# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:

# Copyright 2014-2017 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
#
# This file is part of qutebrowser.
#
# qutebrowser is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# qutebrowser is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""Other utilities which don't fit anywhere else."""

import io
import re
import sys
import enum
import json
import os.path
import collections
import functools
import contextlib
import itertools
import socket
import shlex

from PyQt5.QtCore import Qt, QUrl
from PyQt5.QtGui import QKeySequence, QColor, QClipboard, QDesktopServices
from PyQt5.QtWidgets import QApplication
import pkg_resources

import qutebrowser
from qutebrowser.utils import qtutils, log


fake_clipboard = None
log_clipboard = False


class ClipboardError(Exception):

    """Raised if the clipboard contents are unavailable for some reason."""


class SelectionUnsupportedError(ClipboardError):

    """Raised if [gs]et_clipboard is used and selection=True is unsupported."""

    def __init__(self):
        super().__init__("Primary selection is not supported on this "
                         "platform!")


class ClipboardEmptyError(ClipboardError):

    """Raised if get_clipboard is used and the clipboard is empty."""


def elide(text, length):
    """Elide text so it uses a maximum of length chars."""
    if length < 1:
        raise ValueError("length must be >= 1!")
    if len(text) <= length:
        return text
    else:
        return text[:length - 1] + '\u2026'


def elide_filename(filename, length):
    """Elide a filename to the given length.

    The difference to the elide() is that the text is removed from
    the middle instead of from the end. This preserves file name extensions.
    Additionally, standard ASCII dots are used ("...") instead of the unicode
    "…" (U+2026) so it works regardless of the filesystem encoding.

    This function does not handle path separators.

    Args:
        filename: The filename to elide.
        length: The maximum length of the filename, must be at least 3.

    Return:
        The elided filename.
    """
    elidestr = '...'
    if length < len(elidestr):
        raise ValueError('length must be greater or equal to 3')
    if len(filename) <= length:
        return filename
    # Account for '...'
    length -= len(elidestr)
    left = length // 2
    right = length - left
    if right == 0:
        return filename[:left] + elidestr
    else:
        return filename[:left] + elidestr + filename[-right:]


def compact_text(text, elidelength=None):
    """Remove leading whitespace and newlines from a text and maybe elide it.

    Args:
        text: The text to compact.
        elidelength: To how many chars to elide.
    """
    lines = []
    for line in text.splitlines():
        lines.append(line.strip())
    out = ''.join(lines)
    if elidelength is not None:
        out = elide(out, elidelength)
    return out


def read_file(filename, binary=False):
    """Get the contents of a file contained with qutebrowser.

    Args:
        filename: The filename to open as string.
        binary: Whether to return a binary string.
                If False, the data is UTF-8-decoded.

    Return:
        The file contents as string.
    """
    if hasattr(sys, 'frozen'):
        # cx_Freeze doesn't support pkg_resources :(
        fn = os.path.join(os.path.dirname(sys.executable), filename)
        if binary:
            with open(fn, 'rb') as f:
                return f.read()
        else:
            with open(fn, 'r', encoding='utf-8') as f:
                return f.read()
    else:
        data = pkg_resources.resource_string(qutebrowser.__name__, filename)
        if not binary:
            data = data.decode('UTF-8')
        return data


def resource_filename(filename):
    """Get the absolute filename of a file contained with qutebrowser.

    Args:
        filename: The filename.

    Return:
        The absolute filename.
    """
    if hasattr(sys, 'frozen'):
        return os.path.join(os.path.dirname(sys.executable), filename)
    return pkg_resources.resource_filename(qutebrowser.__name__, filename)


def _get_color_percentage(a_c1, a_c2, a_c3, b_c1, b_c2, b_c3, percent):
    """Get a color which is percent% interpolated between start and end.

    Args:
        a_c1, a_c2, a_c3: Start color components (R, G, B / H, S, V / H, S, L)
        b_c1, b_c2, b_c3: End color components (R, G, B / H, S, V / H, S, L)
        percent: Percentage to interpolate, 0-100.
                 0: Start color will be returned.
                 100: End color will be returned.

