From 2fd583c8ef43786d58beb63aae5d88b65c14dee2 Mon Sep 17 00:00:00 2001
From: Maas Lalani <maas@lalani.dev>
Date: Wed, 1 Jun 2022 10:48:00 -0400
Subject: [PATCH] feat(textarea): Add multi-line text input

---
 README.md                 |   12 +
 cursor/cursor.go          |  207 +++++++
 textarea/textarea.go      | 1120 +++++++++++++++++++++++++++++++++++++
 textarea/textarea_test.go |  446 +++++++++++++++
 4 files changed, 1785 insertions(+)
 create mode 100644 cursor/cursor.go
 create mode 100644 textarea/textarea.go
 create mode 100644 textarea/textarea_test.go

diff --git a/README.md b/README.md
index a6d2768..d699833 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,18 @@ the common, and many customization options.
 * [Example code, one field](https://github.com/charmbracelet/tea/tree/master/examples/textinput/main.go)
 * [Example code, many fields](https://github.com/charmbracelet/tea/tree/master/examples/textinputs/main.go)
 
+## Text Area
+
+<img src="https://stuff.charm.sh/bubbles-examples/textarea.gif" width="400" alt="Text Area Example">
+
+A text area field, akin to an `<textarea />` in HTML. Allows for input that
+spans multiple lines. Supports unicode, pasting, vertical scrolling when the
+value exceeds the width and height of the element,  and many customization
+options.
+
+* [Example code, chat input](https://github.com/charmbracelet/tea/tree/master/examples/chat/main.go)
+* [Example code, story time input](https://github.com/charmbracelet/tea/tree/master/examples/textarea/main.go)
+
 
 ## Progress
 
diff --git a/cursor/cursor.go b/cursor/cursor.go
new file mode 100644
index 0000000..9ad445e
--- /dev/null
+++ b/cursor/cursor.go
@@ -0,0 +1,207 @@
+package cursor
+
+import (
+	"context"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+const defaultBlinkSpeed = time.Millisecond * 530
+
+// initialBlinkMsg initializes cursor blinking.
+type initialBlinkMsg struct{}
+
+// BlinkMsg signals that the cursor should blink. It contains metadata that
+// allows us to tell if the blink message is the one we're expecting.
+type BlinkMsg struct {
+	id  int
+	tag int
+}
+
+// blinkCanceled is sent when a blink operation is canceled.
+type blinkCanceled struct{}
+
+// blinkCtx manages cursor blinking.
+type blinkCtx struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+}
+
+// Mode describes the behavior of the cursor.
+type Mode int
+
+// Available cursor modes.
+const (
+	CursorBlink Mode = iota
+	CursorStatic
+	CursorHide
+)
+
+// String returns the cursor mode in a human-readable format. This method is
+// provisional and for informational purposes only.
+func (c Mode) String() string {
+	return [...]string{
+		"blink",
+		"static",
+		"hidden",
+	}[c]
+}
+
+// Model is the Bubble Tea model for this cursor element.
+type Model struct {
+	BlinkSpeed time.Duration
+	// Style for styling the cursor block.
+	Style lipgloss.Style
+	// TextStyle is the style used for the cursor when it is hidden (when blinking).
+	// I.e. displaying normal text.
+	TextStyle lipgloss.Style
+
+	// char is the character under the cursor
+	char string
+	// The ID of this Model as it relates to other cursors
+	id int
+	// focus indicates whether the containing input is focused
+	focus bool
+	// Cursor Blink state.
+	Blink bool
+	// Used to manage cursor blink
+	blinkCtx *blinkCtx
+	// The ID of the blink message we're expecting to receive.
+	blinkTag int
+	// cursorMode determines the behavior of the cursor
+	cursorMode Mode
+}
+
+// New creates a new model with default settings.
+func New() Model {
+	return Model{
+		BlinkSpeed: defaultBlinkSpeed,
+
+		Blink:      true,
+		cursorMode: CursorBlink,
+
+		blinkCtx: &blinkCtx{
+			ctx: context.Background(),
+		},
+	}
+}
+
+// Update updates the cursor.
+func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case initialBlinkMsg:
+		// We accept all initialBlinkMsgs generated by the Blink command.
+
+		if m.cursorMode != CursorBlink || !m.focus {
+			return m, nil
+		}
+
+		cmd := m.BlinkCmd()
+		return m, cmd
+
+	case BlinkMsg:
+		// We're choosy about whether to accept blinkMsgs so that our cursor
+		// only exactly when it should.
+
+		// Is this model blink-able?
+		if m.cursorMode != CursorBlink || !m.focus {
+			return m, nil
+		}
+
+		// Were we expecting this blink message?
+		if msg.id != m.id || msg.tag != m.blinkTag {
+			return m, nil
+		}
+
+		var cmd tea.Cmd
+		if m.cursorMode == CursorBlink {
+			m.Blink = !m.Blink
+			cmd = m.BlinkCmd()
+		}
+		return m, cmd
+
+	case blinkCanceled: // no-op
+		return m, nil
+	}
+	return m, nil
+}
+
+// CursorMode returns the model's cursor mode. For available cursor modes, see
+// type CursorMode.
+func (m Model) CursorMode() Mode {
+	return m.cursorMode
+}
+
+// SetCursorMode sets the model's cursor mode. This method returns a command.
+//
+// For available cursor modes, see type CursorMode.
+func (m *Model) SetCursorMode(mode Mode) tea.Cmd {
+	m.cursorMode = mode
+	m.Blink = m.cursorMode == CursorHide || !m.focus
+	if mode == CursorBlink {
+		return Blink
+	}
+	return nil
+}
+
+// BlinkCmd is an command used to manage cursor blinking.
+func (m *Model) BlinkCmd() tea.Cmd {
+	if m.cursorMode != CursorBlink {
+		return nil
+	}
+
+	if m.blinkCtx != nil && m.blinkCtx.cancel != nil {
+		m.blinkCtx.cancel()
+	}
+
+	ctx, cancel := context.WithTimeout(m.blinkCtx.ctx, m.BlinkSpeed)
+	m.blinkCtx.cancel = cancel
+
+	m.blinkTag++
+
+	return func() tea.Msg {
+		defer cancel()
+		<-ctx.Done()
+		if ctx.Err() == context.DeadlineExceeded {
+			return BlinkMsg{id: m.id, tag: m.blinkTag}
+		}
+		return blinkCanceled{}
+	}
+}
+
+// Blink is a command used to initialize cursor blinking.
+func Blink() tea.Msg {
+	return initialBlinkMsg{}
+}
+
+// Focus focuses the cursor to allow it to blink if desired.
+func (m *Model) Focus() tea.Cmd {
+	m.focus = true
+	m.Blink = m.cursorMode == CursorHide // show the cursor unless we've explicitly hidden it
+
+	if m.cursorMode == CursorBlink && m.focus {
+		return m.BlinkCmd()
+	}
+	return nil
+}
+
+// Blur blurs the cursor.
+func (m *Model) Blur() {
+	m.focus = false
+	m.Blink = true
+}
+
+// SetChar sets the character under the cursor.
+func (m *Model) SetChar(char string) {
+	m.char = char
+}
+
+// View displays the cursor.
