UserAuthAuthenticate.swift

static func authenticate(credentials: Credentials) throws -> Auth.User {
    switch credentials {
        case let id as Identifier:
            guard let user = try User.find(id.id) else {
                throw Abort.custom(status: .forbidden, message: "Invalid user identifier.")
            }
            
            return user
            
        case let usernamePassword as UsernamePassword:
            let fetchedUser = try User.query().filter("username", usernamePassword.username).first()
            guard let user = fetchedUser else {
                throw Abort.custom(status: .networkAuthenticationRequired, message: "User does not exist")
            }
            if try BCrypt.verify(password: usernamePassword.password, matchesHash: fetchedUser!.password) {
                return user
            } else {
                throw Abort.custom(status: .networkAuthenticationRequired, message: "Invalid user name or password.")
            }
            
            
        default:
            let type = type(of: credentials)
            throw Abort.custom(status: .forbidden, message: "Unsupported credential type: \(type).")
    }
}