feat: side-panel navigation and expansion

main.go

@@ -31,8 +31,9 @@ type model struct {
 
 	leftWidth int
 
-	treeRoot *TreeNode
-	textarea textarea.Model
+	treeRoot   *TreeNode
+	treeCursor int
+	textarea   textarea.Model
 
 	commands []Command
 	viewport viewport.Model
@@ -71,8 +72,10 @@ func main() {
 	}
 }
 
-func flattenTree(n *TreeNode, depth int) []string {
-	var out []string
+// returns both the string representation and corresponding nodes
+func flattenTreeWithNodes(n *TreeNode, depth int) ([]string, []*TreeNode) {
+	var lines []string
+	var nodes []*TreeNode
 	prefix := strings.Repeat("  ", depth)
 	icon := "▸"
 	if n.Expanded && len(n.Children) > 0 {
@@ -80,13 +83,28 @@ func flattenTree(n *TreeNode, depth int) []string {
 	} else if len(n.Children) == 0 {
 		icon = " "
 	}
-	out = append(out, fmt.Sprintf("%s%s %s", prefix, icon, n.Label))
+	lines = append(lines, fmt.Sprintf("%s%s %s", prefix, icon, n.Label))
+	nodes = append(nodes, n)
 	if n.Expanded {
 		for _, c := range n.Children {
-			out = append(out, flattenTree(c, depth+1)...)
+			childLines, childNodes := flattenTreeWithNodes(c, depth+1)
+			lines = append(lines, childLines...)
+			nodes = append(nodes, childNodes...)
 		}
 	}
-	return out
+	return lines, nodes
+}
+
+func flattenTree(n *TreeNode, depth int) []string {
+	lines, _ := flattenTreeWithNodes(n, depth)
+	return lines
+}
+
+// toggleNodeExpansion toggles the expanded state of a node if it has children
+func (m *model) toggleNodeExpansion(node *TreeNode) {
+	if len(node.Children) > 0 {
+		node.Expanded = !node.Expanded
+	}
 }
 
 func (m *model) renderCommandsContent() string {
@@ -225,6 +243,37 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 
 		if m.focusPane == "fileview" {
 			// fileview tree behaviour (navigation, expand/collapse)
+			_, nodes := flattenTreeWithNodes(m.treeRoot, 0)
+			switch msg.String() {
+			case "up", "k":
+				if m.treeCursor > 0 {
+					m.treeCursor--
+				}
+			case "down", "j":
+				if m.treeCursor < len(nodes)-1 {
+					m.treeCursor++
+				}
+			case "left", "h":
+				if m.treeCursor < len(nodes) {
+					node := nodes[m.treeCursor]
+					if node.Expanded && len(node.Children) > 0 {
+						node.Expanded = false
+					}
+				}
+			case "right", "l":
+				if m.treeCursor < len(nodes) {
+					node := nodes[m.treeCursor]
+					if !node.Expanded && len(node.Children) > 0 {
+						node.Expanded = true
+					}
+				}
+			case "enter", " ":
+				// toggle
+				if m.treeCursor < len(nodes) {
+					m.toggleNodeExpansion(nodes[m.treeCursor])
+				}
+			}
+
 			return m, nil
 		}
 
@@ -292,6 +341,14 @@ func (m model) View() string {
 
 	treeLines := flattenTree(m.treeRoot, 0)
 
+	// highlight the current selection when fileview is focused
+	if m.focusPane == "fileview" && m.treeCursor < len(treeLines) {
+		selectedStyle := lipgloss.NewStyle().
+			Background(lipgloss.Color("6")).
+			Foreground(lipgloss.Color("0"))
+		treeLines[m.treeCursor] = selectedStyle.Render(treeLines[m.treeCursor])
+	}
+
 	// show the tree view content
 	fileviewRows = append(fileviewRows, treeLines...)