#!/usr/bin/env python3
import contextlib
import fcntl
import json
import os
import shutil
import signal
from pathlib import Path
import subprocess
import struct
import sys
import tempfile
import termios
import threading
import time

from ninep import Client


@contextlib.contextmanager
def session(binary, root, name, *options, socket_name=None, file=None, tty=False, network=None,
            launch=None, inherited=None, terminal=None):
    env = {key: value for key, value in os.environ.items()
           if not key.startswith('PARDES_')}
    env.update(HOME=str(root), XDG_RUNTIME_DIR=str(root),
               XDG_CONFIG_HOME=str(root / 'config'), PARDES_NOTIME='1',
               PARDES_DUMP=str(root / (name + '.dump.zon')))
    env.update(inherited or {})
    for language in ['RS', 'C', 'GO', 'TS', 'PY']:
        env['PARDES_LSP_' + language] = ''
    fixture = root / (name + '.txt')
    fixture.write_bytes(b'initial\n')
    address = root / ('pardes-9p-' + (socket_name or name) + '.sock')
    child = None
    master = slave = None
    reader = None
    try:
        args = [binary, '--detach=' + name, *options, str(file or fixture)]
        preexec = None
        if tty:
            master, slave = os.openpty()
            fcntl.ioctl(slave, termios.TIOCSWINSZ, struct.pack('HHHH', 24, 80, 0, 0))
            env['TERM'] = 'xterm-256color'
            args = [binary, '--tty', '--9p=' + (socket_name or name), *options, str(file or fixture)]
            preexec = lambda: fcntl.ioctl(0, termios.TIOCSCTTY, 0)
        if launch is not None:
            args = [binary, *launch]
        child = subprocess.Popen(args, cwd=root, env=env, stdin=slave,
                                 stdout=slave if tty else subprocess.DEVNULL,
                                 stderr=subprocess.PIPE, start_new_session=True,
                                 preexec_fn=preexec)
        if terminal is not None:
            # Borrowed handles for input-driving probes, valid inside this context.
            terminal.update(pid=child.pid, input_fd=master)
        if launch is not None and socket_name is None:
            address = root / f'pardes-9p-{child.pid}.sock'
        if slave is not None:
            os.close(slave)
            slave = None
            def drain():
                try:
                    while os.read(master, 65536):
                        pass
                except OSError:
                    pass
            reader = threading.Thread(target=drain, daemon=True)
            reader.start()
        deadline = time.monotonic() + 10
        while not address.exists():
            if child.poll() is not None:
                raise AssertionError((args, child.returncode, child.stderr.read().decode()))
            if time.monotonic() > deadline:
                raise TimeoutError('default 9P socket did not appear')
            time.sleep(.005)
        with Client(address) as client:
            if network is not None:
                for dial in client.read('/listeners').decode().splitlines():
                    parts = dial.split('!')
                    if parts[0] in ['tcp', 'quic']:
                        assert len(parts) == 3 and 0 < int(parts[2]) < 65536, dial
                        network[parts[0].upper()] = int(parts[2])
                assert set(network) == {'TCP', 'QUIC'}, network
            yield client, address
    finally:
        if terminal is not None:
            terminal.clear()
        if child is not None:
            if child.poll() is None:
                child.terminate()
            try:
                child.wait(timeout=5)
            except subprocess.TimeoutExpired:
                child.kill()
                child.wait()
            child.stderr.close()
        if slave is not None:
            os.close(slave)
        if master is not None:
            os.close(master)
        if reader is not None:
            reader.join(timeout=1)
            assert not reader.is_alive(), 'terminal reader did not stop'


def newest(client):
    """The newest pane's serial: /index is ordered by serial."""
    return int(client.read('/index').splitlines()[-1].split()[0])


def new_pane(client, contents):
    """An open of /pane/new makes a pane; the read names it."""
    serial = int(client.read('/pane/new'))
    if contents:
        client.write(f'/pane/{serial}/body', contents)
    return serial


def look(client, path, source=None):
    """A right click on `path` from a pane (a fresh scratch by default)."""
    serial = source if source is not None else new_pane(client, b'')
    client.write(f'/pane/{serial}/look', f'{path}\n'.encode())
    results = [int(row) for row in client.read('/look').split()]
    assert len(results) == 1 and results[0] != serial, (path, results)
    # The scratch it looked from goes: a column holds only so many panes,
    # each its tag and two rows.
    if source is None:
        client.remove(f'/pane/{serial}')
    return results[0]


def execute(client, serial, command):
    """A middle click on `command` from a pane."""
    client.write(f'/pane/{serial}/exec', f'{command}\n'.encode())


def walk_tree(client, path='/', skip=('/log', '/os', '/screen')):
    """Stat every entry below `path`, as `find` does, without opening anything."""
    seen = []
    for name in client.list(path):
        child = (path.rstrip('/') + '/' + name)
        info = client.stat(child)
        seen.append((child, info))
        if info['dir'] and child not in skip:
            seen.extend(walk_tree(client, child, skip))
    return seen


