@startuml confirm-user
!include ../../../pipeline/diagrams/biergarten-weizen-theme.puml
skinparam sequenceMessageAlign center
skinparam maxMessageSize 200

title User Authentication Flow - Confirm User

actor User
participant "API\nController" as API
participant "MediatR pipeline\n(ValidationBehavior)" as Mediator
box "Handler Layer" #F1F3EA
participant "ConfirmUserHandler" as ConfirmHandler
participant "UserManager<ApplicationUser>" as UserMgr
participant "TokenService" as TokenSvc
end box
box "Infrastructure Layer" #EBECE3
participant "JWT\nInfrastructure" as JWT
end box
box "Repository / Cross-slice" #DBEEDD
participant "DapperUserStore\n(IUserStore/IUserPasswordStore/\nIUserEmailStore)" as UserStore
end box
database "SQL Server" as DB

note over UserMgr
  ASP.NET Core Identity's UserManager<TUser>
  replaces the deleted AuthRepository: handlers
  no longer issue SQL or call Argon2 directly,
  they delegate to UserManager, which in turn
  calls DapperUserStore (persistence) and
  Argon2PasswordHasher (IPasswordHasher<TUser>).
end note

User -> API: POST /api/auth/confirm?token=<token>\n(requires Bearer access token)
activate API

API -> Mediator: Send(ConfirmUserCommand(token))
activate Mediator

Mediator -> ConfirmHandler: Handle(command)
activate ConfirmHandler

ConfirmHandler -> TokenSvc: ValidateConfirmationTokenAsync(token)
activate TokenSvc
TokenSvc -> JWT: Validate against confirmation\ntoken secret, extract userId
activate JWT
JWT --> TokenSvc: ValidatedToken or throws
deactivate JWT
TokenSvc --> ConfirmHandler: ValidatedToken
deactivate TokenSvc

alt Token invalid or expired
  ConfirmHandler -> Mediator: throw UnauthorizedException
  Mediator -> API: propagate
  API -> User: 401 Unauthorized
else Token valid

  ConfirmHandler -> UserMgr: FindByIdAsync(validatedToken.UserId)
  activate UserMgr
  UserMgr -> UserStore: FindByIdAsync(userId)
  activate UserStore
  UserStore -> DB: SELECT ...\nFROM dbo.UserAccount\nWHERE UserAccountID = @Id
  activate DB
  DB --> UserStore: row or null
  deactivate DB
  UserStore --> UserMgr: ApplicationUser or null
  deactivate UserStore
  UserMgr --> ConfirmHandler: ApplicationUser or null
  deactivate UserMgr

  alt User not found
    ConfirmHandler -> Mediator: throw UnauthorizedException\n"User account not found"
    Mediator -> API: propagate
    API -> User: 401 Unauthorized
  else User found

    ConfirmHandler -> UserStore: SetEmailConfirmedAsync(user, true)
    note right of UserStore
      IUserEmailStore<ApplicationUser> is injected
      directly into the handler (not via UserManager),
      setting the confirmed flag in-memory here.
    end note

    ConfirmHandler -> UserMgr: UpdateAsync(user)
    activate UserMgr
    UserMgr -> UserStore: UpdateAsync(user)
    activate UserStore
    UserStore -> DB: UPDATE dbo.UserAccount SET ...
    UserStore -> DB: INSERT INTO dbo.UserVerification\n(UserAccountId, VerificationDateTime)
    note right of UserStore
      Idempotent: skipped (duplicate-key
      exception swallowed) if a verification
      row already exists.
    end note
    UserStore --> UserMgr: IdentityResult.Success
    deactivate UserStore
    UserMgr --> ConfirmHandler: IdentityResult
    deactivate UserMgr

    ConfirmHandler --> Mediator: ConfirmationPayload(\n  user.Id, DateTime.UtcNow)
    deactivate ConfirmHandler
    Mediator --> API: ConfirmationPayload
    deactivate Mediator

    API -> User: 200 OK\n{message: "User with ID {id} is confirmed.",\npayload: {...}}
  end
end
deactivate API

@enduml