import re
import functools
from datetime import timedelta
from typing import TYPE_CHECKING, Optional, List, Dict

import discord
from discord.ext import commands as dpy_commands

from . import BadArgument
from ..i18n import Translator
from ..utils.chat_formatting import humanize_timedelta

if TYPE_CHECKING:
    from .context import Context

__all__ = [
    "APIToken",
    "DictConverter",
    "GuildConverter",
    "TimedeltaConverter",
    "get_dict_converter",
    "get_timedelta_converter",
    "parse_timedelta",
]

_ = Translator("commands.converter", __file__)

ID_REGEX = re.compile(r"([0-9]{15,21})")


# Taken with permission from
# https://github.com/mikeshardmind/SinbadCogs/blob/816f3bc2ba860243f75112904b82009a8a9e1f99/scheduler/time_utils.py#L9-L19
TIME_RE_STRING = r"\s?".join(
    [
        r"((?P<weeks>\d+?)\s?(weeks?|w))?",
        r"((?P<days>\d+?)\s?(days?|d))?",
        r"((?P<hours>\d+?)\s?(hours?|hrs|hr?))?",
        r"((?P<minutes>\d+?)\s?(minutes?|mins?|m(?!o)))?",  # prevent matching "months"
        r"((?P<seconds>\d+?)\s?(seconds?|secs?|s))?",
    ]
)

TIME_RE = re.compile(TIME_RE_STRING, re.I)


def parse_timedelta(
    argument: str,
    *,
    maximum: Optional[timedelta] = None,
    minimum: Optional[timedelta] = None,
    allowed_units: Optional[List[str]] = None,
) -> Optional[timedelta]:
    """
    This converts a user provided string into a timedelta

    The units should be in order from largest to smallest. 
    This works with or without whitespace.

    Parameters
    ----------
    argument : str
        The user provided input
    maximum : Optional[timedelta]
        If provided, any parsed value higher than this will raise an exception
    minimum : Optional[timedelta]
        If provided, any parsed value lower than this will raise an exception
    allowed_units : Optional[List[str]]
        If provided, you can constrain a user to expressing the amount of time
        in specific units. The units you can chose to provide are the same as the
        parser understands. `weeks` `days` `hours` `minutes` `seconds`

    Returns
    -------
    Optional[timedelta]
        If matched, the timedelta which was parsed. This can return `None`

    Raises
    ------
    BadArgument
        If the argument passed uses a unit not allowed, but understood
        or if the value is out of bounds.
    """
    matches = TIME_RE.match(argument)
    allowed_units = allowed_units or ["weeks", "days", "hours", "minutes", "seconds"]
    if matches:
        params = {k: int(v) for k, v in matches.groupdict().items() if v is not None}
        for k in params.keys():
            if k not in allowed_units:
                raise BadArgument(
                    _("`{unit}` is not a valid unit of time for this command").format(unit=k)
                )
        if params:
            delta = timedelta(**params)
            if maximum and maximum < delta:
                raise BadArgument(
                    _(
                        "This amount of time is too large for this command. (Maximum: {maximum})"
                    ).format(maximum=humanize_timedelta(timedelta=maximum))
                )
            if minimum and delta < minimum:
                raise BadArgument(
                    _(
                        "This amount of time is too small for this command. (Minimum: {minimum})"
                    ).format(minimum=humanize_timedelta(timedelta=minimum))
                )
            return delta
    return None


class GuildConverter(discord.Guild):
    """Converts to a `discord.Guild` object.

    The lookup strategy is as follows (in order):

    1. Lookup by ID.
    2. Lookup by name.
    """

    @classmethod
    async def convert(cls, ctx: "Context", argument: str) -> discord.Guild:
        match = ID_REGEX.fullmatch(argument)

        if match is None:
            ret = discord.utils.get(ctx.bot.guilds, name=argument)
        else:
            guild_id = int(match.group(1))
            ret = ctx.bot.get_guild(guild_id)

        if ret is None:
            raise BadArgument(_('Server "{name}" not found.').format(name=argument))

        return ret


class APIToken(discord.ext.commands.Converter):
    """Converts to a `dict` object.

    This will parse the input argument separating the key value pairs into a 
    format to be used for the core bots API token storage.
    
    This will split the argument by either `;` ` `, or `,` and return a dict
    to be stored. Since all API's are different and have different naming convention,
    this leaves the onus on the cog creator to clearly define how to setup the correct
    credential names for their cogs.

    Note: Core usage of this has been replaced with DictConverter use instead.

