import os
import re
import typing as t
from gettext import gettext as _

from .core import Argument
from .core import BaseCommand
from .core import Context
from .core import MultiCommand
from .core import Option
from .core import Parameter
from .core import ParameterSource
from .parser import split_arg_string
from .utils import echo


def shell_complete(
    cli: BaseCommand,
    ctx_args: t.Dict[str, t.Any],
    prog_name: str,
    complete_var: str,
    instruction: str,
) -> int:
    """Perform shell completion for the given CLI program.

    :param cli: Command being called.
    :param ctx_args: Extra arguments to pass to
        ``cli.make_context``.
    :param prog_name: Name of the executable in the shell.
    :param complete_var: Name of the environment variable that holds
        the completion instruction.
    :param instruction: Value of ``complete_var`` with the completion
        instruction and shell, in the form ``instruction_shell``.
    :return: Status code to exit with.
    """
    shell, _, instruction = instruction.partition("_")
    comp_cls = get_completion_class(shell)

    if comp_cls is None:
        return 1

    comp = comp_cls(cli, ctx_args, prog_name, complete_var)

    if instruction == "source":
        echo(comp.source())
        return 0

    if instruction == "complete":
        echo(comp.complete())
        return 0

    return 1


class CompletionItem:
    """Represents a completion value and metadata about the value. The
    default metadata is ``type`` to indicate special shell handling,
    and ``help`` if a shell supports showing a help string next to the
    value.

    Arbitrary parameters can be passed when creating the object, and
    accessed using ``item.attr``. If an attribute wasn't passed,
    accessing it returns ``None``.

    :param value: The completion suggestion.
    :param type: Tells the shell script to provide special completion
        support for the type. Click uses ``"dir"`` and ``"file"``.
    :param help: String shown next to the value if supported.
    :param kwargs: Arbitrary metadata. The built-in implementations
        don't use this, but custom type completions paired with custom
        shell support could use it.
    """

    __slots__ = ("value", "type", "help", "_info")

    def __init__(
        self,
        value: t.Any,
        type: str = "plain",
        help: t.Optional[str] = None,
        **kwargs: t.Any,
    ) -> None:
        self.value = value
        self.type = type
        self.help = help
        self._info = kwargs

    def __getattr__(self, name: str) -> t.Any:
        return self._info.get(name)


# Only Bash >= 4.4 has the nosort option.
_SOURCE_BASH = """\
%(complete_func)s() {
    local IFS=$'\\n'
    local response

    response=$(env COMP_WORDS="${COMP_WORDS[*]}" COMP_CWORD=$COMP_CWORD \
%(complete_var)s=bash_complete $1)

    for completion in $response; do
        IFS=',' read type value <<< "$completion"

        if [[ $type == 'dir' ]]; then
            COMREPLY=()
            compopt -o dirnames
        elif [[ $type == 'file' ]]; then
            COMREPLY=()
            compopt -o default
        elif [[ $type == 'plain' ]]; then
            COMPREPLY+=($value)
        fi
    done

    return 0
}

%(complete_func)s_setup() {
    complete -o nosort -F %(complete_func)s %(prog_name)s
}

%(complete_func)s_setup;
"""

_SOURCE_ZSH = """\
#compdef %(prog_name)s

%(complete_func)s() {
    local -a completions
    local -a completions_with_descriptions
    local -a response
    (( ! $+commands[%(prog_name)s] )) && return 1

    response=("${(@f)$(env COMP_WORDS="${words[*]}" COMP_CWORD=$((CURRENT-1)) \
%(complete_var)s=zsh_complete %(prog_name)s)}")

    for type key descr in ${response}; do
        if [[ "$type" == "plain" ]]; then
            if [[ "$descr" == "_" ]]; then
                completions+=("$key")
            else
                completions_with_descriptions+=("$key":"$descr")
            fi
        elif [[ "$type" == "dir" ]]; then
            _path_files -/
        elif [[ "$type" == "file" ]]; then
            _path_files -f
        fi
    done

    if [ -n "$completions_with_descriptions" ]; then
        _describe -V unsorted completions_with_descriptions -U
    fi

    if [ -n "$completions" ]; then
        compadd -U -V unsorted -a completions
    fi
}

compdef %(complete_func)s %(prog_name)s;
"""