def discovery(binary, embedded=False):
    with tempfile.TemporaryDirectory(prefix='pardes-discovery-') as directory:
        root = Path(directory)
        with session(binary, root, 'discovery') as (client, address):
            top = client.list('/')
            # A set: which files the root holds, not the order a listing gives.
            assert set(top) - {'src', 'shaders'} == {'README', 'index', 'status', 'focus', 'ctl', 'commands',
                                                     'look', 'exec', 'log', 'screen', 'listeners', 'layout', 'tag', 'tagexec',
                                                     'pane', 'col', 'os'}, top
            assert 'self' not in top and 'cons' not in top and 'new' not in top, top
            assert ('src' in top) == embedded, (top, embedded)
            before = client.read('/index')
            guide = client.read('/README')
            assert guide.count(b'\n') <= 45 and b'Msg hello' in guide and b'pane/new' in guide, guide
            assert client.stat('/README')['length'] == len(guide)
            # ls/stat/find over the whole tree, without opening, creates nothing.
            seen = walk_tree(client)
            names = {path for path, _ in seen}
            assert {'/index', '/status', '/look', '/exec', '/log', '/pane/1', '/pane/1/body',
                    '/pane/1/name', '/pane/1/sel', '/pane/1/ctl', '/pane/1/tag', '/pane/1/event',
                    '/pane/1/dot', '/pane/1/limit', '/pane/1/dirty', '/pane/1/mark',
                    '/pane/1/scroll', '/pane/1/look', '/pane/1/exec'} <= names, sorted(names)
            assert '/pane/1/pty' not in names, 'the fixture file pane grew a pty/'
            assert not any(name.startswith('/self') or name.endswith('/rdsel') or name.endswith('/wrsel')
                           for name in names), sorted(names)
            for path, info in seen:
                assert info['mode'] in (0o755, 0o644, 0o666, 0o444, 0o222, 0o555), (path, info)
                assert info['mtime'] > 0, (path, info)
            assert client.read('/index') == before, 'browsing created a pane'
            assert client.stat('/index')['length'] == len(before) > 0
            index = client.stat('/index')
            assert index['mode'] == 0o444 and client.stat('/status')['mode'] == 0o444
            assert client.stat('/exec')['mode'] == 0o666
            assert client.stat('/pane/1/body')['mode'] == 0o666 and client.stat('/pane')['mode'] == 0o755
            # A range file reads the pair it takes; a flag file reads 0 or 1.
            assert client.stat('/pane/1/addr')['length'] == 24
            assert client.stat('/pane/1/limit')['length'] == 0
            assert client.read('/pane/1/dirty') == b'0\n'
            assert client.read('/pane/1/scroll') == b'1\n'
            fixture = int(before.split()[0])
            assert before.split()[1:3] == [b'text', b'0'] and before.rsplit(b' ', 1)[0].endswith(b'/discovery.txt'), before
            # /status reports the editor; /exec has nothing to report yet.
            status = dict(line.split(maxsplit=1) for line in client.read('/status').decode().splitlines())
            assert int(status['pid']) > 0 and status['version'] and int(status['panes']) >= 1, status
            assert client.read('/exec') == b''
            # An open of /pane/new makes a pane and the read names it; each
            # open makes another. A stat makes none, which is why new can be
            # listed at all: ls -l stats every name a listing gave it.
            # /log answers the recent past and ends; `follow` written to the
            # same open makes its reads past that wait for new records.
            log = client.open('/log', 2)
            frozen = len(client.read_fid(log))
            client.rpc(118, struct.pack('<IQI', log, 0, 7) + b'follow\n')
            first = int(client.read('/pane/new'))
            assert first == newest(client)
            second = int(client.read('/pane/new'))
            assert first != second and first != fixture, (first, second)
            assert 'new' in client.list('/pane'), 'new should be visible to ls'
            client.stat('/pane/new')
            assert newest(client) == second, 'a stat of new made a pane'
            # What the editor said is in the stream too.
            def pane_event():
                while (record := client.read_fid(log, frozen)).startswith((b'msg ', b'err ')):
                    pass
                return record
            assert pane_event() == f'new {first} {root}/+New\n'.encode()
            assert pane_event() == f'new {second} {root}/+New\n'.encode()
            # A follower that is waiting wakes when the editor logs, not when
            # some unrelated request next happens to wait.
            with Client(address) as follower:
                waiting = follower.open('/log', 2)
                start = len(follower.read_fid(waiting))
                follower.rpc(118, struct.pack('<IQI', waiting, 0, 7) + b'follow\n')
                woke = []
                reader = threading.Thread(target=lambda: woke.append(follower.read_fid(waiting, start)), daemon=True)
                reader.start()
                time.sleep(.2)
                client.write('/exec', b'Msg woken\n')
                reader.join(5)
                assert woke and woke[0].endswith(b' woken\n'), woke
            # A pane's ctl takes acme's lock: a second open's lock fails at
            # once with "file in use" until the holder unlocks, and nothing
            # else waits on it meanwhile.
            with Client(address) as other:
                mine = client.open(f'/pane/{first}/ctl', 2)
                client.rpc(118, struct.pack('<IQI', mine, 0, 5) + b'lock\n')
                theirs = other.open(f'/pane/{first}/ctl', 1)
                try:
                    other.rpc(118, struct.pack('<IQI', theirs, 0, 5) + b'lock\n')
                    raise AssertionError('a second lock was taken')
                except OSError as refused:
                    assert 'file in use' in str(refused), refused
                client.write(f'/pane/{first}/addr', b'#0')
                client.rpc(118, struct.pack('<IQI', mine, 0, 7) + b'unlock\n')
                other.rpc(118, struct.pack('<IQI', theirs, 0, 5) + b'lock\n')
                client.close(mine)
                other.close(theirs)
            # /focus names the pane with the keyboard and moves it, as rio's
            # wctl `current` does; a pane's ctl line ends saying which it is.
            client.write('/focus', f'{first}\n'.encode())
            assert client.read('/focus') == f'{first}\n'.encode()
            assert client.read(f'/pane/{first}/ctl').endswith(b' current ')
            assert client.read(f'/pane/{second}/ctl').endswith(b' notcurrent ')
            try:
                client.write('/focus', b'99999\n')
                raise AssertionError('focus took a serial no pane has')
            except OSError as refused:
                assert 'no such pane' in str(refused), refused
            # /ctl reads the settings as a write takes them and takes the
            # session's builtins; a pane's ctl takes the pane's.
            settings = client.read('/ctl')
            assert b'Verbose ' in settings and b'Platform' not in settings, settings
            client.write('/ctl', settings)
            assert client.read('/ctl') == settings
            client.write('/ctl', b'Verbose off\n')
            assert b'Verbose off\n' in client.read('/ctl')
            for path, line, why in (('/ctl', b'Del\n', 'not a session control message "Del"'),
                                    ('/ctl', b'Nope 3\n', 'unknown control message "Nope 3"'),
                                    (f'/pane/{first}/ctl', b'Newcol\n', 'not a window control message "Newcol"')):
                try:
                    client.write(path, line)
