from flask_babelex import lazy_gettext as _
from flask_wtf import FlaskForm
import pytz
from wtforms import BooleanField, PasswordField, SelectField, StringField
from wtforms.ext.dateutil.fields import DateTimeField
from wtforms.validators import DataRequired, Email, ValidationError
from wtforms.widgets import TextArea


class RegistrationForm(FlaskForm):
    username = StringField(_('Username'), validators=[DataRequired()])
    email = StringField(_('Email address'), validators=[Email()])
    password = PasswordField(_('Password'), validators=[DataRequired()])
    password_retype = PasswordField(_('Password, once more'), validators=[DataRequired()])

    def validate_password_retype(self, field):
        if field.data != self.password.data:
            raise ValidationError(_('The two passwords must match!'))


class TimezoneField(SelectField):
    def __init__(self, *args, **kwargs):
        kwargs.update({
            'choices': [
                (pytz.timezone(tz), tz.replace('_', ' '))
                for tz in pytz.common_timezones
            ],
        })

        SelectField.__init__(self, *args, **kwargs)

    def process_formdata(self, valuelist):
        if not valuelist:
            self.data = None

            return

        try:
            self.data = pytz.timezone(valuelist[0])
        except pytz.exceptions.UnknownTimeZoneError:
            self.data = None

            raise ValueError('Unknown time zone')

    @staticmethod
    def is_pytz_instance(value):
        return value is pytz.UTC or isinstance(value, pytz.tzinfo.BaseTzInfo)

    def process_data(self, value):
        if value is None:
            self.data = None

            return

        if self.is_pytz_instance(value):
            self.data = value

            return

        try:
            self.data = pytz.timezone(value)
        except Exception as exc:
            raise ValueError(f'Unknown time zone {value}')

    def iter_choices(self):
        for value, label in self.choices:
            yield (value, label, value == self.data)


class EventForm(FlaskForm):
    title = StringField(_('Title'), validators=[DataRequired()])
    time_zone = TimezoneField(_('Time zone'), validators=[DataRequired()])
    start_time = DateTimeField(_('Start time'), validators=[DataRequired()])
    end_time = DateTimeField(_('End time'), validators=[DataRequired()])
    all_day = BooleanField(_('All day'))
    description = StringField(_('Description'), widget=TextArea())

    def populate_obj(self, obj):
        FlaskForm.populate_obj(self, obj)

        timezone = self.time_zone.data

        obj.time_zone = str(timezone)
        obj.start_time = timezone.localize(self.start_time.data).astimezone(pytz.utc)
        obj.end_time = timezone.localize(self.end_time.data).astimezone(pytz.utc)

    def validate_end_time(self, field):
        if field.data < self.start_time.data:
            raise ValidationError(_('End time must be later than start time!'))