from datetime import datetime, timedelta, time

from flask import current_app
from notifications_utils.timezones import convert_bst_to_utc
from sqlalchemy import func
from sqlalchemy.dialects.postgresql import insert
from sqlalchemy.sql.expression import literal
from sqlalchemy.types import DateTime, Integer

from app import db
from app.models import Notification, NotificationHistory, FactNotificationStatus, KEY_TYPE_TEST
from app.utils import get_london_midnight_in_utc, midnight_n_days_ago


def fetch_notification_status_for_day(process_day, service_id=None):
    start_date = convert_bst_to_utc(datetime.combine(process_day, time.min))
    end_date = convert_bst_to_utc(datetime.combine(process_day + timedelta(days=1), time.min))
    # use notification_history if process day is older than 7 days
    # this is useful if we need to rebuild the ft_billing table for a date older than 7 days ago.
    current_app.logger.info("Fetch ft_notification_status for {} to {}".format(start_date, end_date))
    table = Notification
    if start_date < datetime.utcnow() - timedelta(days=7):
        table = NotificationHistory

    transit_data = db.session.query(
        table.template_id,
        table.service_id,
        func.coalesce(table.job_id, '00000000-0000-0000-0000-000000000000').label('job_id'),
        table.notification_type,
        table.key_type,
        table.status,
        func.count().label('notification_count')
    ).filter(
        table.created_at >= start_date,
        table.created_at < end_date
    ).group_by(
        table.template_id,
        table.service_id,
        'job_id',
        table.notification_type,
        table.key_type,
        table.status
    )

    if service_id:
        transit_data = transit_data.filter(table.service_id == service_id)

    return transit_data.all()


def update_fact_notification_status(data, process_day):
    table = FactNotificationStatus.__table__
    FactNotificationStatus.query.filter(
        FactNotificationStatus.bst_date == process_day.date()
    ).delete()
    for row in data:
        stmt = insert(table).values(
            bst_date=process_day.date(),
            template_id=row.template_id,
            service_id=row.service_id,
            job_id=row.job_id,
            notification_type=row.notification_type,
            key_type=row.key_type,
            notification_status=row.status,
            notification_count=row.notification_count,
        )
        db.session.connection().execute(stmt)
        db.session.commit()


def fetch_notification_status_for_service_by_month(start_date, end_date, service_id):
    return db.session.query(
        func.date_trunc('month', FactNotificationStatus.bst_date).label('month'),
        FactNotificationStatus.notification_type,
        FactNotificationStatus.notification_status,
        func.sum(FactNotificationStatus.notification_count).label('count')
    ).filter(
        FactNotificationStatus.service_id == service_id,
        FactNotificationStatus.bst_date >= start_date,
        FactNotificationStatus.bst_date < end_date,
        FactNotificationStatus.key_type != KEY_TYPE_TEST
    ).group_by(
        func.date_trunc('month', FactNotificationStatus.bst_date).label('month'),
        FactNotificationStatus.notification_type,
        FactNotificationStatus.notification_status
    ).all()


def fetch_notification_status_for_service_for_day(bst_day, service_id):
    return db.session.query(
        # return current month as a datetime so the data has the same shape as the ft_notification_status query
        literal(bst_day.replace(day=1), type_=DateTime).label('month'),
        Notification.notification_type,
        Notification.status.label('notification_status'),
        func.count().label('count')
    ).filter(
        Notification.created_at >= get_london_midnight_in_utc(bst_day),
        Notification.created_at < get_london_midnight_in_utc(bst_day + timedelta(days=1)),
        Notification.service_id == service_id,
        Notification.key_type != KEY_TYPE_TEST
    ).group_by(
        Notification.notification_type,
        Notification.status
    ).all()


def fetch_notification_status_for_service_for_today_and_7_previous_days(service_id, limit_days=7):
    start_date = midnight_n_days_ago(limit_days)
    now = datetime.utcnow()
    stats_for_7_days = db.session.query(
        FactNotificationStatus.notification_type.label('notification_type'),
        FactNotificationStatus.notification_status.label('status'),
        FactNotificationStatus.notification_count.label('count')
    ).filter(
        FactNotificationStatus.service_id == service_id,
        FactNotificationStatus.bst_date >= start_date,
        FactNotificationStatus.key_type != KEY_TYPE_TEST
    )

    stats_for_today = db.session.query(
        Notification.notification_type.cast(db.Text),
        Notification.status,
        func.count().label('count')
    ).filter(
        Notification.created_at >= get_london_midnight_in_utc(now),
        Notification.service_id == service_id,
        Notification.key_type != KEY_TYPE_TEST
    ).group_by(
        Notification.notification_type,
        Notification.status
    )
    all_stats_table = stats_for_7_days.union_all(stats_for_today).subquery()
    return db.session.query(
        all_stats_table.c.notification_type,
        all_stats_table.c.status,
        func.cast(func.sum(all_stats_table.c.count), Integer).label('count'),
    ).group_by(
        all_stats_table.c.notification_type,
        all_stats_table.c.status,
    ).all()