from __future__ import absolute_import

from pylint.checkers import BaseChecker
from pylint.checkers.utils import check_messages

from pylint_django.__pkginfo__ import BASE_ID


class DjangoInstalledChecker(BaseChecker):
    name = "django-installed-checker"

    msgs = {
        # pylint: disable=implicit-str-concat
        f"F{BASE_ID}01": (
            "Django is not available on the PYTHONPATH",
            "django-not-available",
            "Django could not be imported by the pylint-django plugin, so most Django related "
            "improvements to pylint will fail.",
        ),
        f"W{BASE_ID}99": (
            "Placeholder message to prevent disabling of checker",
            "django-not-available-placeholder",
            "PyLint does not recognise checkers as being enabled unless they have at least"
            " one message which is not fatal...",
        ),
    }

    @check_messages("django-not-available")
    def open(self):
        try:
            __import__("django")
        except ImportError:
            # mild hack: this error is added before any modules have been inspected
            # so we need to set some kind of value to prevent the linter failing to it
            self.linter.set_current_module("pylint_django")
            self.add_message("django-not-available")