_SOURCE_FISH = """\
function %(complete_func)s;
    set -l response;

    for value in (env %(complete_var)s=fish_complete COMP_WORDS=(commandline -cp) \
COMP_CWORD=(commandline -t) %(prog_name)s);
        set response $response $value;
    end;

    for completion in $response;
        set -l metadata (string split "," $completion);

        if test $metadata[1] = "dir";
            __fish_complete_directories $metadata[2];
        else if test $metadata[1] = "file";
            __fish_complete_path $metadata[2];
        else if test $metadata[1] = "plain";
            echo $metadata[2];
        end;
    end;
end;

complete --no-files --command %(prog_name)s --arguments \
"(%(complete_func)s)";
"""


class ShellComplete:
    """Base class for providing shell completion support. A subclass for
    a given shell will override attributes and methods to implement the
    completion instructions (``source`` and ``complete``).

    :param cli: Command being called.
    :param prog_name: Name of the executable in the shell.
    :param complete_var: Name of the environment variable that holds
        the completion instruction.

    .. versionadded:: 8.0
    """

    name: t.ClassVar[str]
    """Name to register the shell as with :func:`add_completion_class`.
    This is used in completion instructions (``{name}_source`` and
    ``{name}_complete``).
    """

    source_template: t.ClassVar[str]
    """Completion script template formatted by :meth:`source`. This must
    be provided by subclasses.
    """

    def __init__(
        self,
        cli: BaseCommand,
        ctx_args: t.Dict[str, t.Any],
        prog_name: str,
        complete_var: str,
    ) -> None:
        self.cli = cli
        self.ctx_args = ctx_args
        self.prog_name = prog_name
        self.complete_var = complete_var

    @property
    def func_name(self) -> str:
        """The name of the shell function defined by the completion
        script.
        """
        safe_name = re.sub(r"\W*", "", self.prog_name.replace("-", "_"), re.ASCII)
        return f"_{safe_name}_completion"

    def source_vars(self) -> t.Dict[str, t.Any]:
        """Vars for formatting :attr:`source_template`.

        By default this provides ``complete_func``, ``complete_var``,
        and ``prog_name``.
        """
        return {
            "complete_func": self.func_name,
            "complete_var": self.complete_var,
            "prog_name": self.prog_name,
        }

    def source(self) -> str:
        """Produce the shell script that defines the completion
        function. By default this ``%``-style formats
        :attr:`source_template` with the dict returned by
        :meth:`source_vars`.
        """
        return self.source_template % self.source_vars()

    def get_completion_args(self) -> t.Tuple[t.List[str], str]:
        """Use the env vars defined by the shell script to return a
        tuple of ``args, incomplete``. This must be implemented by
        subclasses.
        """
        raise NotImplementedError

    def get_completions(
        self, args: t.List[str], incomplete: str
    ) -> t.List[CompletionItem]:
        """Determine the context and last complete command or parameter
        from the complete args. Call that object's ``shell_complete``
        method to get the completions for the incomplete value.

        :param args: List of complete args before the incomplete value.
        :param incomplete: Value being completed. May be empty.
        """
        ctx = _resolve_context(self.cli, self.ctx_args, self.prog_name, args)
        obj, incomplete = _resolve_incomplete(ctx, args, incomplete)
        return obj.shell_complete(ctx, incomplete)

    def format_completion(self, item: CompletionItem) -> str:
        """Format a completion item into the form recognized by the
        shell script. This must be implemented by subclasses.

        :param item: Completion item to format.
        """
        raise NotImplementedError

    def complete(self) -> str:
        """Produce the completion data to send back to the shell.

