fix(ui): hide the tree's up and down keybinds at its ends

internal/ui/chat/guildstree/keymap.go

@@ -4,6 +4,7 @@ import (
 	"slices"
 
 	"github.com/ayn2op/arikawa/v3/discord"
+	uitree "github.com/ayn2op/discordo/internal/ui/tree"
 	"github.com/ayn2op/tview/help"
 	"github.com/ayn2op/tview/keybind"
 	"github.com/ayn2op/tview/tree"
@@ -34,7 +35,7 @@ func (m Model) selectCurrentKeybind() keybind.Keybind {
 
 func (m Model) ShortHelp() []keybind.Keybind {
 	cfg := m.cfg.Keybinds.GuildsTree
-	shortHelp := []keybind.Keybind{cfg.SelectUp.Keybind, cfg.SelectDown.Keybind, m.selectCurrentKeybind()}
+	shortHelp := append(uitree.SelectHelp(m.root, m.selectionState.CurrentNode(), cfg.TreeKeybinds), m.selectCurrentKeybind())
 	if m.canCollapseParent(m.selectionState.CurrentNode()) {
 		shortHelp = append(shortHelp, cfg.CollapseParentNode.Keybind)
 	}

internal/ui/chat/memberstree/keymap.go

@@ -1,6 +1,7 @@
 package memberstree
 
 import (
+	uitree "github.com/ayn2op/discordo/internal/ui/tree"
 	"github.com/ayn2op/tview/help"
 	"github.com/ayn2op/tview/keybind"
 )
@@ -9,7 +10,7 @@ var _ help.KeyMap = Model{}
 
 func (m Model) ShortHelp() []keybind.Keybind {
 	kbs := m.cfg.Keybinds.MembersTree
-	short := []keybind.Keybind{kbs.SelectUp.Keybind, kbs.SelectDown.Keybind}
+	short := uitree.SelectHelp(m.root, m.selectionState.CurrentNode(), kbs)
 	if node := m.selectionState.CurrentNode(); node != nil {
 		if _, ok := node.Reference().(groupRef); ok {
 			desc := "expand"

internal/ui/tree/keymap.go

@@ -0,0 +1,34 @@
+package tree
+
+import (
+	"github.com/ayn2op/discordo/internal/config"
+	"github.com/ayn2op/tview/keybind"
+	"github.com/ayn2op/tview/tree"
+)
+
+// SelectHelp returns the up and down keybinds that move the selection away from current.
+func SelectHelp(root, current *tree.Node, kbs config.TreeKeybinds) []keybind.Keybind {
+	var help []keybind.Keybind
+	if canSelectUp(root, current) {
+		help = append(help, kbs.SelectUp.Keybind)
+	}
+	if canSelectDown(root, current) {
+		help = append(help, kbs.SelectDown.Keybind)
+	}
+	return help
+}
+
+// canSelectUp reports whether a node is shown above current.
+func canSelectUp(root, current *tree.Node) bool {
+	children := root.Children()
+	return current != nil && len(children) > 0 && current != children[0]
+}
+
+// canSelectDown reports whether a node is shown below current.
+func canSelectDown(root, current *tree.Node) bool {
+	last := root
+	for last.Expanded() && len(last.Children()) > 0 {
+		last = last.Children()[len(last.Children())-1]
+	}
+	return last != root && current != last
+}

internal/ui/tree/keymap_test.go

@@ -0,0 +1,33 @@
+package tree
+
+import (
+	"testing"
+
+	"github.com/ayn2op/tview/tree"
+)
+
+func TestCanSelect(t *testing.T) {
+	root := tree.NewNode("")
+	first, last, child := tree.NewNode("first"), tree.NewNode("last"), tree.NewNode("child")
+	root.AddChild(first).AddChild(last.AddChild(child).Collapse())
+
+	check := func(name string, current *tree.Node, up, down bool) {
+		t.Helper()
+		if got := canSelectUp(root, current); got != up {
+			t.Errorf("%s: canSelectUp = %v, want %v", name, got, up)
+		}
+		if got := canSelectDown(root, current); got != down {
+			t.Errorf("%s: canSelectDown = %v, want %v", name, got, down)
+		}
+	}
+
+	check("none", nil, false, true)
+	check("first", first, false, true)
+	check("collapsed last", last, true, false)
+	last.Expand()
+	check("expanded last", last, true, true)
+	check("last child", child, true, false)
+	if canSelectDown(tree.NewNode(""), nil) {
+		t.Error("empty tree: canSelectDown = true, want false")
+	}
+}