from __future__ import annotations

import collections.abc as cabc
import inspect
import io
import itertools
import re
import sys
import typing as t
from contextlib import AbstractContextManager
from contextlib import redirect_stdout
from gettext import gettext as _

from ._compat import isatty
from ._compat import strip_ansi
from ._compat import WIN
from .exceptions import Abort
from .exceptions import UsageError
from .globals import resolve_color_default
from .types import Choice
from .types import convert_type
from .types import ParamType
from .utils import echo
from .utils import LazyFile

if t.TYPE_CHECKING:
    from ._termui_impl import ProgressBar

V = t.TypeVar("V")

# The prompt functions to use.  The doc tools currently override these
# functions to customize how they work.
visible_prompt_func: t.Callable[[str], str] = input

_ansi_colors = {
    "black": 30,
    "red": 31,
    "green": 32,
    "yellow": 33,
    "blue": 34,
    "magenta": 35,
    "cyan": 36,
    "white": 37,
    "reset": 39,
    "bright_black": 90,
    "bright_red": 91,
    "bright_green": 92,
    "bright_yellow": 93,
    "bright_blue": 94,
    "bright_magenta": 95,
    "bright_cyan": 96,
    "bright_white": 97,
}
_ansi_reset_all = "\033[0m"


_HIDDEN_INPUT_MASK = "'***'"


def _mask_hidden_input(message: str, value: str) -> str:
    """Replace occurrences of ``value`` in ``message`` with a fixed mask.

    Both ``repr(value)`` (the form built-in :class:`ParamType` errors use
    via ``{value!r}``) and the raw value are masked. The raw-value pass
    uses word-boundary lookarounds so a substring like ``"1"`` does not
    match inside ``"10"``, and ``"ent"`` does not match inside
    ``"Authentication"``. The empty string is skipped to avoid matching
    at every boundary.
    """
    message = message.replace(repr(value), _HIDDEN_INPUT_MASK)
    if value:
        message = re.sub(
            rf"(?<!\w){re.escape(value)}(?!\w)", _HIDDEN_INPUT_MASK, message
        )
    return message


def hidden_prompt_func(prompt: str) -> str:
    import getpass

    return getpass.getpass(prompt)


def _readline_prompt(func: t.Callable[[str], str], text: str, err: bool) -> str:
    """Call a prompt function, passing the full prompt on non-Windows so
    readline can handle line editing and cursor positioning correctly.

    On Windows the prompt is written separately via :func:`echo` for
    colorama support, with only the last character passed to *func*.
    """
    if WIN:
        # Write the prompt separately so that we get nice coloring
        # through colorama on Windows.
        echo(text[:-1], nl=False, err=err)
        # Echo the last character to stdout to work around an issue
        # where readline causes backspace to clear the whole line.
        return func(text[-1:])
    if err:
        with redirect_stdout(sys.stderr):
            return func(text)
    return func(text)


def _build_prompt(
    text: str,
    suffix: str,
    show_default: bool | str = False,
    default: t.Any | None = None,
    show_choices: bool = True,
    type: ParamType[t.Any] | None = None,
) -> str:
    prompt = text
    if type is not None and show_choices and isinstance(type, Choice):
        prompt += f" ({', '.join(map(str, type.choices))})"
    if isinstance(show_default, str):
        default = f"({show_default})"
    if default is not None and show_default:
        prompt = f"{prompt} [{_format_default(default)}]"
    return f"{prompt}{suffix}"


def _format_default(default: t.Any) -> t.Any:
    if isinstance(default, (io.IOBase, LazyFile)) and hasattr(default, "name"):
        return default.name

    return default


def prompt(
    text: str,
    default: t.Any | None = None,
    hide_input: bool = False,
    confirmation_prompt: bool | str = False,
    type: ParamType[t.Any] | t.Any | None = None,
    value_proc: t.Callable[[str], t.Any] | None = None,
    prompt_suffix: str = ": ",
    show_default: bool | str = True,
    err: bool = False,
    show_choices: bool = True,
) -> t.Any:
    """Prompts a user for input.  This is a convenience function that can
    be used to prompt a user for input later.

