# 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/>.

"""Database models for Calendar.social
"""

from datetime import datetime
from warnings import warn

from flask_security import UserMixin, RoleMixin
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.orm.exc import NoResultFound

db = SQLAlchemy()
users_roles = db.Table(
    'users_roles',
    db.Column('user_id', db.Integer(), db.ForeignKey('users.id')),
    db.Column('role_id', db.Integer(), db.ForeignKey('roles.id')))


class SettingsProxy:
    """Proxy object to get settings for a user
    """

    def __init__(self, user):
        self.user = user

    def __getitem__(self, key):
        setting = UserSetting.query \
                             .filter(UserSetting.user == self.user) \
                             .filter(UserSetting.key == key) \
                             .first()

        if setting is None:
            return None

        return setting.value

    def __setitem__(self, key, value):
        try:
            setting = UserSetting.query \
                                 .filter(UserSetting.user == self.user) \
                                 .filter(UserSetting.key == key) \
                                 .one()
        except NoResultFound:
            setting = UserSetting(user=self.user, key=key)

        setting.value = str(value)
        db.session.add(setting)

    def __repr__(self):
        return f'<SettingsProxy for {self.user}>'


class User(db.Model, UserMixin):
    """Database model for users
    """

    __tablename__ = 'users'
    id = db.Column(db.Integer(), primary_key=True)

    #: The username of the user.  This is also the display name and thus is immutable
    username = db.Column(db.String(length=50), unique=True, nullable=False)

    #: The email address of the user
    email = db.Column(db.String(length=255), unique=True, nullable=True)

    #: The (hashed) password of the user
    password = db.Column(db.String(length=255))

    #: A flag to show whether the user is enabled (active) or not
    active = db.Column(db.Boolean(), default=False)

    #: The timestamp when this user was created
    created_at = db.Column(db.DateTime(), default=datetime.utcnow)

    #: The timestamp when the user was activated
    confirmed_at = db.Column(db.DateTime())

    #: The roles of the user
    roles = db.relationship('Role',
                            secondary=users_roles,
                            backref=db.backref('users', lazy='dynamic'))

    @property
    def settings(self):
        """Get a settings proxy for the user
        """

        proxy = getattr(self, '_settings', None)

        if proxy is None:
            proxy = SettingsProxy(self)
            setattr(self, '_settings', proxy)

        return proxy

    @property
    def timezone(self):
        from flask import current_app
        from pytz import timezone, UTC
        from pytz.exceptions import UnknownTimeZoneError

        timezone_str = self.settings['timezone']

        if not timezone_str:
            timezone_str = current_app.settings.get('DEFAULT_TIMEZONE', 'UTC')

        try:
            return timezone(timezone_str)
        except pytz.exceptions.UnknownTimeZoneError:
            warn(f'Timezone of {user} (or the default timezone) "{timezone_str}" is invalid')
            return UTC

    def __repr__(self):
        return f'<User {self.id}({self.username})>'


class Role(db.Model, RoleMixin):
    """Database model for roles
    """

    __tablename__ = 'roles'
    id = db.Column(db.Integer(), primary_key=True)

    #: The name of the role
    name = db.Column(db.Unicode(length=80), unique=True)

    #: A description of the role
    description = db.Column(db.UnicodeText)

    def __repr__(self):
        return f'<Role {self.id}({self.name})>'


class Event(db.Model):
    """Database model for events
    """

    __tablename__ = 'events'
    id = db.Column(db.Integer(), primary_key=True)

    #: The ID of the user who created the event
    user_id = db.Column(db.Integer(), db.ForeignKey('users.id'), nullable=False)

    user = db.relationship('User', backref=db.backref('events', lazy='dynamic'))

    #: The title of the event
    title = db.Column(db.Unicode(length=200), nullable=False)

    #: The time zone to be used for `start_time` and `end_time`
    time_zone = db.Column(db.String(length=80), nullable=False)

    #: The starting timestamp of the event.  It is in the UTC time zone
    start_time = db.Column(db.DateTime(), nullable=False)

    #: The ending timestamp of the event.  It is in the UTC time zone
    end_time = db.Column(db.DateTime(), nullable=False)

    #: If `True`, the event is a whole-day event
    all_day = db.Column(db.Boolean(), default=False)

    #: The description of the event
    description = db.Column(db.UnicodeText())

    def __as_tz(self, timestamp, as_timezone=None):
        from pytz import timezone, UTC

        utc_timestamp = UTC.localize(timestamp)

        return utc_timestamp.astimezone(as_timezone or timezone(self.time_zone))

    @property
    def start_time_tz(self):
        """The same timestamp as `start_time`, but in the time zone specified by `time_zone`.
        """

        return self.__as_tz(self.start_time)

    @property
    def end_time_tz(self):
        """The same timestamp as `end_time`, but in the time zone specified by `time_zone`.
        """

        return self.__as_tz(self.end_time)

    def start_time_for_user(self, user):
        """The same timestamp as `start_time`, but in the time zone of `user`
        """

        return self.__as_tz(self.start_time, as_timezone=user.timezone)

    def end_time_for_user(self, user):
        """The same timestamp as `end_time`, but in the time zone of `user`
        """

        return self.__as_tz(self.end_time, as_timezone=user.timezone)

    def __repr__(self):
        return f'<Event {self.id} ({self.title}) of {self.user}>'


class UserSetting(db.Model):
    """Database model for user settings
    """

    __tablename__ = 'user_settings'

    #: The ID of the user this setting belongs to
    user_id = db.Column(db.Integer(), db.ForeignKey('users.id'), primary_key=True)

    user = db.relationship('User')

    #: The settings key
    key = db.Column(db.String(length=40), primary_key=True)

    #: The settings value
    value = db.Column(db.UnicodeText())

    def __repr__(self):
        return f'<UserSetting of {self.user}, {self.key}="{self.value}">'