                    raise AssertionError(f'{path} took {line!r}')
                except OSError as refused:
                    assert why in str(refused), refused
            commands = client.read('/commands').decode().splitlines()
            assert 'Newcol root' in commands and 'Save arg pane' in commands, commands
            # word, `arg` if it takes one, its ctl, then a setting's values
            assert all(row.split()[2 if row.split()[1] == 'arg' else 1] in ('root', 'pane') for row in commands), commands
            assert 'Placement arg root acme,pardes' in commands, commands
            assert client.stat('/commands')['length'] == len('\n'.join(commands)) + 1
            client.write(f'/pane/{first}/ctl', b'Msg said through ctl\n')
            assert 'said through ctl' in ''.join(cell[0] for cell in client.screen()['cells'])
            assert set(client.list('/pane')) == {'new', str(fixture), str(first), str(second)}
            client.write(f'/pane/{first}/body', b'first pane', truncate=True)
            assert client.read(f'/pane/{first}/body') == b'first pane'
            assert client.read(f'/pane/{second}/body') == b''
            assert client.stat(f'/pane/{first}/body')['length'] == len(b'first pane')
            rows = {int(row.split()[0]): row.split() for row in client.read('/index').splitlines()}
            assert rows[first][1:3] == [b'text', b'1'] and rows[second][1:3] == [b'text', b'0'], rows
            # name: read the file name, write to rename; sel: the selection.
            assert client.read(f'/pane/{first}/name') == f'{root}/+New\n'.encode()
            client.write(f'/pane/{first}/name', b'notes.txt\n')
            assert client.read(f'/pane/{first}/name') == f'{root}/notes.txt\n'.encode()
            assert pane_event() == f'rename {first} {root}/notes.txt\n'.encode()
            assert client.stat(f'/pane/{first}/name')['length'] == len(f'{root}/notes.txt\n')
            # Copying addr onto dot selects that range; sel reads and replaces it.
            client.write(f'/pane/{first}/addr', b'#0,#5')
            client.write(f'/pane/{first}/dot', client.read(f'/pane/{first}/addr'))
            assert client.read(f'/pane/{first}/dot') == client.read(f'/pane/{first}/addr')
            assert client.read(f'/pane/{first}/sel') == b'first'
            assert client.stat(f'/pane/{first}/sel')['length'] == 5
            client.write(f'/pane/{first}/sel', b'FIRST')
            assert client.read(f'/pane/{first}/body') == b'FIRST pane'
            assert client.read(f'/pane/{first}/sel') == b''
            # exec Msg shows text; exec Save writes the named file; rmdir closes.
            client.write(f'/pane/{first}/exec', b'Msg hello from 9P\n')
            assert 'hello from 9P' in ''.join(cell[0] for cell in client.screen()['cells'])
            assert client.read(f'/pane/{first}/dirty') == b'1\n'
            client.write(f'/pane/{first}/exec', b'Save\n')
            assert (root / 'notes.txt').read_bytes() == b'FIRST pane'
            assert pane_event() == f'save {first} {root}/notes.txt\n'.encode()
            assert client.read('/exec') == f'{first}\n'.encode()
            assert client.read(f'/pane/{first}/dirty') == b'0\n'
            client.remove(f'/pane/{second}')
            assert pane_event() == f'del {second} {root}/+New\n'.encode()
            assert str(second) not in client.list('/pane')
            # look opens a file; the serial reads back.
            (root / 'opened.txt').write_bytes(b'one\ntwo\nthree\n')
            client.write('/look', f'{root}/opened.txt:2\n'.encode())
            opened = int(client.read('/look'))
            assert opened not in (fixture, first, second), opened
            assert client.read(f'/pane/{opened}/body') == b'one\ntwo\nthree\n'
            assert client.read(f'/pane/{opened}/name') == f'{root}/opened.txt\n'.encode()
            assert pane_event() == f'new {opened} {root}/opened.txt\n'.encode()
            client.write(f'/pane/{first}/look', f'{root}/opened.txt:3\n'.encode())
            assert client.read('/look') == f'{opened}\n'.encode(), 'a repeated look targets the open pane'
            assert {str(fixture), str(first), str(opened)} <= set(client.list('/pane'))
            # Writing an event record back still performs the action it names.
            client.write(f'/pane/{first}/body', b'Msg via event', truncate=True)
            client.write(f'/pane/{first}/event', b'FX0 13\n')
            assert 'via event' in ''.join(cell[0] for cell in client.screen()['cells'])
            # A command line may not carry control characters, and nothing else
            # in the tree may be created or removed.
            refused = [lambda: client.write('/exec', b'Msg a\x00b'),
                       lambda: client.write('/status', b'anything\n'),
                       lambda: client.mkdir('/', 'x'),
                       lambda: client.mkdir('/pane', 'one'),
                       lambda: client.create('/pane', 'plain-file'),
                       lambda: client.remove('/pane/1/body'),
                       lambda: client.remove('/index')]
            for index, attempt in enumerate(refused):
                try:
                    attempt()
                except OSError:
                    pass
                else:
                    raise AssertionError(f'refusal {index} was accepted')
            client.close(log)
            if embedded:
                assert client.read('/src/pardes.zig').startswith(b'const std')
                assert client.stat('/src/pardes.zig')['mode'] == 0o444
                assert b'pub const Pardes' in client.read(f'/pane/{look(client, "/virtual/src/pardes.zig")}/body')
            # An open of data with OTRUNC (a shell's >) deletes the addressed
            # range only, so the write after it replaces that range.
            scratch = new_pane(client, b'hello world\nsecond line\n')
            client.write(f'/pane/{scratch}/addr', b'#0,#5')
            client.write(f'/pane/{scratch}/data', b'HOWDY', truncate=True)
            assert client.read(f'/pane/{scratch}/body') == b'HOWDY world\nsecond line\n'
            # sam's regexps: ^ at any line; a miss says so and leaves no
            # address, so the data write after it refuses.
            client.write(f'/pane/{scratch}/addr', b'/^second/')
            assert client.read(f'/pane/{scratch}/addr') == b'         12          18 '
            for path, data, why in ((f'/pane/{scratch}/addr', b'/nowhere/', 'no match for regexp'),
                                    (f'/pane/{scratch}/data', b'LOST', 'no address')):
                try:
                    client.write(path, data)
                    raise AssertionError(f'{path} took {data!r}')
                except OSError as refused:
                    assert why in str(refused), refused
            assert client.read(f'/pane/{scratch}/body') == b'HOWDY world\nsecond line\n'
            # Through a mount both read as EINVAL; the log says which and why.
            assert f'err {scratch} addr: no match for regexp\n'.encode() in client.read('/log')
            client.remove(f'/pane/{scratch}')
            # A save the host cannot do fails the write that asked for it,
            # and the log's err record names the path and why.
            unsaved = new_pane(client, b'unsaved\n')
            try:
                client.write(f'/pane/{unsaved}/ctl', b'Save /nonexistent-pardes-dir/x.txt\n')
                raise AssertionError('a Save into a missing directory succeeded')
            except OSError as refused:
                assert 'Save /nonexistent-pardes-dir/x.txt: ' in str(refused), refused
            assert f'err {unsaved} ctl: Save /nonexistent-pardes-dir/x.txt: '.encode() in client.read('/log'), client.read('/log')
            client.remove(f'/pane/{unsaved}')

