# sql/dml.py
# Copyright (C) 2009-2014 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
from .elements import ClauseElement, _literal_as_text, Null, and_, _clone
from .selectable import _interpret_as_from, _interpret_as_select, HasPrefixes
from .. import util
from .. import exc

class UpdateBase(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()
    _prefixes = ()

    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 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):
        """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
    select = 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):
        """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: Alternatively, 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 single dictionary form
         works the same as the kwargs form::

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

         If a tuple is passed, the tuple should contain the same number
         of columns as the target :class:`.Table`::

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

         The :class:`.Insert` construct also supports multiply-rendered VALUES
         construct, for those backends which support this SQL syntax
         (SQLite, Postgresql, MySQL).  This mode is indicated by passing a list
         of one or more dictionaries/tuples::

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

         In the case of an :class:`.Update`
         construct, only the single dictionary/tuple form is accepted,
         else an exception is raised.  It is also an exception case to
         attempt to mix the single-/multiple- value styles together,
         either through multiple :meth:`.ValuesBase.values` calls
         or by sending a list + kwargs at the same time.

         .. note::

             Passing a multiple values list is *not* the same
             as passing a multiple values list to the :meth:`.Connection.execute`
             method.  Passing a list of parameter sets to :meth:`.ValuesBase.values`
             produces a construct of this form::

                INSERT INTO table (col1, col2, col3) VALUES
                                (col1_0, col2_0, col3_0),
                                (col1_1, col2_1, col3_1),
                                ...

             whereas a multiple list passed to :meth:`.Connection.execute`
             has the effect of using the DBAPI
             `executemany() <http://www.python.org/dev/peps/pep-0249/#id18>`_
             method, which provides a high-performance system of invoking
             a single-row INSERT statement many times against a series
             of parameter sets.   The "executemany" style is supported by
             all database backends, as it does not depend on a special SQL
             syntax.

         .. versionadded:: 0.8
             Support for multiple-VALUES INSERT statements.


        .. 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]
        else:
            v = {}

        if self.parameters is None:
            self.parameters, self._has_multi_parameters = \
                    self._process_colparams(v)
        else:
            if self._has_multi_parameters:
                self.parameters = list(self.parameters)
                p, self._has_multi_parameters = self._process_colparams(v)
                if not self._has_multi_parameters:
                    raise exc.ArgumentError(
                        "Can't mix single-values and multiple values "
                        "formats in one statement")

                self.parameters.extend(p)
            else:
                self.parameters = self.parameters.copy()
                p, self._has_multi_parameters = self._process_colparams(v)
                if self._has_multi_parameters:
                    raise exc.ArgumentError(
                        "Can't mix single-values and multiple values "
                        "formats in one statement")
                self.parameters.update(p)

        if kwargs:
            if self._has_multi_parameters:
                raise exc.ArgumentError(
                            "Can't pass kwargs and multiple parameter sets "
                            "simultaenously")
            else:
                self.parameters.update(kwargs)

    @_generative
    def return_defaults(self, *cols):
        """Make use of a :term:`RETURNING` clause for the purpose
        of fetching server-side expressions and defaults.

        E.g.::

            stmt = table.insert().values(data='newdata').return_defaults()

            result = connection.execute(stmt)

            server_created_at = result.returned_defaults['created_at']

        When used against a backend that supports RETURNING, all column
        values generated by SQL expression or server-side-default will be added
        to any existing RETURNING clause, provided that
        :meth:`.UpdateBase.returning` is not used simultaneously.   The column values
        will then be available on the result using the
        :attr:`.ResultProxy.returned_defaults` accessor as a
        dictionary, referring to values keyed to the :class:`.Column` object
        as well as its ``.key``.

        This method differs from :meth:`.UpdateBase.returning` in these ways:

        1. :meth:`.ValuesBase.return_defaults` is only intended for use with
           an INSERT or an UPDATE statement that matches exactly one row.
           While the RETURNING construct in the general sense supports multiple
           rows for a multi-row UPDATE or DELETE statement, or for special
           cases of INSERT that return multiple rows (e.g. INSERT from SELECT,
           multi-valued VALUES clause), :meth:`.ValuesBase.return_defaults`
           is intended only
           for an "ORM-style" single-row INSERT/UPDATE statement.  The row
           returned by the statement is also consumed implcitly when
           :meth:`.ValuesBase.return_defaults` is used.  By contrast,
           :meth:`.UpdateBase.returning` leaves the RETURNING result-set intact
           with a collection of any number of rows.