+func (m Model) View() string {
+	if m.Blink {
+		return m.TextStyle.Render(m.char)
+	}
+	return m.Style.Inline(true).Reverse(true).Render(m.char)
+}
diff --git a/textarea/textarea.go b/textarea/textarea.go
new file mode 100644
index 0000000..c12ee8e
--- /dev/null
+++ b/textarea/textarea.go
@@ -0,0 +1,1120 @@
+package textarea
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+
+	"github.com/atotto/clipboard"
+	"github.com/charmbracelet/bubbles/cursor"
+	"github.com/charmbracelet/bubbles/key"
+	"github.com/charmbracelet/bubbles/viewport"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+	rw "github.com/mattn/go-runewidth"
+)
+
+const (
+	minHeight        = 1
+	minWidth         = 2
+	defaultHeight    = 6
+	defaultWidth     = 40
+	defaultCharLimit = 400
+	maxHeight        = 99
+	maxWidth         = 500
+)
+
+// Internal messages for clipboard operations.
+type pasteMsg string
+type pasteErrMsg struct{ error }
+
+// KeyMap is the key bindings for different actions within the textarea.
+type KeyMap struct {
+	CharacterBackward       key.Binding
+	CharacterForward        key.Binding
+	DeleteAfterCursor       key.Binding
+	DeleteBeforeCursor      key.Binding
+	DeleteCharacterBackward key.Binding
+	DeleteCharacterForward  key.Binding
+	DeleteWordBackward      key.Binding
+	DeleteWordForward       key.Binding
+	InsertNewline           key.Binding
+	LineEnd                 key.Binding
+	LineNext                key.Binding
+	LinePrevious            key.Binding
+	LineStart               key.Binding
+	Paste                   key.Binding
+	WordBackward            key.Binding
+	WordForward             key.Binding
+}
+
+// DefaultKeyMap is the default set of key bindings for navigating and acting
+// upon the textarea.
+var DefaultKeyMap = KeyMap{
+	CharacterForward:        key.NewBinding(key.WithKeys("right", "ctrl+f")),
+	CharacterBackward:       key.NewBinding(key.WithKeys("left", "ctrl+b")),
+	WordForward:             key.NewBinding(key.WithKeys("alt+right", "alt+f")),
+	WordBackward:            key.NewBinding(key.WithKeys("alt+left", "alt+b")),
+	LineNext:                key.NewBinding(key.WithKeys("down", "ctrl+n")),
+	LinePrevious:            key.NewBinding(key.WithKeys("up", "ctrl+p")),
+	DeleteWordBackward:      key.NewBinding(key.WithKeys("alt+backspace", "ctrl+w")),
+	DeleteWordForward:       key.NewBinding(key.WithKeys("alt+delete", "alt+d")),
+	DeleteAfterCursor:       key.NewBinding(key.WithKeys("ctrl+k")),
+	DeleteBeforeCursor:      key.NewBinding(key.WithKeys("ctrl+u")),
+	InsertNewline:           key.NewBinding(key.WithKeys("enter", "ctrl+m")),
+	DeleteCharacterBackward: key.NewBinding(key.WithKeys("backspace", "ctrl+h")),
+	DeleteCharacterForward:  key.NewBinding(key.WithKeys("delete", "ctrl+d")),
+	LineStart:               key.NewBinding(key.WithKeys("home", "ctrl+a")),
+	LineEnd:                 key.NewBinding(key.WithKeys("end", "ctrl+e")),
+	Paste:                   key.NewBinding(key.WithKeys("ctrl+v")),
+}
+
+// LineInfo is a helper for keeping track of line information regarding
+// soft-wrapped lines.
+type LineInfo struct {
+	// Width is the number of columns in the line.
+	Width int
+	// CharWidth is the number of characters in the line to account for
+	// double-width runes.
+	CharWidth int
+	// Height is the number of rows in the line.
+	Height int
+	// StartColumn is the index of the first column of the line.
+	StartColumn int
+	// ColumnOffset is the number of columns that the cursor is offset from the
+	// start of the line.
+	ColumnOffset int
+	// RowOffset is the number of rows that the cursor is offset from the start
+	// of the line.
+	RowOffset int
+	// CharOffset is the number of characters that the cursor is offset
+	// from the start of the line. This will generally be equivalent to
+	// ColumnOffset, but will be different there are double-width runes before
+	// the cursor.
+	CharOffset int
+}
+
+// Style that will be applied to the text area.
+//
+// Style can be applied to focused and unfocused states to change the styles
+// depending on the focus state.
+//
+// For an introduction to styling with Lip Gloss see:
+// https://github.com/charmbracelet/lipgloss
+type Style struct {
+	Base             lipgloss.Style
+	CursorLine       lipgloss.Style
+	CursorLineNumber lipgloss.Style
+	EndOfBuffer      lipgloss.Style
+	LineNumber       lipgloss.Style
+	Placeholder      lipgloss.Style
+	Prompt           lipgloss.Style
+	Text             lipgloss.Style
+}
+
+// Model is the Bubble Tea model for this text area element.
+type Model struct {
+	Err error
+
+	// General settings.
+	Prompt               string
+	Placeholder          string
+	ShowLineNumbers      bool
+	EndOfBufferCharacter rune
+	KeyMap               KeyMap
+
+	// Styling. FocusedStyle and BlurredStyle are used to style the textarea in
+	// focused and blurred states.
+	FocusedStyle Style
+	BlurredStyle Style
+	// style is the current styling to use.
+	// It is used to abstract the differences in focus state when styling the
+	// model, since we can simply assign the set of styles to this variable
+	// when switching focus states.
+	style *Style
+
+	// Cursor is the text area cursor.
+	Cursor cursor.Model
+
+	// CharLimit is the maximum number of characters this input element will
+	// accept. If 0 or less, there's no limit.
+	CharLimit int
+
+	// width is the maximum number of characters that can be displayed at once.
+	// If 0 or less this setting is ignored.
+	width int
+
+	// height is the maximum number of lines that can be displayed at once. It
+	// essentially treats the text field like a vertically scrolling viewport
+	// if there are more lines than the permitted height.
+	height int
+
+	// Underlying text value.
+	value [][]rune
+
+	// focus indicates whether user input focus should be on this input
+	// component. When false, ignore keyboard input and hide the cursor.
+	focus bool
+
+	// Cursor column.
+	col int
+
+	// Cursor row.
+	row int
+
+	// Last character offset, used to maintain state when the cursor is moved
+	// vertically such that we can maintain the same navigating position.
+	lastCharOffset int
+
+	// lineNumberFormat is the format string used to display line numbers.
+	lineNumberFormat string
+
+	// viewport is the vertically-scrollable viewport of the multi-line text
+	// input.
+	viewport *viewport.Model
+}
+
+// New creates a new model with default settings.
