Struct LoginService 

pub struct LoginService<R, G>
where
    R: AccessHierarchy + Eq,
    G: Eq + Clone,
{ /* private fields */ }

Stateless service implementing constant‑time, enumeration‑resistant authentication logic.

It always performs:

1. Account lookup by user identifier.
2. Credential verification against either the real account UUID or a fixed dummy UUID when the account is absent.

This equalises timing characteristics between “user not found” and “wrong password” cases.

Type Params:

• R - Role type implementing AccessHierarchy
• G - Group type

Implementations

impl<R, G> LoginService<R, G>

where R: AccessHierarchy + Eq, G: Eq + Clone,

pub fn new() -> Self

Creates a new stateless LoginService.

The instance holds no mutable state; it is cheap to clone or recreate.

pub async fn authenticate<CredVeri, AccRepo, C>( &self, credentials: Credentials<String>, registered_claims: RegisteredClaims, credentials_verifier: Arc<CredVeri>, account_repository: Arc<AccRepo>, codec: Arc<C>, ) -> LoginResult

where CredVeri: CredentialsVerifier<Uuid>, AccRepo: AccountRepository<R, G>, C: Codec<Payload = JwtClaims<Account<R, G>>>,

Authenticates a user in a timing‑safe, enumeration‑resistant fashion.

Steps:

1. Query account repository by user identifier.
2. Always invoke credential verification using either the real account UUID or a fixed dummy UUID when the user is absent / lookup failed.
3. Combine (user_exists AND password_matches) with constant‑time bit logic.
4. On success, encode a JWT with the supplied registered claims.

Returns:

• LoginResult::Success with a JWT string on success.
• LoginResult::InvalidCredentials for any auth failure that should not leak detail.
• LoginResult::InternalError for infrastructural issues (these should be logged).

Security: Avoids early returns that would create observable timing differences between “user not found” and “wrong password”.

Trait Implementations

impl<R, G> Default for LoginService<R, G>

where R: AccessHierarchy + Eq, G: Eq + Clone,

fn default() -> Self

Returns the “default value” for a type.