    If the user aborts the input by sending an interrupt signal, this
    function will catch it and raise a :exc:`Abort` exception.

    :param text: the text to show for the prompt.
    :param default: the default value to use if no input happens.  If this
                    is not given it will prompt until it's aborted.
    :param hide_input: if this is set to true then the input value will
                       be hidden.
    :param confirmation_prompt: Prompt a second time to confirm the
        value. Can be set to a string instead of ``True`` to customize
        the message.
    :param type: the type to use to check the value against.
    :param value_proc: if this parameter is provided it's a function that
                       is invoked instead of the type conversion to
                       convert a value.
    :param prompt_suffix: a suffix that should be added to the prompt.
    :param show_default: shows or hides the default value in the prompt.
                         If this value is a string, it shows that string
                         in parentheses instead of the actual value.
    :param err: if set to true the file defaults to ``stderr`` instead of
                ``stdout``, the same as with echo.
    :param show_choices: Show or hide choices if the passed type is a Choice.
                         For example if type is a Choice of either day or week,
                         show_choices is true and text is "Group by" then the
                         prompt will be "Group by (day, week): ".

    .. versionchanged:: 8.3.3
        ``show_default`` can be a string to show a custom value instead
        of the actual default, matching the help text behavior.

    .. versionchanged:: 8.3.1
        A space is no longer appended to the prompt.

    .. versionadded:: 8.0
        ``confirmation_prompt`` can be a custom string.

    .. versionadded:: 7.0
        Added the ``show_choices`` parameter.

    .. versionadded:: 6.0
        Added unicode support for cmd.exe on Windows.

    .. versionadded:: 4.0
        Added the `err` parameter.

    """

    def prompt_func(text: str) -> str:
        f = hidden_prompt_func if hide_input else visible_prompt_func
        try:
            return _readline_prompt(f, text, err)
        except (KeyboardInterrupt, EOFError):
            # getpass doesn't print a newline if the user aborts input with ^C.
            # Allegedly this behavior is inherited from getpass(3).
            # A doc bug has been filed at https://bugs.python.org/issue24711
            if hide_input:
                echo(None, err=err)
            raise Abort() from None

    if value_proc is None:
        value_proc = convert_type(type, default)

    prompt = _build_prompt(
        text, prompt_suffix, show_default, default, show_choices, type
    )

    if confirmation_prompt:
        if confirmation_prompt is True:
            confirmation_prompt = _("Repeat for confirmation")

        confirmation_prompt = _build_prompt(confirmation_prompt, prompt_suffix)

    while True:
        while True:
            value = prompt_func(prompt)
            if value:
                break
            elif default is not None:
                value = default
                break
        try:
            result = value_proc(value)
        except UsageError as e:
            message = _mask_hidden_input(e.message, value) if hide_input else e.message
            echo(_("Error: {message}").format(message=message), err=err)
            continue
        if not confirmation_prompt:
            return result
        while True:
            value2 = prompt_func(confirmation_prompt)
            is_empty = not value and not value2
            if value2 or is_empty:
                break
        if value == value2:
            return result
        echo(_("Error: The two entered values do not match."), err=err)


def confirm(
    text: str,
    default: bool | None = False,
    abort: bool = False,
    prompt_suffix: str = ": ",
    show_default: bool = True,
    err: bool = False,
) -> bool:
    """Prompts for confirmation (yes/no question).

    If the user aborts the input by sending a interrupt signal this
    function will catch it and raise a :exc:`Abort` exception.

    :param text: the question to ask.
    :param default: The default value to use when no input is given. If
        ``None``, repeat until input is given.
    :param abort: if this is set to `True` a negative answer aborts the
                  exception by raising :exc:`Abort`.
    :param prompt_suffix: a suffix that should be added to the prompt.
    :param show_default: shows or hides the default value in the prompt.
    :param err: if set to true the file defaults to ``stderr`` instead of
                ``stdout``, the same as with echo.

    .. versionchanged:: 8.3.1
        A space is no longer appended to the prompt.

    .. versionchanged:: 8.0
        Repeat until input is given if ``default`` is ``None``.