+func New() Model {
+	vp := viewport.New(0, 0)
+	vp.KeyMap = viewport.KeyMap{}
+	cur := cursor.New()
+
+	focusedStyle, blurredStyle := DefaultStyles()
+
+	m := Model{
+		CharLimit:            defaultCharLimit,
+		Prompt:               lipgloss.ThickBorder().Left + " ",
+		style:                &blurredStyle,
+		FocusedStyle:         focusedStyle,
+		BlurredStyle:         blurredStyle,
+		EndOfBufferCharacter: '~',
+		ShowLineNumbers:      true,
+		Cursor:               cur,
+		KeyMap:               DefaultKeyMap,
+
+		value:            make([][]rune, minHeight, maxWidth),
+		focus:            false,
+		col:              0,
+		row:              0,
+		lineNumberFormat: "%2v ",
+
+		viewport: &vp,
+	}
+
+	m.SetHeight(defaultHeight)
+	m.SetWidth(defaultWidth)
+
+	return m
+}
+
+// DefaultStyles returns the default styles for focused and blurred states for
+// the textarea.
+func DefaultStyles() (Style, Style) {
+	focused := Style{
+		Base:             lipgloss.NewStyle(),
+		CursorLine:       lipgloss.NewStyle().Background(lipgloss.AdaptiveColor{Light: "255", Dark: "0"}),
+		CursorLineNumber: lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "240"}),
+		EndOfBuffer:      lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "254", Dark: "0"}),
+		LineNumber:       lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "249", Dark: "7"}),
+		Placeholder:      lipgloss.NewStyle().Foreground(lipgloss.Color("7")),
+		Prompt:           lipgloss.NewStyle().Foreground(lipgloss.Color("7")),
+		Text:             lipgloss.NewStyle(),
+	}
+	blurred := Style{
+		Base:             lipgloss.NewStyle(),
+		CursorLine:       lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "245", Dark: "7"}),
+		CursorLineNumber: lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "249", Dark: "7"}),
+		EndOfBuffer:      lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "254", Dark: "0"}),
+		LineNumber:       lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "249", Dark: "7"}),
+		Placeholder:      lipgloss.NewStyle().Foreground(lipgloss.Color("7")),
+		Prompt:           lipgloss.NewStyle().Foreground(lipgloss.Color("7")),
+		Text:             lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "245", Dark: "7"}),
+	}
+
+	return focused, blurred
+}
+
+// SetValue sets the value of the text input.
+func (m *Model) SetValue(s string) {
+	m.Reset()
+	m.InsertString(s)
+}
+
+// InsertString inserts a string at the cursor position.
+func (m *Model) InsertString(s string) {
+	lines := strings.Split(s, "\n")
+	for l, line := range lines {
+		for _, rune := range line {
+			m.InsertRune(rune)
+		}
+		if l != len(lines)-1 {
+			m.InsertRune('\n')
+		}
+	}
+}
+
+// InsertRune inserts a rune at the cursor position.
+func (m *Model) InsertRune(r rune) {
+	if r == '\n' {
+		m.splitLine(m.row, m.col)
+		return
+	}
+
+	m.value[m.row] = append(m.value[m.row][:m.col], append([]rune{r}, m.value[m.row][m.col:]...)...)
+	m.col++
+}
+
+// Value returns the value of the text input.
+func (m Model) Value() string {
+	if m.value == nil {
+		return ""
+	}
+
+	var v string
+	for _, l := range m.value {
+		v += string(l)
+		v += "\n"
+	}
+
+	return strings.TrimSuffix(v, "\n")
+}
+
+// Length returns the number of characters currently in the text input.
+func (m *Model) Length() int {
+	var l int
+	for _, row := range m.value {
+		l += rw.StringWidth(string(row))
+	}
+	return l
+}
+
+// Line returns the line position.
+func (m Model) Line() int {
+	return m.row
+}
+
+// CursorDown moves the cursor down by one line.
+// Returns whether or not the cursor blink should be reset.
+func (m *Model) CursorDown() {
+	li := m.LineInfo()
+	charOffset := max(m.lastCharOffset, li.CharOffset)
+	m.lastCharOffset = charOffset
+
+	if li.RowOffset+1 >= li.Height && m.row < len(m.value)-1 {
+		m.row++
+		m.col = 0
+	} else {
+		// Move the cursor to the start of the next line. So that we can get
+		// the line information. We need to add 2 columns to account for the
+		// trailing space wrapping.
+		m.col = min(li.StartColumn+li.Width+2, len(m.value[m.row])-1)
+	}
+
+	nli := m.LineInfo()
+	m.col = nli.StartColumn
+
+	if nli.Width <= 0 {
+		return
+	}
+
+	offset := 0
+	for offset < charOffset {
+		if m.col > len(m.value[m.row]) || offset >= nli.CharWidth-1 {
+			break
+		}
+		offset += rw.RuneWidth(m.value[m.row][m.col])
+		m.col++
+	}
+}
+
+// CursorUp moves the cursor up by one line.
+func (m *Model) CursorUp() {
+	li := m.LineInfo()
+	charOffset := max(m.lastCharOffset, li.CharOffset)
+	m.lastCharOffset = charOffset
+
+	if li.RowOffset <= 0 && m.row > 0 {
+		m.row--
+		m.col = len(m.value[m.row])
+	} else {
+		// Move the cursor to the end of the previous line.
+		// This can be done by moving the cursor to the start of the line and
+		// then subtracting 2 to account for the trailing space we keep on
+		// soft-wrapped lines.
+		m.col = li.StartColumn - 2
+	}
+
+	nli := m.LineInfo()
+	m.col = nli.StartColumn
+
+	if nli.Width <= 0 {
+		return
+	}
+
+	offset := 0
+	for offset < charOffset {
+		if m.col >= len(m.value[m.row]) || offset >= nli.CharWidth-1 {
+			break
+		}
+		offset += rw.RuneWidth(m.value[m.row][m.col])
+		m.col++
+	}
+}
+
+// SetCursor moves the cursor to the given position. If the position is
+// out of bounds the cursor will be moved to the start or end accordingly.
+func (m *Model) SetCursor(col int) {
+	m.col = clamp(col, 0, len(m.value[m.row]))
+	// Any time that we move the cursor horizontally we need to reset the last
+	// offset so that the horizontal position when navigating is adjusted.
+	m.lastCharOffset = 0
+}
+
+// CursorStart moves the cursor to the start of the input field.
+func (m *Model) CursorStart() {
+	m.SetCursor(0)
+}
+
+// CursorEnd moves the cursor to the end of the input field.
+func (m *Model) CursorEnd() {
+	m.SetCursor(len(m.value[m.row]))
+}
+
+// Focused returns the focus state on the model.
+func (m Model) Focused() bool {
+	return m.focus
+}
+
+// Focus sets the focus state on the model. When the model is in focus it can
+// receive keyboard input and the cursor will be hidden.
+func (m *Model) Focus() tea.Cmd {
+	m.focus = true
+	m.style = &m.FocusedStyle
+	return m.Cursor.Focus()
+}
+
+// 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.focus = false
+	m.style = &m.BlurredStyle
+	m.Cursor.Blur()
+}
+
+// Reset sets the input to its default state with no input.
+func (m *Model) Reset() {
+	m.value = make([][]rune, minHeight, maxWidth)
+	m.col = 0
+	m.row = 0
+	m.viewport.GotoTop()
+	m.SetCursor(0)
+}
+
+// handle a clipboard paste event, if supported.
