# sql/dml.py
# Copyright (C) 2009-2018 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""
Provide :class:`.Insert`, :class:`.Update` and :class:`.Delete`.

"""

from .base import Executable, _generative, _from_objects, DialectKWArgs, \
    ColumnCollection
from .elements import ClauseElement, _literal_as_text, Null, and_, _clone, \
    _column_as_key
from .selectable import _interpret_as_from, _interpret_as_select, \
    HasPrefixes, HasCTE
from .. import util
from .. import exc


class UpdateBase(
        HasCTE, DialectKWArgs, HasPrefixes, Executable, ClauseElement):
    """Form the base for ``INSERT``, ``UPDATE``, and ``DELETE`` statements.

    """

    __visit_name__ = 'update_base'

    _execution_options = \
        Executable._execution_options.union({'autocommit': True})
    _hints = util.immutabledict()
    _parameter_ordering = None
    _prefixes = ()
    named_with_column = False

    def _process_colparams(self, parameters):
        def process_single(p):
            if isinstance(p, (list, tuple)):
                return dict(
                    (c.key, pval)
                    for c, pval in zip(self.table.c, p)
                )
            else:
                return p

        if self._preserve_parameter_order and parameters is not None:
            if not isinstance(parameters, list) or \
                    (parameters and not isinstance(parameters[0], tuple)):
                raise ValueError(
                    "When preserve_parameter_order is True, "
                    "values() only accepts a list of 2-tuples")
            self._parameter_ordering = [key for key, value in parameters]

            return dict(parameters), False

        if (isinstance(parameters, (list, tuple)) and parameters and
                isinstance(parameters[0], (list, tuple, dict))):

            if not self._supports_multi_parameters:
                raise exc.InvalidRequestError(
                    "This construct does not support "
                    "multiple parameter sets.")

            return [process_single(p) for p in parameters], True
        else:
            return process_single(parameters), False

    def params(self, *arg, **kw):
        """Set the parameters for the statement.

        This method raises ``NotImplementedError`` on the base class,
        and is overridden by :class:`.ValuesBase` to provide the
        SET/VALUES clause of UPDATE and INSERT.

        """
        raise NotImplementedError(
            "params() is not supported for INSERT/UPDATE/DELETE statements."
            " To set the values for an INSERT or UPDATE statement, use"
            " stmt.values(**parameters).")

    def bind(self):
        """Return a 'bind' linked to this :class:`.UpdateBase`
        or a :class:`.Table` associated with it.

        """
        return self._bind or self.table.bind

    def _set_bind(self, bind):
        self._bind = bind
    bind = property(bind, _set_bind)

    @_generative
    def returning(self, *cols):
        r"""Add a :term:`RETURNING` or equivalent clause to this statement.

        e.g.::

            stmt = table.update().\
                      where(table.c.data == 'value').\
                      values(status='X').\
                      returning(table.c.server_flag,
                                table.c.updated_timestamp)

            for server_flag, updated_timestamp in connection.execute(stmt):
                print(server_flag, updated_timestamp)

        The given collection of column expressions should be derived from
        the table that is
        the target of the INSERT, UPDATE, or DELETE.  While :class:`.Column`
        objects are typical, the elements can also be expressions::

            stmt = table.insert().returning(
                (table.c.first_name + " " + table.c.last_name).
                label('fullname'))

        Upon compilation, a RETURNING clause, or database equivalent,
        will be rendered within the statement.   For INSERT and UPDATE,
        the values are the newly inserted/updated values.  For DELETE,
        the values are those of the rows which were deleted.

        Upon execution, the values of the columns to be returned are made
        available via the result set and can be iterated using
        :meth:`.ResultProxy.fetchone` and similar.   For DBAPIs which do not
        natively support returning values (i.e. cx_oracle), SQLAlchemy will
        approximate this behavior at the result level so that a reasonable
        amount of behavioral neutrality is provided.

        Note that not all databases/DBAPIs
        support RETURNING.   For those backends with no support,
        an exception is raised upon compilation and/or execution.
        For those who do support it, the functionality across backends
        varies greatly, including restrictions on executemany()
        and other statements which return multiple rows. Please
        read the documentation notes for the database in use in
        order to determine the availability of RETURNING.

        .. seealso::

          :meth:`.ValuesBase.return_defaults` - an alternative method tailored
          towards efficient fetching of server-side defaults and triggers
          for single-row INSERTs or UPDATEs.


        """
        self._returning = cols

    @_generative
    def with_hint(self, text, selectable=None, dialect_name="*"):
        """Add a table hint for a single table to this
        INSERT/UPDATE/DELETE statement.

        .. note::

         :meth:`.UpdateBase.with_hint` currently applies only to
         Microsoft SQL Server.  For MySQL INSERT/UPDATE/DELETE hints, use
         :meth:`.UpdateBase.prefix_with`.

        The text of the hint is rendered in the appropriate
        location for the database backend in use, relative
        to the :class:`.Table` that is the subject of this
        statement, or optionally to that of the given
        :class:`.Table` passed as the ``selectable`` argument.

