
"""Time humanizing functions.

These are largely borrowed from Django's `contrib.humanize`.
"""

import datetime as dt
import math
from enum import Enum
from functools import total_ordering

from .i18n import gettext as _
from .i18n import ngettext

__all__ = [
    "naturaldelta",
    "naturaltime",
    "naturalday",
    "naturaldate",
    "precisedelta",
]


@total_ordering
class Unit(Enum):
    MICROSECONDS = 0
    MILLISECONDS = 1
    SECONDS = 2
    MINUTES = 3
    HOURS = 4
    DAYS = 5
    MONTHS = 6
    YEARS = 7

    def __lt__(self, other):
        if self.__class__ is other.__class__:
            return self.value < other.value
        return NotImplemented


def _now():
    return dt.datetime.now()


def abs_timedelta(delta):
    """Return an "absolute" value for a timedelta, always representing a time distance.

    Args:
        delta (datetime.timedelta): Input timedelta.

    Returns:
        datetime.timedelta: Absolute timedelta.
    """
    if delta.days < 0:
        now = _now()
        return now - (now + delta)
    return delta


def date_and_delta(value, *, now=None):
    """Turn a value into a date and a timedelta which represents how long ago it was.

    If that's not possible, return `(None, value)`.
    """
    if not now:
        now = _now()
    if isinstance(value, dt.datetime):
        date = value
        delta = now - value
    elif isinstance(value, dt.timedelta):
        date = now - value
        delta = value
    else:
        try:
            value = int(value)
            delta = dt.timedelta(seconds=value)
            date = now - delta
        except (ValueError, TypeError):
            return None, value
    return date, abs_timedelta(delta)


def naturaldelta(
    value,
    months=True,
    minimum_unit="seconds",
    when=None,
) -> str:
    """Return a natural representation of a timedelta or number of seconds.

    This is similar to `naturaltime`, but does not add tense to the result.

    Args:
        value (datetime.timedelta): A timedelta or a number of seconds.
        months (bool): If `True`, then a number of months (based on 30.5 days) will be
            used for fuzziness between years.
        minimum_unit (str): The lowest unit that can be used.
        when (datetime.datetime): Point in time relative to which _value_ is
            interpreted.  Defaults to the current time in the local timezone.

    Returns:
        str: A natural representation of the amount of time elapsed.

    Examples
        Compare two timestamps in a custom local timezone::

        import datetime as dt
        from dateutil.tz import gettz

        berlin = gettz("Europe/Berlin")
        now = dt.datetime.now(tz=berlin)
        later = now + dt.timedelta(minutes=30)

        assert naturaldelta(later, when=now) == "30 minutes"
    """
    tmp = Unit[minimum_unit.upper()]
    if tmp not in (Unit.SECONDS, Unit.MILLISECONDS, Unit.MICROSECONDS):
        raise ValueError(f"Minimum unit '{minimum_unit}' not supported")
    minimum_unit = tmp

    date, delta = date_and_delta(value, now=when)
    if date is None:
        return value

    use_months = months

    seconds = abs(delta.seconds)
    days = abs(delta.days)
    years = days // 365
    days = days % 365
    months = int(days // 30.5)

