDirsStack, &WorkingDir{ path: entryPath, fsys: dir })
+				}
+			}
+		}
+	} else {
+		err = fmt.Errorf("fs.ReadDir failed on path %s: %w", path, err)
+	}
+	return
+}
+
+func (w *WalkDir) Walk(filter Selector[DirEntry]) (err error) {
+	for len(w.subDirsStack) != 0 {
+		var dirPath *WorkingDir
+		dirPath, w.subDirsStack = w.subDirsStack[len(w.subDirsStack) - 1], w.subDirsStack[:len(w.subDirsStack) - 1]
+		if err = w.WalkDirectory(dirPath.fsys, dirPath.path, filter); err != nil {
+			return
+		}
+	}
+	return
+}
+
diff --git a/internal/fs/fs_test.go b/internal/fs/fs_test.go
new file mode 100644
index 0000000..9876232
--- /dev/null
+++ b/internal/fs/fs_test.go
@@ -0,0 +1,46 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package fs
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"os"
+	"log/slog"
+	"decl/tests/tempdir"
+_	"path/filepath"
+)
+
+var TempDir tempdir.Path = "testfswalkdir"
+
+func TestMain(m *testing.M) {
+	err := TempDir.Create()
+	if err != nil || TempDir == "" {
+		slog.Error("Failed creating temp dir", "error", err)
+	}
+	
+	rc := m.Run()
+
+	TempDir.Remove()
+	os.Exit(rc)
+}
+
+func TestNewWalkDir(t *testing.T) {
+	expected := []string { "bar", "foo.txt" }
+	assert.Nil(t, TempDir.CreateFile("foo.txt", "testdata"))
+	assert.Nil(t, TempDir.Mkdir("bar", 0700))
+
+	fileSystem := TempDir.DirFS()
+	i := 0
+	d := NewWalkDir(fileSystem, string(TempDir), func(fsys FS, path string, entry DirEntry) (err error) {
+		slog.Info("TestWalkDir()", "path", path, "entry", entry)
+		assert.Equal(t, expected[i], entry.Name())
+		i++
+		return nil
+	})
+	assert.NotNil(t, d)
+	assert.Nil(t, d.Walk(nil))
+}
+
+func TestWalk(t *testing.T) {
+}