Add genericity to ModalForm, generalize result to hook

from collections.abc import Sequence

from textual.screen import ModalScreen

from textual.widgets import Input

class ModalForm(ModalScreen):

class ModalForm[T](ModalScreen[T]):

    BINDINGS = [

        ("escape", "app.pop_screen", "Abbrechen"),

    ]

    @property

    def _form_inputs(self) -> Sequence[Input]:  # TODO Make this abstract

    def _result(self) -> T:

        raise NotImplementedError()

    def _close(self) -> None:

        form_values = tuple(i.value for i in self._form_inputs)

        self.dismiss(form_values)

    def on_input_submitted(self, event: Input.Submitted) -> None:

        self._close_if_complete()

    def _close_if_complete(self) -> None:

        invalid_field_found = self._focus_next_invalid_field()

        if not invalid_field_found:

            self._close()

            self.dismiss(self._result)

    def _focus_next_invalid_field(self) -> bool:

        for field in self._form_inputs:

        for field in self.query(Input):

            if not field.is_valid or field.value == "":

                field.focus()

                return True