# orm/util.py
# Copyright (C) 2005-2018 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


from .. import sql, util, event, exc as sa_exc, inspection
from ..sql import expression, util as sql_util, operators
from .interfaces import PropComparator, MapperProperty
from . import attributes
import re

from .base import instance_str, state_str, state_class_str, attribute_str, \
    state_attribute_str, object_mapper, object_state, _none_set, _never_set
from .base import class_mapper, _class_to_mapper
from .base import InspectionAttr
from .path_registry import PathRegistry

all_cascades = frozenset(("delete", "delete-orphan", "all", "merge",
                          "expunge", "save-update", "refresh-expire",
                          "none"))


class CascadeOptions(frozenset):
    """Keeps track of the options sent to relationship().cascade"""

    _add_w_all_cascades = all_cascades.difference([
        'all', 'none', 'delete-orphan'])
    _allowed_cascades = all_cascades

    __slots__ = (
        'save_update', 'delete', 'refresh_expire', 'merge',
        'expunge', 'delete_orphan')

    def __new__(cls, value_list):
        if isinstance(value_list, util.string_types) or value_list is None:
            return cls.from_string(value_list)
        values = set(value_list)
        if values.difference(cls._allowed_cascades):
            raise sa_exc.ArgumentError(
                "Invalid cascade option(s): %s" %
                ", ".join([repr(x) for x in
                           sorted(values.difference(cls._allowed_cascades))]))

        if "all" in values:
            values.update(cls._add_w_all_cascades)
        if "none" in values:
            values.clear()
        values.discard('all')

        self = frozenset.__new__(CascadeOptions, values)
        self.save_update = 'save-update' in values
        self.delete = 'delete' in values
        self.refresh_expire = 'refresh-expire' in values
        self.merge = 'merge' in values
        self.expunge = 'expunge' in values
        self.delete_orphan = "delete-orphan" in values

        if self.delete_orphan and not self.delete:
            util.warn("The 'delete-orphan' cascade "
                      "option requires 'delete'.")
        return self

    def __repr__(self):
        return "CascadeOptions(%r)" % (
            ",".join([x for x in sorted(self)])
        )

    @classmethod
    def from_string(cls, arg):
        values = [
            c for c
            in re.split(r'\s*,\s*', arg or "")
            if c
        ]
        return cls(values)


def _validator_events(
        desc, key, validator, include_removes, include_backrefs):
    """Runs a validation method on an attribute value to be set or
    appended.
    """

    if not include_backrefs:
        def detect_is_backref(state, initiator):
            impl = state.manager[key].impl
            return initiator.impl is not impl

    if include_removes:
        def append(state, value, initiator):
            if (
                initiator.op is not attributes.OP_BULK_REPLACE and
                (include_backrefs or not detect_is_backref(state, initiator))
            ):
                return validator(state.obj(), key, value, False)
            else:
                return value

        def bulk_set(state, values, initiator):
            if include_backrefs or not detect_is_backref(state, initiator):
                obj = state.obj()
                values[:] = [
                    validator(obj, key, value, False) for value in values]

        def set_(state, value, oldvalue, initiator):
            if include_backrefs or not detect_is_backref(state, initiator):
                return validator(state.obj(), key, value, False)
            else:
                return value

        def remove(state, value, initiator):
            if include_backrefs or not detect_is_backref(state, initiator):
                validator(state.obj(), key, value, True)

    else:
        def append(state, value, initiator):
            if (
                initiator.op is not attributes.OP_BULK_REPLACE and
                (include_backrefs or not detect_is_backref(state, initiator))
            ):
                return validator(state.obj(), key, value)
            else:
                return value

        def bulk_set(state, values, initiator):
            if include_backrefs or not detect_is_backref(state, initiator):
                obj = state.obj()
                values[:] = [
                    validator(obj, key, value) for value in values]

        def set_(state, value, oldvalue, initiator):
            if include_backrefs or not detect_is_backref(state, initiator):
                return validator(state.obj(), key, value)
            else:
                return value

    event.listen(desc, 'append', append, raw=True, retval=True)
    event.listen(desc, 'bulk_replace', bulk_set, raw=True)
    event.listen(desc, 'set', set_, raw=True, retval=True)
    if include_removes:
        event.listen(desc, "remove", remove, raw=True, retval=True)


def polymorphic_union(table_map, typecolname,
                      aliasname='p_union', cast_nulls=True):
    """Create a ``UNION`` statement used by a polymorphic mapper.

    See  :ref:`concrete_inheritance` for an example of how
    this is used.

    :param table_map: mapping of polymorphic identities to
     :class:`.Table` objects.
    :param typecolname: string name of a "discriminator" column, which will be
     derived from the query, producing the polymorphic identity for
     each row.  If ``None``, no polymorphic discriminator is generated.
    :param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()`
     construct generated.
    :param cast_nulls: if True, non-existent columns, which are represented
     as labeled NULLs, will be passed into CAST.   This is a legacy behavior
     that is problematic on some backends such as Oracle - in which case it
     can be set to False.

