from ... import exc
from ... import util
from ...sql.base import _exclusive_against
from ...sql.base import _generative
from ...sql.base import ColumnCollection
from ...sql.dml import Insert as StandardInsert
from ...sql.elements import ClauseElement
from ...sql.expression import alias
from ...util.langhelpers import public_factory


__all__ = ("Insert", "insert")


class Insert(StandardInsert):
    """MySQL-specific implementation of INSERT.

    Adds methods for MySQL-specific syntaxes such as ON DUPLICATE KEY UPDATE.

    The :class:`~.mysql.Insert` object is created using the
    :func:`sqlalchemy.dialects.mysql.insert` function.

    .. versionadded:: 1.2

    """

    stringify_dialect = "mysql"
    inherit_cache = False

    @property
    def inserted(self):
        """Provide the "inserted" namespace for an ON DUPLICATE KEY UPDATE statement

        MySQL's ON DUPLICATE KEY UPDATE clause allows reference to the row
        that would be inserted, via a special function called ``VALUES()``.
        This attribute provides all columns in this row to be referenceable
        such that they will render within a ``VALUES()`` function inside the
        ON DUPLICATE KEY UPDATE clause.    The attribute is named ``.inserted``
        so as not to conflict with the existing
        :meth:`_expression.Insert.values` method.

        .. tip::  The :attr:`_mysql.Insert.inserted` attribute is an instance
            of :class:`_expression.ColumnCollection`, which provides an
            interface the same as that of the :attr:`_schema.Table.c`
            collection described at :ref:`metadata_tables_and_columns`.
            With this collection, ordinary names are accessible like attributes
            (e.g. ``stmt.inserted.some_column``), but special names and
            dictionary method names should be accessed using indexed access,
            such as ``stmt.inserted["column name"]`` or
            ``stmt.inserted["values"]``.  See the docstring for
            :class:`_expression.ColumnCollection` for further examples.

        .. seealso::

            :ref:`mysql_insert_on_duplicate_key_update` - example of how
            to use :attr:`_expression.Insert.inserted`

        """
        return self.inserted_alias.columns

    @util.memoized_property
    def inserted_alias(self):
        return alias(self.table, name="inserted")

    @_generative
    @_exclusive_against(
        "_post_values_clause",
        msgs={
            "_post_values_clause": "This Insert construct already "
            "has an ON DUPLICATE KEY clause present"
        },
    )
    def on_duplicate_key_update(self, *args, **kw):
        r"""
        Specifies the ON DUPLICATE KEY UPDATE clause.

        :param \**kw:  Column keys linked to UPDATE values.  The
         values may be any SQL expression or supported literal Python
         values.

        .. warning:: This dictionary does **not** take into account
           Python-specified default UPDATE values or generation functions,
           e.g. those specified using :paramref:`_schema.Column.onupdate`.
           These values will not be exercised for an ON DUPLICATE KEY UPDATE
           style of UPDATE, unless values are manually specified here.

        :param \*args: As an alternative to passing key/value parameters,
         a dictionary or list of 2-tuples can be passed as a single positional
         argument.

         Passing a single dictionary is equivalent to the keyword argument
         form::

            insert().on_duplicate_key_update({"name": "some name"})

         Passing a list of 2-tuples indicates that the parameter assignments
         in the UPDATE clause should be ordered as sent, in a manner similar
         to that described for the :class:`_expression.Update`
         construct overall
         in :ref:`updates_order_parameters`::

            insert().on_duplicate_key_update(
                [("name", "some name"), ("value", "some value")])

         .. versionchanged:: 1.3 parameters can be specified as a dictionary
            or list of 2-tuples; the latter form provides for parameter
            ordering.


        .. versionadded:: 1.2

        .. seealso::

            :ref:`mysql_insert_on_duplicate_key_update`

        """
        if args and kw:
            raise exc.ArgumentError(
                "Can't pass kwargs and positional arguments simultaneously"
            )

        if args:
            if len(args) > 1:
                raise exc.ArgumentError(
                    "Only a single dictionary or list of tuples "
                    "is accepted positionally."
                )
            values = args[0]
        else:
            values = kw

        inserted_alias = getattr(self, "inserted_alias", None)
        self._post_values_clause = OnDuplicateClause(inserted_alias, values)


insert = public_factory(
    Insert, ".dialects.mysql.insert", ".dialects.mysql.Insert"
)


class OnDuplicateClause(ClauseElement):
    __visit_name__ = "on_duplicate_key_update"

    _parameter_ordering = None

    stringify_dialect = "mysql"

    def __init__(self, inserted_alias, update):
        self.inserted_alias = inserted_alias

        # auto-detect that parameters should be ordered.   This is copied from
        # Update._proces_colparams(), however we don't look for a special flag
        # in this case since we are not disambiguating from other use cases as
        # we are in Update.values().
        if isinstance(update, list) and (
            update and isinstance(update[0], tuple)
        ):
            self._parameter_ordering = [key for key, value in update]
            update = dict(update)

        if isinstance(update, dict):
            if not update:
                raise ValueError(
                    "update parameter dictionary must not be empty"
                )
        elif isinstance(update, ColumnCollection):
            update = dict(update)
        else:
            raise ValueError(
                "update parameter must be a non-empty dictionary "
                "or a ColumnCollection such as the `.c.` collection "
                "of a Table object"
            )
        self.update = update
