@startuml
class User {
name : string
}

User --> "*" User: listAmis
User --> "*" notification : lesNotif
User --> "*" ask : demandeDamis  
class notification {
text : string
}

interface INotifier {
 notify : void
}
INotifier --|> Observer
abstract UserManager {
currentUser : User
createUser (...data)
getUser(): User
deleteFriends(user1 : int, user2 :int) : void
addFriends(user:id):  void
repondreDemandeAmis(idask : Ask,choice: bool)
getFriends(user: id)
}

class ask {
fromUser : int
toUser : int
}


ask --|> Subject

abstract Subject {
+ attatch(o : Observer): void
+ detach(o : Observer): void
+ notify(): void
}
Subject --> "*" Observer
interface Observer {
update(): void
}

UserManager ..> User
UserManager o-- IUserRepository
UserManager o-- INotifier

interface IUserRepository {
 + findByUsername(username:string): User
 + addUser(user : User) : bool
}
IUserRepository ..> User
@enduml