    .. versionadded:: 4.0
        Added the ``err`` parameter.
    """
    prompt = _build_prompt(
        text,
        prompt_suffix,
        show_default,
        "y/n" if default is None else ("Y/n" if default else "y/N"),
    )

    while True:
        try:
            value = _readline_prompt(visible_prompt_func, prompt, err).lower().strip()
        except (KeyboardInterrupt, EOFError):
            raise Abort() from None
        if value in ("y", "yes"):
            rv = True
        elif value in ("n", "no"):
            rv = False
        elif default is not None and value == "":
            rv = default
        else:
            echo(_("Error: invalid input"), err=err)
            continue
        break
    if abort and not rv:
        raise Abort()
    return rv


def get_pager_file(
    color: bool | None = None,
) -> t.ContextManager[t.TextIO]:
    """Context manager.

    Yields a writable file-like object which can be used as an output pager.

    .. versionadded:: 8.4.0

    :param color: controls if the pager supports ANSI colors or not.  The
                  default is autodetection.
    """
    from ._termui_impl import get_pager_file

    color = resolve_color_default(color)

    return get_pager_file(color=color)


def echo_via_pager(
    text_or_generator: cabc.Iterable[str] | t.Callable[[], cabc.Iterable[str]] | str,
    color: bool | None = None,
) -> None:
    """This function takes a text and shows it via an environment specific
    pager on stdout.

    .. versionchanged:: 3.0
       Added the `color` flag.

    :param text_or_generator: the text to page, or alternatively, a
                              generator emitting the text to page.
    :param color: controls if the pager supports ANSI colors or not.  The
                  default is autodetection.
    """

    if inspect.isgeneratorfunction(text_or_generator):
        i = t.cast("t.Callable[[], cabc.Iterable[str]]", text_or_generator)()
    elif isinstance(text_or_generator, str):
        i = [text_or_generator]
    else:
        i = iter(t.cast("cabc.Iterable[str]", text_or_generator))

    # convert every element of i to a text type if necessary
    text_generator = (el if isinstance(el, str) else str(el) for el in i)

    with get_pager_file(color=color) as pager:
        for text in itertools.chain(text_generator, "\n"):
            pager.write(text)


@t.overload
def progressbar(
    *,
    length: int,
    label: str | None = None,
    hidden: bool = False,
    show_eta: bool = True,
    show_percent: bool | None = None,
    show_pos: bool = False,
    fill_char: str = "#",
    empty_char: str = "-",
    bar_template: str = "%(label)s  [%(bar)s]  %(info)s",
    info_sep: str = "  ",
    width: int = 36,
    file: t.TextIO | None = None,
    color: bool | None = None,
    update_min_steps: int = 1,
) -> ProgressBar[int]: ...


@t.overload
def progressbar(
    iterable: cabc.Iterable[V] | None = None,
    length: int | None = None,
    label: str | None = None,
    hidden: bool = False,
    show_eta: bool = True,
    show_percent: bool | None = None,
    show_pos: bool = False,
    item_show_func: t.Callable[[V | None], str | None] | None = None,
    fill_char: str = "#",
    empty_char: str = "-",
    bar_template: str = "%(label)s  [%(bar)s]  %(info)s",
    info_sep: str = "  ",
    width: int = 36,
    file: t.TextIO | None = None,
    color: bool | None = None,
    update_min_steps: int = 1,
) -> ProgressBar[V]: ...


def progressbar(
    iterable: cabc.Iterable[V] | None = None,
    length: int | None = None,
    label: str | None = None,
    hidden: bool = False,
    show_eta: bool = True,
    show_percent: bool | None = None,
    show_pos: bool = False,
    item_show_func: t.Callable[[V | None], str | None] | None = None,
    fill_char: str = "#",
    empty_char: str = "-",
    bar_template: str = "%(label)s  [%(bar)s]  %(info)s",
    info_sep: str = "  ",
    width: int = 36,
    file: t.TextIO | None = None,
    color: bool | None = None,
    update_min_steps: int = 1,
) -> ProgressBar[V]:
    """This function creates an iterable context manager that can be used
    to iterate over something while showing a progress bar.  It will
    either iterate over the `iterable` or `length` items (that are counted
    up).  While iteration happens, this function will print a rendered
    progress bar to the given `file` (defaults to stdout) and will attempt
    to calculate remaining time and more.  By default, this progress bar
    will not be rendered if the file is not a terminal.

