"""
Where the magic happens.
"""

import calendar
from datetime import datetime, timedelta
import pytz

from .utils import _iteritems


# ----------------------------------------------------------------------------
# Utilities
# ----------------------------------------------------------------------------

def add_month(date, number):
    """Add a number of months to a date."""
    return month_delta(date, number)


def subtract_month(date, number):
    """Subtract a number of months from a date."""
    negative_month = number * -1
    return month_delta(date, negative_month)


def month_delta(date, delta):
    """
    Create a new date with a modified number of months.

    https://stackoverflow.com/a/22443132/485216
    """
    month = (date.month + delta) % 12
    year = date.year + ((date.month) + delta - 1) // 12
    if not month:
        month = 12
    day = min(date.day, [
            31,
            29 if year % 4 == 0 and (not year % 100 == 0 or year % 400 == 0) else 28,
            31, 30, 31, 30, 31, 31, 30, 31, 30, 31
        ][month - 1]
    )
    return date.replace(day=day, month=month, year=year)


# ----------------------------------------------------------------------------
# Main functionality
# ----------------------------------------------------------------------------

class MutableDate(object):
    """Incapsulate mutable dates in one class."""

    def __init__(self, date):
        self._date = date

    def add(self, key=None, amount=None, **kwds):
        """Add time to the original moment."""
        if not key and not amount and len(kwds):
            for k, v in _iteritems(kwds):
                self.add(k, v)
        if key == 'years' or key == 'year':
            self._date = add_month(self._date, amount * 12)
        elif key == 'months' or key == 'month':
            self._date = add_month(self._date, amount)
        elif key == 'weeks' or key == 'week':
            self._date += timedelta(weeks=amount)
        elif key == 'days' or key == 'day':
            self._date += timedelta(days=amount)
        elif key == 'hours' or key == 'hour':
            self._date += timedelta(hours=amount)
        elif key == 'minutes' or key == 'minute':
            self._date += timedelta(minutes=amount)
        elif key == 'seconds' or key == 'second':
            self._date += timedelta(seconds=amount)
        elif key == 'milliseconds' or key == 'millisecond':
            self._date += timedelta(milliseconds=amount)
        elif key == 'microseconds' or key == 'microsecond':
            self._date += timedelta(microseconds=amount)
        return self

    def sub(self, key=None, amount=None, **kwds):
        """Just in case."""
        return self.subtract(key, amount, **kwds)

    def subtract(self, key=None, amount=None, **kwds):
        """Subtract time from the original moment."""
        if not key and not amount and len(kwds):
            for k, v in _iteritems(kwds):
                self.subtract(k, v)
        if key == 'years' or key == 'year':
            self._date = subtract_month(self._date, amount * 12)
        elif key == 'months' or key == 'month':
            self._date = subtract_month(self._date, amount)
        elif key == 'weeks' or key == 'week':
            self._date -= timedelta(weeks=amount)
        elif key == 'days' or key == 'day':
            self._date -= timedelta(days=amount)
        elif key == 'hours' or key == 'hour':
            self._date -= timedelta(hours=amount)
        elif key == 'minutes' or key == 'minute':
            self._date -= timedelta(minutes=amount)
        elif key == 'seconds' or key == 'second':
            self._date -= timedelta(seconds=amount)
        elif key == 'milliseconds' or key == 'millisecond':
            self._date -= timedelta(milliseconds=amount)
        elif key == 'microseconds' or key == 'microsecond':
            self._date -= timedelta(microseconds=amount)
        return self

    def replace(self, **kwds):
        """A Pythonic way to replace various date attributes."""
        for key, value in _iteritems(kwds):
            if key == 'years' or key == 'year':
                self._date = self._date.replace(year=value)
            elif key == 'months' or key == 'month':
                self._date = self._date.replace(month=value)
            elif key == 'days' or key == 'day':
                self._date = self._date.replace(day=value)
            elif key == 'hours' or key == 'hour':
                self._date = self._date.replace(hour=value)
            elif key == 'minutes' or key == 'minute':
                self._date = self._date.replace(minute=value)
            elif key == 'seconds' or key == 'second':
                self._date = self._date.replace(second=value)
            elif key == 'microseconds' or key == 'microsecond':
                self._date = self._date.replace(microsecond=value)
            elif key == 'weekday':
                self._weekday(value)
        return self

    def epoch(self, rounding=True, milliseconds=False):
        """Milliseconds since epoch."""
        zero = datetime.utcfromtimestamp(0)
        try:
            delta = self._date - zero
        except TypeError:
            zero = zero.replace(tzinfo=pytz.utc)
            delta = self._date - zero
        seconds = delta.total_seconds()
        if rounding:
            seconds = round(seconds)
        if milliseconds:
            seconds *= 1000
        return int(seconds)

    def _weekday(self, number):
        """Mutate the original moment by changing the day of the week."""
        weekday = self._date.isoweekday()
        if number < 0:
            days = abs(weekday - number)
        else:
            days = weekday - number
        delta = self._date - timedelta(days)
        self._date = delta
        return self

    def isoformat(self):
        """Return the date's ISO 8601 string."""
        return self._date.isoformat()

    @property
    def zero(self):
        """Get rid of hour, minute, second, and microsecond information."""
        self.replace(hours=0, minutes=0, seconds=0, microseconds=0)
        return self

    @property
    def datetime(self):
        """Return the mutable date's inner datetime format."""
        return self._date

    @property
    def date(self):
        """Access the internal datetime variable."""
        return self._date

    @property
    def year(self):
        return self._date.year

    @property
    def month(self):
        return self._date.month

    @property
    def day(self):
        return self._date.day

    @property
    def weekday(self):
        return self._date.isoweekday()

    @property
    def hour(self):
        return self._date.hour

    @property
    def hours(self):
        return self._date.hour

    @property
    def minute(self):
        return self._date.minute

    @property
    def minutes(self):
        return self._date.minute

    @property
    def second(self):
        return self._date.second

    @property
    def seconds(self):
        return self._date.second

    @property
    def microsecond(self):
        return self._date.microsecond

    @property
    def microseconds(self):
        return self._date.microsecond

    @property
    def tzinfo(self):
        return self._date.tzinfo

    def __sub__(self, other):
        if isinstance(other, datetime):
            return self._date - other
        elif isinstance(other, type(self)):
            return self._date - other.date

    def __rsub__(self, other):
        return self.__sub__(other)

    def __lt__(self, other):
        if isinstance(other, datetime):
            return self._date < other
        elif isinstance(other, type(self)):
            return self._date < other.date

    def __le__(self, other):
        if isinstance(other, datetime):
            return self._date <= other
        elif isinstance(other, type(self)):
            return self._date <= other.date

    def __eq__(self, other):
        if isinstance(other, datetime):
            return self._date == other
        elif isinstance(other, type(self)):
            return self._date == other.date

    def __ne__(self, other):
        if isinstance(other, datetime):
            return self._date != other
        elif isinstance(other, type(self)):
            return self._date != other.date

    def __gt__(self, other):
        if isinstance(other, datetime):
            return self._date > other
        elif isinstance(other, type(self)):
            return self._date > other.date

    def __ge__(self, other):
        if isinstance(other, datetime):
            return self._date >= other
        elif isinstance(other, type(self)):
            return self._date >= other.date