State.elm

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
   case Debug.log "msg" msg of
      SetPassword password ->
        ( { model |
            user = updatePassword (updatePasswordValue model.user.password password) model.user }
        , Cmd.none )
      ShowPassword ->
        ( { model |
            user = updatePassword (toggleVisible model.user.password) model.user }
        , Cmd.none )
      ValidatePassword ->
        let
          error = firstError model.user.password
        in
          ( { model |
              user = updatePassword (updatePasswordError model.user.password error) model.user }
          , Cmd.none )

updatePassword : Password -> User -> User
updatePassword password user =
  { user | password = password }

updatePasswordValue : Password -> String -> Password
updatePasswordValue password newPassword =
  { password | value = newPassword }

toggleVisible: Password -> Password
toggleVisible password =
  { password | visible = not password.visible }

updatePasswordError : Password -> String -> Password
updatePasswordError password error =
  { password | error = error }

firstError : Password -> String
firstError password =
  let
    validate = validatePassword password
  in
    case validate of
      Ok _ -> ""
      Err [] -> ""
      Err (first :: rest) -> first