    The context manager creates the progress bar.  When the context
    manager is entered the progress bar is already created.  With every
    iteration over the progress bar, the iterable passed to the bar is
    advanced and the bar is updated.  When the context manager exits,
    a newline is printed and the progress bar is finalized on screen.

    Note: The progress bar is currently designed for use cases where the
    total progress can be expected to take at least several seconds.
    Because of this, the ProgressBar class object won't display
    progress that is considered too fast, and progress where the time
    between steps is less than a second.

    No printing must happen or the progress bar will be unintentionally
    destroyed.

    Example usage::

        with progressbar(items) as bar:
            for item in bar:
                do_something_with(item)

    Alternatively, if no iterable is specified, one can manually update the
    progress bar through the `update()` method instead of directly
    iterating over the progress bar.  The update method accepts the number
    of steps to increment the bar with::

        with progressbar(length=chunks.total_bytes) as bar:
            for chunk in chunks:
                process_chunk(chunk)
                bar.update(chunks.bytes)

    The ``update()`` method also takes an optional value specifying the
    ``current_item`` at the new position. This is useful when used
    together with ``item_show_func`` to customize the output for each
    manual step::

        with click.progressbar(
            length=total_size,
            label='Unzipping archive',
            item_show_func=lambda a: a.filename
        ) as bar:
            for archive in zip_file:
                archive.extract()
                bar.update(archive.size, archive)

    :param iterable: an iterable to iterate over.  If not provided the length
                     is required.
    :param length: the number of items to iterate over.  By default the
                   progressbar will attempt to ask the iterator about its
                   length, which might or might not work.  If an iterable is
                   also provided this parameter can be used to override the
                   length.  If an iterable is not provided the progress bar
                   will iterate over a range of that length.
    :param label: the label to show next to the progress bar.
    :param hidden: hide the progressbar. Defaults to ``False``. When no tty is
        detected, it will only print the progressbar label. Setting this to
        ``False`` also disables that.
    :param show_eta: enables or disables the estimated time display.  This is
                     automatically disabled if the length cannot be
                     determined.
    :param show_percent: enables or disables the percentage display.  The
                         default is `True` if the iterable has a length or
                         `False` if not.
    :param show_pos: enables or disables the absolute position display.  The
                     default is `False`.
    :param item_show_func: A function called with the current item which
        can return a string to show next to the progress bar. If the
        function returns ``None`` nothing is shown. The current item can
        be ``None``, such as when entering and exiting the bar.
    :param fill_char: the character to use to show the filled part of the
                      progress bar.
    :param empty_char: the character to use to show the non-filled part of
                       the progress bar.
    :param bar_template: the format string to use as template for the bar.
                         The parameters in it are ``label`` for the label,
                         ``bar`` for the progress bar and ``info`` for the
                         info section.
    :param info_sep: the separator between multiple info items (eta etc.)
    :param width: the width of the progress bar in characters, 0 means full
                  terminal width
    :param file: The file to write to. If this is not a terminal then
        only the label is printed.
    :param color: controls if the terminal supports ANSI colors or not.  The
                  default is autodetection.  This is only needed if ANSI
                  codes are included anywhere in the progress bar output
                  which is not the case by default.
    :param update_min_steps: Render only when this many updates have
        completed. This allows tuning for very fast iterators.

    .. versionadded:: 8.2
        The ``hidden`` argument.

    .. versionchanged:: 8.0
        Output is shown even if execution time is less than 0.5 seconds.

    .. versionchanged:: 8.0
        ``item_show_func`` shows the current item, not the previous one.

    .. versionchanged:: 8.0
        Labels are echoed if the output is not a TTY. Reverts a change
        in 7.0 that removed all output.

    .. versionadded:: 8.0
       The ``update_min_steps`` parameter.

    .. versionadded:: 4.0
        The ``color`` parameter and ``update`` method.

