"""
byceps.services.ticketing.attendance_service
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

:Copyright: 2006-2020 Jochen Kupperschmidt
:License: Modified BSD, see LICENSE for details.
"""

from collections import Counter, defaultdict
from datetime import datetime
from itertools import chain
import typing
from typing import Dict, List, Set, Tuple

from sqlalchemy.dialects.postgresql import insert

from ...database import db, upsert
from ...typing import BrandID, PartyID, UserID

from ..party.models.party import Party as DbParty
from ..party import service as party_service
from ..party.transfer.models import Party
from ..user import service as user_service
from ..user.transfer.models import User

from .models.archived_attendance import (
    ArchivedAttendance as DbArchivedAttendance,
)
from .models.category import Category as DbCategory
from .models.ticket import Ticket as DbTicket


def create_archived_attendance(user_id: UserID, party_id: PartyID) -> None:
    """Create an archived attendance of the user at the party."""
    table = DbArchivedAttendance.__table__

    query = insert(table) \
        .values({
            'user_id': str(user_id),
            'party_id': str(party_id),
        }) \
        .on_conflict_do_nothing(constraint=table.primary_key)
    db.session.execute(query)


def delete_archived_attendance(user_id: UserID, party_id: PartyID) -> None:
    """Delete the archived attendance of the user at the party."""
    db.session.query(DbArchivedAttendance) \
        .filter_by(user_id=user_id, party_id=party_id) \
        .delete()
    db.session.commit()


def get_attended_parties(user_id: UserID) -> List[Party]:
    """Return the parties the user has attended in the past."""
    ticket_attendance_party_ids = _get_attended_party_ids(user_id)
    archived_attendance_party_ids = _get_archived_attendance_party_ids(user_id)

    party_ids = set(
        chain(ticket_attendance_party_ids, archived_attendance_party_ids)
    )

    return party_service.get_parties(party_ids)


def _get_attended_party_ids(user_id: UserID) -> Set[PartyID]:
    """Return the IDs of the non-legacy parties the user has attended."""
    party_id_rows = db.session \
        .query(DbParty.id) \
        .filter(DbParty.ends_at < datetime.utcnow()) \
        .join(DbCategory) \
        .join(DbTicket) \
        .filter(DbTicket.revoked == False) \
        .filter(DbTicket.used_by_id == user_id) \
        .all()

    return {row[0] for row in party_id_rows}


def _get_archived_attendance_party_ids(user_id: UserID) -> Set[PartyID]:
    """Return the IDs of the legacy parties the user has attended."""
    party_id_rows = db.session \
        .query(DbArchivedAttendance.party_id) \
        .filter(DbArchivedAttendance.user_id == user_id) \
        .all()

    return {row[0] for row in party_id_rows}


def get_attendees_by_party(party_ids: Set[PartyID]) -> Dict[PartyID, Set[User]]:
    """Return the parties' attendees, indexed by party."""
    if not party_ids:
        return {}

    attendee_ids_by_party_id = get_attendee_ids_for_parties(party_ids)

    all_attendee_ids = set(
        chain.from_iterable(attendee_ids_by_party_id.values())
    )
    all_attendees = user_service.find_users(
        all_attendee_ids, include_avatars=True
    )
    all_attendees_by_id = user_service.index_users_by_id(all_attendees)

    attendees_by_party_id = {}
    for party_id in party_ids:
        attendee_ids = attendee_ids_by_party_id.get(party_id, set())

        attendees = {
            all_attendees_by_id[attendee_id] for attendee_id in attendee_ids
        }

        attendees_by_party_id[party_id] = attendees

    return attendees_by_party_id


def get_attendee_ids_for_parties(
    party_ids: Set[PartyID],
) -> Dict[PartyID, Set[UserID]]:
    """Return the partys' attendee IDs, indexed by party ID."""
    if not party_ids:
        return {}

    ticket_rows = db.session \
        .query(DbCategory.party_id, DbTicket.used_by_id) \
        .filter(DbCategory.party_id.in_(party_ids)) \
        .join(DbTicket) \
        .filter(DbTicket.revoked == False) \
        .filter(DbTicket.used_by_id != None) \
        .all()

    archived_attendance_rows = db.session \
        .query(
            DbArchivedAttendance.party_id,
            DbArchivedAttendance.user_id
        ) \
        .filter(DbArchivedAttendance.party_id.in_(party_ids)) \
        .all()

    rows = ticket_rows + archived_attendance_rows

    attendee_ids_by_party_id: Dict[PartyID, Set[UserID]] = defaultdict(set)
    for party_id, attendee_id in rows:
        attendee_ids_by_party_id[party_id].add(attendee_id)

    return dict(attendee_ids_by_party_id)


def get_top_attendees_for_brand(brand_id: BrandID) -> List[Tuple[UserID, int]]:
    """Return the attendees with the highest number of parties of this
    brand visited.
    """
    parties = party_service.get_parties_for_brand(brand_id)
    party_ids = {p.id for p in parties}

    top_ticket_attendance_counts = _get_top_ticket_attendees_for_parties(
        brand_id
    )

    top_archived_attendance_counts = _get_top_archived_attendees_for_parties(
        brand_id
    )

    top_attendance_counts = _merge_top_attendance_counts(
        [top_ticket_attendance_counts, top_archived_attendance_counts]
    )

    # Select top attendees with more than one attendance.
    top_attendees = top_attendance_counts.most_common(50)
    top_attendees = [
        (user_id, attendance_count)
        for user_id, attendance_count in top_attendees
        if attendance_count > 1
    ]

    return top_attendees


def _get_top_ticket_attendees_for_parties(
    brand_id: BrandID,
) -> List[Tuple[UserID, int]]:
    user_id_column = db.aliased(DbTicket).used_by_id

    attendance_count = db.session \
        .query(
            db.func.count(DbCategory.party_id.distinct()),
        ) \
        .join(DbParty) \
        .filter(DbParty.brand_id == brand_id) \
        .join(DbTicket) \
        .filter(DbTicket.revoked == False) \
        .filter(DbTicket.used_by_id == user_id_column) \
        .subquery() \
        .as_scalar()

    return db.session \
        .query(
            user_id_column.distinct(),
            attendance_count,
        ) \
        .filter(user_id_column != None) \
        .filter(attendance_count > 0) \
        .order_by(attendance_count.desc()) \
        .all()


def _get_top_archived_attendees_for_parties(
    brand_id: BrandID,
) -> List[Tuple[UserID, int]]:
    attendance_count_column = db.func \
        .count(DbArchivedAttendance.user_id) \
        .label('attendance_count')

    return db.session \
        .query(
            DbArchivedAttendance.user_id,
            attendance_count_column,
        ) \
        .join(DbParty) \
        .filter(DbParty.brand_id == brand_id) \
        .group_by(DbArchivedAttendance.user_id) \
        .order_by(attendance_count_column.desc()) \
        .all()


def _merge_top_attendance_counts(
    xs: List[List[Tuple[UserID, int]]]
) -> typing.Counter[UserID]:
    counter = Counter()

    for x in xs:
        counter.update(dict(x))

    return counter