            # Sixteen connections fill the slots; the next is told why.
            extra = [Client(address) for _ in range(15)]
            try:
                try:
                    Client(address).__exit__()
                    raise AssertionError('a seventeenth connection was served')
                except OSError as refused:
                    assert 'too many connections' in str(refused), refused
            finally:
                for other in extra:
                    other.__exit__()
            deadline = time.monotonic() + 5
            while b'err - 9p: too many connections' not in client.read('/log'):
                assert time.monotonic() < deadline, client.read('/log')
                time.sleep(.01)

    print('9P discovery: listing/stat/find are inert; new, remove, look, exec, name, sel, log, ctl lock, focus, the ctl split and commands behave')


def run_file(binary):
    """pty/run: a line in, how it ended out, on the same open."""
    def run(c, serial, line):
        fid = c.open(f'/pane/{serial}/pty/run', 2)
        try:
            c.rpc(118, struct.pack('<IQI', fid, 0, len(line)) + line)
            return c.read_fid(fid)
        finally:
            c.close(fid)
    with tempfile.TemporaryDirectory() as directory:
        root = Path(directory)
        with session(binary, root, 'run') as (client, address):
            client.write('/exec', b'Shell bash\n')
            client.write('/exec', b'Tty\n')
            term = int(max(r.split()[0] for r in client.read('/index').splitlines() if r.split()[1] == b'term'))
            deadline = time.monotonic() + 10
            while run(client, term, b'true\n') == b'busy\n':  # until its first prompt
                assert time.monotonic() < deadline, 'the shell never reached a prompt'
                time.sleep(.05)
            assert run(client, term, b'false\n') == b'exit 1\n'
            assert run(client, term, b'printf "one\\ntwo\\n"\n') == b'exit 0\none\ntwo\n'  # then what it printed
            assert run(client, term, b'sh -c "exit 7"\n') == b'exit 7\n'
            assert run(client, term, b'fi\n') == b'error not run\n'  # a syntax error runs nothing
            assert run(client, term, b"echo 'open\n") == b'error not run\n'  # nor does an open quote
            assert run(client, term, b'true\n') == b'exit 0\n'  # ...and the shell is clear after
            with Client(address) as other:
                slow = []
                waiter = threading.Thread(target=lambda: slow.append(run(other, term, b'sleep 1\n')), daemon=True)
                waiter.start()
                time.sleep(.3)
                # The job the other client ran holds the tty, and says so.
                assert run(client, term, b'true\n') == b'busy: sleep is running\n'
                waiter.join(5)
                assert slow == [b'exit 0\n'], slow
                closing = []
                waiter = threading.Thread(target=lambda: closing.append(run(other, term, b'sleep 30\n')), daemon=True)
                waiter.start()
                time.sleep(.3)
                client.write(f'/pane/{term}/exec', b'Del\n')
                waiter.join(5)
                assert closing == [b'error shell gone\n'], closing


def exit_answers(binary):
    """Exit written to /ctl is answered before the editor quits."""
    with tempfile.TemporaryDirectory(prefix='pardes-exit-') as directory:
        seen = {}
        with session(binary, Path(directory), 'exit', terminal=seen) as (client, _):
            client.write('/ctl', b'Exit\n')
            deadline = time.monotonic() + 5
            while time.monotonic() < deadline:
                try:
                    # a zombie has quit; the session reaps it
                    if Path(f'/proc/{seen["pid"]}/stat').read_text().split(') ')[1][0] == 'Z':
                        break
                except FileNotFoundError:
                    break
                time.sleep(.01)
            else:
                raise AssertionError("Exit did not quit the editor")


def unattended_messages_expire(binary):
    """With nothing attached, a message leaves after MessageLinger on its own
    clock: no key, no click, no other request comes to move it along."""
    with tempfile.TemporaryDirectory(prefix='pardes-msg-') as directory:
        with session(binary, Path(directory), 'msg') as (client, _):
            client.write('/pane/1/ctl', b'Msg lingering-words\n')
            def shown():
                screen = json.loads(client.read('/screen'))
                return 'lingering-words' in ''.join(cell[0] for cell in screen['cells'])
            assert shown()
            # Reading /screen is itself a request, so wait without asking.
            time.sleep(2.5)
            assert not shown(), 'an unattended message outlived MessageLinger'


def python_repl_runs_one_line(binary):
    """A one-line exec sent to Python's own REPL (3.13's pyrepl, which asks
    for bracketed paste) runs at once, with no second Enter: the Enter
    reaches it after the paste, not inside it. A real pty, a real python3."""
    python = shutil.which('python3')
    if python is None:
        return
    version = subprocess.run([python, '-c', 'import sys; print(sys.version_info >= (3, 13))'],
                             capture_output=True, text=True).stdout.strip()
    if version != 'True':
        return
    with tempfile.TemporaryDirectory(prefix='pardes-repl-') as directory:
        with session(binary, Path(directory), 'repl') as (client, _):
            def panes(client):
                return {int(row.split()[0]) for row in client.read('/index').splitlines()}
            before = panes(client)
            client.write('/pane/1/ctl', b'Tty\n')
            deadline = time.monotonic() + 10
            while time.monotonic() < deadline and panes(client) == before:
                time.sleep(.05)
            tty = max(panes(client) - before)
            def body():
                return client.read(f'/pane/{tty}/body').decode('utf-8', 'replace')
            def wait_for(text, seconds=15):
                deadline = time.monotonic() + seconds
                while time.monotonic() < deadline:
                    if text in body():
                        return True
                    time.sleep(.1)
                return False
            assert wait_for('$') or wait_for('>'), body()
            client.write(f'/pane/{tty}/pty/data', python.encode() + b' -q\r')
            assert wait_for('>>>'), body()
            client.write(f'/pane/{tty}/ctl', b'Repl python\n')
            # An exec on the REPL's own body goes to the REPL, as its event
            # record written back does: an empty range acts on its text.
            fid = client.open(f'/pane/{tty}/event', 2)
            try:
                record = b'MX0 0 0 10 print(6*7)\n'
                client.rpc(118, struct.pack('<IQI', fid, 0, len(record)) + record)
                assert wait_for('\n42'), body()
                # After the session has sat idle, the Enter still waits for
                # the paste: core time is as old as the last frame then.
                for n in range(5):
                    time.sleep(2)
                    line = f'print({1000 + n})'.encode()
                    record = b'MX0 0 0 %d %s\n' % (len(line), line)
                    client.rpc(118, struct.pack('<IQI', fid, 0, len(record)) + record)
                    assert wait_for(f'\n{1000 + n}'), (n, body())
                # More than one line, with and without a newline at the end,
                # and a block with a statement after it: each runs whole,
                # and the REPL is back at its prompt, not at `...`.
                for code, outputs in [(b'print(11)\nprint(22)', ['11', '22']),
                                      (b'print(33)\nprint(44)\n', ['33', '44']),
                                      (b'for i in range(2):\n    print(55 + i)\nprint(77)\n', ['55', '56', '77'])]:
                    record = b'MX0 0 0 %d %s\n' % (len(code), code)
                    client.rpc(118, struct.pack('<IQI', fid, 0, len(record)) + record)
                    for out in outputs:
                        assert wait_for(f'\n{out}\n'), (code, out, body())
                    time.sleep(.5)
                    assert body().rstrip().endswith('>>>'), (code, body()[-200:])
            finally:
                client.close(fid)