    """

    colnames = util.OrderedSet()
    colnamemaps = {}
    types = {}
    for key in table_map:
        table = table_map[key]

        # mysql doesn't like selecting from a select;
        # make it an alias of the select
        if isinstance(table, sql.Select):
            table = table.alias()
            table_map[key] = table

        m = {}
        for c in table.c:
            colnames.add(c.key)
            m[c.key] = c
            types[c.key] = c.type
        colnamemaps[table] = m

    def col(name, table):
        try:
            return colnamemaps[table][name]
        except KeyError:
            if cast_nulls:
                return sql.cast(sql.null(), types[name]).label(name)
            else:
                return sql.type_coerce(sql.null(), types[name]).label(name)

    result = []
    for type, table in table_map.items():
        if typecolname is not None:
            result.append(
                sql.select([col(name, table) for name in colnames] +
                           [sql.literal_column(
                               sql_util._quote_ddl_expr(type)).
                               label(typecolname)],
                           from_obj=[table]))
        else:
            result.append(sql.select([col(name, table) for name in colnames],
                                     from_obj=[table]))
    return sql.union_all(*result).alias(aliasname)


def identity_key(*args, **kwargs):
    """Generate "identity key" tuples, as are used as keys in the
    :attr:`.Session.identity_map` dictionary.

    This function has several call styles:

    * ``identity_key(class, ident, identity_token=token)``

      This form receives a mapped class and a primary key scalar or
      tuple as an argument.

      E.g.::

        >>> identity_key(MyClass, (1, 2))
        (<class '__main__.MyClass'>, (1, 2), None)

      :param class: mapped class (must be a positional argument)
      :param ident: primary key, may be a scalar or tuple argument.
      ;param identity_token: optional identity token

        .. versionadded:: 1.2 added identity_token


    * ``identity_key(instance=instance)``

      This form will produce the identity key for a given instance.  The
      instance need not be persistent, only that its primary key attributes
      are populated (else the key will contain ``None`` for those missing
      values).

      E.g.::

        >>> instance = MyClass(1, 2)
        >>> identity_key(instance=instance)
        (<class '__main__.MyClass'>, (1, 2), None)

      In this form, the given instance is ultimately run though
      :meth:`.Mapper.identity_key_from_instance`, which will have the
      effect of performing a database check for the corresponding row
      if the object is expired.

      :param instance: object instance (must be given as a keyword arg)

    * ``identity_key(class, row=row, identity_token=token)``

      This form is similar to the class/tuple form, except is passed a
      database result row as a :class:`.RowProxy` object.

      E.g.::

        >>> row = engine.execute("select * from table where a=1 and b=2").\
first()
        >>> identity_key(MyClass, row=row)
        (<class '__main__.MyClass'>, (1, 2), None)

      :param class: mapped class (must be a positional argument)
      :param row: :class:`.RowProxy` row returned by a :class:`.ResultProxy`
       (must be given as a keyword arg)
      ;param identity_token: optional identity token

        .. versionadded:: 1.2 added identity_token

    """
    if args:
        row = None
        largs = len(args)
        if largs == 1:
            class_ = args[0]
            try:
                row = kwargs.pop("row")
            except KeyError:
                ident = kwargs.pop("ident")
        elif largs in (2, 3):
            class_, ident = args
        else:
            raise sa_exc.ArgumentError(
                "expected up to three positional arguments, "
                "got %s" % largs)

        identity_token = kwargs.pop("identity_token", None)
        if kwargs:
            raise sa_exc.ArgumentError("unknown keyword arguments: %s"
                                       % ", ".join(kwargs))
        mapper = class_mapper(class_)
        if row is None:
            return mapper.identity_key_from_primary_key(
                util.to_list(ident), identity_token=identity_token)
        else:
            return mapper.identity_key_from_row(
                row, identity_token=identity_token)
    else:
        instance = kwargs.pop("instance")
        if kwargs:
            raise sa_exc.ArgumentError("unknown keyword arguments: %s"
                                       % ", ".join(kwargs.keys))
        mapper = object_mapper(instance)
        return mapper.identity_key_from_instance(instance)


class ORMAdapter(sql_util.ColumnAdapter):
    """ColumnAdapter subclass which excludes adaptation of entities from
    non-matching mappers.

    """

    def __init__(self, entity, equivalents=None, adapt_required=False,
                 chain_to=None, allow_label_resolve=True,
                 anonymize_labels=False):
        info = inspection.inspect(entity)

        self.mapper = info.mapper
        selectable = info.selectable
        is_aliased_class = info.is_aliased_class
        if is_aliased_class:
            self.aliased_class = entity
        else:
            self.aliased_class = None

        sql_util.ColumnAdapter.__init__(
            self, selectable, equivalents, chain_to,
            adapt_required=adapt_required,
            allow_label_resolve=allow_label_resolve,
            anonymize_labels=anonymize_labels,
            include_fn=self._include_fn
        )

    def _include_fn(self, elem):
        entity = elem._annotations.get('parentmapper', None)
        return not entity or entity.isa(self.mapper)


class AliasedClass(object):
    r"""Represents an "aliased" form of a mapped class for usage with Query.

    The ORM equivalent of a :func:`sqlalchemy.sql.expression.alias`