        By default this calls :meth:`get_completion_args`, gets the
        completions, then calls :meth:`format_completion` for each
        completion.
        """
        args, incomplete = self.get_completion_args()
        completions = self.get_completions(args, incomplete)
        out = [self.format_completion(item) for item in completions]
        return "\n".join(out)


class BashComplete(ShellComplete):
    """Shell completion for Bash."""

    name = "bash"
    source_template = _SOURCE_BASH

    def _check_version(self) -> None:
        import subprocess

        output = subprocess.run(
            ["bash", "-c", "echo ${BASH_VERSION}"], stdout=subprocess.PIPE
        )
        match = re.search(r"^(\d+)\.(\d+)\.\d+", output.stdout.decode())

        if match is not None:
            major, minor = match.groups()

            if major < "4" or major == "4" and minor < "4":
                raise RuntimeError(
                    _(
                        "Shell completion is not supported for Bash"
                        " versions older than 4.4."
                    )
                )
        else:
            raise RuntimeError(
                _("Couldn't detect Bash version, shell completion is not supported.")
            )

    def source(self) -> str:
        self._check_version()
        return super().source()

    def get_completion_args(self) -> t.Tuple[t.List[str], str]:
        cwords = split_arg_string(os.environ["COMP_WORDS"])
        cword = int(os.environ["COMP_CWORD"])
        args = cwords[1:cword]

        try:
            incomplete = cwords[cword]
        except IndexError:
            incomplete = ""

        return args, incomplete

    def format_completion(self, item: CompletionItem) -> str:
        return f"{item.type},{item.value}"


class ZshComplete(ShellComplete):
    """Shell completion for Zsh."""

    name = "zsh"
    source_template = _SOURCE_ZSH

    def get_completion_args(self) -> t.Tuple[t.List[str], str]:
        cwords = split_arg_string(os.environ["COMP_WORDS"])
        cword = int(os.environ["COMP_CWORD"])
        args = cwords[1:cword]

        try:
            incomplete = cwords[cword]
        except IndexError:
            incomplete = ""

        return args, incomplete

    def format_completion(self, item: CompletionItem) -> str:
        return f"{item.type}\n{item.value}\n{item.help if item.help else '_'}"


class FishComplete(ShellComplete):
    """Shell completion for Fish."""

    name = "fish"
    source_template = _SOURCE_FISH

    def get_completion_args(self) -> t.Tuple[t.List[str], str]:
        cwords = split_arg_string(os.environ["COMP_WORDS"])
        incomplete = os.environ["COMP_CWORD"]
        args = cwords[1:]

        # Fish stores the partial word in both COMP_WORDS and
        # COMP_CWORD, remove it from complete args.
        if incomplete and args and args[-1] == incomplete:
            args.pop()

        return args, incomplete

    def format_completion(self, item: CompletionItem) -> str:
        if item.help:
            return f"{item.type},{item.value}\t{item.help}"

        return f"{item.type},{item.value}"


_available_shells: t.Dict[str, t.Type[ShellComplete]] = {
    "bash": BashComplete,
    "fish": FishComplete,
    "zsh": ZshComplete,
}


def add_completion_class(
    cls: t.Type[ShellComplete], name: t.Optional[str] = None
) -> None:
    """Register a :class:`ShellComplete` subclass under the given name.
    The name will be provided by the completion instruction environment
    variable during completion.

    :param cls: The completion class that will handle completion for the
        shell.
    :param name: Name to register the class under. Defaults to the
        class's ``name`` attribute.
    """
    if name is None:
        name = cls.name

    _available_shells[name] = cls


def get_completion_class(shell: str) -> t.Optional[t.Type[ShellComplete]]:
    """Look up a registered :class:`ShellComplete` subclass by the name
    provided by the completion instruction environment variable. If the
    name isn't registered, returns ``None``.

    :param shell: Name the class is registered under.
    """
    return _available_shells.get(shell)


def _is_incomplete_argument(ctx: Context, param: Parameter) -> bool:
    """Determine if the given parameter is an argument that can still
    accept values.

