# Calendar.social
# Copyright (C) 2018 Gergely Polonkai
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

"""Forms for Calendar.social
"""

from flask_babelex import lazy_gettext as _
from flask_security.forms import LoginForm as BaseLoginForm
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, StopValidation, ValidationError
from wtforms.widgets import TextArea


class UsernameAvailable(object):  # pylint: disable=too-few-public-methods
    """Checks if a username is available
    """

    def __init__(self, message=None):
        self.message = message

    def __call__(self, form, field):
        from sqlalchemy.orm.exc import NoResultFound

        from calsocial.models import User

        # If there is no data, we don’t raise an error; it’s not the task of this validator to
        # check the validity of the username
        if not field.data:
            return

        try:
            User.query.filter(User.username == field.data).one()
        except NoResultFound:
            return

        if self.message is None:
            message = field.gettext('This username is not available')
        else:
            message = self.message

        field.errors[:] = []
        raise StopValidation(message)


class EmailAvailable(object):  # pylint: disable=too-few-public-methods
    """Checks if an email address is available
    """

    def __init__(self, message=None):
        self.message = message

    def __call__(self, form, field):
        from sqlalchemy.orm.exc import NoResultFound

        from calsocial.models import User

        # If there is no data, we don’t raise an error; it’s not the task of this validator to
        # check the validity of the username
        if not field.data:
            return

        try:
            User.query.filter(User.email == field.data).one()
        except NoResultFound:
            return

        if self.message is None:
            message = field.gettext('This email address can not be used')
        else:
            message = self.message

        field.errors[:] = []
        raise StopValidation(message)


class RegistrationForm(FlaskForm):
    """Registration form
    """

    username = StringField(_('Username'), validators=[DataRequired(), UsernameAvailable()])
    email = StringField(_('Email address'), validators=[Email(), EmailAvailable()])
    password = PasswordField(_('Password'), validators=[DataRequired()])
    password_retype = PasswordField(_('Password, once more'), validators=[DataRequired()])

    def validate_password_retype(self, field):
        """Validate the ``password_retype`` field

        Its value must match the ``password`` field’s.
        """

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


class TimezoneField(SelectField):
    """Field for selecting a time zone

    Note: this field overrides whatever is passed to the ``choices`` parameter, and fills
    ``choices`` with the common timezones of pytz.  In every other aspects, it behaves exactly
    like `SelectField`.
    """

    def __init__(self, *args, **kwargs):
        self.data = None

        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):
        """Check if ``value`` is a valid pytz time zone instance
        """

        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 pytz.exceptions.UnknownTimeZoneError:
            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):
    """Form for event creation/editing
    """

    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):
        """Populate ``obj`` with event data
        """

        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):
        """Validate the ``end_time`` field

        Its value must be later than the value of the ``start_time`` field.
        """

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


class SettingsForm(FlaskForm):
    """Form for user settings
    """

    timezone = TimezoneField(_('Time zone'), validators=[DataRequired()])

    def __init__(self, user, *args, **kwargs):
        self.user = user

        kwargs.setdefault('timezone', user.timezone)

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

    def populate_obj(self, user):
        """Populate ``obj`` with event data
        """

        for name, field in self._fields.items():
            if not (hasattr(self.__class__, name) and not hasattr(FlaskForm, name)):
                continue

            user.settings[name] = str(field.data)


class LoginForm(BaseLoginForm):
    """Login form for Calendar.social
    """

    email = StringField(_('Username or email'), validators=[DataRequired()])

    def __init__(self, *args, **kwargs):
        super(LoginForm, self).__init__(*args, **kwargs)

        self.user = None

    def validate(self):
        from flask_security.utils import _datastore
        from flask_security.utils import verify_and_update_password

        from .models import AuditLog

        ret = super(LoginForm, self).validate()

        if self.user is None:
            self.user = _datastore.get_user(self.email.data)

            if self.user is None:
                # We can’t figure out the user that’s trying to log in, just return
                return ret

        if not verify_and_update_password(self.password.data, self.user):
            AuditLog.log(self.user, AuditLog.TYPE_LOGIN_FAIL)

        return ret


class ProfileField(StringField):
    """Input field for profiles
    """

    def process_formdata(self, valuelist):
        from sqlalchemy.orm.exc import NoResultFound

        from .models import User, Profile

        if not valuelist:
            self.data = None

            return

        value = valuelist[0]

        if value.startswith('@'):
            value = value[1:]

        try:
            self.data = Profile.query.join(User).filter(User.username == value).one()
        except NoResultFound:
            self.data = None

            raise ValueError('Unknown user')

    def _value(self):
        if self.data:
            return self.data.fqn

        return ''


class InviteForm(FlaskForm):
    """Form for event invitations
    """

    invitee = ProfileField(validators=[DataRequired()])

    def __init__(self, event, *args, **kwargs):
        FlaskForm.__init__(self, *args, **kwargs)

        self.event = event

    def validate_invitee(self, field):
        """Validate the value of the invitee field

        :raises ValidationError: If the given user is already invited
        """

        from sqlalchemy.orm.exc import NoResultFound

        from .models import Invitation

        try:
            Invitation.query \
                      .filter(Invitation.event == self.event) \
                      .filter(Invitation.invitee == field.data) \
                      .one()

            raise ValidationError(_('User is already invited'))
        except NoResultFound:
            pass