    if not years and days < 1:
        if seconds == 0:
            if minimum_unit == Unit.MICROSECONDS and delta.microseconds < 1000:
                return (
                    ngettext("%d microsecond", "%d microseconds", delta.microseconds)
                    % delta.microseconds
                )
            elif minimum_unit == Unit.MILLISECONDS or (
                minimum_unit == Unit.MICROSECONDS
                and 1000 <= delta.microseconds < 1_000_000
            ):
                milliseconds = delta.microseconds / 1000
                return (
                    ngettext("%d millisecond", "%d milliseconds", milliseconds)
                    % milliseconds
                )
            return _("a moment")
        elif seconds == 1:
            return _("a second")
        elif seconds < 60:
            return ngettext("%d second", "%d seconds", seconds) % seconds
        elif 60 <= seconds < 120:
            return _("a minute")
        elif 120 <= seconds < 3600:
            minutes = seconds // 60
            return ngettext("%d minute", "%d minutes", minutes) % minutes
        elif 3600 <= seconds < 3600 * 2:
            return _("an hour")
        elif 3600 < seconds:
            hours = seconds // 3600
            return ngettext("%d hour", "%d hours", hours) % hours
    elif years == 0:
        if days == 1:
            return _("a day")
        if not use_months:
            return ngettext("%d day", "%d days", days) % days
        else:
            if not months:
                return ngettext("%d day", "%d days", days) % days
            elif months == 1:
                return _("a month")
            else:
                return ngettext("%d month", "%d months", months) % months
    elif years == 1:
        if not months and not days:
            return _("a year")
        elif not months:
            return ngettext("1 year, %d day", "1 year, %d days", days) % days
        elif use_months:
            if months == 1:
                return _("1 year, 1 month")
            else:
                return (
                    ngettext("1 year, %d month", "1 year, %d months", months) % months
                )
        else:
            return ngettext("1 year, %d day", "1 year, %d days", days) % days
    else:
        return ngettext("%d year", "%d years", years) % years


def naturaltime(
    value,
    future=False,
    months=True,
    minimum_unit="seconds",
    when=None,
) -> str:
    """Return a natural representation of a time in a resolution that makes sense.

    This is more or less compatible with Django's `naturaltime` filter.

    Args:
        value (datetime.datetime, int): A `datetime` or a number of seconds.
        future (bool): Ignored for `datetime`s, where the tense is always figured out
            based on the current time. For integers, the return value will be past tense
            by default, unless future is `True`.
        months (bool): If `True`, then a number of months (based on 30.5 days) will be
            used for fuzziness between years.
        minimum_unit (str): The lowest unit that can be used.
        when (datetime.datetime): Point in time relative to which _value_ is
            interpreted.  Defaults to the current time in the local timezone.

    Returns:
        str: A natural representation of the input in a resolution that makes sense.
    """
    now = when or _now()
    date, delta = date_and_delta(value, now=now)
    if date is None:
        return value
    # determine tense by value only if datetime/timedelta were passed
    if isinstance(value, (dt.datetime, dt.timedelta)):
        future = date > now

    ago = _("%s from now") if future else _("%s ago")
    delta = naturaldelta(delta, months, minimum_unit, when=when)

    if delta == _("a moment"):
        return _("now")

    return ago % delta


def naturalday(value, format="%b %d") -> str:
    """Return a natural day.

    For date values that are tomorrow, today or yesterday compared to
    present day return representing string. Otherwise, return a string
    formatted according to `format`.

    """
    try:
        value = dt.date(value.year, value.month, value.day)
    except AttributeError:
        # Passed value wasn't date-ish
        return value
    except (OverflowError, ValueError):
        # Date arguments out of range
        return value
    delta = value - dt.date.today()
    if delta.days == 0:
        return _("today")
    elif delta.days == 1:
        return _("tomorrow")
    elif delta.days == -1:
        return _("yesterday")
    return value.strftime(format)


def naturaldate(value) -> str:
    """Like `naturalday`, but append a year for dates more than ~five months away."""
    try:
        value = dt.date(value.year, value.month, value.day)
    except AttributeError:
        # Passed value wasn't date-ish
        return value
    except (OverflowError, ValueError):
        # Date arguments out of range
        return value
    delta = abs_timedelta(value - dt.date.today())
    if delta.days >= 5 * 365 / 12:
        return naturalday(value, "%b %d %Y")
    return naturalday(value)


def _quotient_and_remainder(value, divisor, unit, minimum_unit, suppress):
    """Divide `value` by `divisor` returning the quotient and remainder.

    If `unit` is `minimum_unit`, makes the quotient a float number and the remainder
    will be zero. The rational is that if `unit` is the unit of the quotient, we cannot
    represent the remainder because it would require a unit smaller than the
    `minimum_unit`.

    >>> from humanize.time import _quotient_and_remainder, Unit
    >>> _quotient_and_remainder(36, 24, Unit.DAYS, Unit.DAYS, [])
    (1.5, 0)

    If unit is in `suppress`, the quotient will be zero and the remainder will be the
    initial value. The idea is that if we cannot use `unit`, we are forced to use a
    lower unit so we cannot do the division.