def signal_cleans_up(binary):
    """A detached session told to stop by a signal unlinks its sockets."""
    for sig in [signal.SIGTERM, signal.SIGINT, signal.SIGHUP]:
        with tempfile.TemporaryDirectory(prefix='pardes-sig-') as directory:
            root = Path(directory)
            seen = {}
            with session(binary, root, 'sig', terminal=seen) as (client, address):
                detached = root / 'pardes-detached-sig.sock'
                assert address.exists() and detached.exists()
                os.kill(seen['pid'], sig)
                deadline = time.monotonic() + 5
                while (address.exists() or detached.exists()) and time.monotonic() < deadline:
                    time.sleep(.01)
                assert not address.exists() and not detached.exists(), (sig, list(root.iterdir()))


def cut_writes(binary):
    """A write bigger than a 9P message comes as several, cut anywhere: each
    command line runs once, whole, an Edit block once it ends, and a last
    line with no newline when the open closes. Never a fragment."""
    with tempfile.TemporaryDirectory(prefix='pardes-cut-') as directory:
        with session(binary, Path(directory), 'cut') as (client, _):
            burst = b''.join(b'Msg burst-%04d\n' % i for i in range(1000))
            assert len(burst) > client.msize
            client.write('/exec', burst)
            log = client.read('/log').decode()
            said = [line.split(' ', 2)[2] for line in log.splitlines() if line.startswith('msg ') and 'burst-' in line]
            assert said == ['burst-%04d' % i for i in range(1000)], said[:3] + said[-3:]
            assert '\nrun ' not in log and 'exit 127' not in log, log[-400:]
            client.write('/exec', b'Msg no-newline-at-end')
            assert 'msg ' in client.read('/log').decode().split('no-newline-at-end')[0][-40:]
            serial = new_pane(client, b'')
            block = b'Edit ,a\n' + b''.join(b'line %05d of the block\n' % i for i in range(2500)) + b'.\n'
            assert len(block) > 50000
            client.write(f'/pane/{serial}/ctl', block)
            body = client.read(f'/pane/{serial}/body').decode().splitlines()
            assert body == ['line %05d of the block' % i for i in range(2500)], (len(body), body[:2])
            # A detached session with no frontend is 80x24 until told.
            screen = client.screen()
            assert (screen['cols'], screen['rows']) == (80, 24), (screen['cols'], screen['rows'])
            client.write('/ctl', b'size 132 50\n')
            screen = client.screen()
            assert (screen['cols'], screen['rows']) == (132, 50), (screen['cols'], screen['rows'])


def test(binary, quic=False):
    started = time.monotonic()
    cut_writes(binary)
    run_file(binary)
    exit_answers(binary)
    unattended_messages_expire(binary)
    python_repl_runs_one_line(binary)
    signal_cleans_up(binary)
    for options, message in [
        (['--fs'], b'no such option'),
        (['--fs9'], b'no such option'),
        (['--9p'], b'--9p needs a socket name'),
        (['--9p='], b'invalid 9P socket name'),
        (['--9p=a/b'], b'invalid 9P socket name'),
        (['--attach=work', '--9p=work'], b'--attach has none'),
        (['--9p-tcp'], b'--9p-tcp needs'),
        (['--9p-tcp='], b'--9p-tcp needs'),
        (['--9p-tcp=tcp!localhost!5640'], b'--9p-tcp needs'),
        (['--9p-tcp=quic!127.0.0.1!5640'], b'--9p-tcp needs'),
        (['--9p-tcp=tcp!127.0.0.1!5640', '--9p-tcp=tcp!127.0.0.1!5641'], b'specified twice'),
        (['--attach=work', '--9p-tcp=tcp!127.0.0.1!5640'], b'--attach has none'),
        (['--9p-quic'], b'--9p-quic needs'),
        (['--9p-quic='], b'--9p-quic needs'),
        (['--9p-quic=tcp!127.0.0.1!5640'], b'--9p-quic needs'),
        (['--mount=os=work'], b'invalid mount name'),
        (['--mount=peer='], b'invalid mount name or dial'),
        (['--mount=peer=one', '--mount=peer=two'], b'duplicate mount'),
        (['--mount=peer=tcp!127.0.0.1!0'], b'invalid mount dial'),
        (['--attach=work', '--mount=peer=one'], b'--attach has none'),
    ]:
        result = subprocess.run([binary, *options], capture_output=True, timeout=5)
        assert result.returncode == 1 and message in result.stderr, (options, result)
    with tempfile.TemporaryDirectory(prefix='pardes-fs-') as directory:
        root = Path(directory)
        with session(binary, root, 'renamed', '--9p=explicit', socket_name='explicit') as (named, named_address):
            assert named_address.name == 'pardes-9p-explicit.sock'
            assert not (root / 'pardes-9p-renamed.sock').exists()
            assert named.read('/pane/1/body') == b'initial\n'
        with session(binary, root, 'first') as (client, address):
            assert {'pane', 'index', 'status', 'look', 'exec', 'log', 'os'} <= set(client.list('/'))
            assert 'self' not in client.list('/')
            assert client.read('/pane/1/body') == b'initial\n'
            assert client.read('/os' + str(root / 'first.txt')) == b'initial\n'
            assert 'first.txt' in client.list('/os' + str(root))
            assert client.read('/pane/1/../1/body') == b'initial\n'
            assert client.read('/os' + str(root) + '/../' + root.name + '/first.txt') == b'initial\n'

            listing = root / 'listing'
            listing.mkdir()
            (listing / 'broken').symlink_to(listing / 'missing')
            for number in range(24):
                (listing / f'entry-{number:02}').touch()
            with Client(address, msize=256) as small:
                assert set(small.list('/os' + str(listing))) == {
                    f'entry-{number:02}' for number in range(24)}

            frozen = client.open('/screen')
            before = bytearray(client.read_fid(frozen, count=31))
            client.write('/pane/1/body', b'screen changed\n')
            while chunk := client.read_fid(frozen, len(before)):
                before.extend(chunk)
            client.close(frozen)
            old_screen = json.loads(before)
            old_text = ''.join(cell[0] for cell in old_screen['cells'])
            assert 'initial' in old_text and 'screen changed' not in old_text
            assert 'screen changed' in ''.join(cell[0] for cell in client.screen()['cells'])

            payload = ('const value = "λ";\n' * 3000).encode()
            serial = new_pane(client, payload)
            body = f'/pane/{serial}/body'
            assert client.read(body) == payload
            client.write(body, b'replaced\n', truncate=True)
            assert client.read(body) == b'replaced\n'

            event = client.open(f'/pane/{serial}/event')
            client.write(body, b'event\n')
            record = client.read_fid(event)
            assert record.startswith(b'EI') and b'event\n' in record, record
            client.close(event)

            os_path = '/os' + str(root / 'first.txt')
            client.write(os_path, b'written through 9P\n', truncate=True)
            assert (root / 'first.txt').read_bytes() == b'written through 9P\n'
            assert client.read(os_path) == b'written through 9P\n'

            for index in range(12):
                with Client(address) as other:
                    assert other.read(body) == b'replaced\nevent\n', index

            missing = False
            try:
                client.read('/pane/4294967295/body')
            except OSError:
                missing = True
            assert missing
            assert client.read(body) == b'replaced\nevent\n'

            if 'src' in client.list('/'):
                source = look(client, '/virtual/src/pardes.zig')
                assert b'pub const Pardes' in client.read(f'/pane/{source}/body')

