BaseTemplateModelAdmin

class FilesAdminInline(admin.TabularInline):
    model = Files
    extra = 0


"""
    Available presets:
        TEMPLATE_NAMES.template_name: [],
        TEMPLATE_NAMES.template_name: ['', ['field1', 'field2']],
        TEMPLATE_NAMES.template_name: ['', [], [inline1, inline2]],
        TEMPLATE_NAMES.template_name: ['', ['field1', 'field2'], [inline1, inline2]],
        TEMPLATE_NAMES.template_name: ['tab_name', ['field1', 'field2'], [inline1, inline2]],
"""
presets = {

    TEMPLATE_NAMES.base: ['', ['html']],

    TEMPLATE_NAMES.about: ['', ['html'], [FilesAdminInline]],

    TEMPLATE_NAMES.proprietors: [],

    TEMPLATE_NAMES.often_questions: ['', [], []],

    TEMPLATE_NAMES.contacts: [],
}


@admin.register(BaseTemplateModel)
class BaseTemplateModelAdmin(admin.ModelAdmin):
    list_display = ['title', 'slug', 'template_name', 'get_href']

    def update_fieldsets(self, _fieldsets, _preset):
        names = [tab[0] for tab in _fieldsets if len(tab)]

        _name = _preset[0] if len(_preset) else ''
        _fields = _preset[1] if len(_preset) > 1 else []

        self.inlines = _preset[2] if len(_preset) > 2 else []

        if _name not in names:
            return _fieldsets.append([_name, {'fields': _fields}])

        if _fields:
            _fieldsets[names.index(_name)][1]['fields'].extend(_fields)
        return _fieldsets

    def get_fieldsets(self, request, obj=None):
        fieldsets = [['', {'fields': ['template_name', 'slug', 'background', 'title']}]]
        if obj:
            fieldsets[0][1]['fields'].append('get_link')
            self.readonly_fields += ('get_link',)

            self.update_fieldsets(fieldsets, presets[obj.template_name])
        return fieldsets

    def get_link(self, obj):
        return mark_safe(f'<a href="{obj.get_absolute_url()}">{_("Перейти")}</a>')
    get_link.short_description = 'Ссылка'
    get_link.allow_tags = True

    def get_href(self, obj):
        return obj.get_absolute_url()
    get_href.short_description = 'Ссылки'
    get_href.allow_tags = True