from __future__ import absolute_import

import datetime
import logging

from django.db import models
from django.core.exceptions import PermissionDenied

from acls.models import AccessEntry
from documents.models import Document
from history.api import create_history
from permissions.models import Permission

from .events import (HISTORY_DOCUMENT_CHECKED_IN, HISTORY_DOCUMENT_AUTO_CHECKED_IN,
    HISTORY_DOCUMENT_FORCEFUL_CHECK_IN)
from .exceptions import DocumentNotCheckedOut
from .literals import STATE_CHECKED_OUT, STATE_CHECKED_IN
from .permissions import PERMISSION_DOCUMENT_RESTRICTIONS_OVERRIDE

logger = logging.getLogger(__name__)


class DocumentCheckoutManager(models.Manager):
    def checked_out_documents(self):
        return Document.objects.filter(pk__in=self.model.objects.all().values_list('document__pk', flat=True))

    def expired_check_outs(self):
        expired_list = Document.objects.filter(pk__in=self.model.objects.filter(expiration_datetime__lte=datetime.datetime.now()).values_list('document__pk', flat=True))
        logger.debug('expired_list: %s' % expired_list)
        return expired_list

    def check_in_expired_check_outs(self):
        for document in self.expired_check_outs():
            document.check_in()

    def is_document_checked_out(self, document):
        if self.model.objects.filter(document=document):
            return True
        else:
            return False

    def check_in_document(self, document, user=None):
        try:
            document_checkout = self.model.objects.get(document=document)
        except self.model.DoesNotExist:
            raise DocumentNotCheckedOut
        else:
            if user:
                if self.document_checkout_info(document).user_object != user:
                    create_history(HISTORY_DOCUMENT_FORCEFUL_CHECK_IN, source_object=document, data={'user': user, 'document': document})
                else:
                    create_history(HISTORY_DOCUMENT_CHECKED_IN, source_object=document, data={'user': user, 'document': document})
            else:
                create_history(HISTORY_DOCUMENT_AUTO_CHECKED_IN, source_object=document, data={'document': document})

            document_checkout.delete()

    def document_checkout_info(self, document):
        try:
            return self.model.objects.get(document=document)
        except self.model.DoesNotExist:
            raise DocumentNotCheckedOut

    def document_checkout_state(self, document):
        if self.is_document_checked_out(document):
            return STATE_CHECKED_OUT
        else:
            return STATE_CHECKED_IN

    def is_document_new_versions_allowed(self, document, user=None):
        try:
            checkout_info = self.document_checkout_info(document)
        except DocumentNotCheckedOut:
            return True
        else:
            if not user:
                return not checkout_info.block_new_version
            else:
                if user.is_staff or user.is_superuser:
                    # Allow anything to superusers and staff
                    return True

                if user == checkout_info.user_object:
                    # Allow anything to the user who checked out this document
                    True
                else:
                    # If not original user check to see if user has global or this document's PERMISSION_DOCUMENT_RESTRICTIONS_OVERRIDE permission
                    try:
                        Permission.objects.check_permissions(user, [PERMISSION_DOCUMENT_RESTRICTIONS_OVERRIDE])
                    except PermissionDenied:
                        try:
                            AccessEntry.objects.check_accesses([PERMISSION_DOCUMENT_RESTRICTIONS_OVERRIDE], user, document)
                        except PermissionDenied:
                            # Last resort check if original user enabled restriction
                            return not checkout_info.block_new_version
                        else:
                            return True
                    else:
                        return True