            (root / 'index').write_bytes(b'OS takes precedence\n')
            opened = look(client, 'index')
            assert client.read(f'/pane/{opened}/body') == b'OS takes precedence\n'
            opened = look(client, '/n/self/index')
            index = client.read(f'/pane/{opened}/body')
            assert index.split()[0] == b'1' and b'first.txt' in index, index
            (root / 'explicit.txt').write_bytes(b'explicit OS mount\n')
            opened = look(client, '/n/os' + str(root / 'explicit.txt'))
            assert client.read(f'/pane/{opened}/body') == b'explicit OS mount\n'

            own = root / 'pardes-9p-second.sock'
            with session(binary, root, 'second', '--mount=peer=' + str(address),
                         '--mount=own=' + str(own)) as (remote, _):
                opened = look(remote, '/n/own/pane/1/body')
                assert remote.read(f'/pane/{opened}/body') == b'initial\n'
                opened = look(remote, '/n/peer/pane/' + str(serial) + '/body')
                assert remote.read(f'/pane/{opened}/body') == b'replaced\nevent\n'
                remote.write(f'/pane/{opened}/body', b'saved to peer\n', truncate=True)
                remote.write(f'/pane/{opened}/exec', b'Save\n')
                assert client.read(body) == b'saved to peer\n'

                large = b'mounted file contents\n' * 60000
                large_path = root / 'large.txt'
                large_path.write_bytes(large)
                opened = look(remote, '/n/peer/os' + str(large_path))
                assert remote.read(f'/pane/{opened}/body') == large
                edited = large[:-3] + b'edited\n'
                remote.write(f'/pane/{opened}/body', edited, truncate=True)
                remote.write(f'/pane/{opened}/exec', b'Save\n')
                assert large_path.read_bytes() == edited
                assert client.read('/os' + str(large_path)) == edited

            with session(binary, root, 'runtime') as (remote, own_address):
                control = new_pane(remote, b'')
                execute(remote, control, 'Mount peer ' + str(address))
                opened = look(remote, '/n/peer/pane/1/body', source=control)
                assert remote.read(f'/pane/{opened}/body') == client.read('/pane/1/body')
                execute(remote, control, 'Mount peer ' + str(own_address))
                execute(remote, control, 'Unmount peer')
                remote.write(f'/pane/{opened}/body', b'runtime mounted Save\n', truncate=True)
                remote.write(f'/pane/{opened}/exec', b'Save\n')
                assert client.read('/pane/1/body') == b'runtime mounted Save\n'
                assert remote.read('/pane/1/body') == b'initial\n'
                roots = look(remote, '/n', source=control)
                assert b'/n/peer/\n' in remote.read(f'/pane/{roots}/body')
                remote.write(f'/pane/{opened}/exec', b'Del\n')
                execute(remote, control, 'Unmount peer')
                remote.write(f'/pane/{roots}/ctl', b'get\n')
                assert remote.read(f'/pane/{roots}/body') == b'/n/os/\n/n/self/\n'
                execute(remote, control, 'Mount peer ' + str(own_address))
                opened = look(remote, '/n/peer/pane/1/body', source=control)
                assert remote.read(f'/pane/{opened}/body') == b'initial\n'

            with session(binary, root, 'mounted-startup', '--mount=peer=' + str(address),
                         file='/n/peer/pane/1/body:1') as (remote, _):
                assert remote.read('/pane/1/body') == b'runtime mounted Save\n'

            client.write(f'/pane/{serial}/exec', b'Del\n')
            assert str(serial) not in client.list('/pane')

        for tty in [False, True]:
            name = 'restore tty space' if tty else 'restore detached space'
            with session(binary, root, name, tty=tty) as (old, address):
                old.write('/pane/1/body', b'dumped state\n', truncate=True)
                control = new_pane(old, b'')
                execute(old, control, 'Restore ' + str(root / 'missing dump.zon'))
                assert old.read('/pane/1/body') == b'dumped state\n'
                execute(old, control, 'Mount own ' + str(address))
                execute(old, control, 'Dump')
                saved = root / (name + '.dump.zon')
                deadline = time.monotonic() + 5
                while not saved.exists():
                    assert time.monotonic() < deadline, 'Dump did not write its state'
                    time.sleep(.005)
                held_body = old.open('/pane/1/body')
                held_screen = old.open('/screen')
                old_ids = {int(row.split()[0]) for row in old.read('/index').splitlines()}
                assert old.read_fid(held_body) == b'dumped state\n'
                assert old.read_fid(held_screen, count=1) == b'{'
                old.write('/pane/1/body', b'changed after dump\n', truncate=True)
                # Unsaved text is asked about once, as Exit asks; the second
                # Restore goes ahead, and is answered before the hang-up.
                try:
                    execute(old, control, 'Restore ' + str(saved))
                except OSError as refused:
                    assert 'Modified' in str(refused), refused
                assert old.read('/pane/1/body') == b'changed after dump\n'
                execute(old, control, 'Restore ' + str(saved))
                # Refused while the connections are cut, or cut already.
                try:
                    old.read_fid(held_body)
                except (EOFError, OSError):
                    pass
                else:
                    raise AssertionError('Restore left an old body fid usable')
                with Client(address) as restored:
                    # The new log names its panes, then where they came from.
                    log = restored.read('/log')
                    assert b'\nrestore ' + str(saved).encode() + b'\n' in log, log
                    # then which serial each pane had: restored <old> <new>
                    assert (b'\n'.join(b'restored %d %d' % (old, new) for old, new in zip(sorted(old_ids), sorted(int(r.split()[0]) for r in restored.read('/index').splitlines()))) + b'\nrestoredcol ') in log, log
                    restored_ids = [int(row.split()[0]) for row in restored.read('/index').splitlines()]
                    assert len(restored_ids) == 2 and old_ids.isdisjoint(restored_ids), restored_ids
                    file_id, control_id = restored_ids
                    contents = restored.read(f'/pane/{file_id}/body')
                    assert contents == b'dumped state\n', (contents, saved.read_text(), restored.read('/index'))
                    assert restored.read(f'/pane/{control_id}/body') == b'', 'commands ran through exec, not the body'
                    assert restored.screen()['cols'] == 80
                    opened = look(restored, '/n/own/os' + str(root / (name + '.txt')), source=control_id)
                    assert restored.read(f'/pane/{opened}/body') == b'initial\n'

