add keyboard based movement on the file tree

fstree/fs.go

@@ -12,6 +12,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"sort"
 )
 
 func walkFileSystemAndBuildTree(rootPath string, node *FsNode) error {
@@ -60,6 +61,14 @@ func walkFileSystemAndBuildTree(rootPath string, node *FsNode) error {
 		}
 	}
 
+	// Sort children: files first, then folders
+	sort.Slice(node.children, func(i, j int) bool {
+		if node.children[i].nodeType == node.children[j].nodeType {
+			return node.children[i].FileName() < node.children[j].FileName()
+		}
+		return node.children[i].nodeType == FileNode
+	})
+
 	return nil
 }
 

fstree/fstree.go

@@ -34,7 +34,7 @@ type FsNode struct {
 	children []*FsNode
 	parent   *FsNode // for fast traversal up the tree
 	// for view layer
-	expanded bool
+	expanded bool // makes sense only for folder nodes
 }
 
 func (n *FsNode) FileName() string {
@@ -43,7 +43,8 @@ func (n *FsNode) FileName() string {
 
 // ==================== FsNode definition ====================
 type FsTree struct {
-	root *FsNode
+	root     *FsNode
+	selected *FsNode // currently selected node
 }
 
 func NewFsTree(rootPath string) *FsTree {
@@ -55,6 +56,12 @@ func NewFsTree(rootPath string) *FsTree {
 	}
 	walkFileSystemAndBuildTree(rootPath, root)
 
+	if len(root.children) > 0 {
+		return &FsTree{
+			root:     root,
+			selected: root.children[0],
+		}
+	}
 	return &FsTree{
 		root: root,
 	}
@@ -108,6 +115,86 @@ func (t *FsTree) ToggleExpand(node *FsNode) error {
 	return nil
 }
 
+// At this point I think there HAS to be a simpler way to do this
+// but since I'm going to refactor it some day let's leave this
+// as it is
+func (t *FsTree) move(delta int) error {
+	if t.selected == nil {
+		return errors.New("no node is currently selected")
+	}
+	if delta != -1 && delta != 1 {
+		return errors.New("delta must be either -1 (up) or 1 (down)")
+	}
+
+	// base case: if it's a folder and expanded and going down
+	if delta == 1 && t.selected.nodeType == FolderNode && t.selected.expanded && len(t.selected.children) > 0 {
+		t.selected = t.selected.children[0]
+		return nil
+	}
+	// base case: if it's the first element of a folder and going up
+	if delta == -1 && t.selected.parent != t.root {
+		parent := t.selected.parent
+		if len(parent.children) > 0 && parent.children[0] == t.selected {
+			t.selected = parent
+			return nil
+		}
+	}
+
+	// same level sibling move
+	// the idea is really simple for now:
+	// - go up the parent and find the sibling in the direction
+	//   - if no sibling go up again
+	// - if no parent stop
+	siblingFor := t.selected
+	for siblingFor.parent != nil {
+		parent := siblingFor.parent
+		// O(n) for now, though easy to obtimize with index tracking
+		nextIdx := -1
+		for idx, child := range parent.children {
+			if child == siblingFor {
+				nextIdx = idx + delta
+				break
+			}
+		}
+
+		if nextIdx >= 0 && nextIdx < len(parent.children) {
+			// found case
+			t.selected = parent.children[nextIdx]
+			break
+		}
+		// not found case, go up again
+		siblingFor = parent
+	}
+
+	// case: folder and I'm going up, I want to go as deep and last
+	if delta == -1 && t.selected.nodeType == FolderNode {
+		current := t.selected
+		for {
+			if len(current.children) == 0 || !current.expanded {
+				break
+			}
+			current = current.children[len(current.children)-1]
+		}
+		t.selected = current
+	}
+	return nil
+}
+
+func (t *FsTree) MoveUp() error   { return t.move(-1) }
+func (t *FsTree) MoveDown() error { return t.move(1) }
+
+func (t *FsTree) ToggleSelectedExpand() error {
+	if t.selected == nil {
+		return errors.New("no node is currently selected")
+	}
+	if t.selected.nodeType != FolderNode {
+		return errors.New("only folder nodes can be expanded or collapsed")
+	}
+
+	t.ToggleExpand(t.selected)
+	return nil
+}
+
 func (t *FsTree) Render() string {
 	builder := &strings.Builder{}
 	t.renderNode(t.root, 0, builder)
@@ -135,7 +222,13 @@ func (t *FsTree) renderNode(node *FsNode, depth int, builder *strings.Builder) {
 		icon = lipgloss.NewStyle().Faint(true).Render(prevIndent + icon + indent)
 	}
 
-	line := icon + " " + node.FileName() + "\n"
+	// Apply highlight if selected
+	fileName := node.FileName()
+	if node == t.selected {
+		fileName = lipgloss.NewStyle().Foreground(styles.Highlight).Bold(true).Render(fileName)
+	}
+
+	line := icon + " " + fileName + "\n"
 	builder.WriteString(line)
 
 	if node.expanded {

main.go

@@ -95,6 +95,18 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		switch msg.String() {
 		case "q", "ctrl+c":
 			return m, tea.Quit
+		case "up", "k":
+			if err := m.tree.MoveUp(); err != nil {
+				fmt.Println("Error moving up:", err)
+			}
+		case "down", "j":
+			if err := m.tree.MoveDown(); err != nil {
+				fmt.Println("Error moving down:", err)
+			}
+		case "enter", " ":
+			if err := m.tree.ToggleSelectedExpand(); err != nil {
+				fmt.Println("Error toggling expand:", err)
+			}
 		}
 	}
 	return m, nil

styles/styles.go

@@ -14,6 +14,7 @@ var (
 	Primary    = lipgloss.Color("#7D56F4")
 	Secondary  = lipgloss.Color("#FF5C8F")
 	Background = lipgloss.Color("#1E1E2E")
+	Highlight  = lipgloss.Color("#FFA500") // Orange highlight for selected node
 	// TODO: to extend as needed, right now this is just a
 	// placeholder
 )