hishtory/client/tui/tui.go

765 lines
22 KiB
Go

package tui
import (
"context"
"fmt"
"os"
"regexp"
"strings"
"time"
_ "embed" // for embedding config.sh
"github.com/charmbracelet/bubbles/help"
"github.com/charmbracelet/bubbles/key"
"github.com/charmbracelet/bubbles/spinner"
"github.com/charmbracelet/bubbles/textinput"
tea "github.com/charmbracelet/bubbletea"
"github.com/charmbracelet/lipgloss"
"github.com/ddworken/hishtory/client/data"
"github.com/ddworken/hishtory/client/hctx"
"github.com/ddworken/hishtory/client/lib"
"github.com/ddworken/hishtory/client/table"
"github.com/ddworken/hishtory/shared"
"github.com/muesli/termenv"
"golang.org/x/term"
)
const TABLE_HEIGHT = 20
const PADDED_NUM_ENTRIES = TABLE_HEIGHT * 5
var CURRENT_QUERY_FOR_HIGHLIGHTING string = ""
var SELECTED_COMMAND string = ""
// Globally shared monotonically increasing IDs used to prevent race conditions in handling async queries.
// If the user types 'l' and then 's', two queries will be dispatched: One for 'l' and one for 'ls'. These
// counters are used to ensure that we don't process the query results for 'ls' and then promptly overwrite
// them with the results for 'l'.
var LAST_DISPATCHED_QUERY_ID = 0
var LAST_PROCESSED_QUERY_ID = -1
var baseStyle = lipgloss.NewStyle().
BorderStyle(lipgloss.NormalBorder()).
BorderForeground(lipgloss.Color("240"))
type keyMap struct {
Up key.Binding
Down key.Binding
PageUp key.Binding
PageDown key.Binding
SelectEntry key.Binding
SelectEntryAndChangeDir key.Binding
Left key.Binding
Right key.Binding
TableLeft key.Binding
TableRight key.Binding
DeleteEntry key.Binding
Help key.Binding
Quit key.Binding
}
var fakeTitleKeyBinding key.Binding = key.NewBinding(
key.WithKeys(""),
key.WithHelp("hiSHtory: Search your shell history", ""),
)
var fakeEmptyKeyBinding key.Binding = key.NewBinding(
key.WithKeys(""),
key.WithHelp("", ""),
)
func (k keyMap) ShortHelp() []key.Binding {
return []key.Binding{fakeTitleKeyBinding, k.Help}
}
func (k keyMap) FullHelp() [][]key.Binding {
return [][]key.Binding{
{fakeTitleKeyBinding, k.Up, k.Left, k.SelectEntry, k.SelectEntryAndChangeDir},
{fakeEmptyKeyBinding, k.Down, k.Right, k.DeleteEntry},
{fakeEmptyKeyBinding, k.PageUp, k.TableLeft, k.Quit},
{fakeEmptyKeyBinding, k.PageDown, k.TableRight, k.Help},
}
}
var keys = keyMap{
Up: key.NewBinding(
key.WithKeys("up", "alt+OA", "ctrl+p"),
key.WithHelp("↑ ", "scroll up "),
),
Down: key.NewBinding(
key.WithKeys("down", "alt+OB", "ctrl+n"),
key.WithHelp("↓ ", "scroll down "),
),
PageUp: key.NewBinding(
key.WithKeys("pgup"),
key.WithHelp("pgup", "page up "),
),
PageDown: key.NewBinding(
key.WithKeys("pgdown"),
key.WithHelp("pgdn", "page down "),
),
SelectEntry: key.NewBinding(
key.WithKeys("enter"),
key.WithHelp("enter", "select an entry "),
),
SelectEntryAndChangeDir: key.NewBinding(
key.WithKeys("ctrl+x"),
key.WithHelp("ctrl+x", "select an entry and cd into that directory"),
),
Left: key.NewBinding(
key.WithKeys("left"),
key.WithHelp("← ", "move left "),
),
Right: key.NewBinding(
key.WithKeys("right"),
key.WithHelp("→ ", "move right "),
),
TableLeft: key.NewBinding(
key.WithKeys("shift+left"),
key.WithHelp("shift+← ", "scroll the table left "),
),
TableRight: key.NewBinding(
key.WithKeys("shift+right"),
key.WithHelp("shift+→ ", "scroll the table right "),
),
DeleteEntry: key.NewBinding(
key.WithKeys("ctrl+k"),
key.WithHelp("ctrl+k", "delete the highlighted entry "),
),
Help: key.NewBinding(
key.WithKeys("ctrl+h"),
key.WithHelp("ctrl+h", "help "),
),
Quit: key.NewBinding(
key.WithKeys("esc", "ctrl+c", "ctrl+d"),
key.WithHelp("esc", "exit hiSHtory "),
),
}
type SelectStatus int64
const (
NotSelected SelectStatus = iota
Selected
SelectedWithChangeDir
)
type model struct {
// context
ctx context.Context
// Model for the loading spinner.