        with session(binary, root, 'forwarding') as (client, address):
            child_dir = root / 'child-working-directory'
            child_dir.mkdir()
            spaced = child_dir / 'space name.txt'
            spaced.write_bytes(b'first line\nsecond line\n')
            env = os.environ.copy()
            # PARDES_PID is what says "you are inside a pardes"; the socket
            # and the pane only say how to reach it. Without the pid the child
            # starts its own session, so this test used to pass only when the
            # runner itself happened to be running inside one.
            status = dict(line.split(maxsplit=1) for line in client.read('/status').decode().splitlines())
            env.update(PARDES_9P=str(address), PARDES_PANE='1', PARDES_PID=status['pid'])
            env.pop('PARDES_FORWARD_LOOK', None)
            for word, expected, selected, reuse in [('space name.txt:2:4', spaced.read_bytes(), [14, 14], False),
                                                    ('/n/self/pane/1/body', b'initial\n', None, False),
                                                    ('/virtual/pane/1/body:1:2-4', b'initial\n', [1, 4], True)]:
                before = {int(row.split()[0]) for row in client.read('/index').splitlines()}
                result = subprocess.run([binary, '--tty', word], cwd=child_dir, env=env,
                                        capture_output=True, timeout=3)
                assert result.returncode == 0, (word, result.stderr)
                after = {int(row.split()[0]) for row in client.read('/index').splitlines()}
                if reuse:
                    assert after == before
                else:
                    opened, = after - before
                assert client.read(f'/pane/{opened}/body') == expected
                assert client.read('/pane/1/body') == b'initial\n'
                if selected is not None:
                    # The selection is dot; reading it takes no command at all.
                    actual = list(map(int, client.read(f'/pane/{opened}/dot').split()))
                    assert actual == selected, (word, actual, selected)
            addr = client.open('/pane/1/addr', 2)
            limit = client.open('/pane/1/limit', 2)
            for fid, text in [(addr, b'#0,#3'), (limit, b'#0,#3'), (addr, b'#0')]:
                client.rpc(118, struct.pack('<IQI', fid, 0, len(text)) + text)
            try:
                for _ in range(8):
                    result = subprocess.run([binary], cwd=child_dir, env=env,
                                            capture_output=True, timeout=3)
                    assert result.returncode == 1 and b'already inside pardes' in result.stderr
                    text = b'/tial/'
                    try:
                        client.rpc(118, struct.pack('<IQI', addr, 0, len(text)) + text)
                    except OSError:
                        pass
                    else:
                        raise AssertionError('no-argument child cleared the parent address limit')
            finally:
                client.close(addr)
                client.close(limit)
            client.read('/pane/1/ctl')

            control = new_pane(client, b'')
            execute(client, control, 'Dump')
            saved = root / 'forwarding.dump.zon'
            deadline = time.monotonic() + 3
            while not saved.exists():
                assert time.monotonic() < deadline, 'forwarding fixture Dump did not finish'
                time.sleep(.005)
            before = client.read('/index')
            inherited = {key: env[key] for key in ['PARDES_9P', 'PARDES_PANE', 'PARDES_PID']}
            cases = [
                ('mount', ['--mount=peer=' + str(address), '/n/peer/pane/1/body'], None),
                ('name', ['--9p=forwarded-name'], 'forwarded-name'),
                ('tcp', ['--9p-tcp=tcp!127.0.0.1!0'], None),
                ('load', ['-l', str(saved)], None),
                ('shells', ['-n', '3'], None),
                ('toggle', ['--tty-toggle=q'], None),
                ('toggle-arg', ['--tty-toggle', 'q'], None),
            ]
            if quic:
                cases.append(('quic', ['--9p-quic=quic!127.0.0.1!0'], None))
            for name, options, socket_name in cases:
                with session(binary, root, 'forward-' + name, tty=True, socket_name=socket_name,
                             launch=[*([] if name == 'shells' else ['--tty']), *options],
                             inherited=inherited) as (local, local_address):
                    assert local_address != address
                    index = local.read('/index').splitlines()
                    if name == 'mount':
                        assert len(index) == 1 and b'/n/peer/' in index[0], index
                        assert local.read('/pane/1/body') == b'initial\n'
                    elif name == 'load':
                        assert local.read('/index') == before
                        assert local.read('/pane/1/body') == b'initial\n'
                    else:
                        # A bare tty launch is a shell plus the empty text pane
                        # the boot puts under it; --shells=3 is the classic
                        # three-shell layout and has no scratch.
                        assert len(index) == (3 if name == 'shells' else 2), index
                    if name in ['tcp', 'quic']:
                        assert (name + '!127.0.0.1!').encode() in local.read('/listeners')
                    assert client.read('/index') == before
                    assert client.read('/pane/1/body') == b'initial\n'

            for name, identity, word in [
                ('stale-file', dict(inherited, PARDES_9P=str(root / 'absent.sock')), str(spaced)),
                ('stale-missing', dict(inherited, PARDES_9P=str(root / 'absent.sock')), 'missing-child-file.txt'),
                ('stale-noarg', dict(inherited, PARDES_9P=str(root / 'absent.sock')), None),
                ('stale-pane', dict(inherited, PARDES_PANE='4294967295'), str(spaced)),
                # No pid means "not inside a pardes at all", which is what
                # --nested withholds and what a plain shell has.
                ('not-nested', {k: v for k, v in inherited.items() if k != 'PARDES_PID'}, str(spaced)),
            ]:
                with session(binary, root, name, tty=True, inherited=identity,
                             launch=['--tty', *([word] if word else [])]) as (local, local_address):
                    assert local_address != address
                    if word == str(spaced):
                        assert local.read('/pane/1/body') == spaced.read_bytes()
                    elif word:
                        assert word.encode() in local.read('/index') or word in ''.join(
                            cell[0] for cell in local.screen()['cells'])
                    assert client.read('/index') == before

        for tty in [False, True]:
            name = 'lsp-tty' if tty else 'lsp-detached'
            with session(binary, root, name, tty=tty) as (client, _):
                control = new_pane(client, b'')
                execute(client, control, 'Lspinfo')
                deadline = time.monotonic() + 3
                while True:
                    matches = [int(row.split()[0]) for row in client.read('/index').splitlines()
                               if b'+Lsp' in row]
                    if matches:
                        break
                    assert time.monotonic() < deadline, (name, 'Lspinfo did not complete')
                    time.sleep(.005)
                assert len(matches) == 1, matches
                result = client.read(f'/pane/{matches[0]}/body')
                assert result.startswith(b'backend: zls-inproc+lsp-client\n'), result
                assert b'protocol servers (lsp-client):' in result, result
                assert client.read('/pane/1/body') == b'initial\n'
                assert '+Lsp' in ''.join(cell[0] for cell in client.screen()['cells'])