+func (m *Model) handlePaste(v string) {
+	paste := []rune(v)
+
+	var availSpace int
+	if m.CharLimit > 0 {
+		availSpace = m.CharLimit - m.Length()
+	}
+
+	// If the char limit's been reached cancel
+	if m.CharLimit > 0 && availSpace <= 0 {
+		return
+	}
+
+	// If there's not enough space to paste the whole thing cut the pasted
+	// runes down so they'll fit
+	if m.CharLimit > 0 && availSpace < len(paste) {
+		paste = paste[:len(paste)-availSpace]
+	}
+
+	// Stuff before and after the cursor
+	head := m.value[m.row][:m.col]
+	tailSrc := m.value[m.row][m.col:]
+	tail := make([]rune, len(tailSrc))
+	copy(tail, tailSrc)
+
+	// Insert pasted runes
+	for _, r := range paste {
+		head = append(head, r)
+		m.col++
+		if m.CharLimit > 0 {
+			availSpace--
+			if availSpace <= 0 {
+				break
+			}
+		}
+	}
+
+	// Reset blink state if necessary and run overflow checks
+	m.SetCursor(m.col + len(paste))
+}
+
+// deleteBeforeCursor deletes all text before the cursor. Returns whether or
+// not the cursor blink should be reset.
+func (m *Model) deleteBeforeCursor() {
+	m.value[m.row] = m.value[m.row][m.col:]
+	m.SetCursor(0)
+}
+
+// deleteAfterCursor deletes all text after the cursor. Returns whether or not
+// the cursor blink should be reset. If input is masked delete everything after
+// the cursor so as not to reveal word breaks in the masked input.
+func (m *Model) deleteAfterCursor() {
+	m.value[m.row] = m.value[m.row][:m.col]
+	m.SetCursor(len(m.value[m.row]))
+}
+
+// deleteWordLeft deletes the word left to the cursor. Returns whether or not
+// the cursor blink should be reset.
+func (m *Model) deleteWordLeft() {
+	if m.col == 0 || len(m.value[m.row]) == 0 {
+		return
+	}
+
+	// Linter note: it's critical that we acquire the initial cursor position
+	// here prior to altering it via SetCursor() below. As such, moving this
+	// call into the corresponding if clause does not apply here.
+	oldCol := m.col //nolint:ifshort
+
+	m.SetCursor(m.col - 1)
+	for unicode.IsSpace(m.value[m.row][m.col]) {
+		if m.col <= 0 {
+			break
+		}
+		// ignore series of whitespace before cursor
+		m.SetCursor(m.col - 1)
+	}
+
+	for m.col > 0 {
+		if !unicode.IsSpace(m.value[m.row][m.col]) {
+			m.SetCursor(m.col - 1)
+		} else {
+			if m.col > 0 {
+				// keep the previous space
+				m.SetCursor(m.col + 1)
+			}
+			break
+		}
+	}
+
+	if oldCol > len(m.value[m.row]) {
+		m.value[m.row] = m.value[m.row][:m.col]
+	} else {
+		m.value[m.row] = append(m.value[m.row][:m.col], m.value[m.row][oldCol:]...)
+	}
+}
+
+// deleteWordRight deletes the word right to the cursor.
+func (m *Model) deleteWordRight() {
+	if m.col >= len(m.value[m.row]) || len(m.value[m.row]) == 0 {
+		return
+	}
+
+	oldCol := m.col
+	m.SetCursor(m.col + 1)
+	for unicode.IsSpace(m.value[m.row][m.col]) {
+		// ignore series of whitespace after cursor
+		m.SetCursor(m.col + 1)
+
+		if m.col >= len(m.value[m.row]) {
+			break
+		}
+	}
+
+	for m.col < len(m.value[m.row]) {
+		if !unicode.IsSpace(m.value[m.row][m.col]) {
+			m.SetCursor(m.col + 1)
+		} else {
+			break
+		}
+	}
+
+	if m.col > len(m.value[m.row]) {
+		m.value[m.row] = m.value[m.row][:oldCol]
+	} else {
+		m.value[m.row] = append(m.value[m.row][:oldCol], m.value[m.row][m.col:]...)
+	}
+
+	m.SetCursor(oldCol)
+}
+
+// wordLeft moves the cursor one word to the left. Returns whether or not the
+// cursor blink should be reset. If input is masked, move input to the start
+// so as not to reveal word breaks in the masked input.
+func (m *Model) wordLeft() {
+	if m.col == 0 || len(m.value[m.row]) == 0 {
+		return
+	}
+
+	i := m.col - 1
+	for i >= 0 {
+		if unicode.IsSpace(m.value[m.row][min(i, len(m.value[m.row])-1)]) {
+			m.SetCursor(m.col - 1)
+			i--
+		} else {
+			break
+		}
+	}
+
+	for i >= 0 {
+		if !unicode.IsSpace(m.value[m.row][min(i, len(m.value[m.row])-1)]) {
+			m.SetCursor(m.col - 1)
+			i--
+		} else {
+			break
+		}
+	}
+}
+
+// wordRight moves the cursor one word to the right. Returns whether or not the
+// cursor blink should be reset. If the input is masked, move input to the end
+// so as not to reveal word breaks in the masked input.
+func (m *Model) wordRight() {
+	if m.col >= len(m.value[m.row]) || len(m.value[m.row]) == 0 {
+		return
+	}
+
+	i := m.col
+	for i < len(m.value[m.row]) {
+		if unicode.IsSpace(m.value[m.row][i]) {
+			m.SetCursor(m.col + 1)
+			i++
+		} else {
+			break
+		}
+	}
+
+	for i < len(m.value[m.row]) {
+		if !unicode.IsSpace(m.value[m.row][i]) {
+			m.SetCursor(m.col + 1)
+			i++
+		} else {
+			break
+		}
+	}
+}
+
+// LineInfo returns the number of characters from the start of the
+// (soft-wrapped) line and the (soft-wrapped) line width.
+func (m Model) LineInfo() LineInfo {
+	grid := wrap(m.value[m.row], m.width)
+
+	// Find out which line we are currently on. This can be determined by the
+	// m.col and counting the number of runes that we need to skip.
+	var counter int
+	for i, line := range grid {
+		// We've found the line that we are on
+		if counter+len(line) == m.col && i+1 < len(grid) {
+			// We wrap around to the next line if we are at the end of the
+			// previous line so that we can be at the very beginning of the row
+			return LineInfo{
+				CharOffset:   0,
+				ColumnOffset: 0,
+				Height:       len(grid),
+				RowOffset:    i + 1,
+				StartColumn:  m.col,
+				Width:        len(grid[i+1]),
+				CharWidth:    rw.StringWidth(string(line)),
+			}
+		}
+
+		if counter+len(line) >= m.col {
+			return LineInfo{
+				CharOffset:   rw.StringWidth(string(line[:max(0, m.col-counter)])),
+				ColumnOffset: m.col - counter,
+				Height:       len(grid),
+				RowOffset:    i,
+				StartColumn:  counter,
+				Width:        len(line),
+				CharWidth:    rw.StringWidth(string(line)),
+			}
+		}
+
+		counter += len(line)
+	}
+	return LineInfo{}
+}
+
+// repositionView repositions the view of the viewport based on the defined
+// scrolling behavior.
+func (m *Model) repositionView() {
+	min := m.viewport.YOffset
+	max := min + m.viewport.Height - 1
+
+	if row := m.cursorLineNumber(); row < min {
+		m.viewport.LineUp(min - row)
+	} else if row > max {
+		m.viewport.LineDown(row - max)
+	}
+}
+
+// Width returns the width of the textarea.