    .. versionadded:: 2.0
    """
    from ._termui_impl import ProgressBar

    color = resolve_color_default(color)
    return ProgressBar(
        iterable=iterable,
        length=length,
        hidden=hidden,
        show_eta=show_eta,
        show_percent=show_percent,
        show_pos=show_pos,
        item_show_func=item_show_func,
        fill_char=fill_char,
        empty_char=empty_char,
        bar_template=bar_template,
        info_sep=info_sep,
        file=file,
        label=label,
        width=width,
        color=color,
        update_min_steps=update_min_steps,
    )


def clear() -> None:
    """Clears the terminal screen.  This will have the effect of clearing
    the whole visible space of the terminal and moving the cursor to the
    top left.  This does not do anything if not connected to a terminal.

    .. versionadded:: 2.0
    """
    if not isatty(sys.stdout):
        return

    # ANSI escape \033[2J clears the screen, \033[1;1H moves the cursor
    echo("\033[2J\033[1;1H", nl=False)


def _interpret_color(color: int | tuple[int, int, int] | str, offset: int = 0) -> str:
    if isinstance(color, int):
        return f"{38 + offset};5;{color:d}"

    if isinstance(color, (tuple, list)):
        r, g, b = color
        return f"{38 + offset};2;{r:d};{g:d};{b:d}"

    return str(_ansi_colors[color] + offset)


def style(
    text: t.Any,
    fg: int | tuple[int, int, int] | str | None = None,
    bg: int | tuple[int, int, int] | str | None = None,
    bold: bool | None = None,
    dim: bool | None = None,
    underline: bool | None = None,
    overline: bool | None = None,
    italic: bool | None = None,
    blink: bool | None = None,
    reverse: bool | None = None,
    strikethrough: bool | None = None,
    reset: bool = True,
) -> str:
    """Styles a text with ANSI styles and returns the new string.  By
    default the styling is self contained which means that at the end
    of the string a reset code is issued.  This can be prevented by
    passing ``reset=False``.

    Examples::

        click.echo(click.style('Hello World!', fg='green'))
        click.echo(click.style('ATTENTION!', blink=True))
        click.echo(click.style('Some things', reverse=True, fg='cyan'))
        click.echo(click.style('More colors', fg=(255, 12, 128), bg=117))

    Supported color names:

    * ``black`` (might be a gray)
    * ``red``
    * ``green``
    * ``yellow`` (might be an orange)
    * ``blue``
    * ``magenta``
    * ``cyan``
    * ``white`` (might be light gray)
    * ``bright_black``
    * ``bright_red``
    * ``bright_green``
    * ``bright_yellow``
    * ``bright_blue``
    * ``bright_magenta``
    * ``bright_cyan``
    * ``bright_white``
    * ``reset`` (reset the color code only)

    If the terminal supports it, color may also be specified as:

    -   An integer in the interval [0, 255]. The terminal must support
        8-bit/256-color mode.
    -   An RGB tuple of three integers in [0, 255]. The terminal must
        support 24-bit/true-color mode.

    See https://en.wikipedia.org/wiki/ANSI_color and
    https://gist.github.com/XVilka/8346728 for more information.

    :param text: the string to style with ansi codes.
    :param fg: if provided this will become the foreground color.
    :param bg: if provided this will become the background color.
    :param bold: if provided this will enable or disable bold mode.
    :param dim: if provided this will enable or disable dim mode.  This is
                badly supported.
    :param underline: if provided this will enable or disable underline.
    :param overline: if provided this will enable or disable overline.
    :param italic: if provided this will enable or disable italic.
    :param blink: if provided this will enable or disable blinking.
    :param reverse: if provided this will enable or disable inverse
                    rendering (foreground becomes background and the
                    other way round).
    :param strikethrough: if provided this will enable or disable
        striking through text.
    :param reset: by default a reset-all code is added at the end of the
                  string which means that styles do not carry over.  This
                  can be disabled to compose styles.

    .. versionchanged:: 8.0
        A non-string ``message`` is converted to a string.

    .. versionchanged:: 8.0
       Added support for 256 and RGB color codes.

    .. versionchanged:: 8.0
        Added the ``strikethrough``, ``italic``, and ``overline``
        parameters.

    .. versionchanged:: 7.0
        Added support for bright colors.

