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

title User Authentication Flow - Resend Confirmation Email

actor User
participant "API\nController" as API
participant "MediatR pipeline\n(ValidationBehavior)" as Mediator
box "Handler Layer" #F1F3EA
participant "ResendConfirmationEmailHandler" as ResendHandler
participant "UserManager<ApplicationUser>" as UserMgr
participant "TokenService" as TokenSvc
end box
box "Infrastructure Layer" #EBECE3
participant "Email\nProvider" as SMTP
participant "Template\nProvider" as Template
end box
box "Repository / Cross-slice" #DBEEDD
participant "DapperUserStore\n(IUserStore/IUserPasswordStore/\nIUserEmailStore)" as UserStore
participant "EmailDispatcher\n(Features.Emails)" as EmailDispatcher
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/resend?userId=<id>\n(requires Bearer access token)
activate API

API -> Mediator: Send(ResendConfirmationEmailCommand(userId))
activate Mediator

Mediator -> ResendHandler: Handle(command)
activate ResendHandler

ResendHandler -> UserMgr: FindByIdAsync(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 --> ResendHandler: ApplicationUser or null
deactivate UserMgr

alt User not found
  ResendHandler -> ResendHandler: return silently\n(prevents user enumeration)
else User found

  ResendHandler -> UserMgr: IsEmailConfirmedAsync(user)
  UserMgr --> ResendHandler: bool

  alt Already confirmed
    ResendHandler -> ResendHandler: return silently (no-op)
  else Not yet confirmed

    ResendHandler -> TokenSvc: GenerateConfirmationToken(user)
    activate TokenSvc
    TokenSvc --> ResendHandler: confirmation token
    deactivate TokenSvc

    ResendHandler -> Mediator: Send(SendResendConfirmationEmailCommand)
    activate Mediator
    Mediator -> EmailDispatcher: SendResendConfirmationEmailAsync(\n  firstName, email, confirmationToken)
    activate EmailDispatcher
    EmailDispatcher -> Template: Render email\n(same Razor pipeline as registration)
    EmailDispatcher -> SMTP: SendAsync(email, subject, body)
    deactivate EmailDispatcher
    deactivate Mediator
  end
end

ResendHandler --> Mediator: (void)
deactivate ResendHandler
Mediator --> API: (void)
deactivate Mediator

API -> User: 200 OK\n{message: "confirmation email has been resent"}
note right of API
  Always 200 OK regardless of outcome above -
  same user-enumeration precaution as a not-found
  user or an already-confirmed account.
end note
deactivate API

@enduml