    Return:
        A (c1, c2, c3) tuple with the interpolated color components.
    """
    if not 0 <= percent <= 100:
        raise ValueError("percent needs to be between 0 and 100!")
    out_c1 = round(a_c1 + (b_c1 - a_c1) * percent / 100)
    out_c2 = round(a_c2 + (b_c2 - a_c2) * percent / 100)
    out_c3 = round(a_c3 + (b_c3 - a_c3) * percent / 100)
    return (out_c1, out_c2, out_c3)


def interpolate_color(start, end, percent, colorspace=QColor.Rgb):
    """Get an interpolated color value.

    Args:
        start: The start color.
        end: The end color.
        percent: Which value to get (0 - 100)
        colorspace: The desired interpolation color system,
                    QColor::{Rgb,Hsv,Hsl} (from QColor::Spec enum)
                    If None, start is used except when percent is 100.

    Return:
        The interpolated QColor, with the same spec as the given start color.
    """
    qtutils.ensure_valid(start)
    qtutils.ensure_valid(end)

    if colorspace is None:
        if percent == 100:
            return QColor(*end.getRgb())
        else:
            return QColor(*start.getRgb())

    out = QColor()
    if colorspace == QColor.Rgb:
        a_c1, a_c2, a_c3, _alpha = start.getRgb()
        b_c1, b_c2, b_c3, _alpha = end.getRgb()
        components = _get_color_percentage(a_c1, a_c2, a_c3, b_c1, b_c2, b_c3,
                                           percent)
        out.setRgb(*components)
    elif colorspace == QColor.Hsv:
        a_c1, a_c2, a_c3, _alpha = start.getHsv()
        b_c1, b_c2, b_c3, _alpha = end.getHsv()
        components = _get_color_percentage(a_c1, a_c2, a_c3, b_c1, b_c2, b_c3,
                                           percent)
        out.setHsv(*components)
    elif colorspace == QColor.Hsl:
        a_c1, a_c2, a_c3, _alpha = start.getHsl()
        b_c1, b_c2, b_c3, _alpha = end.getHsl()
        components = _get_color_percentage(a_c1, a_c2, a_c3, b_c1, b_c2, b_c3,
                                           percent)
        out.setHsl(*components)
    else:
        raise ValueError("Invalid colorspace!")
    out = out.convertTo(start.spec())
    qtutils.ensure_valid(out)
    return out


def format_seconds(total_seconds):
    """Format a count of seconds to get a [H:]M:SS string."""
    prefix = '-' if total_seconds < 0 else ''
    hours, rem = divmod(abs(round(total_seconds)), 3600)
    minutes, seconds = divmod(rem, 60)
    chunks = []
    if hours:
        chunks.append(str(hours))
        min_format = '{:02}'
    else:
        min_format = '{}'
    chunks.append(min_format.format(minutes))
    chunks.append('{:02}'.format(seconds))
    return prefix + ':'.join(chunks)


def format_size(size, base=1024, suffix=''):
    """Format a byte size so it's human readable.

    Inspired by http://stackoverflow.com/q/1094841
    """
    prefixes = ['', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y']
    if size is None:
        return '?.??' + suffix
    for p in prefixes:
        if -base < size < base:
            return '{:.02f}{}{}'.format(size, p, suffix)
        size /= base
    return '{:.02f}{}{}'.format(size, prefixes[-1], suffix)


def key_to_string(key):
    """Convert a Qt::Key member to a meaningful name.

    Args:
        key: A Qt::Key member.

