Add vertical layout

layouts/vertical.go

@@ -0,0 +1,118 @@
+package layouts
+
+import (
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+// Model is the Bubble Tea model for a vertical layout element.
+type Model struct {
+	Index int
+	Items []tea.Model
+
+	// Focus indicates whether user focus should be on this component
+	focus bool
+}
+
+type FocusItem interface {
+	Focus() tea.Model
+	Blur() tea.Model
+}
+
+// NewModel creates a new model with default settings.
+func NewModel() Model {
+	return Model{}
+}
+
+// Update is the Tea update loop.
+func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
+	if !m.focus {
+		return m, nil
+	}
+
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch msg.String() {
+		case "shift+tab", "up":
+			m.Index--
+			if m.Index < 0 {
+				m.Index = len(m.Items) - 1
+			}
+			m.updateFocus()
+
+		case "tab", "down":
+			m.Index++
+			if m.Index >= len(m.Items) {
+				m.Index = 0
+			}
+			m.updateFocus()
+		}
+	}
+
+	cmd := m.updateItems(msg)
+	return m, cmd
+}
+
+// View renders the layout in its current state.
+func (m Model) View() string {
+	var view string
+
+	for _, v := range m.Items {
+		if mi, ok := v.(tea.Model); ok {
+			view += mi.View() + "\n"
+		}
+	}
+
+	return view
+}
+
+func (m *Model) updateFocus() {
+	for i, v := range m.Items {
+		if m.Index == i {
+			if fi, ok := v.(FocusItem); ok {
+				// new focused item
+				m.Items[i] = fi.Focus()
+			}
+		} else {
+			if fi, ok := v.(FocusItem); ok {
+				m.Items[i] = fi.Blur()
+			}
+		}
+	}
+}
+
+// Pass messages and models through to text input components. Only text inputs
+// with Focus() set will respond, so it's safe to simply update all of them
+// here without any further logic.
+func (m *Model) updateItems(msg tea.Msg) tea.Cmd {
+	var (
+		cmd  tea.Cmd
+		cmds []tea.Cmd
+	)
+
+	for i, v := range m.Items {
+		if mi, ok := v.(tea.Model); ok {
+			m.Items[i], cmd = mi.Update(msg)
+			if cmd != nil {
+				cmds = append(cmds, cmd)
+			}
+		}
+	}
+
+	return tea.Batch(cmds...)
+}
+
+// Focused returns the focus state on the model.
+func (m Model) Focused() bool {
+	return m.focus
+}
+
+// Focus sets the focus state on the model.
+func (m *Model) Focus() {
+	m.focus = true
+	m.updateFocus()
+}
+
+// Blur removes the focus state on the model.
+func (m *Model) Blur() {
+	m.focus = false
+}