+func (m Model) Width() int {
+	return m.width
+}
+
+// SetWidth sets the width of the textarea to fit exactly within the given width.
+// This means that the textarea will account for the width of the prompt and
+// whether or not line numbers are being shown.
+//
+// Ensure that SetWidth is called after setting the Prompt and ShowLineNumbers,
+// If it important that the width of the textarea be exactly the given width
+// and no more.
+func (m *Model) SetWidth(w int) {
+	m.viewport.Width = clamp(w, minWidth, maxWidth)
+
+	// Since the width of the textarea input is dependant on the width of the
+	// prompt and line numbers, we need to calculate it by subtracting.
+	inputWidth := w
+	if m.ShowLineNumbers {
+		inputWidth -= rw.StringWidth(fmt.Sprintf(m.lineNumberFormat, 0))
+	}
+	inputWidth -= rw.StringWidth(m.Prompt)
+	m.width = clamp(inputWidth, minWidth, maxWidth)
+}
+
+// Height returns the current height of the textarea.
+func (m Model) Height() int {
+	return m.height
+}
+
+// SetHeight sets the height of the textarea.
+func (m *Model) SetHeight(h int) {
+	m.height = clamp(h, minHeight, maxHeight)
+	m.viewport.Height = clamp(h, minHeight, maxHeight)
+}
+
+// Update is the Bubble Tea update loop.
+func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
+	if !m.focus {
+		m.Cursor.Blur()
+		return m, nil
+	}
+
+	// Used to determine if the cursor should blink.
+	oldRow, oldCol := m.cursorLineNumber(), m.col
+
+	var cmds []tea.Cmd
+
+	if m.value[m.row] == nil {
+		m.value[m.row] = make([]rune, 0)
+	}
+
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch {
+		case key.Matches(msg, m.KeyMap.DeleteAfterCursor):
+			m.col = clamp(m.col, 0, len(m.value[m.row]))
+			if m.col >= len(m.value[m.row]) {
+				m.mergeLineBelow(m.row)
+				break
+			}
+			m.deleteAfterCursor()
+		case key.Matches(msg, m.KeyMap.DeleteBeforeCursor):
+			m.col = clamp(m.col, 0, len(m.value[m.row]))
+			if m.col <= 0 {
+				m.mergeLineAbove(m.row)
+				break
+			}
+			m.deleteBeforeCursor()
+		case key.Matches(msg, m.KeyMap.DeleteCharacterBackward):
+			m.col = clamp(m.col, 0, len(m.value[m.row]))
+			if m.col <= 0 {
+				m.mergeLineAbove(m.row)
+				break
+			}
+			if len(m.value[m.row]) > 0 {
+				m.value[m.row] = append(m.value[m.row][:max(0, m.col-1)], m.value[m.row][m.col:]...)
+				if m.col > 0 {
+					m.SetCursor(m.col - 1)
+				}
+			}
+		case key.Matches(msg, m.KeyMap.DeleteCharacterForward):
+			if len(m.value[m.row]) > 0 && m.col < len(m.value[m.row]) {
+				m.value[m.row] = append(m.value[m.row][:m.col], m.value[m.row][m.col+1:]...)
+			}
+			if m.col >= len(m.value[m.row]) {
+				m.mergeLineBelow(m.row)
+				break
+			}
+		case key.Matches(msg, m.KeyMap.DeleteWordBackward):
+			if m.col <= 0 {
+				m.mergeLineAbove(m.row)
+				break
+			}
+			m.deleteWordLeft()
+		case key.Matches(msg, m.KeyMap.DeleteWordForward):
+		case key.Matches(msg, m.KeyMap.InsertNewline):
+			if len(m.value) >= maxHeight {
+				return m, nil
+			}
+			m.col = clamp(m.col, 0, len(m.value[m.row]))
+			m.splitLine(m.row, m.col)
+		case key.Matches(msg, m.KeyMap.LineEnd):
+			m.CursorEnd()
+		case key.Matches(msg, m.KeyMap.LineStart):
+			m.CursorStart()
+		case key.Matches(msg, m.KeyMap.CharacterForward):
+			if m.col < len(m.value[m.row]) {
+				m.SetCursor(m.col + 1)
+			} else {
+				if m.row < len(m.value)-1 {
+					m.row++
+					m.CursorStart()
+				}
+			}
+		case key.Matches(msg, m.KeyMap.LineNext):
+			m.CursorDown()
+		case key.Matches(msg, m.KeyMap.WordForward):
+			m.wordRight()
+		case key.Matches(msg, m.KeyMap.Paste):
+			return m, Paste
+		case key.Matches(msg, m.KeyMap.CharacterBackward):
+			if m.col == 0 && m.row != 0 {
+				m.row--
+				m.CursorEnd()
+				break
+			}
+			if m.col > 0 {
+				m.SetCursor(m.col - 1)
+			}
+		case key.Matches(msg, m.KeyMap.LinePrevious):
+			m.CursorUp()
+		case key.Matches(msg, m.KeyMap.WordBackward):
+			m.wordLeft()
+		default:
+			if rw.StringWidth(m.Value()) >= m.CharLimit {
+				break
+			}
+
+			m.col = min(m.col, len(m.value[m.row]))
+			m.value[m.row] = append(m.value[m.row][:m.col], append(msg.Runes, m.value[m.row][m.col:]...)...)
+			m.SetCursor(m.col + len(msg.Runes))
+		}
+
+	case pasteMsg:
+		m.handlePaste(string(msg))
+
+	case pasteErrMsg:
+		m.Err = msg
+	}
+
+	vp, cmd := m.viewport.Update(msg)
+	m.viewport = &vp
+	cmds = append(cmds, cmd)
+
+	newRow, newCol := m.cursorLineNumber(), m.col
+	m.Cursor, cmd = m.Cursor.Update(msg)
+	if newRow != oldRow || newCol != oldCol {
+		m.Cursor.Blink = false
+		cmd = m.Cursor.BlinkCmd()
+	}
+	cmds = append(cmds, cmd)
+
+	m.repositionView()
+
+	return m, tea.Batch(cmds...)
+}
+
+// View renders the text area in its current state.
+func (m Model) View() string {
+	if m.Value() == "" && m.row == 0 && m.col == 0 && m.Placeholder != "" {
+		return m.placeholderView()
+	}
+	m.Cursor.TextStyle = m.style.CursorLine
+
+	var s strings.Builder
+	var style lipgloss.Style
+	lineInfo := m.LineInfo()
+
+	var newLines int
+
+	for l, line := range m.value {
+		wrappedLines := wrap(line, m.width)
+
+		if m.row == l {
+			style = m.style.CursorLine
+		} else {
+			style = m.style.Text
+		}
+
+		for wl, wrappedLine := range wrappedLines {
+			s.WriteString(style.Render(m.style.Prompt.Render(m.Prompt)))
+
+			if m.ShowLineNumbers {
+				if wl == 0 {
+					if m.row == l {
+						s.WriteString(style.Render(m.style.CursorLineNumber.Render(fmt.Sprintf(m.lineNumberFormat, l+1))))
+					} else {
+						s.WriteString(style.Render(m.style.LineNumber.Render(fmt.Sprintf(m.lineNumberFormat, l+1))))
+					}
+				} else {
+					s.WriteString(m.style.LineNumber.Render(style.Render("   ")))
+				}
+			}
+
+			strwidth := rw.StringWidth(string(wrappedLine))
+			padding := m.width - strwidth
+			// If the trailing space causes the line to be wider than the
+			// width, we should not draw it to the screen since it will result
+			// in an extra space at the end of the line which can look off when
+			// the cursor line is showing.