spinner spinner.Model
// Whether data is still loading and the spinner should still be displayed.
isLoading bool
// Model for the help bar at the bottom of the page
help help.Model
// Whether the TUI is quitting.
quitting bool
// The table used for displaying search results. Nil if the initial search query hasn't returned yet.
table *table.Model
// The entries in the table
tableEntries []*data.HistoryEntry
// Whether the user has hit enter to select an entry and the TUI is thus about to quit.
selected SelectStatus
// The search box for the query
queryInput textinput.Model
// The query to run. Reset to nil after it was run.
runQuery *string
// The previous query that was run.
lastQuery string
// Unrecoverable error.
fatalErr error
// An error while searching. Recoverable and displayed as a warning message.
searchErr error
// Whether the device is offline. If so, a warning will be displayed.
isOffline bool
// A banner from the backend to be displayed. Generally an empty string.
banner string
}
type doneDownloadingMsg struct{}
type offlineMsg struct{}
type bannerMsg struct {
banner string
}
type asyncQueryFinishedMsg struct {
// The query ID finished running. Used to ensure that we only process this message if it is the latest query to finish.
queryId int
// The table rows and entries
rows []table.Row
entries []*data.HistoryEntry
// An error from searching, if one occurred
searchErr error
// Whether to force a full refresh of the table
forceUpdateTable bool
// Whether to maintain the cursor position
maintainCursor bool
// An updated search query. May be used for initial queries when they're invalid.
overriddenSearchQuery *string
}
func initialModel(ctx context.Context, initialQuery string) model {
s := spinner.New()
s.Spinner = spinner.Dot
s.Style = lipgloss.NewStyle().Foreground(lipgloss.Color("205"))
queryInput := textinput.New()
queryInput.Placeholder = "ls"
queryInput.Focus()
queryInput.CharLimit = 200
width, _, err := getTerminalSize()
if err == nil {
queryInput.Width = width
} else {
hctx.GetLogger().Infof("getTerminalSize() return err=%#v, defaulting queryInput to a width of 50", err)
queryInput.Width = 50
}
if initialQuery != "" {
queryInput.SetValue(initialQuery)
}
CURRENT_QUERY_FOR_HIGHLIGHTING = initialQuery
return model{ctx: ctx, spinner: s, isLoading: true, table: nil, tableEntries: []*data.HistoryEntry{}, runQuery: &initialQuery, queryInput: queryInput, help: help.New()}
}
func (m model) Init() tea.Cmd {
return m.spinner.Tick
}
func updateTable(m model, rows []table.Row, entries []*data.HistoryEntry, searchErr error, forceUpdateTable, maintainCursor bool) model {
if m.runQuery == nil {
m.runQuery = &m.lastQuery
}
m.searchErr = searchErr
if searchErr != nil {
return m
}
m.tableEntries = entries
initialCursor := 0
if m.table != nil {
initialCursor = m.table.Cursor()
}
if forceUpdateTable || m.table == nil {
t, err := makeTable(m.ctx, rows)
if err != nil {
m.fatalErr = err
return m
}
m.table = &t
}
m.table.SetRows(rows)
if maintainCursor {
m.table.SetCursor(initialCursor)
} else {
m.table.SetCursor(0)
}
m.lastQuery = *m.runQuery
m.runQuery = nil
if m.table.Cursor() >= len(m.tableEntries) {
// Ensure that we can't scroll past the end of the table
m.table.SetCursor(len(m.tableEntries) - 1)
}
return m
}
func preventTableOverscrolling(m model) {
if m.table != nil {
if m.table.Cursor() >= len(m.tableEntries) {
// Ensure that we can't scroll past the end of the table
m.table.SetCursor(len(m.tableEntries) - 1)
}
}
}
func runQueryAndUpdateTable(m model, forceUpdateTable, maintainCursor bool) tea.Cmd {
