use "collections"
use "files"
use "promises"
use strings = "strings"
class Readline is ANSINotify
"""
Line editing, history, and tab completion.
"""
let _notify: ReadlineNotify
let _out: OutStream
let _path: (FilePath | None)
embed _history: Array[String]
embed _queue: Array[String] = Array[String]
let _maxlen: USize
var _edit: String iso = recover String end
var _cur_prompt: String = ""
var _cur_line: USize = 0
var _cur_pos: ISize = 0
var _blocked: Bool = true
new iso create(
notify: ReadlineNotify iso,
out: OutStream,
path: (FilePath | None) = None,
maxlen: USize = 0)
=>
"""
Create a readline handler to be passed to stdin. It begins blocked. Set an
initial prompt on the ANSITerm to begin processing.
"""
_notify = consume notify
_out = out
_path = path
_history = Array[String](maxlen)
_maxlen = maxlen
_load_history()
fun ref apply(term: ANSITerm ref, input: U8) =>
"""
Receives input.
"""
match \exhaustive\ input
| 0x01 => home() // ctrl-a
| 0x02 => left() // ctrl-b
| 0x04 =>
// ctrl-d
if _edit.size() == 0 then
_out.write("\n")
term.dispose()
else
delete()
end
| 0x05 => end_key() // ctrl-e
| 0x06 => right() // ctrl-f
| 0x08 => _backspace() // ctrl-h
| 0x09 => _tab()
| 0x0A => _dispatch(term) // LF
| 0x0B =>
// ctrl-k, delete to the end of the line.
_edit.truncate(_cur_pos.usize())
_refresh_line()
| 0x0C => _clear() // ctrl-l
| 0x0D => _dispatch(term) // CR
| 0x0E => down() // ctrl-n
| 0x10 => up() // ctrl-p
| 0x14 => _swap() // ctrl-t
| 0x15 =>
// ctrl-u, delete the whole line.
_edit.clear()
home()
| 0x17 => _delete_prev_word() // ctrl-w
| 0x7F => _backspace() // backspace
| if input < 0x20 => None // unknown control character
else
// Insert.
_edit.insert_byte(_cur_pos, input)
_cur_pos = _cur_pos + 1
_refresh_line()
end
fun ref prompt(term: ANSITerm ref, value: String) =>
"""
Set a new prompt, unblock, and handle the pending queue.
"""
_cur_prompt = value
_blocked = false
try
let line = _queue.shift()?
_add_history(line)
_out.print(_cur_prompt + line)
_handle_line(term, line)
else
_refresh_line()
end
fun ref closed() =>
"""
No more input is available.
"""
_save_history()
fun ref up(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Previous line.
"""
try
if _cur_line > 0 then
_cur_line = _cur_line - 1
_edit = _history(_cur_line)?.clone()
end_key()
end
end
fun ref down(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Next line.
"""
// With no history there is no next line, and _history.size() - 1 would
// underflow. Do nothing, as up does when there is no previous line.
if _history.size() == 0 then
return
end
try
if _cur_line < (_history.size() - 1) then
_cur_line = _cur_line + 1
_edit = _history(_cur_line)?.clone()
else
_cur_line = _history.size()
_edit.clear()
end
end_key()
end
fun ref left(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Move left.
"""
if _cur_pos == 0 then
return
end
try
repeat
_cur_pos = _cur_pos - 1
until
(_cur_pos == 0) or
((_edit.at_offset(_cur_pos)? and 0xC0) != 0x80)
end
_refresh_line()
end
fun ref right(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Move right.
"""
try
if _cur_pos < _edit.size().isize() then
_cur_pos = _cur_pos + 1
end
while
(_cur_pos < _edit.size().isize()) and
((_edit.at_offset(_cur_pos)? and 0xC0) == 0x80)
do
_cur_pos = _cur_pos + 1
end
_refresh_line()
end
fun ref home(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Beginning of the line.
"""
_cur_pos = 0
_refresh_line()
fun ref end_key(
ctrl: Bool = false,
alt: Bool = false,
shift: Bool = false)
=>
"""
End of the line.
"""
_cur_pos = _edit.size().isize()
_refresh_line()
fun ref _backspace() =>
"""
Backward delete.