+			if strwidth > m.width {
+				// The character causing the line to be wider than the width is
+				// guaranteed to be a space since any other character would
+				// have been wrapped.
+				wrappedLine = []rune(strings.TrimSuffix(string(wrappedLine), " "))
+				padding -= m.width - strwidth
+			}
+			if m.row == l && lineInfo.RowOffset == wl {
+				s.WriteString(style.Render(string(wrappedLine[:lineInfo.ColumnOffset])))
+				if m.col >= len(line) && lineInfo.CharOffset >= m.width {
+					m.Cursor.SetChar(" ")
+					s.WriteString(m.Cursor.View())
+				} else {
+					m.Cursor.SetChar(string(wrappedLine[lineInfo.ColumnOffset]))
+					s.WriteString(style.Render(m.Cursor.View()))
+					s.WriteString(style.Render(string(wrappedLine[lineInfo.ColumnOffset+1:])))
+				}
+			} else {
+				s.WriteString(style.Render(string(wrappedLine)))
+			}
+			s.WriteString(style.Render(strings.Repeat(" ", max(0, padding))))
+			s.WriteRune('\n')
+			newLines++
+		}
+	}
+
+	// Always show at least `m.Height` lines at all times.
+	// To do this we can simply pad out a few extra new lines in the view.
+	for i := 0; i < m.height; i++ {
+		s.WriteString(m.style.Prompt.Render(m.Prompt))
+
+		if m.ShowLineNumbers {
+			lineNumber := m.style.EndOfBuffer.Render((fmt.Sprintf(m.lineNumberFormat, string(m.EndOfBufferCharacter))))
+			s.WriteString(lineNumber)
+		}
+		s.WriteRune('\n')
+	}
+
+	m.viewport.SetContent(s.String())
+	return m.style.Base.Render(m.viewport.View())
+}
+
+// placeholderView returns the prompt and placeholder view, if any.
+func (m Model) placeholderView() string {
+	var (
+		s     strings.Builder
+		p     = rw.Truncate(m.Placeholder, m.width, "...")
+		style = m.style.Placeholder.Inline(true)
+	)
+
+	prompt := m.style.Prompt.Render(m.Prompt)
+	s.WriteString(m.style.CursorLine.Render(prompt))
+
+	if m.ShowLineNumbers {
+		s.WriteString(m.style.CursorLine.Render(m.style.CursorLineNumber.Render((fmt.Sprintf(m.lineNumberFormat, 1)))))
+	}
+
+	m.Cursor.TextStyle = m.style.Placeholder
+	m.Cursor.SetChar(string(p[0]))
+	s.WriteString(m.style.CursorLine.Render(m.Cursor.View()))
+
+	// The rest of the placeholder text
+	s.WriteString(m.style.CursorLine.Render(style.Render(p[1:] + strings.Repeat(" ", max(0, m.width-rw.StringWidth(p))))))
+
+	// The rest of the new lines
+	for i := 1; i < m.height; i++ {
+		s.WriteRune('\n')
+		s.WriteString(prompt)
+
+		if m.ShowLineNumbers {
+			eob := m.style.EndOfBuffer.Render((fmt.Sprintf(m.lineNumberFormat, string(m.EndOfBufferCharacter))))
+			s.WriteString(eob)
+		}
+	}
+
+	m.viewport.SetContent(s.String())
+	return m.style.Base.Render(m.viewport.View())
+}
+
+// Blink returns the blink command for the cursor.
+func Blink() tea.Msg {
+	return cursor.Blink()
+}
+
+// cursorLineNumber returns the line number that the cursor is on.
+// This accounts for soft wrapped lines.
+func (m Model) cursorLineNumber() int {
+	line := 0
+	for i := 0; i < m.row; i++ {
+		// Calculate the number of lines that the current line will be split
+		// into.
+		line += len(wrap(m.value[i], m.width))
+	}
+	line += m.LineInfo().RowOffset
+	return line
+}
+
+// mergeLineBelow merges the current line with the line below.
+func (m *Model) mergeLineBelow(row int) {
+	if row >= len(m.value)-1 {
+		return
+	}
+
+	// To perform a merge, we will need to combine the two lines and then
+	m.value[row] = append(m.value[row], m.value[row+1]...)
+
+	// Shift all lines up by one
+	for i := row + 1; i < len(m.value)-1; i++ {
+		m.value[i] = m.value[i+1]
+	}
+
+	// And, remove the last line
+	if len(m.value) > 0 {
+		m.value = m.value[:len(m.value)-1]
+	}
+}
+
+// mergeLineAbove merges the current line the cursor is on with the line above.
+func (m *Model) mergeLineAbove(row int) {
+	if row <= 0 {
+		return
+	}
+
+	m.col = len(m.value[row-1])
+	m.row = m.row - 1
+
+	// To perform a merge, we will need to combine the two lines and then
+	m.value[row-1] = append(m.value[row-1], m.value[row]...)
+
+	// Shift all lines up by one
+	for i := row; i < len(m.value)-1; i++ {
+		m.value[i] = m.value[i+1]
+	}
+
+	// And, remove the last line
+	if len(m.value) > 0 {
+		m.value = m.value[:len(m.value)-1]
+	}
+}
+
+func (m *Model) splitLine(row, col int) {
+	// To perform a split, take the current line and keep the content before
+	// the cursor, take the content after the cursor and make it the content of
+	// the line underneath, and shift the remaining lines down by one
+	head, tailSrc := m.value[row][:col], m.value[row][col:]
+	tail := make([]rune, len(tailSrc))
+	copy(tail, tailSrc)
+
+	m.value = append(m.value[:row+1], m.value[row:]...)
+
+	m.value[row] = head
+	m.value[row+1] = tail
+
+	m.col = 0
+	m.row++
+}
+
+// Paste is a command for pasting from the clipboard into the text input.
+func Paste() tea.Msg {
+	str, err := clipboard.ReadAll()
+	if err != nil {
+		return pasteErrMsg{err}
+	}
+	return pasteMsg(str)
+}
+
+func wrap(runes []rune, width int) [][]rune {
+	var (
+		lines  = [][]rune{{}}
+		word   = []rune{}
+		row    int
+		spaces int
+	)
+
+	// Word wrap the runes
+	for _, r := range runes {
+		if unicode.IsSpace(r) {
+			spaces++
+		} else {
+			word = append(word, r)
+		}
+
+		if spaces > 0 {
+			if rw.StringWidth(string(lines[row]))+rw.StringWidth(string(word))+spaces > width {
+				row++
+				lines = append(lines, []rune{})
+				lines[row] = append(lines[row], word...)
+				lines[row] = append(lines[row], repeatSpaces(spaces)...)
