shootismoke/backend

import { Frequency, User as IUser } from '@shootismoke/graphql';
import { Document } from 'mongoose';

import { PushTicket, User } from '../models';
import { findTimezonesAt } from '../util';

/**
 * Show notifications at these hours of the day.
 */
const NOTIFICATION_HOUR = {
    daily: 9,
    weekly: 21,
    monthly: 21,
};

/**
 * Based on the time now and the frequency of notifications, find the timezones
 * that should receive a notifications now.
 *
 * @param frequency - The frequency of notifications.
 * @param now - The time now.
 */
export function getTimezones(frequency: Frequency, now: Date): string[] {
    let timezones: string[] = [];
    if (frequency === 'daily') {
        timezones = findTimezonesAt(NOTIFICATION_HOUR.daily, now);
    } else if (frequency === 'weekly' && now.getUTCDay() === 0) {
        // Show weekly notifications on Sundays
        timezones = findTimezonesAt(NOTIFICATION_HOUR.weekly, now);
    } else if (frequency === 'monthly' && now.getUTCDate() === 1) {
        // Show monthly notifications on the 1st of the month
        timezones = findTimezonesAt(NOTIFICATION_HOUR.monthly, now);
    }

    return timezones;
}

/**
 * Generate the mongodb users aggregation pipeline for finding users to send
 * notifications to.
 */
export function usersPipeline(frequency: Frequency, now: Date): unknown[] {
    const timezones = getTimezones(frequency, now);

    return [
        // Get all users matching frequency and timezone.
        {
            $match: {
                'notifications.frequency': frequency,
                'notifications.timezone': {
                    $in: timezones,
                },
            },
        },
        // Check if user has any active pushTickets from Expo.
        {
            $lookup: {
                as: 'pushTickets',
                from: PushTicket.collection.name,
                localField: '_id',
                foreignField: 'userId',
            },
        },
        // Only return users with no puchTickets.
        {
            $match: {
                pushTickets: { $size: 0 },
            },
        },
    ];
}

/**
 * Find in DB all users to show notifications with frequency `frequency`.
 *
 * @param frequency - The frequency to show the timezones.
 * @todo Unpure.
 */
export async function findUsersForNotifications(): Promise<
    (IUser & Document)[]
> {
    const now = new Date();
    // Return a tuple [dailyUsers, weeklyUsers, monthlyUsers]
    const allUsers = await Promise.all(
        (['daily', 'weekly', 'monthly'] as const).map((frequency) =>
            User.aggregate(usersPipeline(frequency, now))
        )
    );

    return allUsers.flat() as (IUser & Document)[];
}