Add dynamic elements

bubbles/frame/frame.go

@@ -9,14 +9,37 @@ import (
 	tea "github.com/charmbracelet/bubbletea"
 )
 
+// VisibleElement allows UI elements to be conditionally hidden, but still present in the model state
+type VisibleElement interface {
+	IsHidden() bool
+}
+
+// TerminalElement allows UI elements to have a lifecycle, where at the end of the lifecycle the element is removed
+// from the model state entirely
+type TerminalElement interface {
+	IsAlive() bool
+}
+
+// ImprintableElement is a special case of a TerminalElement, where the element is removed from the model state after a
+// printing the model state as a trail behind the current model and removing the element on the next update
+type ImprintableElement interface {
+	ShouldImprint() bool
+}
+
 type Frame struct {
 	footer         *bytes.Buffer
-	models         []tea.Model
+	models         []annotatedModel
 	windowSize     tea.WindowSizeMsg
 	showFooter     bool
 	truncateFooter bool
 }
 
+type annotatedModel struct {
+	model   tea.Model
+	expired bool
+	hidden  bool
+}
+
 func New() *Frame {
 	return &Frame{
 		footer:         &bytes.Buffer{},
@@ -38,39 +61,76 @@ func (f *Frame) TruncateFooter(set bool) {
 }
 
 func (f *Frame) AppendModel(uiElement tea.Model) {
-	f.models = append(f.models, uiElement)
+	f.models = append(f.models, annotatedModel{model: uiElement})
 }
 
 func (f Frame) Init() tea.Cmd {
 	return nil
 }
 
-func (f *Frame) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
-	// note: we need a pointer receiver such that the same instance of UI used in Teardown is referenced (to keep finalize events)
-
+func (f Frame) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	if msg, ok := msg.(tea.WindowSizeMsg); ok {
 		f.windowSize = msg
 	}
 
 	var cmds []tea.Cmd
+
+	// 1. prune any models that are no longer alive
+	// 2. hide/show any models based on the latest state
+	// 3. trail any models that are expired, pruning them on the next update
+	for i := 0; i < len(f.models); i++ {
+		if p, ok := f.models[i].model.(TerminalElement); ok && !p.IsAlive() {
+			f.models = append(f.models[:i], f.models[i+1:]...)
+			i--
+			continue
+		}
+
+		if f.models[i].expired {
+			f.models = append(f.models[:i], f.models[i+1:]...)
+			i--
+			continue
+		}
+
+		if p, ok := f.models[i].model.(VisibleElement); ok && p.IsHidden() {
+			f.models[i].hidden = true
+		} else {
+			f.models[i].hidden = false
+		}
+
+		if p, ok := f.models[i].model.(ImprintableElement); ok && p.ShouldImprint() {
+			f.models[i].expired = true
+
+			cmd := tea.Printf("%s", f.models[i].model.View())
+			cmds = append(cmds, cmd)
+		}
+	}
+
 	for i, el := range f.models {
-		newEl, cmd := el.Update(msg)
+		if el.expired {
+			continue
+		}
+		newEl, cmd := el.model.Update(msg)
 		cmds = append(cmds, cmd)
-		f.models[i] = newEl
+		f.models[i].model = newEl
 	}
 	return f, tea.Batch(cmds...)
 }
 
 func (f Frame) View() string {
 	// all UI elements
-	str := ""
+	var strs []string
 	for _, p := range f.models {
-		rendered := p.View()
+		if p.hidden {
+			continue
+		}
+		rendered := p.model.View()
 		if len(rendered) > 0 {
-			str += rendered + "\n"
+			strs = append(strs, rendered)
 		}
 	}
 
+	str := strings.Join(strs, "\n")
+
 	// log events
 	if f.showFooter {
 		contents := f.footer.String()

