# -*- encoding: utf-8 -*-
from __future__ import unicode_literals

from django.apps import apps

from .. import Warning, register


@register('compatibility')
def check_1_6_compatibility(**kwargs):
    errors = []
    errors.extend(_check_test_runner(**kwargs))
    errors.extend(_check_boolean_field_default_value(**kwargs))
    return errors


def _check_test_runner(app_configs=None, **kwargs):
    """
    Checks if the user has *not* overridden the ``TEST_RUNNER`` setting &
    warns them about the default behavior changes.

    If the user has overridden that setting, we presume they know what they're
    doing & avoid generating a message.
    """
    from django.conf import settings

    # We need to establish if this is a project defined on the 1.5 project template,
    # because if the project was generated on the 1.6 template, it will have be been
    # developed with the new TEST_RUNNER behavior in mind.

    # There's no canonical way to do this; so we leverage off the fact that 1.6
    # also introduced a new project template, removing a bunch of settings from the
    # default that won't be in common usage.

    # We make this determination on a balance of probabilities. Each of these factors
    # contributes a weight; if enough of them trigger, we've got a likely 1.6 project.
    weight = 0

    # If TEST_RUNNER is explicitly set, it's all a moot point - if it's been explicitly set,
    # the user has opted into a specific set of behaviors, which won't change as the
    # default changes.
    if not settings.is_overridden('TEST_RUNNER'):
        # Strong markers:
        # SITE_ID = 1 is in 1.5 template, not defined in 1.6 template
        try:
            settings.SITE_ID
            weight += 2
        except AttributeError:
            pass

        # BASE_DIR is not defined in 1.5 template, set in 1.6 template
        try:
            settings.BASE_DIR
        except AttributeError:
            weight += 2

        # TEMPLATE_LOADERS defined in 1.5 template, not defined in 1.6 template
        if settings.is_overridden('TEMPLATE_LOADERS'):
            weight += 2

        # MANAGERS defined in 1.5 template, not defined in 1.6 template
        if settings.is_overridden('MANAGERS'):
            weight += 2

        # Weaker markers - These are more likely to have been added in common usage
        # ADMINS defined in 1.5 template, not defined in 1.6 template
        if settings.is_overridden('ADMINS'):
            weight += 1

        # Clickjacking enabled by default in 1.6
        if 'django.middleware.clickjacking.XFrameOptionsMiddleware' not in set(settings.MIDDLEWARE_CLASSES):
            weight += 1

    if weight >= 6:
        return [
            Warning(
                "Some project unittests may not execute as expected.",
                hint=("Django 1.6 introduced a new default test runner. It looks like "
                      "this project was generated using Django 1.5 or earlier. You should "
                      "ensure your tests are all running & behaving as expected. See "
                      "https://docs.djangoproject.com/en/dev/releases/1.6/#discovery-of-tests-in-any-test-module "
                      "for more information."),
                obj=None,
                id='1_6.W001',
            )
        ]
    else:
        return []


def _check_boolean_field_default_value(app_configs=None, **kwargs):
    """
    Checks if there are any BooleanFields without a default value, &
    warns the user that the default has changed from False to None.
    """
    from django.db import models

    problem_fields = [
        field
        for model in apps.get_models(**kwargs)
        if app_configs is None or model._meta.app_config in app_configs
        for field in model._meta.local_fields
        if isinstance(field, models.BooleanField) and not field.has_default()
    ]

    return [
        Warning(
            "BooleanField does not have a default value.",
            hint=("Django 1.6 changed the default value of BooleanField from False to None. "
                  "See https://docs.djangoproject.com/en/1.6/ref/models/fields/#booleanfield "
                  "for more information."),
            obj=field,
            id='1_6.W002',
        )
        for field in problem_fields
    ]