    .. versionadded:: 2.0
    """
    if not isinstance(text, str):
        text = str(text)

    bits = []

    if fg:
        try:
            bits.append(f"\033[{_interpret_color(fg)}m")
        except KeyError:
            raise TypeError(_("Unknown color {colour!r}").format(colour=fg)) from None

    if bg:
        try:
            bits.append(f"\033[{_interpret_color(bg, 10)}m")
        except KeyError:
            raise TypeError(_("Unknown color {colour!r}").format(colour=bg)) from None

    if bold is not None:
        bits.append(f"\033[{1 if bold else 22}m")
    if dim is not None:
        bits.append(f"\033[{2 if dim else 22}m")
    if underline is not None:
        bits.append(f"\033[{4 if underline else 24}m")
    if overline is not None:
        bits.append(f"\033[{53 if overline else 55}m")
    if italic is not None:
        bits.append(f"\033[{3 if italic else 23}m")
    if blink is not None:
        bits.append(f"\033[{5 if blink else 25}m")
    if reverse is not None:
        bits.append(f"\033[{7 if reverse else 27}m")
    if strikethrough is not None:
        bits.append(f"\033[{9 if strikethrough else 29}m")
    bits.append(text)
    if reset:
        bits.append(_ansi_reset_all)
    return "".join(bits)


def unstyle(text: str) -> str:
    """Removes ANSI styling information from a string.  Usually it's not
    necessary to use this function as Click's echo function will
    automatically remove styling if necessary.

    .. versionadded:: 2.0

    :param text: the text to remove style information from.
    """
    return strip_ansi(text)


def secho(
    message: t.Any | None = None,
    file: t.IO[t.AnyStr] | None = None,
    nl: bool = True,
    err: bool = False,
    color: bool | None = None,
    **styles: t.Any,
) -> None:
    """This function combines :func:`echo` and :func:`style` into one
    call.  As such the following two calls are the same::

        click.secho('Hello World!', fg='green')
        click.echo(click.style('Hello World!', fg='green'))

    All keyword arguments are forwarded to the underlying functions
    depending on which one they go with.

    Non-string types will be converted to :class:`str`. However,
    :class:`bytes` are passed directly to :meth:`echo` without applying
    style. If you want to style bytes that represent text, call
    :meth:`bytes.decode` first.

    .. versionchanged:: 8.0
        A non-string ``message`` is converted to a string. Bytes are
        passed through without style applied.

    .. versionadded:: 2.0
    """
    if message is not None and not isinstance(message, (bytes, bytearray)):
        message = style(message, **styles)

    return echo(message, file=file, nl=nl, err=err, color=color)


@t.overload
def edit(
    text: bytes | bytearray,
    editor: str | None = None,
    env: cabc.Mapping[str, str] | None = None,
    require_save: bool = False,
    extension: str = ".txt",
) -> bytes | None: ...


@t.overload
def edit(
    text: str,
    editor: str | None = None,
    env: cabc.Mapping[str, str] | None = None,
    require_save: bool = True,
    extension: str = ".txt",
) -> str | None: ...


@t.overload
def edit(
    text: None = None,
    editor: str | None = None,
    env: cabc.Mapping[str, str] | None = None,
    require_save: bool = True,
    extension: str = ".txt",
    filename: str | cabc.Iterable[str] | None = None,
) -> None: ...


def edit(
    text: str | bytes | bytearray | None = None,
    editor: str | None = None,
    env: cabc.Mapping[str, str] | None = None,
    require_save: bool = True,
    extension: str = ".txt",
    filename: str | cabc.Iterable[str] | None = None,
) -> str | bytes | bytearray | None:
    r"""Edits the given text in the defined editor.  If an editor is given
    (should be the full path to the executable but the regular operating
    system search path is used for finding the executable) it overrides
    the detected editor.  Optionally, some environment variables can be
    used.  If the editor is closed without changes, `None` is returned.  In
    case a file is edited directly the return value is always `None` and
    `require_save` and `extension` are ignored.

    If the editor cannot be opened a :exc:`UsageError` is raised.