    Return:
        A name of the key as a string.
    """
    special_names_str = {
        # Some keys handled in a weird way by QKeySequence::toString.
        # See https://bugreports.qt.io/browse/QTBUG-40030
        # Most are unlikely to be ever needed, but you never know ;)
        # For dead/combining keys, we return the corresponding non-combining
        # key, as that's easier to add to the config.
        'Key_Blue': 'Blue',
        'Key_Calendar': 'Calendar',
        'Key_ChannelDown': 'Channel Down',
        'Key_ChannelUp': 'Channel Up',
        'Key_ContrastAdjust': 'Contrast Adjust',
        'Key_Dead_Abovedot': '˙',
        'Key_Dead_Abovering': '˚',
        'Key_Dead_Acute': '´',
        'Key_Dead_Belowdot': 'Belowdot',
        'Key_Dead_Breve': '˘',
        'Key_Dead_Caron': 'ˇ',
        'Key_Dead_Cedilla': '¸',
        'Key_Dead_Circumflex': '^',
        'Key_Dead_Diaeresis': '¨',
        'Key_Dead_Doubleacute': '˝',
        'Key_Dead_Grave': '`',
        'Key_Dead_Hook': 'Hook',
        'Key_Dead_Horn': 'Horn',
        'Key_Dead_Iota': 'Iota',
        'Key_Dead_Macron': '¯',
        'Key_Dead_Ogonek': '˛',
        'Key_Dead_Semivoiced_Sound': 'Semivoiced Sound',
        'Key_Dead_Tilde': '~',
        'Key_Dead_Voiced_Sound': 'Voiced Sound',
        'Key_Exit': 'Exit',
        'Key_Green': 'Green',
        'Key_Guide': 'Guide',
        'Key_Info': 'Info',
        'Key_LaunchG': 'LaunchG',
        'Key_LaunchH': 'LaunchH',
        'Key_MediaLast': 'MediaLast',
        'Key_Memo': 'Memo',
        'Key_MicMute': 'Mic Mute',
        'Key_Mode_switch': 'Mode switch',
        'Key_Multi_key': 'Multi key',
        'Key_PowerDown': 'Power Down',
        'Key_Red': 'Red',
        'Key_Settings': 'Settings',
        'Key_SingleCandidate': 'Single Candidate',
        'Key_ToDoList': 'Todo List',
        'Key_TouchpadOff': 'Touchpad Off',
        'Key_TouchpadOn': 'Touchpad On',
        'Key_TouchpadToggle': 'Touchpad toggle',
        'Key_Yellow': 'Yellow',
        'Key_Alt': 'Alt',
        'Key_AltGr': 'AltGr',
        'Key_Control': 'Control',
        'Key_Direction_L': 'Direction L',
        'Key_Direction_R': 'Direction R',
        'Key_Hyper_L': 'Hyper L',
        'Key_Hyper_R': 'Hyper R',
        'Key_Meta': 'Meta',
        'Key_Shift': 'Shift',
        'Key_Super_L': 'Super L',
        'Key_Super_R': 'Super R',
        'Key_unknown': 'Unknown',
    }
    # We now build our real special_names dict from the string mapping above.
    # The reason we don't do this directly is that certain Qt versions don't
    # have all the keys, so we want to ignore AttributeErrors.
    special_names = {}
    for k, v in special_names_str.items():
        try:
            special_names[getattr(Qt, k)] = v
        except AttributeError:
            pass
    # Now we check if the key is any special one - if not, we use
    # QKeySequence::toString.
    try:
        return special_names[key]
    except KeyError:
        name = QKeySequence(key).toString()
        morphings = {
            'Backtab': 'Tab',
            'Esc': 'Escape',
        }
        if name in morphings:
            return morphings[name]
        else:
            return name


def keyevent_to_string(e):
    """Convert a QKeyEvent to a meaningful name.

    Args:
        e: A QKeyEvent.

    Return:
        A name of the key (combination) as a string or
        None if only modifiers are pressed..
    """
    if sys.platform == 'darwin':
        # Qt swaps Ctrl/Meta on OS X, so we switch it back here so the user can
        # use it in the config as expected. See:
        # https://github.com/qutebrowser/qutebrowser/issues/110
        # http://doc.qt.io/qt-5.4/osx-issues.html#special-keys
        modmask2str = collections.OrderedDict([
            (Qt.MetaModifier, 'Ctrl'),
            (Qt.AltModifier, 'Alt'),
            (Qt.ControlModifier, 'Meta'),
            (Qt.ShiftModifier, 'Shift'),
        ])
    else:
        modmask2str = collections.OrderedDict([
            (Qt.ControlModifier, 'Ctrl'),
            (Qt.AltModifier, 'Alt'),
            (Qt.MetaModifier, 'Meta'),
            (Qt.ShiftModifier, 'Shift'),
        ])
    modifiers = (Qt.Key_Control, Qt.Key_Alt, Qt.Key_Shift, Qt.Key_Meta,
                 Qt.Key_AltGr, Qt.Key_Super_L, Qt.Key_Super_R, Qt.Key_Hyper_L,
                 Qt.Key_Hyper_R, Qt.Key_Direction_L, Qt.Key_Direction_R)
    if e.key() in modifiers:
        # Only modifier pressed
        return None
    mod = e.modifiers()
    parts = []
    for (mask, s) in modmask2str.items():
        if mod & mask and s not in parts:
            parts.append(s)
    parts.append(key_to_string(e.key()))
    return '+'.join(parts)


class KeyInfo:

    """Stores information about a key, like used in a QKeyEvent.