if (m.runQuery != nil && *m.runQuery != m.lastQuery) || forceUpdateTable || m.searchErr != nil {
query := m.lastQuery
if m.runQuery != nil {
query = *m.runQuery
}
queryId := LAST_DISPATCHED_QUERY_ID
LAST_DISPATCHED_QUERY_ID += 1
return func() tea.Msg {
rows, entries, searchErr := getRows(m.ctx, hctx.GetConf(m.ctx).DisplayedColumns, query, PADDED_NUM_ENTRIES)
return asyncQueryFinishedMsg{queryId, rows, entries, searchErr, forceUpdateTable, maintainCursor, nil}
}
}
return nil
}
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
switch msg := msg.(type) {
case tea.KeyMsg:
switch {
case key.Matches(msg, keys.Quit):
m.quitting = true
return m, tea.Quit
case key.Matches(msg, keys.SelectEntry):
if len(m.tableEntries) != 0 && m.table != nil {
m.selected = Selected
}
return m, tea.Quit
case key.Matches(msg, keys.SelectEntryAndChangeDir):
if len(m.tableEntries) != 0 && m.table != nil {
m.selected = SelectedWithChangeDir
}
return m, tea.Quit
case key.Matches(msg, keys.DeleteEntry):
if m.table == nil {
return m, nil
}
err := deleteHistoryEntry(m.ctx, *m.tableEntries[m.table.Cursor()])
if err != nil {
m.fatalErr = err
return m, nil
}
cmd := runQueryAndUpdateTable(m, true, true)
preventTableOverscrolling(m)
return m, cmd
case key.Matches(msg, keys.Help):
m.help.ShowAll = !m.help.ShowAll
return m, nil
default:
pendingCommands := tea.Batch()
if m.table != nil {
t, cmd1 := m.table.Update(msg)
m.table = &t
if strings.HasPrefix(msg.String(), "alt+") {
return m, tea.Batch(cmd1)
}
pendingCommands = tea.Batch(pendingCommands, cmd1)
}
i, cmd2 := m.queryInput.Update(msg)
m.queryInput = i
searchQuery := m.queryInput.Value()
m.runQuery = &searchQuery
CURRENT_QUERY_FOR_HIGHLIGHTING = searchQuery
cmd3 := runQueryAndUpdateTable(m, false, false)
preventTableOverscrolling(m)
return m, tea.Batch(pendingCommands, cmd2, cmd3)
}
case tea.WindowSizeMsg:
m.help.Width = msg.Width
m.queryInput.Width = msg.Width
cmd := runQueryAndUpdateTable(m, true, true)
return m, cmd
case offlineMsg:
m.isOffline = true
return m, nil
case bannerMsg:
m.banner = msg.banner
return m, nil
case doneDownloadingMsg:
m.isLoading = false
return m, nil
case asyncQueryFinishedMsg:
if msg.queryId > LAST_PROCESSED_QUERY_ID {
LAST_PROCESSED_QUERY_ID = msg.queryId
m = updateTable(m, msg.rows, msg.entries, msg.searchErr, msg.forceUpdateTable, msg.maintainCursor)
if msg.overriddenSearchQuery != nil {
m.queryInput.SetValue(*msg.overriddenSearchQuery)
}
}
return m, nil
default:
var cmd tea.Cmd
if m.isLoading {
m.spinner, cmd = m.spinner.Update(msg)
return m, cmd
} else {
if m.table != nil {
t, cmd := m.table.Update(msg)
m.table = &t
return m, cmd
}
return m, nil
}
}
}
func (m model) View() string {
if m.fatalErr != nil {
return fmt.Sprintf("An unrecoverable error occured: %v\n", m.fatalErr)
}
if m.selected == Selected || m.selected == SelectedWithChangeDir {
SELECTED_COMMAND = m.tableEntries[m.table.Cursor()].Command
if m.selected == SelectedWithChangeDir {
changeDir := m.tableEntries[m.table.Cursor()].CurrentWorkingDirectory
SELECTED_COMMAND = "cd \"" + changeDir + "\" && " + SELECTED_COMMAND
}
return ""
}
if m.quitting {
return ""
}
loadingMessage := ""
if m.isLoading {
loadingMessage = fmt.Sprintf("%s Loading hishtory entries from other devices...", m.spinner.View())
}
warning := ""
if loadingMessage != "" {
warning += "\n"
}
if m.isOffline {
warning += "Warning: failed to contact the hishtory backend (are you offline?), so some results may be stale"
}
if m.searchErr != nil {
if strings.TrimSpace(warning) != "" {
warning += "\n"
}
warning += fmt.Sprintf("Warning: failed to search: %v", m.searchErr)
