from django.db.models import Q
from django_filters.rest_framework import BooleanFilter
from django_filters.rest_framework import Filter
from django_filters.rest_framework import FilterSet
from rest_framework_guardian.filters import ObjectPermissionsFilter

from .models import Correspondent
from .models import Document
from .models import DocumentType
from .models import Log
from .models import StoragePath
from .models import Tag

CHAR_KWARGS = ["istartswith", "iendswith", "icontains", "iexact"]
ID_KWARGS = ["in", "exact"]
INT_KWARGS = ["exact", "gt", "gte", "lt", "lte", "isnull"]
DATE_KWARGS = ["year", "month", "day", "date__gt", "gt", "date__lt", "lt"]


class CorrespondentFilterSet(FilterSet):
    class Meta:
        model = Correspondent
        fields = {"name": CHAR_KWARGS}


class TagFilterSet(FilterSet):
    class Meta:
        model = Tag
        fields = {"name": CHAR_KWARGS}


class DocumentTypeFilterSet(FilterSet):
    class Meta:
        model = DocumentType
        fields = {"name": CHAR_KWARGS}


class ObjectFilter(Filter):
    def __init__(self, exclude=False, in_list=False, field_name=""):
        super().__init__()
        self.exclude = exclude
        self.in_list = in_list
        self.field_name = field_name

    def filter(self, qs, value):
        if not value:
            return qs

        try:
            object_ids = [int(x) for x in value.split(",")]
        except ValueError:
            return qs

        if self.in_list:
            qs = qs.filter(**{f"{self.field_name}__id__in": object_ids}).distinct()
        else:
            for obj_id in object_ids:
                if self.exclude:
                    qs = qs.exclude(**{f"{self.field_name}__id": obj_id})
                else:
                    qs = qs.filter(**{f"{self.field_name}__id": obj_id})

        return qs


class InboxFilter(Filter):
    def filter(self, qs, value):
        if value == "true":
            return qs.filter(tags__is_inbox_tag=True)
        elif value == "false":
            return qs.exclude(tags__is_inbox_tag=True)
        else:
            return qs


class TitleContentFilter(Filter):
    def filter(self, qs, value):
        if value:
            return qs.filter(Q(title__icontains=value) | Q(content__icontains=value))
        else:
            return qs


class DocumentFilterSet(FilterSet):
    is_tagged = BooleanFilter(
        label="Is tagged",
        field_name="tags",
        lookup_expr="isnull",
        exclude=True,
    )

    tags__id__all = ObjectFilter(field_name="tags")

    tags__id__none = ObjectFilter(field_name="tags", exclude=True)

    tags__id__in = ObjectFilter(field_name="tags", in_list=True)

    correspondent__id__none = ObjectFilter(field_name="correspondent", exclude=True)

    document_type__id__none = ObjectFilter(field_name="document_type", exclude=True)

    storage_path__id__none = ObjectFilter(field_name="storage_path", exclude=True)

    is_in_inbox = InboxFilter()

    title_content = TitleContentFilter()

    class Meta:
        model = Document
        fields = {
            "title": CHAR_KWARGS,
            "content": CHAR_KWARGS,
            "archive_serial_number": INT_KWARGS,
            "created": DATE_KWARGS,
            "added": DATE_KWARGS,
            "modified": DATE_KWARGS,
            "correspondent": ["isnull"],
            "correspondent__id": ID_KWARGS,
            "correspondent__name": CHAR_KWARGS,
            "tags__id": ID_KWARGS,
            "tags__name": CHAR_KWARGS,
            "document_type": ["isnull"],
            "document_type__id": ID_KWARGS,
            "document_type__name": CHAR_KWARGS,
            "storage_path": ["isnull"],
            "storage_path__id": ID_KWARGS,
            "storage_path__name": CHAR_KWARGS,
        }


class LogFilterSet(FilterSet):
    class Meta:
        model = Log
        fields = {"level": INT_KWARGS, "created": DATE_KWARGS, "group": ID_KWARGS}


class StoragePathFilterSet(FilterSet):
    class Meta:
        model = StoragePath
        fields = {
            "name": CHAR_KWARGS,
            "path": CHAR_KWARGS,
        }


class ObjectOwnedOrGrantedPermissionsFilter(ObjectPermissionsFilter):
    """
    A filter backend that limits results to those where the requesting user
    has read object level permissions, owns the objects, or objects without
    an owner (for backwards compat)
    """

    def filter_queryset(self, request, queryset, view):
        objects_with_perms = super().filter_queryset(request, queryset, view)
        objects_owned = queryset.filter(owner=request.user)
        objects_unowned = queryset.filter(owner__isnull=True)
        return objects_with_perms | objects_owned | objects_unowned