        2. It is compatible with the existing logic to fetch auto-generated
           primary key values, also known as "implicit returning".  Backends that
           support RETURNING will automatically make use of RETURNING in order
           to fetch the value of newly generated primary keys; while the
           :meth:`.UpdateBase.returning` method circumvents this behavior,
           :meth:`.ValuesBase.return_defaults` leaves it intact.

        3. It can be called against any backend.  Backends that don't support
           RETURNING will skip the usage of the feature, rather than raising
           an exception.  The return value of :attr:`.ResultProxy.returned_defaults`
           will be ``None``

        :meth:`.ValuesBase.return_defaults` is used by the ORM to provide
        an efficient implementation for the ``eager_defaults`` feature of
        :func:`.mapper`.

        :param cols: optional list of column key names or :class:`.Column`
         objects.  If omitted, all column expressions evaulated on the server
         are added to the returning list.

        .. versionadded:: 0.9.0

        .. seealso::

            :meth:`.UpdateBase.returning`

            :attr:`.ResultProxy.returned_defaults`

        """
        self._return_defaults = cols or True


class Insert(ValuesBase):
    """Represent an INSERT construct.

    The :class:`.Insert` object is created using the
    :func:`~.expression.insert()` function.

    .. seealso::

        :ref:`coretutorial_insert_expressions`

    """
    __visit_name__ = 'insert'

    _supports_multi_parameters = True

    def __init__(self,
                table,
                values=None,
                inline=False,
                bind=None,
                prefixes=None,
                returning=None,
                return_defaults=False,
                **dialect_kw):
        """Construct an :class:`.Insert` object.

        Similar functionality is available via the
        :meth:`~.TableClause.insert` method on
        :class:`~.schema.Table`.

        :param table: :class:`.TableClause` which is the subject of the insert.

        :param values: collection of values to be inserted; see
         :meth:`.Insert.values` for a description of allowed formats here.
         Can be omitted entirely; a :class:`.Insert` construct will also
         dynamically render the VALUES clause at execution time based on
         the parameters passed to :meth:`.Connection.execute`.

        :param inline: if True, SQL defaults will be compiled 'inline' into the
          statement and not pre-executed.

        If both `values` and compile-time bind parameters are present, the
        compile-time bind parameters override the information specified
        within `values` on a per-key basis.

        The keys within `values` can be either :class:`~sqlalchemy.schema.Column`
        objects or their string identifiers. Each key may reference one of:

        * a literal data value (i.e. string, number, etc.);
        * a Column object;
        * a SELECT statement.

        If a ``SELECT`` statement is specified which references this
        ``INSERT`` statement's table, the statement will be correlated
        against the ``INSERT`` statement.

        .. seealso::

            :ref:`coretutorial_insert_expressions` - SQL Expression Tutorial

            :ref:`inserts_and_updates` - SQL Expression Tutorial

        """
        ValuesBase.__init__(self, table, values, prefixes)
        self._bind = bind
        self.select = self.select_names = None
        self.inline = inline
        self._returning = returning
        self._validate_dialect_kwargs(dialect_kw)
        self._return_defaults = return_defaults

    def get_children(self, **kwargs):
        if self.select is not None:
            return self.select,
        else:
            return ()

    @_generative
    def from_select(self, names, select):
        """Return a new :class:`.Insert` construct which represents
        an ``INSERT...FROM SELECT`` statement.

        e.g.::

            sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5)
            ins = table2.insert().from_select(['a', 'b'], sel)

        :param names: a sequence of string column names or :class:`.Column`
         objects representing the target columns.
        :param select: a :func:`.select` construct, :class:`.FromClause`
         or other construct which resolves into a :class:`.FromClause`,
         such as an ORM :class:`.Query` object, etc.  The order of
         columns returned from this FROM clause should correspond to the
         order of columns sent as the ``names`` parameter;  while this
         is not checked before passing along to the database, the database
         would normally raise an exception if these column lists don't
         correspond.