}
warning += "\n"
helpView := m.help.View(keys)
return fmt.Sprintf("\n%s%s%s\nSearch Query: %s\n\n%s\n", loadingMessage, warning, m.banner, m.queryInput.View(), renderNullableTable(m)) + helpView
}
func renderNullableTable(m model) string {
if m.table == nil {
return strings.Repeat("\n", TABLE_HEIGHT+3)
}
return baseStyle.Render(m.table.View())
}
func getRows(ctx context.Context, columnNames []string, query string, numEntries int) ([]table.Row, []*data.HistoryEntry, error) {
db := hctx.GetDb(ctx)
config := hctx.GetConf(ctx)
searchResults, err := lib.Search(ctx, db, query, numEntries)
if err != nil {
return nil, nil, err
}
var rows []table.Row
var filteredData []*data.HistoryEntry
lastCommand := ""
for i := 0; i < numEntries; i++ {
if i < len(searchResults) {
entry := searchResults[i]
if strings.TrimSpace(entry.Command) == strings.TrimSpace(lastCommand) && config.FilterDuplicateCommands {
continue
}
entry.Command = strings.ReplaceAll(entry.Command, "\n", "\\n")
row, err := lib.BuildTableRow(ctx, columnNames, *entry)
if err != nil {
return nil, nil, fmt.Errorf("failed to build row for entry=%#v: %w", entry, err)
}
rows = append(rows, row)
filteredData = append(filteredData, entry)
lastCommand = entry.Command
} else {
rows = append(rows, table.Row{})
}
}
return rows, filteredData, nil
}
func calculateColumnWidths(rows []table.Row, numColumns int) []int {
neededColumnWidth := make([]int, numColumns)
for _, row := range rows {
for i, v := range row {
neededColumnWidth[i] = max(neededColumnWidth[i], len(v))
}
}
return neededColumnWidth
}
func getTerminalSize() (int, int, error) {
return term.GetSize(2)
}
var bigQueryResults []table.Row
func makeTableColumns(ctx context.Context, columnNames []string, rows []table.Row) ([]table.Column, error) {
// Handle an initial query with no results
if len(rows) == 0 || len(rows[0]) == 0 {
allRows, _, err := getRows(ctx, columnNames, "", 25)
if err != nil {
return nil, err
}
if len(allRows) == 0 || len(allRows[0]) == 0 {
// There are truly zero history entries. Let's still display a table in this case rather than erroring out.
allRows = make([]table.Row, 0)
row := make([]string, 0)
for range columnNames {
row = append(row, " ")
}
allRows = append(allRows, row)
}
return makeTableColumns(ctx, columnNames, allRows)
}
// Calculate the minimum amount of space that we need for each column for the current actual search
columnWidths := calculateColumnWidths(rows, len(columnNames))
totalWidth := 20
for i, name := range columnNames {
columnWidths[i] = max(columnWidths[i], len(name))
totalWidth += columnWidths[i]
}
// Calculate the maximum column width that is useful for each column if we search for the empty string
if bigQueryResults == nil {
bigRows, _, err := getRows(ctx, columnNames, "", 1000)
if err != nil {
return nil, err
}
bigQueryResults = bigRows
}
maximumColumnWidths := calculateColumnWidths(bigQueryResults, len(columnNames))
// Get the actual terminal width. If we're below this, opportunistically add some padding aiming for the maximum column widths
terminalWidth, _, err := getTerminalSize()
if err != nil {
return nil, fmt.Errorf("failed to get terminal size: %w", err)
}
for totalWidth < (terminalWidth - len(columnNames)) {
prevTotalWidth := totalWidth
for i := range columnNames {
if columnWidths[i] < maximumColumnWidths[i]+5 {
columnWidths[i] += 1
totalWidth += 1
}
}
if totalWidth == prevTotalWidth {
break
}
}
// And if we are too large from the initial query, let's shrink things to make the table fit. We'll use the heuristic of always shrinking the widest column.