    >>> _quotient_and_remainder(36, 24, Unit.DAYS, Unit.HOURS, [Unit.DAYS])
    (0, 36)

    In other case return quotient and remainder as `divmod` would do it.

    >>> _quotient_and_remainder(36, 24, Unit.DAYS, Unit.HOURS, [])
    (1, 12)

    """
    if unit == minimum_unit:
        return (value / divisor, 0)
    elif unit in suppress:
        return (0, value)
    else:
        return divmod(value, divisor)


def _carry(value1, value2, ratio, unit, min_unit, suppress):
    """Return a tuple with two values.

    If the unit is in `suppress`, multiply `value1` by `ratio` and add it to `value2`
    (carry to right). The idea is that if we cannot represent `value1` we need to
    represent it in a lower unit.

    >>> from humanize.time import _carry, Unit
    >>> _carry(2, 6, 24, Unit.DAYS, Unit.SECONDS, [Unit.DAYS])
    (0, 54)

    If the unit is the minimum unit, `value2` is divided by `ratio` and added to
    `value1` (carry to left). We assume that `value2` has a lower unit so we need to
    carry it to `value1`.

    >>> _carry(2, 6, 24, Unit.DAYS, Unit.DAYS, [])
    (2.25, 0)

    Otherwise, just return the same input:

    >>> _carry(2, 6, 24, Unit.DAYS, Unit.SECONDS, [])
    (2, 6)
    """
    if unit == min_unit:
        return (value1 + value2 / ratio, 0)
    elif unit in suppress:
        return (0, value2 + value1 * ratio)
    else:
        return (value1, value2)


def _suitable_minimum_unit(min_unit, suppress):
    """Return a minimum unit suitable that is not suppressed.

    If not suppressed, return the same unit:

    >>> from humanize.time import _suitable_minimum_unit, Unit
    >>> _suitable_minimum_unit(Unit.HOURS, []).name
    'HOURS'

    But if suppressed, find a unit greather than the original one that is not
    suppressed:

    >>> _suitable_minimum_unit(Unit.HOURS, [Unit.HOURS]).name
    'DAYS'

    >>> _suitable_minimum_unit(Unit.HOURS, [Unit.HOURS, Unit.DAYS]).name
    'MONTHS'
    """
    if min_unit in suppress:
        for unit in Unit:
            if unit > min_unit and unit not in suppress:
                return unit

        raise ValueError(
            "Minimum unit is suppressed and no suitable replacement was found"
        )

    return min_unit


def _suppress_lower_units(min_unit, suppress):
    """Extend suppressed units (if any) with all units lower than the minimum unit.

    >>> from humanize.time import _suppress_lower_units, Unit
    >>> [x.name for x in sorted(_suppress_lower_units(Unit.SECONDS, [Unit.DAYS]))]
    ['MICROSECONDS', 'MILLISECONDS', 'DAYS']
    """
    suppress = set(suppress)
    for u in Unit:
        if u == min_unit:
            break
        suppress.add(u)

    return suppress


def precisedelta(value, minimum_unit="seconds", suppress=(), format="%0.2f") -> str:
    """Return a precise representation of a timedelta.

    ```pycon
    >>> import datetime as dt
    >>> from humanize.time import precisedelta

    >>> delta = dt.timedelta(seconds=3633, days=2, microseconds=123000)
    >>> precisedelta(delta)
    '2 days, 1 hour and 33.12 seconds'

    ```

    A custom `format` can be specified to control how the fractional part
    is represented:

    ```pycon
    >>> precisedelta(delta, format="%0.4f")
    '2 days, 1 hour and 33.1230 seconds'

    ```

    Instead, the `minimum_unit` can be changed to have a better resolution;
    the function will still readjust the unit to use the greatest of the
    units that does not lose precision.