    Attributes:
        key: Qt::Key
        modifiers: Qt::KeyboardModifiers
        text: str
    """

    def __init__(self, key, modifiers, text):
        self.key = key
        self.modifiers = modifiers
        self.text = text

    def __repr__(self):
        # Meh, dependency cycle...
        from qutebrowser.utils.debug import qenum_key
        if self.modifiers is None:
            modifiers = None
        else:
            #modifiers = qflags_key(Qt, self.modifiers)
            modifiers = hex(int(self.modifiers))
        return get_repr(self, constructor=True, key=qenum_key(Qt, self.key),
                        modifiers=modifiers, text=self.text)

    def __eq__(self, other):
        return (self.key == other.key and self.modifiers == other.modifiers and
                self.text == other.text)


class KeyParseError(Exception):

    """Raised by _parse_single_key/parse_keystring on parse errors."""

    def __init__(self, keystr, error):
        super().__init__("Could not parse {!r}: {}".format(keystr, error))


def is_special_key(keystr):
    """True if keystr is a 'special' keystring (e.g. <ctrl-x> or <space>)."""
    return keystr.startswith('<') and keystr.endswith('>')


def _parse_single_key(keystr):
    """Convert a single key string to a (Qt.Key, Qt.Modifiers, text) tuple."""
    if is_special_key(keystr):
        # Special key
        keystr = keystr[1:-1]
    elif len(keystr) == 1:
        # vim-like key
        pass
    else:
        raise KeyParseError(keystr, "Expecting either a single key or a "
                            "<Ctrl-x> like keybinding.")

    seq = QKeySequence(normalize_keystr(keystr), QKeySequence.PortableText)
    if len(seq) != 1:
        raise KeyParseError(keystr, "Got {} keys instead of 1.".format(
            len(seq)))
    result = seq[0]

    if result == Qt.Key_unknown:
        raise KeyParseError(keystr, "Got unknown key.")

    modifier_mask = int(Qt.ShiftModifier | Qt.ControlModifier |
                        Qt.AltModifier | Qt.MetaModifier | Qt.KeypadModifier |
                        Qt.GroupSwitchModifier)
    assert Qt.Key_unknown & ~modifier_mask == Qt.Key_unknown

    modifiers = result & modifier_mask
    key = result & ~modifier_mask

    if len(keystr) == 1 and keystr.isupper():
        modifiers |= Qt.ShiftModifier

    assert key != 0, key
    key = Qt.Key(key)
    modifiers = Qt.KeyboardModifiers(modifiers)

    # Let's hope this is accurate...
    if len(keystr) == 1 and not modifiers:
        text = keystr
    elif len(keystr) == 1 and modifiers == Qt.ShiftModifier:
        text = keystr.upper()
    else:
        text = ''

    return KeyInfo(key, modifiers, text)


def parse_keystring(keystr):
    """Parse a keystring like <Ctrl-x> or xyz and return a KeyInfo list."""
    if is_special_key(keystr):
        return [_parse_single_key(keystr)]
    else:
        return [_parse_single_key(char) for char in keystr]


def normalize_keystr(keystr):
    """Normalize a keystring like Ctrl-Q to a keystring like Ctrl+Q.

    Args:
        keystr: The key combination as a string.

    Return:
        The normalized keystring.
    """
    keystr = keystr.lower()
    replacements = (
        ('control', 'ctrl'),
        ('windows', 'meta'),
        ('mod1', 'alt'),
        ('mod4', 'meta'),
    )
    for (orig, repl) in replacements:
        keystr = keystr.replace(orig, repl)
    for mod in ['ctrl', 'meta', 'alt', 'shift']:
        keystr = keystr.replace(mod + '-', mod + '+')
    return keystr


class FakeIOStream(io.TextIOBase):

    """A fake file-like stream which calls a function for write-calls."""

    def __init__(self, write_func):
        super().__init__()
        self.write = write_func


@contextlib.contextmanager
def fake_io(write_func):
    """Run code with stdout and stderr replaced by FakeIOStreams.

