# Source code for django_tables2.data

    import warnings

    from django.utils.functional import cached_property

    from .utils import OrderBy, OrderByTuple, segment

    class TableData:
        """Base class for table data containers."""

        def __init__(self, data):
            self.data = data

        def __getitem__(self, key):
            """Slicing returns a new `.TableData` instance, indexing returns a single record."""
            return self.data[key]

        def __iter__(self):
            """
            Iterate over the table data (for ... in ... defaults to using this).

            There's a bug in Django 1.3 with indexing into QuerySets, so this side-steps that problem (as well
            as just being a better way to iterate).
            """
            return iter(self.data)

        def set_table(self, table):
            """
            `Table.__init__` calls this method to inject an instance of itself into the `TableData` instance.

            Good place to do additional checks if Table and TableData instance will work together properly.
            """
            self.table = table

        @property
        def model(self):
            return getattr(self.data, "model", None)

        @property
        def ordering(self):
            return None

        @property
        def verbose_name(self):
            return "item"

        @property
        def verbose_name_plural(self):
            return "items"

        @staticmethod
        def from_data(data):
            # allow explicit child classes of TableData to be passed to Table()
            if isinstance(data, TableData):
                return data
            if TableQuerysetData.validate(data):
                return TableQuerysetData(data)
            elif TableListData.validate(data):
                return TableListData(list(data))

            raise ValueError(
                "data must be QuerySet-like (have count() and order_by()) or support"
                f" list(data) -- {type(data).__name__} has neither"
            )

    class TableListData(TableData):
        """
        Table data container for a list of dicts.

        For example::
            [
                {'name': 'John', 'age': 20},
                {'name': 'Brian', 'age': 25}
            ]

        .. note::

            Other structures might have worked in the past, but are not explicitly supported or tested.
        """

        @staticmethod
        def validate(data):
            """Validate `data` for use in this container."""
            return hasattr(data, "__iter__") or (
                hasattr(data, "__len__") and hasattr(data, "__getitem__")
            )

        def __len__(self):
            return len(self.data)

        @property
        def verbose_name(self):
            return getattr(self.data, "verbose_name", super().verbose_name)

        @property
        def verbose_name_plural(self):
            return getattr(self.data, "verbose_name_plural", super().verbose_name_plural)

        def order_by(self, aliases):
            """
            Order the data based on order by aliases (prefixed column names) in the table.

            Arguments:
                aliases (`~.utils.OrderByTuple`): optionally prefixed names of
                    columns ('-' indicates descending order) in order of
                    significance with regard to data ordering.
            """
            accessors = []
            for alias in aliases:
                bound_column = self.table.columns[OrderBy(alias).bare]

                # bound_column.order_by reflects the current ordering applied to
                # the table. As such we need to check the current ordering on the
                # column and use the opposite if it doesn't match the alias prefix.
                if alias[0] != bound_column.order_by_alias[0]:
                    accessors += bound_column.order_by.opposite
                else:
                    accessors += bound_column.order_by

            self.data.sort(key=OrderByTuple(accessors).key)

    class TableQuerysetData(TableData):
        """Table data container for a QuerySet."""

        @staticmethod
        def validate(data):
            """Validate `data` for use in this container."""
            return (
                hasattr(data, "count")
                and callable(data.count)
                and hasattr(data, "order_by")
                and callable(data.order_by)
            )

        def __len__(self):
            """Length of the data (cached)."""
            if not hasattr(self, "_length") or self._length is None:
                if hasattr(self.table, "paginator"):
                    # for paginated tables, use QuerySet.count() as we are interested in total number of records.
                    self._length = self.data.count()
                else:
                    # for non-paginated tables, use the length of the QuerySet
                    self._length = len(self.data)

            return self._length

        def set_table(self, table):
            super().set_table(table)
            if (
                self.model
                and getattr(table._meta, "model", None)
                and not issubclass(self.model, table._meta.model)
            ):
                warnings.warn(
                    f"Table data is of type {self.model} but {table._meta.model} is specified in Table.Meta.model"
                )

        @property
        def ordering(self):
            """
            Return the list of order by aliases that are enforcing ordering on the data.

            If the data is unordered, an empty sequence is returned. If the
            ordering can not be determined, `None` is returned.

            This works by inspecting the actual underlying data. As such it's only
            supported for querysets.
            """
            aliases = {}
            for bound_column in self.table.columns:
                aliases[bound_column.order_by_alias] = bound_column.order_by
            try:
                return next(segment(self.data.query.order_by, aliases))
            except StopIteration:
                pass

        def order_by(self, aliases):
            """
            Order the data based on order by aliases (prefixed column names) in the table.

            Arguments:
                aliases (`~.utils.OrderByTuple`): optionally prefixed names of
                    columns ('-' indicates descending order) in order of
                    significance with regard to data ordering.
            """
            modified_any = False
            accessors = []
            for alias in aliases:
                bound_column = self.table.columns[OrderBy(alias).bare]
                # bound_column.order_by reflects the current ordering applied to
                # the table. As such we need to check the current ordering on the
                # column and use the opposite if it doesn't match the alias prefix.
                if alias[0] != bound_column.order_by_alias[0]:
                    accessors += bound_column.order_by.opposite
                else:
                    accessors += bound_column.order_by

                if bound_column:
                    queryset, modified = bound_column.order(self.data, alias[0] == "-")

                    if modified:
                        self.data = queryset
                        modified_any = True

            # custom ordering
            if modified_any:
                return

            # Traditional ordering
            if accessors:
                order_by_accessors = (a.for_queryset() for a in accessors)
                self.data = self.data.order_by(*order_by_accessors)

        @cached_property
        def verbose_name(self):
            """
            Full (singular) name for the data.

            Model's `~django.db.Model.Meta.verbose_name` is honored.
            """
            return self.data.model._meta.verbose_name

        @cached_property
        def verbose_name_plural(self):
            """
            Full (plural) name for the data.

            Model's `~django.db.Model.Meta.verbose_name` is honored.
            """
            return self.data.model._meta.verbose_name_plural