    For example setting microseconds but still representing the date with milliseconds:

    ```pycon
    >>> precisedelta(delta, minimum_unit="microseconds")
    '2 days, 1 hour, 33 seconds and 123 milliseconds'

    ```

    If desired, some units can be suppressed: you will not see them represented and the
    time of the other units will be adjusted to keep representing the same timedelta:

    ```pycon
    >>> precisedelta(delta, suppress=['days'])
    '49 hours and 33.12 seconds'

    ```

    Note that microseconds precision is lost if the seconds and all
    the units below are suppressed:

    ```pycon
    >>> delta = dt.timedelta(seconds=90, microseconds=100)
    >>> precisedelta(delta, suppress=['seconds', 'milliseconds', 'microseconds'])
    '1.50 minutes'

    ```

    If the delta is too small to be represented with the minimum unit,
    a value of zero will be returned:

    ```pycon
    >>> delta = dt.timedelta(seconds=1)
    >>> precisedelta(delta, minimum_unit="minutes")
    '0.02 minutes'

    >>> delta = dt.timedelta(seconds=0.1)
    >>> precisedelta(delta, minimum_unit="minutes")
    '0 minutes'

    ```
    """
    date, delta = date_and_delta(value)
    if date is None:
        return value

    suppress = [Unit[s.upper()] for s in suppress]

    # Find a suitable minimum unit (it can be greater the one that the
    # user gave us if it is suppressed).
    min_unit = Unit[minimum_unit.upper()]
    min_unit = _suitable_minimum_unit(min_unit, suppress)
    del minimum_unit

    # Expand the suppressed units list/set to include all the units
    # that are below the minimum unit
    suppress = _suppress_lower_units(min_unit, suppress)

    # handy aliases
    days = delta.days
    secs = delta.seconds
    usecs = delta.microseconds

    MICROSECONDS, MILLISECONDS, SECONDS, MINUTES, HOURS, DAYS, MONTHS, YEARS = list(
        Unit
    )

    # Given DAYS compute YEARS and the remainder of DAYS as follows:
    #   if YEARS is the minimum unit, we cannot use DAYS so
    #   we will use a float for YEARS and 0 for DAYS:
    #       years, days = years/days, 0
    #
    #   if YEARS is suppressed, use DAYS:
    #       years, days = 0, days
    #
    #   otherwise:
    #       years, days = divmod(years, days)
    #
    # The same applies for months, hours, minutes and milliseconds below
    years, days = _quotient_and_remainder(days, 365, YEARS, min_unit, suppress)
    months, days = _quotient_and_remainder(days, 30.5, MONTHS, min_unit, suppress)

    # If DAYS is not in suppress, we can represent the days but
    # if it is a suppressed unit, we need to carry it to a lower unit,
    # seconds in this case.
    #
    # The same applies for secs and usecs below
    days, secs = _carry(days, secs, 24 * 3600, DAYS, min_unit, suppress)

    hours, secs = _quotient_and_remainder(secs, 3600, HOURS, min_unit, suppress)
    minutes, secs = _quotient_and_remainder(secs, 60, MINUTES, min_unit, suppress)

    secs, usecs = _carry(secs, usecs, 1e6, SECONDS, min_unit, suppress)

    msecs, usecs = _quotient_and_remainder(
        usecs, 1000, MILLISECONDS, min_unit, suppress
    )

    # if _unused != 0 we had lost some precision
    usecs, _unused = _carry(usecs, 0, 1, MICROSECONDS, min_unit, suppress)

    fmts = [
        ("%d year", "%d years", years),
        ("%d month", "%d months", months),
        ("%d day", "%d days", days),
        ("%d hour", "%d hours", hours),
        ("%d minute", "%d minutes", minutes),
        ("%d second", "%d seconds", secs),
        ("%d millisecond", "%d milliseconds", msecs),
        ("%d microsecond", "%d microseconds", usecs),
    ]

    texts = []
    for unit, fmt in zip(reversed(Unit), fmts):
        singular_txt, plural_txt, value = fmt
        if value > 0 or (not texts and unit == min_unit):
            fmt_txt = ngettext(singular_txt, plural_txt, value)
            if unit == min_unit and math.modf(value)[0] > 0:
                fmt_txt = fmt_txt.replace("%d", format)

            texts.append(fmt_txt % value)

        if unit == min_unit:
            break

    if len(texts) == 1:
        return texts[0]

    head = ", ".join(texts[:-1])
    tail = texts[-1]

    return _("%s and %s") % (head, tail)