+				spaces = 0
+				word = nil
+			} else {
+				lines[row] = append(lines[row], word...)
+				lines[row] = append(lines[row], repeatSpaces(spaces)...)
+				spaces = 0
+				word = nil
+			}
+		} else {
+			// If the last character is a double-width rune, then we may not be able to add it to this line
+			// as it might cause us to go past the width.
+			lastCharLen := rw.RuneWidth(word[len(word)-1])
+			if rw.StringWidth(string(word))+lastCharLen > width {
+				// If the current line has any content, let's move to the next
+				// line because the current word fills up the entire line.
+				if len(lines[row]) > 0 {
+					row++
+					lines = append(lines, []rune{})
+				}
+				lines[row] = append(lines[row], word...)
+				word = nil
+			}
+		}
+	}
+
+	if rw.StringWidth(string(lines[row]))+rw.StringWidth(string(word))+spaces >= width {
+		lines = append(lines, []rune{})
+		lines[row+1] = append(lines[row+1], word...)
+		// We add an extra space at the end of the line to account for the
+		// trailing space at the end of the previous soft-wrapped lines so that
+		// behaviour when navigating is consistent and so that we don't need to
+		// continually add edges to handle the last line of the wrapped input.
+		spaces++
+		lines[row+1] = append(lines[row+1], repeatSpaces(spaces)...)
+	} else {
+		lines[row] = append(lines[row], word...)
+		spaces++
+		lines[row] = append(lines[row], repeatSpaces(spaces)...)
+	}
+
+	return lines
+}
+
+func repeatSpaces(n int) []rune {
+	return []rune(strings.Repeat(string(' '), n))
+}
+
+func clamp(v, low, high int) int {
+	if high < low {
+		low, high = high, low
+	}
+	return min(high, max(low, v))
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
diff --git a/textarea/textarea_test.go b/textarea/textarea_test.go
new file mode 100644
index 0000000..17395bc
--- /dev/null
+++ b/textarea/textarea_test.go
@@ -0,0 +1,446 @@
+package textarea
+
+import (
+	"strings"
+	"testing"
+
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+func TestNew(t *testing.T) {
+	textarea := newTextArea()
+	view := textarea.View()
+
+	if !strings.Contains(view, ">") {
+		t.Log(view)
+		t.Error("Text area did not render the prompt")
+	}
+
+	if !strings.Contains(view, "World!") {
+		t.Log(view)
+		t.Error("Text area did not render the placeholder")
+	}
+}
+
+func TestInput(t *testing.T) {
+	textarea := newTextArea()
+
+	input := "foo"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	view := textarea.View()
+
+	if !strings.Contains(view, input) {
+		t.Log(view)
+		t.Error("Text area did not render the input")
+	}
+
+	if textarea.col != len(input) {
+		t.Log(view)
+		t.Error("Text area did not move the cursor to the correct position")
+	}
+}
+
+func TestSoftWrap(t *testing.T) {
+	textarea := newTextArea()
+	textarea.Prompt = ""
+	textarea.ShowLineNumbers = false
+	textarea.SetWidth(5)
+	textarea.SetHeight(5)
+	textarea.CharLimit = 60
+
+	textarea, _ = textarea.Update(nil)
+
+	input := "foo bar baz"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	view := textarea.View()
+
+	for _, word := range strings.Split(input, " ") {
+		if !strings.Contains(view, word) {
+			t.Log(view)
+			t.Error("Text area did not render the input")
+		}
+	}
+
+	// Due to the word wrapping, each word will be on a new line and the
+	// text area will look like this:
+	//
+	// > foo
+	// > bar
+	// > baz█
+	//
+	// However, due to soft-wrapping the column will still be at the end of the line.
+	if textarea.row != 0 || textarea.col != len(input) {
+		t.Log(view)
+		t.Error("Text area did not move the cursor to the correct position")
+	}
+}
+
+func TestCharLimit(t *testing.T) {
+	textarea := newTextArea()
+
+	// First input (foo bar) should be accepted as it will fall within the
+	// CharLimit. Second input (baz) should not appear in the input.
+	input := []string{"foo bar", "baz"}
+	textarea.CharLimit = len(input[0])
+
+	for _, k := range []rune(strings.Join(input, " ")) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	view := textarea.View()
+	if strings.Contains(view, input[1]) {
+		t.Log(view)
+		t.Error("Text area should not include input past the character limit")
+	}
+}
+
+func TestVerticalScrolling(t *testing.T) {
+	textarea := newTextArea()
+	textarea.Prompt = ""
+	textarea.ShowLineNumbers = false
+	textarea.SetHeight(1)
+	textarea.SetWidth(20)
+	textarea.CharLimit = 100
+
+	textarea, _ = textarea.Update(nil)
+
+	input := "This is a really long line that should wrap around the text area."
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	view := textarea.View()
+
+	// The view should contain the first "line" of the input.
+	if !strings.Contains(view, "This is a really") {
+		t.Log(view)
+		t.Error("Text area did not render the input")
+	}
+
+	// But we should be able to scroll to see the next line.
+	// Let's scroll down for each line to view the full input.
+	lines := []string{
+		"long line that",
+		"should wrap around",
+		"the text area.",
+	}
+	for _, line := range lines {
+		textarea.viewport.LineDown(1)
+		view = textarea.View()
+		if !strings.Contains(view, line) {
+			t.Log(view)
+			t.Error("Text area did not render the correct scrolled input")
+		}
+	}
+}
+
+func TestWordWrapOverflowing(t *testing.T) {
+	// An interesting edge case is when the user enters many words that fill up
+	// the text area and then goes back up and inserts a few words which causes
+	// a cascading wrap and causes an overflow of the last line.
+	//
+	// In this case, we should not let the user insert more words if, after the
+	// entire wrap is complete, the last line is overflowing.
+	textarea := newTextArea()
+
+	textarea.SetHeight(3)
+	textarea.SetWidth(20)
+	textarea.CharLimit = 500
+
+	textarea, _ = textarea.Update(nil)
+
+	input := "Testing Testing Testing Testing Testing Testing Testing Testing"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+		textarea.View()
+	}
+
+	// We have essentially filled the text area with input.
+	// Let's see if we can cause wrapping to overflow the last line.
