# 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/>.

"""Main module for the Calendar.social app
"""

from datetime import datetime
import os

from flask import Flask, abort, current_app, redirect, render_template, request, url_for
from flask_babelex import Babel, get_locale as babel_get_locale
from flask_security import SQLAlchemyUserDatastore, current_user, login_required
from sqlalchemy.orm.exc import NoResultFound, MultipleResultsFound


def get_locale():
    """Locale selector

    Selects the best locale based on values sent by the browser.
    """

    supported_languages = ['en', 'hu']

    if 'l' in request.args and request.args['l'].lower() in supported_languages:
        return request.args['l'].lower()

    return request.accept_languages.best_match(supported_languages)


def template_vars():
    """Function to inject global template variables
    """

    now = datetime.utcnow()

    return {
        'lang': babel_get_locale().language,
        'now': now,
        'now_ts': now.timestamp(),
    }


def route(*args, **kwargs):
    """Mark a function as a future route

    Such functions will be iterated over when the application is initialised.  ``*args`` and
    ``**kwargs`` will be passed verbatim to `Flask.route()`.
    """

    def decorator(func):  # pylint: disable=missing-docstring
        setattr(func, 'routing', (args, kwargs))

        return func

    return decorator


class CalendarSocialApp(Flask):
    """The Calendar.social app
    """

    def __init__(self, name, config=None):  # pylint: disable=too-many-locals
        from .forms import LoginForm
        from .models import db, User, Role
        from .security import security, AnonymousUser

        Flask.__init__(self, name)

        self._timezone = None

        config_name = os.environ.get('ENV', config or 'dev')
        self.config.from_pyfile(f'config_{config_name}.py', True)
        # Make sure we look up users both by their usernames and email addresses
        self.config['SECURITY_USER_IDENTITY_ATTRIBUTES'] = ('username', 'email')
        self.config['SECURITY_LOGIN_USER_TEMPLATE'] = 'login.html'

        self.jinja_env.policies['ext.i18n.trimmed'] = True  # pylint: disable=no-member

        db.init_app(self)

        babel = Babel(app=self)
        babel.localeselector(get_locale)

        user_store = SQLAlchemyUserDatastore(db, User, Role)
        security.init_app(self, datastore=user_store,
                          anonymous_user=AnonymousUser,
                          login_form=LoginForm)

        self.context_processor(template_vars)

        for attr_name in self.__dir__():
            attr = getattr(self, attr_name)

            if not callable(attr):
                continue

            args, kwargs = getattr(attr, 'routing', (None, None))

            if args is None:
                continue

            self.route(*args, **kwargs)(attr)

        self.before_request(self.goto_first_steps)

    @staticmethod
    def goto_first_steps():
        """Check if the current user has a profile and if not, redirect to the first steps page
        """

        if current_user.is_authenticated and \
           not current_user.profile and \
           request.endpoint != 'first_steps':
            return redirect(url_for('first_steps'))

        return None

    @property
    def timezone(self):
        """The default time zone of the app
        """

        from warnings import warn

        from flask import has_app_context
        from pytz import timezone, utc
        from pytz.exceptions import UnknownTimeZoneError

        if not has_app_context():
            return utc

        if not self._timezone:
            timezone_str = current_app.config.get('DEFAULT_TIMEZONE', 'UTC')

            try:
                self._timezone = timezone(timezone_str)
            except UnknownTimeZoneError:
                warn(f'Timezone of {self} (or the default timezone) "{timezone_str}" is invalid')

                self._timezone = utc

        return self._timezone

    @staticmethod
    @route('/')
    def hello():
        """View for the main page

        This will display a welcome message for users not logged in; for others, their main
        calendar view is displayed.
        """

        from .calendar_system.gregorian import GregorianCalendar

        try:
            timestamp = datetime.fromtimestamp(float(request.args.get('date')))
        except TypeError:
            timestamp = datetime.utcnow()

        calendar = GregorianCalendar(timestamp.timestamp())

        if not current_user.is_authenticated:
            login_form_class = current_app.extensions['security'].login_form
            login_form = login_form_class()
            return render_template('welcome.html',
                                   calendar=calendar,
                                   user_only=False,
                                   login_form=login_form)

        return render_template('index.html', calendar=calendar, user_only=True)

    @staticmethod
    @route('/register', methods=['POST', 'GET'])
    def register():
        """View for user registration

        If the ``REGISTRATION_FAILED`` configuration value is set to ``True`` it displays the
        registration disabled template.  Otherwise, it performs user registration.
        """

        if not current_app.config['REGISTRATION_ENABLED']:
            return render_template('registration-disabled.html')

        from .forms import RegistrationForm
        from .models import db, User

        form = RegistrationForm()

        if form.validate_on_submit():
            # TODO: This might become False later, if we want registrations to be confirmed via
            #       e-mail
            user = User(active=True)

            form.populate_obj(user)
            db.session.add(user)
            db.session.commit()

            return redirect(url_for('hello'))

        return render_template('registration.html', form=form)

    @staticmethod
    @route('/new-event', methods=['GET', 'POST'])
    @login_required
    def new_event():
        """View for creating a new event

        This presents a form to the user that allows entering event details.
        """

        from .forms import EventForm
        from .models import db, Event

        form = EventForm()

        if form.validate_on_submit():
            event = Event(profile=current_user.profile)
            form.populate_obj(event)

            db.session.add(event)
            db.session.commit()

            return redirect(url_for('hello'))

        return render_template('event-edit.html', form=form)