for totalWidth > terminalWidth {
largestColumnIdx := -1
largestColumnSize := -1
for i := range columnNames {
if columnWidths[i] > largestColumnSize {
largestColumnIdx = i
largestColumnSize = columnWidths[i]
}
}
columnWidths[largestColumnIdx] -= 2
totalWidth -= 2
}
// And finally, create some actual columns!
columns := make([]table.Column, 0)
for i, name := range columnNames {
columns = append(columns, table.Column{Title: name, Width: columnWidths[i]})
}
return columns, nil
}
func max(a, b int) int {
if a > b {
return a
}
return b
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
func makeTable(ctx context.Context, rows []table.Row) (table.Model, error) {
config := hctx.GetConf(ctx)
columns, err := makeTableColumns(ctx, config.DisplayedColumns, rows)
if err != nil {
return table.Model{}, err
}
km := table.KeyMap{
LineUp: keys.Up,
LineDown: keys.Down,
PageUp: keys.PageUp,
PageDown: keys.PageDown,
GotoTop: key.NewBinding(
key.WithKeys("home"),
key.WithHelp("home", "go to start"),
),
GotoBottom: key.NewBinding(
key.WithKeys("end"),
key.WithHelp("end", "go to end"),
),
MoveLeft: keys.TableLeft,
MoveRight: keys.TableRight,
}
_, terminalHeight, err := getTerminalSize()
if err != nil {
return table.Model{}, err
}
tableHeight := min(TABLE_HEIGHT, terminalHeight-12)
t := table.New(
table.WithColumns(columns),
table.WithRows(rows),
table.WithFocused(true),
table.WithHeight(tableHeight),
table.WithKeyMap(km),
)
s := table.DefaultStyles()
s.Header = s.Header.
BorderStyle(lipgloss.NormalBorder()).
BorderForeground(lipgloss.Color("240")).
BorderBottom(true).
Bold(false)
s.Selected = s.Selected.
Foreground(lipgloss.Color("229")).
Background(lipgloss.Color("57")).
Bold(false)
if config.HighlightMatches {
MATCH_NOTHING_REGEXP := regexp.MustCompile("a^")
s.RenderCell = func(model table.Model, value string, position table.CellPosition) string {
var re *regexp.Regexp
CURRENT_QUERY_FOR_HIGHLIGHTING = strings.TrimSpace(CURRENT_QUERY_FOR_HIGHLIGHTING)
if CURRENT_QUERY_FOR_HIGHLIGHTING == "" {
// If there is no search query, then there is nothing to highlight
re = MATCH_NOTHING_REGEXP
} else {
queryRegex := lib.MakeRegexFromQuery(CURRENT_QUERY_FOR_HIGHLIGHTING)
r, err := regexp.Compile(queryRegex)
if err != nil {
// Failed to compile the regex for highlighting matches, this should never happen. In this
// case, just use a regexp that matches nothing to ensure that the TUI doesn't crash.
re = MATCH_NOTHING_REGEXP
} else {
re = r
}
}
// func to render a given chunk of `value`. `isMatching` is whether `v` matches the search query (and
// thus needs to be highlighted). `isLeftMost` and `isRightMost` determines whether additional
// padding is added (to reproduce the padding that `s.Cell` normally adds).