        .. note::

           Depending on backend, it may be necessary for the :class:`.Insert`
           statement to be constructed using the ``inline=True`` flag; this
           flag will prevent the implicit usage of ``RETURNING`` when the
           ``INSERT`` statement is rendered, which isn't supported on a backend
           such as Oracle in conjunction with an ``INSERT..SELECT`` combination::

             sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5)
             ins = table2.insert(inline=True).from_select(['a', 'b'], sel)

        .. note::

           A SELECT..INSERT construct in SQL has no VALUES clause.  Therefore
           :class:`.Column` objects which utilize Python-side defaults
           (e.g. as described at :ref:`metadata_defaults_toplevel`)
           will **not** take effect when using :meth:`.Insert.from_select`.

        .. versionadded:: 0.8.3

        """
        if self.parameters:
            raise exc.InvalidRequestError(
                        "This construct already inserts value expressions")

        self.parameters, self._has_multi_parameters = \
                self._process_colparams(dict((n, Null()) for n in names))

        self.select_names = names
        self.select = _interpret_as_select(select)

    def _copy_internals(self, clone=_clone, **kw):
        # TODO: coverage
        self.parameters = self.parameters.copy()
        if self.select is not None:
            self.select = _clone(self.select)


class Update(ValuesBase):
    """Represent an Update construct.

    The :class:`.Update` object is created using the :func:`update()` function.

    """
    __visit_name__ = 'update'

    def __init__(self,
                table,
                whereclause=None,
                values=None,
                inline=False,
                bind=None,
                prefixes=None,
                returning=None,
                return_defaults=False,
                **dialect_kw):
        """Construct an :class:`.Update` object.

        E.g.::

            from sqlalchemy import update

            stmt = update(users).where(users.c.id==5).\\
                    values(name='user #5')

        Similar functionality is available via the
        :meth:`~.TableClause.update` method on
        :class:`.Table`::

            stmt = users.update().\\
                        where(users.c.id==5).\\
                        values(name='user #5')

        :param table: A :class:`.Table` object representing the database
         table to be updated.

        :param whereclause: Optional SQL expression describing the ``WHERE``
         condition of the ``UPDATE`` statement.   Modern applications
         may prefer to use the generative :meth:`~Update.where()`
         method to specify the ``WHERE`` clause.

         The WHERE clause can refer to multiple tables.
         For databases which support this, an ``UPDATE FROM`` clause will
         be generated, or on MySQL, a multi-table update.  The statement
         will fail on databases that don't have support for multi-table
         update statements.  A SQL-standard method of referring to
         additional tables in the WHERE clause is to use a correlated
         subquery::

            users.update().values(name='ed').where(
                    users.c.name==select([addresses.c.email_address]).\\
                                where(addresses.c.user_id==users.c.id).\\
                                as_scalar()
                    )

         .. versionchanged:: 0.7.4
             The WHERE clause can refer to multiple tables.

        :param values:
          Optional dictionary which specifies the ``SET`` conditions of the
          ``UPDATE``.  If left as ``None``, the ``SET``
          conditions are determined from those parameters passed to the
          statement during the execution and/or compilation of the
          statement.   When compiled standalone without any parameters,
          the ``SET`` clause generates for all columns.

          Modern applications may prefer to use the generative
          :meth:`.Update.values` method to set the values of the
          UPDATE statement.

        :param inline:
          if True, SQL defaults present on :class:`.Column` objects via
          the ``default`` keyword will be compiled 'inline' into the statement
          and not pre-executed.  This means that their values will not
          be available in the dictionary returned from
          :meth:`.ResultProxy.last_updated_params`.

        If both ``values`` and compile-time bind parameters are present, the
        compile-time bind parameters override the information specified
        within ``values`` on a per-key basis.