    :param ctx: Invocation context for the command represented by the
        parsed complete args.
    :param param: Argument object being checked.
    """
    if not isinstance(param, Argument):
        return False

    assert param.name is not None
    value = ctx.params[param.name]
    return (
        param.nargs == -1
        or ctx.get_parameter_source(param.name) is not ParameterSource.COMMANDLINE
        or (
            param.nargs > 1
            and isinstance(value, (tuple, list))
            and len(value) < param.nargs
        )
    )


def _start_of_option(value: str) -> bool:
    """Check if the value looks like the start of an option."""
    if not value:
        return False

    c = value[0]
    # Allow "/" since that starts a path.
    return not c.isalnum() and c != "/"


def _is_incomplete_option(args: t.List[str], param: Parameter) -> bool:
    """Determine if the given parameter is an option that needs a value.

    :param args: List of complete args before the incomplete value.
    :param param: Option object being checked.
    """
    if not isinstance(param, Option):
        return False

    if param.is_flag:
        return False

    last_option = None

    for index, arg in enumerate(reversed(args)):
        if index + 1 > param.nargs:
            break

        if _start_of_option(arg):
            last_option = arg

    return last_option is not None and last_option in param.opts


def _resolve_context(
    cli: BaseCommand, ctx_args: t.Dict[str, t.Any], prog_name: str, args: t.List[str]
) -> Context:
    """Produce the context hierarchy starting with the command and
    traversing the complete arguments. This only follows the commands,
    it doesn't trigger input prompts or callbacks.

    :param cli: Command being called.
    :param prog_name: Name of the executable in the shell.
    :param args: List of complete args before the incomplete value.
    """
    ctx_args["resilient_parsing"] = True
    ctx = cli.make_context(prog_name, args.copy(), **ctx_args)
    args = ctx.protected_args + ctx.args

    while args:
        command = ctx.command

        if isinstance(command, MultiCommand):
            if not command.chain:
                name, cmd, args = command.resolve_command(ctx, args)

                if cmd is None:
                    return ctx

                ctx = cmd.make_context(name, args, parent=ctx, resilient_parsing=True)
                args = ctx.protected_args + ctx.args
            else:
                while args:
                    name, cmd, args = command.resolve_command(ctx, args)

                    if cmd is None:
                        return ctx

                    sub_ctx = cmd.make_context(
                        name,
                        args,
                        parent=ctx,
                        allow_extra_args=True,
                        allow_interspersed_args=False,
                        resilient_parsing=True,
                    )
                    args = sub_ctx.args

                ctx = sub_ctx
                args = [*sub_ctx.protected_args, *sub_ctx.args]
        else:
            break

    return ctx


def _resolve_incomplete(
    ctx: Context, args: t.List[str], incomplete: str
) -> t.Tuple[t.Union[BaseCommand, Parameter], str]:
    """Find the Click object that will handle the completion of the
    incomplete value. Return the object and the incomplete value.

    :param ctx: Invocation context for the command represented by
        the parsed complete args.
    :param args: List of complete args before the incomplete value.
    :param incomplete: Value being completed. May be empty.
    """
    # Different shells treat an "=" between a long option name and
    # value differently. Might keep the value joined, return the "="
    # as a separate item, or return the split name and value. Always
    # split and discard the "=" to make completion easier.
    if incomplete == "=":
        incomplete = ""
    elif "=" in incomplete and _start_of_option(incomplete):
        name, _, incomplete = incomplete.partition("=")
        args.append(name)

    # The "--" marker tells Click to stop treating values as options
    # even if they start with the option character. If it hasn't been
    # given and the incomplete arg looks like an option, the current
    # command will provide option name completions.
    if "--" not in args and _start_of_option(incomplete):
        return ctx.command, incomplete

    params = ctx.command.get_params(ctx)

    # If the last complete arg is an option name with an incomplete
    # value, the option will provide value completions.
    for param in params:
        if _is_incomplete_option(args, param):
            return param, incomplete

    # It's not an option name or value. The first argument without a
    # parsed value will provide value completions.
    for param in params:
        if _is_incomplete_argument(ctx, param):
            return param, incomplete

    # There were no unparsed arguments, the command may be a group that
    # will provide command name completions.
    return ctx.command, incomplete