bubbles/frame/frame_test.go

@@ -0,0 +1,224 @@
+package frame
+
+import (
+	"testing"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type mockModel struct {
+	updateCalled bool
+	view         string
+}
+
+func (m mockModel) Init() tea.Cmd {
+	return nil
+}
+
+func (m mockModel) Update(_ tea.Msg) (tea.Model, tea.Cmd) {
+	m.updateCalled = true
+	return m, nil
+}
+
+func (m mockModel) View() string {
+	return m.view
+}
+
+type mockTerminalElement struct {
+	mockModel
+	isAlive bool
+}
+
+func (m mockTerminalElement) IsAlive() bool {
+	return m.isAlive
+}
+
+type mockVisibleElement struct {
+	mockModel
+	isHidden bool
+}
+
+func (m mockVisibleElement) IsHidden() bool {
+	return m.isHidden
+}
+
+type mockImprintableElement struct {
+	mockModel
+	shouldImprint bool
+}
+
+func (m mockImprintableElement) ShouldImprint() bool {
+	return m.shouldImprint
+}
+
+func TestFrame_Update_PruneTerminalElement(t *testing.T) {
+	frame := New()
+	model := &mockTerminalElement{isAlive: false}
+
+	frame.AppendModel(model)
+
+	m, _ := frame.Update(nil)
+	actual := m.(Frame)
+
+	assert.Empty(t, actual.models)
+}
+
+func TestFrame_Update_HideVisibleElement(t *testing.T) {
+	frame := New()
+	model := mockVisibleElement{isHidden: true}
+
+	frame.AppendModel(model)
+
+	m, _ := frame.Update(nil)
+	actual := m.(Frame)
+
+	require.NotEmpty(t, actual.models)
+	assert.True(t, actual.models[0].hidden)
+}
+
+func TestFrame_Update_ImprintImprintableElement(t *testing.T) {
+	frame := New()
+	model := &mockImprintableElement{shouldImprint: true, mockModel: mockModel{view: "imprinted!"}}
+
+	frame.AppendModel(model)
+
+	m, cmds := frame.Update(nil)
+	actual := m.(Frame)
+
+	assert.True(t, actual.models[0].expired)
+	assert.NotNil(t, cmds)
+}
+
+func TestFrame_Update_UpdateElement(t *testing.T) {
+	frame := New()
+	model := &mockModel{}
+
+	frame.AppendModel(model)
+
+	m, cmds := frame.Update(nil)
+	actual := m.(Frame)
+
+	assert.Nil(t, cmds)
+	assert.True(t, actual.models[0].model.(mockModel).updateCalled)
+}
+
+// Mock model for VisibleElement and TerminalElement
+type mockVisibleTerminalModel struct {
+	view          string
+	isHidden      bool
+	isAlive       bool
+	shouldImprint bool
+}
+
+func (m mockVisibleTerminalModel) Init() tea.Cmd {
+	return nil
+}
+
+func (m mockVisibleTerminalModel) Update(_ tea.Msg) (tea.Model, tea.Cmd) {
+	return m, nil
+}
+
+func (m mockVisibleTerminalModel) View() string {
+	return m.view
+}
+
+func (m mockVisibleTerminalModel) IsHidden() bool {
+	return m.isHidden
+}
+
+func (m mockVisibleTerminalModel) IsAlive() bool {
+	return m.isAlive
+}
+
+func (m mockVisibleTerminalModel) ShouldImprint() bool {
+	return m.shouldImprint
+}
+
+func TestFrame_View_HiddenElement(t *testing.T) {
+	frame := New()
+	model := mockVisibleTerminalModel{view: "visible", isHidden: true, isAlive: true}
+
+	frame.AppendModel(model)
+
+	m, _ := frame.Update(nil)
+
+	assert.Empty(t, m.View())
+}
+
+func TestFrame_View_VisibleElement(t *testing.T) {
+	frame := New()
+	model := mockVisibleTerminalModel{view: "visible", isHidden: false, isAlive: true}
+
+	frame.AppendModel(model)
+
+	m, _ := frame.Update(nil)
+
+	assert.Contains(t, m.View(), "visible")
+}
+
+func TestFrame_View_DeadElement(t *testing.T) {
+	frame := New()
+	model := mockVisibleTerminalModel{view: "should not be seen", isHidden: false, isAlive: false}
+
+	frame.AppendModel(model)
+
+	m, _ := frame.Update(nil)
+
+	assert.NotContains(t, m.View(), "should not be seen")
+}
+
+func TestFrame_View_WithFooter(t *testing.T) {
+	frame := New()
+	frame.ShowFooter(true)
+	frame.TruncateFooter(false)
+	model := mockVisibleTerminalModel{view: "visible", isHidden: false, isAlive: true}
+
+	frame.AppendModel(model)
+	frame.Footer().Write([]byte("log line 1\nlog line 2"))
+
+	m, _ := frame.Update(nil)
+
+	viewOutput := m.View()
+
+	assert.Contains(t, viewOutput, "visible")
+	assert.Contains(t, viewOutput, "log line 1")
+	assert.Contains(t, viewOutput, "log line 2")
+}
+
+func TestFrame_View_WithTruncatedFooter(t *testing.T) {
+	frame := New()
+	frame.ShowFooter(true)
+	frame.TruncateFooter(true)
+	frame.windowSize = tea.WindowSizeMsg{Height: 2} // but there are 3 lines!
+	model := mockVisibleTerminalModel{view: "visible", isHidden: false, isAlive: true}
+
+	frame.AppendModel(model)
+	frame.Footer().Write([]byte("log line 1\nlog line 2\nlog line 3"))
+
+	m, _ := frame.Update(nil)
+
+	viewOutput := m.View()
+
+	assert.Contains(t, viewOutput, "visible")
+	assert.Contains(t, viewOutput, "log line 3")
+	assert.NotContains(t, viewOutput, "log line 1")
+}
+
+func TestFrame_View_NoFooter(t *testing.T) {
+	frame := New()
+	frame.ShowFooter(false)
+	model := mockVisibleTerminalModel{view: "visible", isHidden: false, isAlive: true}
+
+	frame.AppendModel(model)
+	frame.Footer().Write([]byte("log line 1\nlog line 2"))
+
+	m, _ := frame.Update(nil)
+
+	viewOutput := m.View()
+
+	assert.Contains(t, viewOutput, "visible")
+	assert.NotContains(t, viewOutput, "log line 1")
+	assert.NotContains(t, viewOutput, "log line 2")
+}