    This may be removed at a later date (with warning)
    """

    async def convert(self, ctx, argument) -> dict:
        bot = ctx.bot
        result = {}
        match = re.split(r";|,| ", argument)
        # provide two options to split incase for whatever reason one is part of the api key we're using
        if len(match) > 1:
            result[match[0]] = "".join(r for r in match[1:])
        else:
            raise BadArgument(_("The provided tokens are not in a valid format."))
        if not result:
            raise BadArgument(_("The provided tokens are not in a valid format."))
        return result


class DictConverter(dpy_commands.Converter):
    """
    Converts pairs of space seperated values to a dict
    """

    def __init__(self, *expected_keys: str, delims: Optional[List[str]] = None):
        self.expected_keys = expected_keys
        self.delims = delims or [" "]
        self.pattern = re.compile(r"|".join(re.escape(d) for d in self.delims))

    async def convert(self, ctx: "Context", argument: str) -> Dict[str, str]:

        ret: Dict[str, str] = {}
        args = self.pattern.split(argument)

        if len(args) % 2 != 0:
            raise BadArgument()

        iterator = iter(args)

        for key in iterator:
            if self.expected_keys and key not in self.expected_keys:
                raise BadArgument(_("Unexpected key {key}").format(key=key))

            ret[key] = next(iterator)

        return ret


def get_dict_converter(*expected_keys: str, delims: Optional[List[str]] = None) -> type:
    """
    Returns a typechecking safe `DictConverter` suitable for use with discord.py
    """

    class PartialMeta(type(DictConverter)):
        __call__ = functools.partialmethod(
            type(DictConverter).__call__, *expected_keys, delims=delims
        )

    class ValidatedConverter(DictConverter, metaclass=PartialMeta):
        pass

    return ValidatedConverter


class TimedeltaConverter(dpy_commands.Converter):
    """
    This is a converter for timedeltas.
    The units should be in order from largest to smallest.
    This works with or without whitespace.

    See `parse_timedelta` for more information about how this functions.

    Attributes
    ----------
    maximum : Optional[timedelta]
        If provided, any parsed value higher than this will raise an exception
    minimum : Optional[timedelta]
        If provided, any parsed value lower than this will raise an exception
    allowed_units : Optional[List[str]]
        If provided, you can constrain a user to expressing the amount of time
        in specific units. The units you can chose to provide are the same as the
        parser understands: `weeks` `days` `hours` `minutes` `seconds`
    default_unit : Optional[str]
        If provided, it will additionally try to match integer-only input into
        a timedelta, using the unit specified. Same units as in `allowed_units`
        apply.
    """

    def __init__(self, *, minimum=None, maximum=None, allowed_units=None, default_unit=None):
        self.allowed_units = allowed_units
        self.default_unit = default_unit
        self.minimum = minimum
        self.maximum = maximum

    async def convert(self, ctx: "Context", argument: str) -> timedelta:
        if self.default_unit and argument.isdecimal():
            delta = timedelta(**{self.default_unit: int(argument)})
        else:
            delta = parse_timedelta(
                argument,
                minimum=self.minimum,
                maximum=self.maximum,
                allowed_units=self.allowed_units,
            )
        if delta is not None:
            return delta
        raise BadArgument()  # This allows this to be a required argument.


def get_timedelta_converter(
    *,
    default_unit: Optional[str] = None,
    maximum: Optional[timedelta] = None,
    minimum: Optional[timedelta] = None,
    allowed_units: Optional[List[str]] = None,
) -> type:
    """
    This creates a type suitable for typechecking which works with discord.py's
    commands.
    
    See `parse_timedelta` for more information about how this functions.

    Parameters
    ----------
    maximum : Optional[timedelta]
        If provided, any parsed value higher than this will raise an exception
    minimum : Optional[timedelta]
        If provided, any parsed value lower than this will raise an exception
    allowed_units : Optional[List[str]]
        If provided, you can constrain a user to expressing the amount of time
        in specific units. The units you can chose to provide are the same as the
        parser understands: `weeks` `days` `hours` `minutes` `seconds`
    default_unit : Optional[str]
        If provided, it will additionally try to match integer-only input into
        a timedelta, using the unit specified. Same units as in `allowed_units`
        apply.

    Returns
    -------
    type
        The converter class, which will be a subclass of `TimedeltaConverter`
    """

    class PartialMeta(type(TimedeltaConverter)):
        __call__ = functools.partialmethod(
            type(DictConverter).__call__,
            allowed_units=allowed_units,
            default_unit=default_unit,
            minimum=minimum,
            maximum=maximum,
        )

    class ValidatedConverter(TimedeltaConverter, metaclass=PartialMeta):
        pass

    return ValidatedConverter