Addressing common scenarios on a client platform involving notifications:

• User posts an answer to a question: Questioner and other answerers receive a notification.
• User posts a comment on an answer: Answerer and users who commented before receive a notification.
• User upvotes an answer: Answerer receives a notification.

To accommodate future notification types with different message templates, design a flexible solution.

1. Notifications should be sent to the right recipients, excluding the sender.
2. Notifications must be merged if they are from the same question/answer.
3. Batch notifications up to 3 before sending or if the last notification(s) hasn't been sent after 30 seconds.

Create a CLI with a function getNotificationsForUser(notifications, user_id) that takes input JSON and prints the solution.

• user_id: Receiving user's ID.
• notification_type_id: Notification type (1 for Post Answer, 2 for Post Comment, 3 for Upvote Answer).
• sender_id: ID of the user triggering the notification.
• sender_type: Sender type (User).
• target_id: ID of the entity the sender acts upon (e.g., Question).
• target_type: Type of the entity (Question).
• created_at: Timestamp when the action is triggered.

[{
  "user_id": "hackamorevisiting",
  "notification_type_id": 2,
  "sender_id": "makerchorse",
  "sender_type": "User",
  "target_id": 46,
  "target_type": "Question",
  "created_at": 1574325866040
}, {
  "user_id": "hackamorevisiting",
  "notification_type_id": 1,
  "sender_id": "gratuitystopper",
  "sender_type": "User",
  "target_id": 37,
  "target_type": "Question",
  "created_at": 1574325903935
},
...
]

$ ruby notification.rb [inputFile] [user_id]
$ ruby notification.rb notifications.json hackamorevisiting

[2019-11-21 16:45:03] gratuitystopper answered a question
[2019-11-21 16:45:59] backwarddusty and makerchorse commented on a question
[2019-11-21 16:45:17] funeralpierce upvoted a question
[2019-11-21 16:47:08] makerchorse commented on a question