        The ``dialect_name`` option will limit the rendering of a particular
        hint to a particular backend. Such as, to add a hint
        that only takes effect for SQL Server::

            mytable.insert().with_hint("WITH (PAGLOCK)", dialect_name="mssql")

        .. versionadded:: 0.7.6

        :param text: Text of the hint.
        :param selectable: optional :class:`.Table` that specifies
         an element of the FROM clause within an UPDATE or DELETE
         to be the subject of the hint - applies only to certain backends.
        :param dialect_name: defaults to ``*``, if specified as the name
         of a particular dialect, will apply these hints only when
         that dialect is in use.
         """
        if selectable is None:
            selectable = self.table

        self._hints = self._hints.union(
            {(selectable, dialect_name): text})


class ValuesBase(UpdateBase):
    """Supplies support for :meth:`.ValuesBase.values` to
    INSERT and UPDATE constructs."""

    __visit_name__ = 'values_base'

    _supports_multi_parameters = False
    _has_multi_parameters = False
    _preserve_parameter_order = False
    select = None
    _post_values_clause = None

    def __init__(self, table, values, prefixes):
        self.table = _interpret_as_from(table)
        self.parameters, self._has_multi_parameters = \
            self._process_colparams(values)
        if prefixes:
            self._setup_prefixes(prefixes)

    @_generative
    def values(self, *args, **kwargs):
        r"""specify a fixed VALUES clause for an INSERT statement, or the SET
        clause for an UPDATE.

        Note that the :class:`.Insert` and :class:`.Update` constructs support
        per-execution time formatting of the VALUES and/or SET clauses,
        based on the arguments passed to :meth:`.Connection.execute`.
        However, the :meth:`.ValuesBase.values` method can be used to "fix" a
        particular set of parameters into the statement.

        Multiple calls to :meth:`.ValuesBase.values` will produce a new
        construct, each one with the parameter list modified to include
        the new parameters sent.  In the typical case of a single
        dictionary of parameters, the newly passed keys will replace
        the same keys in the previous construct.  In the case of a list-based
        "multiple values" construct, each new list of values is extended
        onto the existing list of values.

        :param \**kwargs: key value pairs representing the string key
          of a :class:`.Column` mapped to the value to be rendered into the
          VALUES or SET clause::

                users.insert().values(name="some name")

                users.update().where(users.c.id==5).values(name="some name")

        :param \*args: As an alternative to passing key/value parameters,
         a dictionary, tuple, or list of dictionaries or tuples can be passed
         as a single positional argument in order to form the VALUES or
         SET clause of the statement.  The forms that are accepted vary
         based on whether this is an :class:`.Insert` or an :class:`.Update`
         construct.

         For either an :class:`.Insert` or :class:`.Update` construct, a
         single dictionary can be passed, which works the same as that of
         the kwargs form::

            users.insert().values({"name": "some name"})

            users.update().values({"name": "some new name"})

         Also for either form but more typically for the :class:`.Insert`
         construct, a tuple that contains an entry for every column in the
         table is also accepted::

            users.insert().values((5, "some name"))

         The :class:`.Insert` construct also supports being passed a list
         of dictionaries or full-table-tuples, which on the server will
         render the less common SQL syntax of "multiple values" - this
         syntax is supported on backends such as SQLite, PostgreSQL, MySQL,
         but not necessarily others::

            users.insert().values([
                                {"name": "some name"},
                                {"name": "some other name"},
                                {"name": "yet another name"},
                            ])

         The above form would render a multiple VALUES statement similar to::

                INSERT INTO users (name) VALUES
                                (:name_1),
                                (:name_2),
                                (:name_3)

         It is essential to note that **passing multiple values is
         NOT the same as using traditional executemany() form**.  The above
         syntax is a **special** syntax not typically used.  To emit an
         INSERT statement against multiple rows, the normal method is
         to pass a multiple values list to the :meth:`.Connection.execute`
         method, which is supported by all database backends and is generally
         more efficient for a very large number of parameters.

           .. seealso::

               :ref:`execute_multiple` - an introduction to
               the traditional Core method of multiple parameter set
               invocation for INSERTs and other statements.

           .. versionchanged:: 1.0.0 an INSERT that uses a multiple-VALUES
              clause, even a list of length one,
              implies that the :paramref:`.Insert.inline` flag is set to
              True, indicating that the statement will not attempt to fetch
              the "last inserted primary key" or other defaults.  The
              statement deals with an arbitrary number of rows, so the
              :attr:`.ResultProxy.inserted_primary_key` accessor does not
              apply.

           .. versionchanged:: 1.0.0 A multiple-VALUES INSERT now supports
              columns with Python side default values and callables in the
              same way as that of an "executemany" style of invocation; the
              callable is invoked for each row.   See :ref:`bug_3288`
              for other details.

         The :class:`.Update` construct supports a special form which is a
         list of 2-tuples, which when provided must be passed in conjunction
         with the
         :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`
         parameter.
         This form causes the UPDATE statement to render the SET clauses
         using the order of parameters given to :meth:`.Update.values`, rather
         than the ordering of columns given in the :class:`.Table`.

           .. versionadded:: 1.0.10 - added support for parameter-ordered
              UPDATE statements via the
              :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`
              flag.

           .. seealso::

              :ref:`updates_order_parameters` - full example of the
              :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`
              flag

        .. seealso::

            :ref:`inserts_and_updates` - SQL Expression
            Language Tutorial

            :func:`~.expression.insert` - produce an ``INSERT`` statement

            :func:`~.expression.update` - produce an ``UPDATE`` statement

        """
        if self.select is not None:
            raise exc.InvalidRequestError(
                "This construct already inserts from a SELECT")
        if self._has_multi_parameters and kwargs:
            raise exc.InvalidRequestError(
                "This construct already has multiple parameter sets.")

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