"""
if _cur_pos == 0 then
return
end
try
var c = U8(0)
repeat
_cur_pos = _cur_pos - 1
c = _edit.at_offset(_cur_pos)?
_edit.delete(_cur_pos, 1)
until
(_cur_pos == 0) or ((c and 0xC0) != 0x80)
end
_refresh_line()
end
fun ref delete(ctrl: Bool = false, alt: Bool = false, shift: Bool = false) =>
"""
Forward delete.
"""
try
if _cur_pos < _edit.size().isize() then
_edit.delete(_cur_pos, 1)
end
while
(_cur_pos < _edit.size().isize()) and
((_edit.at_offset(_cur_pos)? and 0xC0) == 0x80)
do
_edit.delete(_cur_pos, 1)
end
_refresh_line()
end
fun ref _clear() =>
"""
Clear the screen.
"""
_out.write(ANSI.clear())
_refresh_line()
fun ref _swap() =>
"""
Swap the previous character with the current one.
"""
try
if (_cur_pos > 0) and (_cur_pos < _edit.size().isize()) then
_edit(_cur_pos.usize())? =
_edit((_cur_pos - 1).usize())? =
_edit(_cur_pos.usize())?
end
_refresh_line()
end
fun ref _delete_prev_word() =>
"""
Delete the previous word.
"""
try
let old = _cur_pos
while (_cur_pos > 0) and (_edit((_cur_pos - 1).usize())? == ' ') do
_cur_pos = _cur_pos - 1
end
while (_cur_pos > 0) and (_edit((_cur_pos - 1).usize())? != ' ') do
_cur_pos = _cur_pos - 1
end
_edit.delete(_cur_pos, (old - _cur_pos).usize())
_refresh_line()
end
fun ref _tab() =>
"""
Tab completion.
TODO: Improve this.
"""
let r = _notify.tab(_edit.clone())
match r.size()
| 0 => None
| 1 =>
try
_edit = r(0)?.clone()
end_key()
end
else
_out.write("\n")
for completion in r.values() do
_out.print(completion)
end
_edit = strings.CommonPrefix(r)
end_key()
end
fun ref _dispatch(term: ANSITerm) =>
"""
Send a finished line to the notifier.
"""
if _edit.size() > 0 then
let line: String = _edit = recover String end
if _blocked then
_queue.push(line)
else
_add_history(line)
_out.write("\n")
_handle_line(term, line)
end
end
fun ref _handle_line(term: ANSITerm, line: String) =>
"""
Dispatch a single line.
"""
let promise = Promise[String]
promise.next[Any tag](
recover term~prompt() end,
recover term~dispose() end)
_notify(line, promise)
_cur_pos = 0
_blocked = true
fun ref _refresh_line() =>
"""
Refresh the line on screen.
"""
if not _blocked then
let len = 40 + _cur_prompt.size() + _edit.size()
let out = recover String(len) end
// Move to the left edge.
out.append("\r")
// Print the prompt.
out.append(_cur_prompt)
// Print the current line.
out.append(_edit.clone())
// Erase to the right edge.
out.append(ANSI.erase())
// Set the cursor position.
var pos = _cur_prompt.codepoints()
if _cur_pos > 0 then
pos = pos + _edit.codepoints(0, _cur_pos)
end
out.append("\r")
// Only move right when the cursor is off the left edge. ANSI.right(0)
// emits a one-column move, so appending it here would nudge the cursor
// right on an empty line with an empty prompt.
if pos > 0 then
out.append(ANSI.right(pos.u32()))
end
_out.write(consume out)
end
fun ref _add_history(line: String) =>
"""
Add a line to the history, trimming an earlier line if necessary.
"""
try
if (_history.size() > 0) and (_history(_history.size() - 1)? == line) then
_cur_line = _history.size()
return
end
end
if (_maxlen > 0) and (_history.size() >= _maxlen) then
try
_history.shift()?
end
end
_history.push(line)
_cur_line = _history.size()
fun ref _load_history() =>
"""
Load the history from a file.
"""
_history.clear()
try
with file = File.open(_path as FilePath) do
for line in file.lines() do
_add_history(consume line)
end
end
end
fun _save_history() =>
"""
Write the history back to a file.
"""
try
with file = File(_path as FilePath) do
for line in _history.values() do
file.print(line)
end
end
end