        The keys within ``values`` can be either :class:`.Column`
        objects or their string identifiers (specifically the "key" of the
        :class:`.Column`, normally but not necessarily equivalent to
        its "name").  Normally, the
        :class:`.Column` objects used here are expected to be
        part of the target :class:`.Table` that is the table
        to be updated.  However when using MySQL, a multiple-table
        UPDATE statement can refer to columns from any of
        the tables referred to in the WHERE clause.

        The values referred to in ``values`` are typically:

        * a literal data value (i.e. string, number, etc.)
        * a SQL expression, such as a related :class:`.Column`,
          a scalar-returning :func:`.select` construct,
          etc.

        When combining :func:`.select` constructs within the values
        clause of an :func:`.update` construct,
        the subquery represented by the :func:`.select` should be
        *correlated* to the parent table, that is, providing criterion
        which links the table inside the subquery to the outer table
        being updated::

            users.update().values(
                    name=select([addresses.c.email_address]).\\
                            where(addresses.c.user_id==users.c.id).\\
                            as_scalar()
                )

        .. seealso::

            :ref:`inserts_and_updates` - SQL Expression
            Language Tutorial


        """
        ValuesBase.__init__(self, table, values, prefixes)
        self._bind = bind
        self._returning = returning
        if whereclause is not None:
            self._whereclause = _literal_as_text(whereclause)
        else:
            self._whereclause = None
        self.inline = inline
        self._validate_dialect_kwargs(dialect_kw)
        self._return_defaults = return_defaults


    def get_children(self, **kwargs):
        if self._whereclause is not None:
            return self._whereclause,
        else:
            return ()

    def _copy_internals(self, clone=_clone, **kw):
        # TODO: coverage
        self._whereclause = clone(self._whereclause, **kw)
        self.parameters = self.parameters.copy()

    @_generative
    def where(self, whereclause):
        """return a new update() construct with the given expression added to
        its WHERE clause, joined to the existing clause via AND, if any.

        """
        if self._whereclause is not None:
            self._whereclause = and_(self._whereclause,
                    _literal_as_text(whereclause))
        else:
            self._whereclause = _literal_as_text(whereclause)

    @property
    def _extra_froms(self):
        # TODO: this could be made memoized
        # if the memoization is reset on each generative call.
        froms = []
        seen = set([self.table])

        if self._whereclause is not None:
            for item in _from_objects(self._whereclause):
                if not seen.intersection(item._cloned_set):
                    froms.append(item)
                seen.update(item._cloned_set)

        return froms


class Delete(UpdateBase):
    """Represent a DELETE construct.

    The :class:`.Delete` object is created using the :func:`delete()` function.

    """

    __visit_name__ = 'delete'

    def __init__(self,
            table,
            whereclause=None,
            bind=None,
            returning=None,
            prefixes=None,
            **dialect_kw):
        """Construct :class:`.Delete` object.

        Similar functionality is available via the
        :meth:`~.TableClause.delete` method on
        :class:`~.schema.Table`.

        :param table: The table to be updated.

        :param whereclause: A :class:`.ClauseElement` describing the ``WHERE``
          condition of the ``UPDATE`` statement. Note that the
          :meth:`~Delete.where()` generative method may be used instead.

        .. seealso::

            :ref:`deletes` - SQL Expression Tutorial

        """
        self._bind = bind
        self.table = _interpret_as_from(table)
        self._returning = returning

        if prefixes:
            self._setup_prefixes(prefixes)

        if whereclause is not None:
            self._whereclause = _literal_as_text(whereclause)
        else:
            self._whereclause = None

        self._validate_dialect_kwargs(dialect_kw)

    def get_children(self, **kwargs):
        if self._whereclause is not None:
            return self._whereclause,
        else:
            return ()

    @_generative
    def where(self, whereclause):
        """Add the given WHERE clause to a newly returned delete construct."""

        if self._whereclause is not None:
            self._whereclause = and_(self._whereclause,
                    _literal_as_text(whereclause))
        else:
            self._whereclause = _literal_as_text(whereclause)

    def _copy_internals(self, clone=_clone, **kw):
        # TODO: coverage
        self._whereclause = clone(self._whereclause, **kw)