        with session(binary, root, 'highlight') as (client, _):
            client.write('/pane/1/name', b'keywords.zig\n')
            source = b'// padding\n' * 9999 + b'fn check() void {\n    if (true) return;\n}\n'
            client.write('/pane/1/body', source, truncate=True)
            screen = client.screen()
            assert len(screen['cells']) == screen['cols'] * screen['rows']
            found = set()
            for row in range(screen['rows']):
                cells = screen['cells'][row * screen['cols']:(row + 1) * screen['cols']]
                text = ''.join(cell[0] for cell in cells)
                for word in ['fn', 'if']:
                    start = text.find(word + ' ')
                    if start < 0:
                        continue
                    styles = [screen['styles'][cell[1]] for cell in cells[start:start + len(word)]]
                    # Weight is opt-in (SyntaxBold, off by default); colour is
                    # not, so the keyword must differ from the text beside it.
                    plain = screen['styles'][cells[start + len(word)][1]]
                    assert all(not style['bold'] and style['fg'] == styles[0]['fg'] for style in styles), (word, styles)
                    assert styles[0]['fg'] != plain['fg'], (word, styles[0], plain)
                    found.add(word)
            assert found == {'fn', 'if'}, screen

        with session(binary, root, 'long-names') as (client, _):
            directory = root / ('directory-' + 'd' * 54)
            directory.mkdir()
            for length in [29, 63, 127, 255]:
                name = 'f' * (length - 4) + '.txt'
                path = directory / name
                path.write_bytes(b'long filename\n')
                wire_path = '/os' + str(path)
                assert name in client.list('/os' + str(directory))
                assert client.read(wire_path) == b'long filename\n'
                client.write(wire_path, b'written through long filename\n', truncate=True)
                assert path.read_bytes() == b'written through long filename\n'
                opened = look(client, '/n/os' + str(path))
                assert client.read(f'/pane/{opened}/body') == path.read_bytes()
                client.remove(f'/pane/{opened}')  # a long name's tag takes rows
            opened = look(client, '/n/os' + str(directory))
            listing = client.read(f'/pane/{opened}/body')
            for path in directory.iterdir():
                assert ('/n/os' + str(path)).encode() in listing
    if quic:
        quic_test(binary)
    print(f'9P integration: passed ({time.monotonic() - started:.3f}s)')


def quic_test(binary):
    for tty in [False, True]:
        for host in ['127.0.0.1', '::1']:
            with tempfile.TemporaryDirectory(prefix='pardes-quic-fs-') as directory:
                root = Path(directory)
                ports = {}
                with session(binary, root, 'server', '--9p-tcp=tcp!' + host + '!0',
                             '--9p-quic=quic!' + host + '!0', tty=tty, network=ports) as (unix, address):
                    assert set(unix.read('/listeners').decode().splitlines()) == {
                        'unix!' + str(address), 'tcp!' + host + '!' + str(ports['TCP']),
                        'quic!' + host + '!' + str(ports['QUIC'])}
                    with Client((host, ports['TCP'])) as tcp:
                        unix_body = unix.open('/pane/1/body')
                        tcp_body = tcp.open('/pane/1/body')
                        with session(binary, root, 'client') as (remote, _):
                            control = new_pane(remote, b'')
                            dial = 'quic!' + host + '!' + str(ports['QUIC'])
                            execute(remote, control, 'Mount peer ' + dial)
                            opened = look(remote, '/n/peer/pane/1/body', source=control)
                            body = f'/pane/{opened}/body'
                            assert remote.read(body) == b'initial\n'
                            payload = 'saved café λ\n'.encode() + b'x' * (3 * 8192 + 27) + b'\n'
                            remote.write(body, payload, truncate=True)
                            remote.write(f'/pane/{opened}/exec', b'Save\n')
                            assert unix.read_fid(unix_body) == payload[:unix.msize - 11]
                            assert tcp.read('/pane/1/body') == payload
                            tcp.write('/pane/1/body', b'TCP to QUIC Get\n', truncate=True)
                            remote.write(f'/pane/{opened}/ctl', b'get\n')
                            assert remote.read(body) == b'TCP to QUIC Get\n'
                            assert unix.read_fid(unix_body) == b'TCP to QUIC Get\n'
                            assert tcp.read_fid(tcp_body) == b'TCP to QUIC Get\n'
                            screen_pane = look(remote, '/n/peer/screen', source=control)
                            screen = json.loads(remote.read(f'/pane/{screen_pane}/body'))
                            assert len(screen['cells']) == screen['cols'] * screen['rows']
                            # The peer's own screen, whole, over QUIC. Its pane's
                            # tag, not its text: where the view sits after the
                            # body shrank from a long wrapped line depends on
                            # whether a frame was drawn meanwhile (sometimes
                            # on the empty last line, `     2`, text off-screen).
                            assert 'server.txt Save' in ''.join(cell[0] for cell in screen['cells'])
                            large = ('normal λ line\n' * 20000).encode()
                            fixture = root / 'large.txt'
                            fixture.write_bytes(large)
                            large_pane = look(remote, '/n/peer/os' + str(fixture), source=control)
                            assert remote.read(f'/pane/{large_pane}/body') == large
                            edited = b'QUIC file saved\n'
                            remote.write(f'/pane/{large_pane}/body', edited, truncate=True)
                            remote.write(f'/pane/{large_pane}/exec', b'Save\n')
                            assert fixture.read_bytes() == edited
                            for pane in [opened, screen_pane, large_pane]:
                                remote.write(f'/pane/{pane}/exec', b'Del\n')
                            execute(remote, control, 'Unmount peer')
                            roots = look(remote, '/n', source=control)
                            assert remote.read(f'/pane/{roots}/body') == b'/n/os/\n/n/self/\n'
                            assert unix.read_fid(unix_body) == b'TCP to QUIC Get\n'
                            assert tcp.read_fid(tcp_body) == b'TCP to QUIC Get\n'
                        # Not checked: a session Looking at its OWN tree through
                        # a QUIC mount ('Mount own quic!...'). QUIC is still
                        # answered on the editor's thread (cloud9's QUIC adapter
                        # is not std.Io based), so that Look waits on the loop
                        # it is running in and opens nothing; features.txt lists
                        # it under "Left as they are". Unix and TCP self-mounts
                        # are covered by test/selfmount.py.
                        unix.close(unix_body)
                        tcp.close(tcp_body)


if __name__ == '__main__':
    if len(sys.argv) in [3, 4] and sys.argv[2] == '--discovery':
        discovery(str(Path(sys.argv[1]).resolve()), embedded=sys.argv[3:] == ['--embedded'])
        raise SystemExit(0)
    if len(sys.argv) not in [2, 3] or (len(sys.argv) == 3 and sys.argv[2] != '--quic'):
        raise SystemExit('usage: fs.py <pardes> [--quic | --discovery]')
    test(str(Path(sys.argv[1]).resolve()), quic=len(sys.argv) == 3)