add fs lib to walk file tree

fs_test.go

@@ -0,0 +1,153 @@
+/*
+another test that is entirely ae ayee generated
+- ruinivist, 30Dec25
+*/
+
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWalkFileSystemAndBuildTree(t *testing.T) {
+	t.Run("build tree from real directory", func(t *testing.T) {
+		// Create temporary directory structure
+		tmpDir := t.TempDir()
+
+		// Create test structure:
+		// tmpDir/
+		//   file1.txt
+		//   file2.go
+		//   folder1/
+		//     nested.txt
+		//   folder2/
+		os.WriteFile(filepath.Join(tmpDir, "file1.txt"), []byte("content"), 0644)
+		os.WriteFile(filepath.Join(tmpDir, "file2.go"), []byte("code"), 0644)
+		os.Mkdir(filepath.Join(tmpDir, "folder1"), 0755)
+		os.WriteFile(filepath.Join(tmpDir, "folder1", "nested.txt"), []byte("nested"), 0644)
+		os.Mkdir(filepath.Join(tmpDir, "folder2"), 0755)
+
+		// Build tree
+		root := &FsNode{
+			nodeType: FolderNode,
+			path:     tmpDir,
+			children: make([]*FsNode, 0),
+			expanded: true,
+		}
+
+		err := walkFileSystemAndBuildTree(tmpDir, root)
+		if err != nil {
+			t.Fatalf("walkFileSystemAndBuildTree() error = %v", err)
+		}
+
+		// Verify structure
+		if len(root.children) != 4 {
+			t.Fatalf("root children count = %d, want 4", len(root.children))
+		}
+
+		// Check children exist and have correct types
+		fileCount := 0
+		folderCount := 0
+		var folder1 *FsNode
+
+		for _, child := range root.children {
+			if child.parent != root {
+				t.Errorf("child %q parent pointer incorrect", child.FileName())
+			}
+
+			if child.nodeType == FileNode {
+				fileCount++
+			} else if child.nodeType == FolderNode {
+				folderCount++
+				if child.FileName() == "folder1" {
+					folder1 = child
+				}
+			}
+		}
+
+		if fileCount != 2 {
+			t.Errorf("file count = %d, want 2", fileCount)
+		}
+		if folderCount != 2 {
+			t.Errorf("folder count = %d, want 2", folderCount)
+		}
+
+		// Verify nested structure
+		if folder1 == nil {
+			t.Fatal("folder1 not found")
+		}
+		if len(folder1.children) != 1 {
+			t.Errorf("folder1 children count = %d, want 1", len(folder1.children))
+		}
+		if folder1.children[0].FileName() != "nested.txt" {
+			t.Errorf("nested file name = %q, want %q", folder1.children[0].FileName(), "nested.txt")
+		}
+		if folder1.children[0].nodeType != FileNode {
+			t.Errorf("nested node type = %v, want %v", folder1.children[0].nodeType, FileNode)
+		}
+	})
+
+	t.Run("error when node is nil", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		err := walkFileSystemAndBuildTree(tmpDir, nil)
+		if err == nil {
+			t.Fatal("walkFileSystemAndBuildTree() with nil node should return error")
+		}
+		if err.Error() != "node cannot be nil" {
+			t.Errorf("error message = %q", err.Error())
+		}
+	})
+
+	t.Run("error when node already has children", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		root := &FsNode{
+			nodeType: FolderNode,
+			path:     tmpDir,
+			children: []*FsNode{{nodeType: FileNode, path: "dummy"}},
+			expanded: true,
+		}
+
+		err := walkFileSystemAndBuildTree(tmpDir, root)
+		if err == nil {
+			t.Fatal("walkFileSystemAndBuildTree() with existing children should return error")
+		}
+		if err.Error() != "node already has children" {
+			t.Errorf("error message = %q", err.Error())
+		}
+	})
+
+	t.Run("error when path does not exist", func(t *testing.T) {
+		root := &FsNode{
+			nodeType: FolderNode,
+			path:     "/nonexistent/path",
+			children: make([]*FsNode, 0),
+			expanded: true,
+		}
+
+		err := walkFileSystemAndBuildTree("/nonexistent/path", root)
+		if err == nil {
+			t.Fatal("walkFileSystemAndBuildTree() with nonexistent path should return error")
+		}
+	})
+
+	t.Run("empty directory", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		root := &FsNode{
+			nodeType: FolderNode,
+			path:     tmpDir,
+			children: make([]*FsNode, 0),
+			expanded: true,
+		}
+
+		err := walkFileSystemAndBuildTree(tmpDir, root)
+		if err != nil {
+			t.Fatalf("walkFileSystemAndBuildTree() error = %v", err)
+		}
+
+		if len(root.children) != 0 {
+			t.Errorf("empty directory should have 0 children, got %d", len(root.children))
+		}
+	})
+}