feat(textinput): store and recover history

This adds the history functionality to the textinput model. Specific
actions can push a new value into the history and they can be switched
back to via key presses.

This is done in relation to nobe4/gh-not#190
I was considering implementing that in my project, and realized that it
could just be part of bubbles instead.

Looking forward to getting some feedback on this. Especially the
comments below.

textinput/textinput.go

@@ -59,6 +59,8 @@ type KeyMap struct {
 	AcceptSuggestion        key.Binding
 	NextSuggestion          key.Binding
 	PrevSuggestion          key.Binding
+	NextHistory             key.Binding
+	PrevHistory             key.Binding
 }
 
 // DefaultKeyMap is the default set of key bindings for navigating and acting
@@ -78,8 +80,11 @@ var DefaultKeyMap = KeyMap{
 	LineEnd:                 key.NewBinding(key.WithKeys("end", "ctrl+e")),
 	Paste:                   key.NewBinding(key.WithKeys("ctrl+v")),
 	AcceptSuggestion:        key.NewBinding(key.WithKeys("tab")),
-	NextSuggestion:          key.NewBinding(key.WithKeys("down", "ctrl+n")),
-	PrevSuggestion:          key.NewBinding(key.WithKeys("up", "ctrl+p")),
+	NextSuggestion:          key.NewBinding(key.WithKeys("ctrl+n")),
+	PrevSuggestion:          key.NewBinding(key.WithKeys("ctrl+p")),
+	// TODO: discuss moving `down` and `up` to this instead of Next/PrevSuggestion
+	NextHistory: key.NewBinding(key.WithKeys("down")),
+	PrevHistory: key.NewBinding(key.WithKeys("up")),
 }
 
 // Model is the Bubble Tea model for this text input element.
@@ -152,6 +157,10 @@ type Model struct {
 	suggestions            [][]rune
 	matchedSuggestions     [][]rune
 	currentSuggestionIndex int
+
+	// history of inputs
+	history      [][]rune
+	historyIndex int
 }
 
 // New creates a new model with default settings.
@@ -170,6 +179,9 @@ func New() Model {
 		value:       nil,
 		focus:       false,
 		pos:         0,
+
+		history:      [][]rune{},
+		historyIndex: 0,
 	}
 }
 
@@ -184,6 +196,7 @@ func (m *Model) SetValue(s string) {
 	// caller. This avoids bugs due to e.g. tab characters and whatnot.
 	runes := m.san().Sanitize([]rune(s))
 	err := m.validate(runes)
+	m.SaveHistory()
 	m.setValueInternal(runes, err)
 }
 
@@ -245,12 +258,14 @@ func (m *Model) Focus() tea.Cmd {
 // Blur removes the focus state on the model.  When the model is blurred it can
 // not receive keyboard input and the cursor will be hidden.
 func (m *Model) Blur() {
+	m.SaveHistory()
 	m.focus = false
 	m.Cursor.Blur()
 }
 
 // Reset sets the input to its default state with no input.
 func (m *Model) Reset() {
+	m.SaveHistory()
 	m.value = nil
 	m.SetCursor(0)
 }
@@ -614,6 +629,10 @@ func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
 			m.nextSuggestion()
 		case key.Matches(msg, m.KeyMap.PrevSuggestion):
 			m.previousSuggestion()
+		case key.Matches(msg, m.KeyMap.NextHistory):
+			m.nextHistory()
+		case key.Matches(msg, m.KeyMap.PrevHistory):
+			m.prevHistory()
 		default:
 			// Input one or more regular characters.
 			m.insertRunesFromUserInput(msg.Runes)
@@ -624,6 +643,7 @@ func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
 		m.updateSuggestions()
 
 	case pasteMsg:
+		m.SaveHistory()
 		m.insertRunesFromUserInput([]rune(msg))
 
 	case pasteErrMsg:
@@ -899,3 +919,56 @@ func (m Model) validate(v []rune) error {
 	}
 	return nil
 }
+
+func (m *Model) SaveHistory() {
+	if len(m.value) == 0 {
+		return
+	}
+
+	if m.EchoMode != EchoNormal {
+		return
+	}
+
+	// XXX: It seems that doing `append(m.history, m.value)` copies a reference
+	// to the value, which leads to all history items being similar.
+	// This is quite surprising given this other test:
+	// https://go.dev/play/p/MZGpcUzSVch
+	newRecord := make([]rune, len(m.value))
+	for i, r := range m.value {
+		newRecord[i] = r
+	}
+
+	m.history = append(m.history, newRecord)
+	m.historyIndex = len(m.history) - 1
+}
+
+func (m Model) History() []string {
+	// TODO: rename getSuggestions to getStrings
+	return m.getSuggestions(m.history)
+}
+
+func (m *Model) nextHistory() {
+	if len(m.history) == 0 {
+		return
+	}
+
+	m.historyIndex = (m.historyIndex + 1)
+	if m.historyIndex > len(m.history)-1 {
+		m.historyIndex = 0
+	}
+
+	m.setValueInternal(m.history[m.historyIndex], nil)
+}
+
+func (m *Model) prevHistory() {
+	if len(m.history) == 0 {
+		return
+	}
+
+	m.historyIndex = (m.historyIndex - 1)
+	if m.historyIndex < 0 {
+		m.historyIndex = len(m.history) - 1
+	}
+
+	m.setValueInternal(m.history[m.historyIndex], nil)
+}