    @staticmethod
    @route('/settings', methods=['GET', 'POST'])
    @login_required
    def settings():
        """View for user settings
        """

        from .forms import SettingsForm
        from .models import db

        form = SettingsForm(current_user)

        if form.validate_on_submit():
            form.populate_obj(current_user)

            db.session.commit()

            return redirect(url_for('hello'))

        return render_template('user-settings.html', form=form)

    @staticmethod
    @route('/event/<string:event_uuid>', methods=['GET', 'POST'])
    def event_details(event_uuid):
        """View to display event details
        """

        from .forms import InviteForm
        from .models import db, Event

        try:
            event = Event.query.filter(Event.event_uuid == event_uuid).one()
        except NoResultFound:
            abort(404)
        except MultipleResultsFound:
            abort(500)

        form = InviteForm(event)

        if form.validate_on_submit():
            event.invite(current_user.profile, invitee=form.invitee.data)

            db.session.commit()

            return redirect(url_for('event_details', event_uuid=event.event_uuid))

        return render_template('event-details.html', event=event, form=form)

    @staticmethod
    @route('/profile/@<string:username>')
    def display_profile(username):
        """View to display profile details
        """

        from .models import Profile, User

        try:
            profile = Profile.query.join(User).filter(User.username == username).one()
        except NoResultFound:
            abort(404)

        return render_template('profile-details.html', profile=profile)

    @staticmethod
    @route('/profile/@<string:username>/follow')
    @login_required
    def follow_user(username):
        """View for following a user
        """

        from .models import db, Profile, User

        try:
            profile = Profile.query.join(User).filter(User.username == username).one()
        except NoResultFound:
            abort(404)

        if profile.user != current_user:
            profile.follow(follower=current_user.profile)

            db.session.commit()

        return redirect(url_for('display_profile', username=username))

    @staticmethod
    @route('/notifications')
    def notifications():
        """View to list the notifications for the current user
        """

        from .models import Notification

        if current_user.is_authenticated:
            notifs = Notification.query.filter(Notification.profile == current_user.profile)
        else:
            notifs = []

        return render_template('notifications.html', notifs=notifs)

    @staticmethod
    @route('/accept/<int:invite_id>')
    def accept_invite(invite_id):
        """View to accept an invitation
        """

        from .models import db, Invitation, Response, ResponseType

        invitation = Invitation.query.get_or_404(invite_id)

        if invitation.invitee != current_user.profile:
            abort(403)

        try:
            Response.query \
                    .filter(Response.event == invitation.event) \
                    .filter(Response.profile == current_user.profile) \
                    .one()
        except NoResultFound:
            response = Response(profile=current_user.profile,
                                event=invitation.event,
                                invitation=invitation,
                                response=ResponseType.going)
            db.session.add(response)
            db.session.commit()
        except MultipleResultsFound:
            pass

        return redirect(url_for('event_details', event_uuid=invitation.event.event_uuid))

    @staticmethod
    @route('/first-steps', methods=['GET', 'POST'])
    @login_required
    def first_steps():
        """View to set up a new registrant’s profile
        """

        from .forms import FirstStepsForm
        from .models import db, Profile

        if current_user.profile:
            return redirect(url_for('hello'))

        form = FirstStepsForm()

        if form.validate_on_submit():
            profile = Profile(user=current_user, display_name=form.display_name.data)
            db.session.add(profile)

            current_user.settings['timezone'] = str(form.time_zone.data)

            db.session.commit()

            return redirect(url_for('hello'))

        return render_template('first-steps.html', form=form)

    @staticmethod
    @route('/edit-profile', methods=['GET', 'POST'])
    @login_required
    def edit_profile():
        """View for editing one’s profile
        """

        from .forms import ProfileForm
        from .models import db

        form = ProfileForm(current_user.profile)

        if form.validate_on_submit():
            form.populate_obj(current_user.profile)
            db.session.add(current_user.profile)
            db.session.commit()

            return redirect(url_for('edit_profile'))

        return render_template('profile-edit.html', form=form)

    @staticmethod
    @route('/all-events')
    def all_events():
        """View for listing all available events
        """

        from .calendar_system.gregorian import GregorianCalendar

        try:
            timestamp = datetime.fromtimestamp(float(request.args.get('date')))
        except TypeError:
            timestamp = datetime.utcnow()

        calendar = GregorianCalendar(timestamp.timestamp())

        return render_template('index.html', calendar=calendar, user_only=False)

    @staticmethod
    @route('/follow-requests')
    @login_required
    def follow_requests():
        """View for listing follow requests
        """

        from .models import UserFollow

        requests = UserFollow.query \
                             .filter(UserFollow.followed == current_user.profile) \
                             .filter(UserFollow.accepted_at.is_(None))

        return render_template('follow-requests.html', requests=requests)

    @staticmethod
    @route('/follow-request/<int:follower_id>/accept')
    @login_required
    def accept_follow(follower_id):
        """View for accepting a follow request
        """

        from .models import db, UserFollow

        try:
            req = UserFollow.query \
                            .filter(UserFollow.followed == current_user.profile) \
                            .filter(UserFollow.follower_id == follower_id) \
                            .one()
        except NoResultFound:
            abort(404)

        if req.accepted_at is None:
            req.accept()

            db.session.add(req)
            db.session.commit()

        return redirect(url_for('follow_requests'))


app = CalendarSocialApp(__name__)