+	textarea.row = 0
+	textarea.col = 0
+
+	input = "Testing"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+		textarea.View()
+	}
+
+	lastLineWidth := textarea.LineInfo().Width
+	if lastLineWidth > 20 {
+		t.Log(lastLineWidth)
+		t.Log(textarea.View())
+		t.Fail()
+	}
+}
+
+func TestValueSoftWrap(t *testing.T) {
+	textarea := newTextArea()
+	textarea.SetWidth(16)
+	textarea.SetHeight(10)
+	textarea.CharLimit = 500
+
+	textarea, _ = textarea.Update(nil)
+
+	input := "Testing Testing Testing Testing Testing Testing Testing Testing"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+		textarea.View()
+	}
+
+	value := textarea.Value()
+	if value != input {
+		t.Log(value)
+		t.Log(input)
+		t.Fatal("The text area does not have the correct value")
+	}
+}
+
+func TestSetValue(t *testing.T) {
+	textarea := newTextArea()
+	textarea.SetValue(strings.Join([]string{"Foo", "Bar", "Baz"}, "\n"))
+
+	if textarea.row != 2 && textarea.col != 3 {
+		t.Log(textarea.row, textarea.col)
+		t.Fatal("Cursor Should be on row 2 column 3 after inserting 2 new lines")
+	}
+
+	value := textarea.Value()
+	if value != "Foo\nBar\nBaz" {
+		t.Fatal("Value should be Foo\nBar\nBaz")
+	}
+
+	// SetValue should reset text area
+	textarea.SetValue("Test")
+	value = textarea.Value()
+	if value != "Test" {
+		t.Log(value)
+		t.Fatal("Text area was not reset when SetValue() was called")
+	}
+}
+
+func TestInsertString(t *testing.T) {
+	textarea := newTextArea()
+
+	// Insert some text
+	input := "foo baz"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	// Put cursor in the middle of the text
+	textarea.col = 4
+
+	textarea.InsertString("bar ")
+
+	value := textarea.Value()
+	if value != "foo bar baz" {
+		t.Log(value)
+		t.Fatal("Expected insert string to insert bar between foo and baz")
+	}
+}
+
+func TestCanHandleEmoji(t *testing.T) {
+	textarea := newTextArea()
+	input := "🧋"
+
+	for _, k := range []rune(input) {
+		textarea, _ = textarea.Update(keyPress(k))
+	}
+
+	value := textarea.Value()
+	if value != input {
+		t.Log(value)
+		t.Fatal("Expected emoji to be inserted")
+	}
+
+	input = "🧋🧋🧋"
+
+	textarea.SetValue(input)
+
+	value = textarea.Value()
+	if value != input {
+		t.Log(value)
+		t.Fatal("Expected emoji to be inserted")
+	}
+
+	if textarea.col != 3 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the third character")
+	}
+
+	if charOffset := textarea.LineInfo().CharOffset; charOffset != 6 {
+		t.Log(charOffset)
+		t.Fatal("Expected cursor to be on the sixth character")
+	}
+}
+
+func TestVerticalNavigationKeepsCursorHorizontalPosition(t *testing.T) {
+	textarea := newTextArea()
+	textarea.SetWidth(20)
+
+	textarea.SetValue(strings.Join([]string{"你好你好", "Hello"}, "\n"))
+
+	textarea.row = 0
+	textarea.col = 2
+
+	// 你好|你好
+	// Hell|o
+	// 1234|
+
+	// Let's imagine our cursor is on the first line where the pipe is.
+	// We press the down arrow to get to the next line.
+	// The issue is that if we keep the cursor on the same column, the cursor will jump to after the `e`.
+	//
+	// 你好|你好
+	// He|llo
+	//
+	// But this is wrong because visually we were at the 4th character due to
+	// the first line containing double-width runes.
+	// We want to keep the cursor on the same visual column.
+	//
+	// 你好|你好
+	// Hell|o
+	//
+	// This test ensures that the cursor is kept on the same visual column by
+	// ensuring that the column offset goes from 2 -> 4.
+
+	lineInfo := textarea.LineInfo()
+	if lineInfo.CharOffset != 4 || lineInfo.ColumnOffset != 2 {
+		t.Log(lineInfo.CharOffset)
+		t.Log(lineInfo.ColumnOffset)
+		t.Fatal("Expected cursor to be on the fourth character because there two double width runes on the first line.")
+	}
+
+	downMsg := tea.KeyMsg{Type: tea.KeyDown, Alt: false, Runes: []rune{}}
+	textarea, _ = textarea.Update(downMsg)
+
+	lineInfo = textarea.LineInfo()
+	if lineInfo.CharOffset != 4 || lineInfo.ColumnOffset != 4 {
+		t.Log(lineInfo.CharOffset)
+		t.Log(lineInfo.ColumnOffset)
+		t.Fatal("Expected cursor to be on the fourth character because we came down from the first line.")
+	}
+}
+
+func TestVerticalNavigationShouldRememberPositionWhileTraversing(t *testing.T) {
+	textarea := newTextArea()
+	textarea.SetWidth(40)
+
+	// Let's imagine we have a text area with the following content:
+	//
+	// Hello
+	// World
+	// This is a long line.
+	//
+	// If we are at the end of the last line and go up, we should be at the end
+	// of the second line.
+	// And, if we go up again we should be at the end of the first line.
+	// But, if we go back down twice, we should be at the end of the last line
+	// again and not the fifth (length of second line) character of the last line.
+	//
+	// In other words, we should remember the last horizontal position while
+	// traversing vertically.
+
+	textarea.SetValue(strings.Join([]string{"Hello", "World", "This is a long line."}, "\n"))
+
+	// We are at the end of the last line.
+	if textarea.col != 20 || textarea.row != 2 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 20th character of the last line")
+	}
+
+	// Let's go up.
+	upMsg := tea.KeyMsg{Type: tea.KeyUp, Alt: false, Runes: []rune{}}
+	textarea, _ = textarea.Update(upMsg)
+
+	// We should be at the end of the second line.
+	if textarea.col != 5 || textarea.row != 1 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 5th character of the second line")
+	}
+
+	// And, again.
+	textarea, _ = textarea.Update(upMsg)
+
+	// We should be at the end of the first line.
+	if textarea.col != 5 || textarea.row != 0 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 5th character of the first line")
+	}
+
+	// Let's go down, twice.
+	downMsg := tea.KeyMsg{Type: tea.KeyDown, Alt: false, Runes: []rune{}}
+	textarea, _ = textarea.Update(downMsg)
+	textarea, _ = textarea.Update(downMsg)
+
+	// We should be at the end of the last line.
+	if textarea.col != 20 || textarea.row != 2 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 20th character of the last line")
+	}
+
+	// Now, for correct behavior, if we move right or left, we should forget
+	// (reset) the saved horizontal position. Since we assume the user wants to
+	// keep the cursor where it is horizontally. This is how most text areas
+	// work.
+
+	textarea, _ = textarea.Update(upMsg)
+	leftMsg := tea.KeyMsg{Type: tea.KeyLeft, Alt: false, Runes: []rune{}}
+	textarea, _ = textarea.Update(leftMsg)
+
+	if textarea.col != 4 || textarea.row != 1 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 5th character of the second line")
+	}
+
+	// Going down now should keep us at the 4th column since we moved left and
+	// reset the horizontal position saved state.
+	textarea, _ = textarea.Update(downMsg)
+	if textarea.col != 4 || textarea.row != 2 {
+		t.Log(textarea.col)
+		t.Fatal("Expected cursor to be on the 4th character of the last line")
+	}
+}
+
+func TestRendersEndOfLineBuffer(t *testing.T) {
+	textarea := newTextArea()
+	textarea.ShowLineNumbers = true
+	textarea.SetWidth(20)
+
+	view := textarea.View()
+	if !strings.Contains(view, "~") {
+		t.Log(view)
+		t.Fatal("Expected to see a tilde at the end of the line")
+	}
+}
+
+func newTextArea() Model {
+	textarea := New()
+
+	textarea.Prompt = "> "
+	textarea.Placeholder = "Hello, World!"
+
+	textarea.Focus()
+
+	textarea, _ = textarea.Update(nil)
+
+	return textarea
+}
+
+func keyPress(key rune) tea.Msg {
+	return tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{key}, Alt: false}
+}