    Args:
        write_func: The function to call when write is called.
    """
    old_stdout = sys.stdout
    old_stderr = sys.stderr
    fake_stderr = FakeIOStream(write_func)
    fake_stdout = FakeIOStream(write_func)
    sys.stderr = fake_stderr
    sys.stdout = fake_stdout
    try:
        yield
    finally:
        # If the code we did run did change sys.stdout/sys.stderr, we leave it
        # unchanged. Otherwise, we reset it.
        if sys.stdout is fake_stdout:
            sys.stdout = old_stdout
        if sys.stderr is fake_stderr:
            sys.stderr = old_stderr


@contextlib.contextmanager
def disabled_excepthook():
    """Run code with the exception hook temporarily disabled."""
    old_excepthook = sys.excepthook
    sys.excepthook = sys.__excepthook__
    try:
        yield
    finally:
        # If the code we did run did change sys.excepthook, we leave it
        # unchanged. Otherwise, we reset it.
        if sys.excepthook is sys.__excepthook__:
            sys.excepthook = old_excepthook


class prevent_exceptions:  # pylint: disable=invalid-name

    """Decorator to ignore and log exceptions.

    This needs to be used for some places where PyQt segfaults on exceptions or
    silently ignores them.

    We used to re-raise the exception with a single-shot QTimer in a similar
    case, but that lead to a strange problem with a KeyError with some random
    jinja template stuff as content. For now, we only log it, so it doesn't
    pass 100% silently.

    This could also be a function, but as a class (with a "wrong" name) it's
    much cleaner to implement.

    Attributes:
        _retval: The value to return in case of an exception.
        _predicate: The condition which needs to be True to prevent exceptions
    """

    def __init__(self, retval, predicate=True):
        """Save decorator arguments.

        Gets called on parse-time with the decorator arguments.

        Args:
            See class attributes.
        """
        self._retval = retval
        self._predicate = predicate

    def __call__(self, func):
        """Called when a function should be decorated.

        Args:
            func: The function to be decorated.

        Return:
            The decorated function.
        """
        if not self._predicate:
            return func

        retval = self._retval

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs)
            except BaseException:
                log.misc.exception("Error in {}".format(qualname(func)))
                return retval

        return wrapper


def is_enum(obj):
    """Check if a given object is an enum."""
    try:
        return issubclass(obj, enum.Enum)
    except TypeError:
        return False


def get_repr(obj, constructor=False, **attrs):
    """Get a suitable __repr__ string for an object.

    Args:
        obj: The object to get a repr for.
        constructor: If True, show the Foo(one=1, two=2) form instead of
                     <Foo one=1 two=2>.
        attrs: The attributes to add.
    """
    cls = qualname(obj.__class__)
    parts = []
    items = sorted(attrs.items())
    for name, val in items:
        parts.append('{}={!r}'.format(name, val))
    if constructor:
        return '{}({})'.format(cls, ', '.join(parts))
    else:
        if parts:
            return '<{} {}>'.format(cls, ' '.join(parts))
        else:
            return '<{}>'.format(cls)


def qualname(obj):
    """Get the fully qualified name of an object.

    Based on twisted.python.reflect.fullyQualifiedName.

    Should work with:
        - functools.partial objects
        - functions
        - classes
        - methods
        - modules
    """
    if isinstance(obj, functools.partial):
        obj = obj.func

    if hasattr(obj, '__module__'):
        prefix = '{}.'.format(obj.__module__)
    else:
        prefix = ''

    if hasattr(obj, '__qualname__'):
        return '{}{}'.format(prefix, obj.__qualname__)
    elif hasattr(obj, '__name__'):
        return '{}{}'.format(prefix, obj.__name__)
    else:
        return repr(obj)


def raises(exc, func, *args):
    """Check if a function raises a given exception.

    Args:
        exc: A single exception or an iterable of exceptions.
        func: A function to call.
        *args: The arguments to pass to the function.

    Returns:
        True if the exception was raised, False otherwise.
    """
    try:
        func(*args)
    except exc:
        return True
    else:
        return False


def force_encoding(text, encoding):
    """Make sure a given text is encodable with the given encoding.

    This replaces all chars not encodable with question marks.
    """
    return text.encode(encoding, errors='replace').decode(encoding)


def sanitize_filename(name, replacement='_'):
    """Replace invalid filename characters.

    Note: This should be used for the basename, as it also removes the path
    separator.