    Note for Windows: to simplify cross-platform usage, the newlines are
    automatically converted from POSIX to Windows and vice versa.  As such,
    the message here will have ``\n`` as newline markers.

    :param text: the text to edit.
    :param editor: optionally the editor to use.  Defaults to automatic
                   detection.
    :param env: environment variables to forward to the editor.
    :param require_save: if this is true, then not saving in the editor
                         will make the return value become `None`.
    :param extension: the extension to tell the editor about.  This defaults
                      to `.txt` but changing this might change syntax
                      highlighting.
    :param filename: if provided it will edit this file instead of the
                     provided text contents.  It will not use a temporary
                     file as an indirection in that case. If the editor supports
                     editing multiple files at once, a sequence of files may be
                     passed as well. Invoke `click.file` once per file instead
                     if multiple files cannot be managed at once or editing the
                     files serially is desired.

    .. versionchanged:: 8.2.0
        ``filename`` now accepts any ``Iterable[str]`` in addition to a ``str``
        if the ``editor`` supports editing multiple files at once.

    """
    from ._termui_impl import Editor

    ed = Editor(editor=editor, env=env, require_save=require_save, extension=extension)

    if filename is None:
        return ed.edit(text)

    if isinstance(filename, str):
        filename = (filename,)

    ed.edit_files(filenames=filename)
    return None


def launch(url: str, wait: bool = False, locate: bool = False) -> int:
    """This function launches the given URL (or filename) in the default
    viewer application for this file type.  If this is an executable, it
    might launch the executable in a new session.  The return value is
    the exit code of the launched application.  Usually, ``0`` indicates
    success.

    Examples::

        click.launch('https://click.palletsprojects.com/')
        click.launch('/my/downloaded/file', locate=True)

    .. versionadded:: 2.0

    :param url: URL or filename of the thing to launch.
    :param wait: Wait for the program to exit before returning. This
        only works if the launched program blocks. In particular,
        ``xdg-open`` on Linux does not block.
    :param locate: if this is set to `True` then instead of launching the
                   application associated with the URL it will attempt to
                   launch a file manager with the file located.  This
                   might have weird effects if the URL does not point to
                   the filesystem.
    """
    from ._termui_impl import open_url

    return open_url(url, wait=wait, locate=locate)


# If this is provided, getchar() calls into this instead.  This is used
# for unittesting purposes.
_getchar: t.Callable[[bool], str] | None = None


def getchar(echo: bool = False) -> str:
    """Fetches a single character from the terminal and returns it.  This
    will always return a unicode character and under certain rare
    circumstances this might return more than one character.  The
    situations which more than one character is returned is when for
    whatever reason multiple characters end up in the terminal buffer or
    standard input was not actually a terminal.

    Note that this will always read from the terminal, even if something
    is piped into the standard input.

    Note for Windows: in rare cases when typing non-ASCII characters, this
    function might wait for a second character and then return both at once.
    This is because certain Unicode characters look like special-key markers.

    .. versionadded:: 2.0

    :param echo: if set to `True`, the character read will also show up on
                 the terminal.  The default is to not show it.
    """
    global _getchar

    if _getchar is None:
        from ._termui_impl import getchar as f

        _getchar = f

    return _getchar(echo)


def raw_terminal() -> AbstractContextManager[int]:
    from ._termui_impl import raw_terminal as f

    return f()


def pause(info: str | None = None, err: bool = False) -> None:
    """This command stops execution and waits for the user to press any
    key to continue.  This is similar to the Windows batch "pause"
    command.  If the program is not run through a terminal, this command
    will instead do nothing.

    .. versionadded:: 2.0

    .. versionadded:: 4.0
       Added the `err` parameter.

    :param info: The message to print before pausing. Defaults to
        ``"Press any key to continue..."``.
    :param err: if set to message goes to ``stderr`` instead of
                ``stdout``, the same as with echo.
    """
    if not isatty(sys.stdin) or not isatty(sys.stdout):
        return

    if info is None:
        info = _("Press any key to continue...")

    try:
        if info:
            echo(info, nl=False, err=err)
        try:
            getchar()
        except (KeyboardInterrupt, EOFError):
            pass
    finally:
        if info:
            echo(err=err)
