"""
The `compat` module provides support for backwards compatibility with older
versions of Django/Python, and compatibility wrappers around optional packages.
"""

# flake8: noqa
from __future__ import unicode_literals

import django
from django.conf import settings
from django.db import connection, transaction
from django.template import Context, RequestContext, Template
from django.utils import six
from django.views.generic import View

try:
    import importlib  # Available in Python 3.1+
except ImportError:
    from django.utils import importlib  # Will be removed in Django 1.9


def unicode_repr(instance):
    # Get the repr of an instance, but ensure it is a unicode string
    # on both python 3 (already the case) and 2 (not the case).
    if six.PY2:
        return repr(instance).decode('utf-8')
    return repr(instance)


def unicode_to_repr(value):
    # Coerce a unicode string to the correct repr return type, depending on
    # the Python version. We wrap all our `__repr__` implementations with
    # this and then use unicode throughout internally.
    if six.PY2:
        return value.encode('utf-8')
    return value


def unicode_http_header(value):
    # Coerce HTTP header value to unicode.
    if isinstance(value, six.binary_type):
        return value.decode('iso-8859-1')
    return value


def total_seconds(timedelta):
    # TimeDelta.total_seconds() is only available in Python 2.7
    if hasattr(timedelta, 'total_seconds'):
        return timedelta.total_seconds()
    else:
        return (timedelta.days * 86400.0) + float(timedelta.seconds) + (timedelta.microseconds / 1000000.0)


def distinct(queryset, base):
    if settings.DATABASES[queryset.db]["ENGINE"] == "django.db.backends.oracle":
        # distinct analogue for Oracle users
        return base.filter(pk__in=set(queryset.values_list('pk', flat=True)))
    return queryset.distinct()


# contrib.postgres only supported from 1.8 onwards.
try:
    from django.contrib.postgres import fields as postgres_fields
except ImportError:
    postgres_fields = None


# JSONField is only supported from 1.9 onwards
try:
    from django.contrib.postgres.fields import JSONField
except ImportError:
    JSONField = None


# django-filter is optional
try:
    import django_filters
except ImportError:
    django_filters = None


# django-crispy-forms is optional
try:
    import crispy_forms
except ImportError:
    crispy_forms = None


# Django-guardian is optional. Import only if guardian is in INSTALLED_APPS
# Fixes (#1712). We keep the try/except for the test suite.
guardian = None
try:
    if 'guardian' in settings.INSTALLED_APPS:
        import guardian
        import guardian.shortcuts  # Fixes #1624
except ImportError:
    pass


# PATCH method is not implemented by Django
if 'patch' not in View.http_method_names:
    View.http_method_names = View.http_method_names + ['patch']


# Markdown is optional
try:
    import markdown

    if markdown.version <= '2.2':
        HEADERID_EXT_PATH = 'headerid'
    else:
        HEADERID_EXT_PATH = 'markdown.extensions.headerid'

    def apply_markdown(text):
        """
        Simple wrapper around :func:`markdown.markdown` to set the base level
        of '#' style headers to <h2>.
        """
        extensions = [HEADERID_EXT_PATH]
        extension_configs = {
            HEADERID_EXT_PATH: {
                'level': '2'
            }
        }
        md = markdown.Markdown(
            extensions=extensions, extension_configs=extension_configs
        )
        return md.convert(text)
except ImportError:
    apply_markdown = None


# `separators` argument to `json.dumps()` differs between 2.x and 3.x
# See: http://bugs.python.org/issue22767
if six.PY3:
    SHORT_SEPARATORS = (',', ':')
    LONG_SEPARATORS = (', ', ': ')
    INDENT_SEPARATORS = (',', ': ')
else:
    SHORT_SEPARATORS = (b',', b':')
    LONG_SEPARATORS = (b', ', b': ')
    INDENT_SEPARATORS = (b',', b': ')

try:
    # DecimalValidator is unavailable in Django < 1.9
    from django.core.validators import DecimalValidator
except ImportError:
    DecimalValidator = None


def set_rollback():
    if hasattr(transaction, 'set_rollback'):
        if connection.settings_dict.get('ATOMIC_REQUESTS', False):
            # If running in >=1.6 then mark a rollback as required,
            # and allow it to be handled by Django.
            if connection.in_atomic_block:
                transaction.set_rollback(True)
    elif transaction.is_managed():
        # Otherwise handle it explicitly if in managed mode.
        if transaction.is_dirty():
            transaction.rollback()
        transaction.leave_transaction_management()
    else:
        # transaction not managed
        pass


def template_render(template, context=None, request=None):
    """
    Passing Context or RequestContext to Template.render is deprecated in 1.9+,
    see https://github.com/django/django/pull/3883 and
    https://github.com/django/django/blob/1.9/django/template/backends/django.py#L82-L84

    :param template: Template instance
    :param context: dict
    :param request: Request instance
    :return: rendered template as SafeText instance
    """
    if isinstance(template, Template):
        if request:
            context = RequestContext(request, context)
        else:
            context = Context(context)
        return template.render(context)
    # backends template, e.g. django.template.backends.django.Template
    else:
        return template.render(context, request=request)