Decouple business logic from views

[yld-weng]

Introduce the service layer (services.py) and separate business logic from views.

E.g.

    def form_valid(self, form):
        email = form.cleaned_data['email']

        survey = Survey.objects.first()

        invitation = Invitation.objects.create(survey=survey)

        token = invitation.token

        # Generate the survey link with the token
        survey_link = f"http://localhost:8000/survey/{survey.pk}/{token}/"

        # Send the email
        send_mail(
            'Your Survey Invitation',
            f'Click here to start the survey: {survey_link}',
            '[email protected]',
            [email],
            fail_silently=False,
        )

        # Show success message
        messages.success(self.request, f'Invitation sent to {email}.')
        return super().form_valid(form)

can be rewritten as:

def send_survey_invitation(email, request):
    survey = Survey.objects.first()

    if not survey:
        raise ValueError("No survey available to send invitations.")

    # Create an invitation
    invitation = Invitation.objects.create(survey=survey)
    token = invitation.token

    # Generate the survey link with the token
    survey_link = f"http://localhost:8000/survey/{survey.pk}/{token}/"

    # Send the email
    send_mail(
        'Your Survey Invitation',
        f'Click here to start the survey: {survey_link}',
        '[email protected]',
        [email],
        fail_silently=False,
    )

    # Add a success message
    add_message(request, message_constants.SUCCESS, f'Invitation sent to {email}.')

and

    def form_valid(self, form):
        email = form.cleaned_data['email']

        try:
            # Call the service to handle the business logic
            send_survey_invitation(email, self.request)
        except ValueError as e:
            # Handle cases where the service raises an error
            messages.error(self.request, str(e))
            return self.form_invalid(form)

        return super().form_valid(form)

This separation makes the send_survey_invitation function easier to test.