    Args:
        name: The filename.
        replacement: The replacement character (or None).
    """
    if replacement is None:
        replacement = ''
    # Bad characters taken from Windows, there are even fewer on Linux
    # See also
    # https://en.wikipedia.org/wiki/Filename#Reserved_characters_and_words
    bad_chars = '\\/:*?"<>|'
    for bad_char in bad_chars:
        name = name.replace(bad_char, replacement)
    return name


def newest_slice(iterable, count):
    """Get an iterable for the n newest items of the given iterable.

    Args:
        count: How many elements to get.
               0: get no items:
               n: get the n newest items
              -1: get all items
    """
    if count < -1:
        raise ValueError("count can't be smaller than -1!")
    elif count == 0:
        return []
    elif count == -1 or len(iterable) < count:
        return iterable
    else:
        return itertools.islice(iterable, len(iterable) - count, len(iterable))


def set_clipboard(data, selection=False):
    """Set the clipboard to some given data."""
    if selection and not supports_selection():
        raise SelectionUnsupportedError
    if log_clipboard:
        what = 'primary selection' if selection else 'clipboard'
        log.misc.debug("Setting fake {}: {}".format(what, json.dumps(data)))
    else:
        mode = QClipboard.Selection if selection else QClipboard.Clipboard
        QApplication.clipboard().setText(data, mode=mode)


def get_clipboard(selection=False, fallback=False):
    """Get data from the clipboard.

    Args:
        selection: Use the primary selection.
        fallback: Fall back to the clipboard if primary selection is
                  unavailable.
    """
    global fake_clipboard
    if fallback and not selection:
        raise ValueError("fallback given without selection!")

    if selection and not supports_selection():
        if fallback:
            selection = False
        else:
            raise SelectionUnsupportedError

    if fake_clipboard is not None:
        data = fake_clipboard
        fake_clipboard = None
    else:
        mode = QClipboard.Selection if selection else QClipboard.Clipboard
        data = QApplication.clipboard().text(mode=mode)

    target = "Primary selection" if selection else "Clipboard"
    if not data.strip():
        raise ClipboardEmptyError("{} is empty.".format(target))
    log.misc.debug("{} contained: {!r}".format(target, data))

    return data


def supports_selection():
    """Check if the OS supports primary selection."""
    return QApplication.clipboard().supportsSelection()


def random_port():
    """Get a random free port."""
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.bind(('localhost', 0))
    port = sock.getsockname()[1]
    sock.close()
    return port


def open_file(filename, cmdline=None):
    """Open the given file.

    If cmdline is not given, general->default-open-dispatcher is used.
    If default-open-dispatcher is unset, the system's default application is
    used.

    Args:
        filename: The filename to open.
        cmdline: The command to use as string. A `{}` is expanded to the
                 filename. None means to use the system's default application
                 or `default-open-dispatcher` if set. If no `{}` is found, the
                 filename is appended to the cmdline.
    """
    # Import late to avoid circular imports:
    # utils -> config -> configdata -> configtypes -> cmdutils -> command ->
    # utils
    from qutebrowser.misc import guiprocess
    from qutebrowser.config import config
    # the default program to open downloads with - will be empty string
    # if we want to use the default
    override = config.get('general', 'default-open-dispatcher')

    # precedence order: cmdline > default-open-dispatcher > openUrl

    if cmdline is None and not override:
        log.misc.debug("Opening {} with the system application"
                       .format(filename))
        url = QUrl.fromLocalFile(filename)
        QDesktopServices.openUrl(url)
        return

    if cmdline is None and override:
        cmdline = override

    cmd, *args = shlex.split(cmdline)
    args = [arg.replace('{}', filename) for arg in args]
    if '{}' not in cmdline:
        args.append(filename)
    log.misc.debug("Opening {} with {}"
                   .format(filename, [cmd] + args))
    proc = guiprocess.GUIProcess(what='open-file')
    proc.start_detached(cmd, args)


def unused(_arg):
    """Function which does nothing to avoid pylint complaining."""
    pass


def expand_windows_drive(path):
    r"""Expand a drive-path like E: into E:\.

    Does nothing for other paths.

    Args:
        path: The path to expand.
    """
    # Usually, "E:" on Windows refers to the current working directory on drive
    # E:\. The correct way to specifify drive E: is "E:\", but most users
    # probably don't use the "multiple working directories" feature and expect
    # "E:" and "E:\" to be equal.
    if re.match(r'[A-Z]:$', path, re.IGNORECASE):
        return path + "\\"
    else:
        return path