renderChunk := func(v string, isMatching, isLeftMost, isRightMost bool) string {
chunkStyle := lipgloss.NewStyle()
if position.IsRowSelected {
// Apply the selected style as the base style if this is the highlighted row of the table
chunkStyle = s.Selected.Copy()
}
if isLeftMost {
chunkStyle = chunkStyle.PaddingLeft(1)
}
if isRightMost {
chunkStyle = chunkStyle.PaddingRight(1)
}
if isMatching {
chunkStyle = chunkStyle.Bold(true)
}
return chunkStyle.Render(v)
}
matches := re.FindAllStringIndex(value, -1)
if len(matches) == 0 {
// No matches, so render the entire value
return renderChunk(value /*isMatching = */, false /*isLeftMost = */, true /*isRightMost = */, true)
}
// Iterate through the chunks of the value and highlight the relevant pieces
ret := ""
lastIncludedIdx := 0
for _, match := range re.FindAllStringIndex(value, -1) {
matchStartIdx := match[0]
matchEndIdx := match[1]
beforeMatch := value[lastIncludedIdx:matchStartIdx]
if beforeMatch != "" {
ret += renderChunk(beforeMatch, false, lastIncludedIdx == 0, false)
}
match := value[matchStartIdx:matchEndIdx]
ret += renderChunk(match, true, matchStartIdx == 0, matchEndIdx == len(value))
lastIncludedIdx = matchEndIdx
}
if lastIncludedIdx != len(value) {
ret += renderChunk(value[lastIncludedIdx:], false, false, true)
}
return ret
}
}
t.SetStyles(s)
t.Focus()
return t, nil
}
func deleteHistoryEntry(ctx context.Context, entry data.HistoryEntry) error {
db := hctx.GetDb(ctx)
// Delete locally
r := db.Model(&data.HistoryEntry{}).Where("device_id = ? AND end_time = ?", entry.DeviceId, entry.EndTime).Delete(&data.HistoryEntry{})
if r.Error != nil {
return r.Error
}
// Delete remotely
config := hctx.GetConf(ctx)
if config.IsOffline {
return nil
}
dr := shared.DeletionRequest{
UserId: data.UserId(hctx.GetConf(ctx).UserSecret),
SendTime: time.Now(),
}
dr.Messages.Ids = append(dr.Messages.Ids,
shared.MessageIdentifier{DeviceId: entry.DeviceId, EndTime: entry.EndTime, EntryId: entry.EntryId},
)
return lib.SendDeletionRequest(ctx, dr)
}
func TuiQuery(ctx context.Context, initialQuery string) error {
lipgloss.SetColorProfile(termenv.ANSI)
p := tea.NewProgram(initialModel(ctx, initialQuery), tea.WithOutput(os.Stderr))
// Async: Get the initial set of rows
go func() {
queryId := LAST_DISPATCHED_QUERY_ID
LAST_DISPATCHED_QUERY_ID++
rows, entries, err := getRows(ctx, hctx.GetConf(ctx).DisplayedColumns, initialQuery, PADDED_NUM_ENTRIES)
if err == nil || initialQuery == "" {
p.Send(asyncQueryFinishedMsg{queryId: queryId, rows: rows, entries: entries, searchErr: err, forceUpdateTable: true, maintainCursor: false, overriddenSearchQuery: nil})
} else {
// initialQuery is likely invalid in some way, let's just drop it
emptyQuery := ""
rows, entries, err := getRows(ctx, hctx.GetConf(ctx).DisplayedColumns, emptyQuery, PADDED_NUM_ENTRIES)
p.Send(asyncQueryFinishedMsg{queryId: queryId, rows: rows, entries: entries, searchErr: err, forceUpdateTable: true, maintainCursor: false, overriddenSearchQuery: &emptyQuery})
}
}()
// Async: Retrieve additional entries from the backend
go func() {
err := lib.RetrieveAdditionalEntriesFromRemote(ctx, "tui")
if err != nil {
p.Send(err)
}
p.Send(doneDownloadingMsg{})
}()
// Async: Process deletion requests
go func() {
err := lib.ProcessDeletionRequests(ctx)
if err != nil {
p.Send(err)
}
}()
// Async: Check for any banner from the server
go func() {
banner, err := lib.GetBanner(ctx)
if err != nil {
if lib.IsOfflineError(ctx, err) {
p.Send(offlineMsg{})
} else {
p.Send(err)
}
}
p.Send(bannerMsg{banner: string(banner)})
}()
// Blocking: Start the TUI
_, err := p.Run()
if err != nil {
return err
}
if SELECTED_COMMAND == "" && os.Getenv("HISHTORY_TERM_INTEGRATION") != "" {
// Print out the initialQuery instead so that we don't clear the terminal
SELECTED_COMMAND = initialQuery
}
fmt.Printf("%s\n", strings.ReplaceAll(SELECTED_COMMAND, "\\n", "\n"))
return nil
}
// TODO: support custom key bindings
// TODO: make the help page wrap