Create a Notification System Based on User Preferences - mongodb

Question

I am trying to develop a notification system, but I am not sure if I do certain parts correctly. To simplify the case I will use some generic naming.
How the system should work:
A registered user can subscribe for notifications based on chosen filters from a data table grid. ( for example, notify me when the quantity of an item is X, or have multiple filters set up like set1.slug.quantity > X, some_value = false and some_int = 52)
How I store such preferences:
Example object
"O:8:"stdClass":2:{s:9:"set1.slug";a:1:{s:3:"$eq";s:10:"item_slug1";}s:13:"set1.quantity";a:1:{s:4:"$gte";i:1;}}"
Generation simplified
$object = new \stdClass();
$object->{'set1.slug'} = ['$eq' => 'item_slug1'];
$object->{'set1.quantity'} = ['$gte' => 1];
$object = serialize($object);
It attaches also the user_id and all the data serialized from the form to a partial MongoDB raw query.
Database stored object - predefined filter set for a user. Md is an md5 hash of the object for easier access and edit.
+----+-----------------------------------------------------------------------------------------------------------------+---------+----------------------------------+
| id | object | user_id | md |
+----+-----------------------------------------------------------------------------------------------------------------+---------+----------------------------------+
| 1 | O:8:"stdClass":2:{s:9:"set1.slug";a:1:{s:3:"$eq";s:10:"item_slug1";}s:13:"set1.quantity";a:1:{s:4:"$gte";i:1;}} | 22 | d5003ba3227c4db3189827329815b053 |
+----+-----------------------------------------------------------------------------------------------------------------+---------+----------------------------------+
This is how I would use it - my vision of how it would work.
I would call findByFilterMD in the API parser in a loop, while the table Items is populated.
// MongoDB query ( items database )
protected function executeUserFilter($array)
{
$list = Items::raw(function ($collection) use (&$array) {
return $collection->find(
$array, ["typeMap" => ['root' => 'array', 'document' => 'array']])
->toArray();
});
return $list;
}
// MySQL query - stored filters
protected function findByFilterMD($id)
{
$user = Auth::user();
$filter = PredefinedFilters::where('md', '=', $id)->first();
$deserialize = unserialize($filter->object);
$results = $this->executeUserFilter($deserialize);
// here would probably be a notification function like pusher or onesignal
}
I am aware that my attempt of achieving this might be totally wrong and I might reinvent the wheel since some tools might do that already.
Here is an example Item MongoDB object
{
"_id": {
"$oid": "5c0406abdc04e7007f17f4ef"
},
"name": "myObject",
"inner_ID": "0db0b19a-9c01-4c21-8e10-6879dbcb37f1",
"some_value": false,
"some_int": 52,
"set1": [
{
"slug": "item_slug1",
"quantity": 88,
"extra": {
"value": 0
}
},
],
"set2": [
{
"slug": "item_slug2",
"quantity": 88,
"extra": {
"value": 0
}
},
{
"slug": "item_slug3",
"quantity": 88,
"extra": {
"value": 0
}
}
],
"expires": "2018-12-02 22:21:30"
}
Here comes my questions
Is this way of doing it proper?
Where should the notification system kick in? I assume it might be in the place where I parse the api of items, then I should loop over the user filter data and run the stored object query - or should it be a separate system called with cron?
I am open to any suggestions, redesigns.

Answer 1

I developed an app kinda like this. My approach is to make use of Laravel notification found here:
https://laravel.com/docs/5.7/notifications#creating-notifications
Let's say, in your case, if someone modify/create data, the other users who subscribe will get notification.
Create notification
php artisan make:notification UserUpdateQuantity
Make User model notifiable, also create scope that subscribe for something
<?php
namespace App;
use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;
class User extends Authenticatable
{
use Notifiable;
public function scopeSubscribe($query)
{
return $query->where('subscribe', true);
}
}
the $query in method scopeSubscribe needs to be adjusted based on your business logic
Send notification
$subscriber = User::subscribe()->get();
Notification::send($subscriber, new UserUpdateQuantity());
Create event & listener
You can find the event and listener here https://laravel.com/docs/5.7/events
In the EventServiceProvider
protected $listen = [
'App\Events\QuantityUpdated' => [
'App\Listeners\SendUpdateQuantiryNotification',
],
];
Then run the command php artisan event:generate
Event listener
In the event listener, we send notification
public function handle(QuantityUpdated $event)
{
$subscriber = User::subscribe()->get();
Notification::send($subscriber, new UserUpdateQuantity());
}
Eloquent event
Add event on your eloquent model, so when someone update quantity, it triggers event and the listener will send notification to subscribed users
// In your model
protected $dispatchesEvents = [
'updated' => App\Events\QuantityUpdated::class
];