try:
    from collections import OrderedDict
except ImportError:
    from ordereddict import OrderedDict
from functools import partial
from itertools import groupby
from inspect import isclass
from operator import attrgetter
import sqlalchemy as sa
from sqlalchemy import inspect
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.orm import mapperlib
from sqlalchemy.orm.attributes import InstrumentedAttribute
from sqlalchemy.orm.exc import UnmappedInstanceError
from sqlalchemy.orm.mapper import Mapper
from sqlalchemy.orm.query import _ColumnEntity
from sqlalchemy.orm.session import object_session
from sqlalchemy.orm.util import AliasedInsp
from ..query_chain import QueryChain


def get_mapper(mixed):
    """
    Return related SQLAlchemy Mapper for given SQLAlchemy object.

    :param mixed: SQLAlchemy Table object

    .. versionadded: 0.26.1
    """
    if isinstance(mixed, sa.orm.Mapper):
        return mixed
    if isinstance(mixed, sa.orm.util.AliasedClass):
        return sa.inspect(mixed).mapper
    if isinstance(mixed, sa.sql.selectable.Alias):
        mixed = mixed.element
    if isinstance(mixed, sa.Table):
        mappers = [
            mapper for mapper in mapperlib._mapper_registry
            if mixed in mapper.tables
        ]
        if len(mappers) > 1:
            raise ValueError(
                "Could not get mapper for '%r'. Multiple mappers found."
                % mixed
            )
        else:
            return mappers[0]
    if not isclass(mixed):
        mixed = type(mixed)
    return sa.inspect(mixed)


def get_bind(obj):
    """
    Return the bind for given SQLAlchemy Engine / Connection / declarative
    model object.

    :param obj: SQLAlchemy Engine / Connection / declarative model object

    ::

        from sqlalchemy_utils import get_bind


        get_bind(session)  # Connection object

        get_bind(user)

    """
    if hasattr(obj, 'bind'):
        conn = obj.bind
    else:
        try:
            conn = object_session(obj).bind
        except UnmappedInstanceError:
            conn = obj

    if not hasattr(conn, 'execute'):
        raise TypeError(
            'This method accepts only Session, Engine, Connection and '
            'declarative model objects.'
        )
    return conn


def dependent_objects(obj, foreign_keys=None):
    """
    Return a :class:`~sqlalchemy_utils.query_chain.QueryChain` that iterates
    through all dependent objects for given SQLAlchemy object.

    Consider a User object is referenced in various articles and also in
    various orders. Getting all these dependent objects is as easy as:

    ::

        from sqlalchemy_utils import dependent_objects


        dependent_objects(user)


    If you expect an object to have lots of dependent_objects it might be good
    to limit the results::


        dependent_objects(user).limit(5)



    The common use case is checking for all restrict dependent objects before
    deleting parent object and inform the user if there are dependent objects
    with ondelete='RESTRICT' foreign keys. If this kind of checking is not used
    it will lead to nasty IntegrityErrors being raised.

    In the following example we delete given user if it doesn't have any
    foreign key restricted dependent objects.

    ::


        from sqlalchemy_utils import get_referencing_foreign_keys


        user = session.query(User).get(some_user_id)


        deps = list(
            dependent_objects(
                user,
                (
                    fk for fk in get_referencing_foreign_keys(User)
                    # On most databases RESTRICT is the default mode hence we
                    # check for None values also
                    if fk.ondelete == 'RESTRICT' or fk.ondelete is None
                )
            ).limit(5)
        )

        if deps:
            # Do something to inform the user
            pass
        else:
            session.delete(user)


    :param obj: SQLAlchemy declarative model object
    :param foreign_keys:
        A sequence of foreign keys to use for searching the dependent_objects
        for given object. By default this is None, indicating that all foreign
        keys referencing the object will be used.

    .. note::
        This function does not support exotic mappers that use multiple tables

    .. seealso:: :func:`get_referencing_foreign_keys`

    .. versionadded: 0.26.0
    """
    if foreign_keys is None:
        foreign_keys = get_referencing_foreign_keys(obj)

    session = object_session(obj)

    chain = QueryChain([])
    classes = obj.__class__._decl_class_registry

    for table, keys in group_foreign_keys(foreign_keys):
        for class_ in classes.values():
            if hasattr(class_, '__table__') and class_.__table__ == table:
                criteria = []
                visited_constraints = []
                for key in keys:
                    if key.constraint not in visited_constraints:
                        visited_constraints.append(key.constraint)
                        subcriteria = [
                            getattr(class_, column.key) ==
                            getattr(
                                obj,
                                key.constraint.elements[index].column.key
                            )
                            for index, column
                            in enumerate(key.constraint.columns)
                        ]
                        criteria.append(sa.and_(*subcriteria))

                query = session.query(class_).filter(
                    sa.or_(
                        *criteria
                    )
                )
                chain.queries.append(query)
        return chain


def group_foreign_keys(foreign_keys):
    """
    Return a groupby iterator that groups given foreign keys by table.

    :param foreign_keys: a sequence of foreign keys


    ::

        foreign_keys = get_referencing_foreign_keys(User)

        for table, fks in group_foreign_keys(foreign_keys):
            # do something
            pass


    .. also:: :func:`get_referencing_foreign_keys`

    .. versionadded: 0.26.1
    """
    foreign_keys = sorted(
        foreign_keys, key=lambda key: key.constraint.table.name
    )
    return groupby(foreign_keys, lambda key: key.constraint.table)


def get_referencing_foreign_keys(mixed):
    """
    Returns referencing foreign keys for given Table object or declarative
    class.

    :param mixed:
        SA Table object or SA declarative class

    ::

        get_referencing_foreign_keys(User)  # set([ForeignKey('user.id')])

        get_referencing_foreign_keys(User.__table__)


    This function also understands inheritance. This means it returns
    all foreign keys that reference any table in the class inheritance tree.

    Let's say you have three classes which use joined table inheritance,
    namely TextItem, Article and BlogPost with Article and BlogPost inheriting
    TextItem.

    ::

        # This will check all foreign keys that reference either article table
        # or textitem table.
        get_referencing_foreign_keys(Article)

    .. seealso:: :func:`get_tables`
    """
    if isinstance(mixed, sa.Table):
        tables = [mixed]
    else:
        tables = get_tables(mixed)

    referencing_foreign_keys = set()

    for table in mixed.metadata.tables.values():
        if table not in tables:
            for constraint in table.constraints:
                if isinstance(constraint, sa.sql.schema.ForeignKeyConstraint):
                    for fk in constraint.elements:
                        if any(fk.references(t) for t in tables):
                            referencing_foreign_keys.add(fk)
    return referencing_foreign_keys


def get_primary_keys(mixed):
    """
    Return an OrderedDict of all primary keys for given Table object,
    declarative class or declarative class instance.

    :param mixed:
        SA Table object, SA declarative class or SA declarative class instance

    ::

        get_primary_keys(User)

        get_primary_keys(User())

        get_primary_keys(User.__table__)

        get_primary_keys(User.__mapper__)

        get_primary_keys(sa.orm.aliased(User))

        get_primary_keys(sa.orm.aliased(User.__table__))


    .. versionchanged: 0.25.3
        Made the function return an ordered dictionary instead of generator.
        This change was made to support primary key aliases.

        Renamed this function to 'get_primary_keys', formerly 'primary_keys'

    .. seealso:: :func:`get_columns`
    """
    return OrderedDict(
        (
            (key, column) for key, column in get_columns(mixed).items()
            if column.primary_key
        )
    )


def get_tables(mixed):
    """
    Return a list of tables associated with given SQLAlchemy object.

    Let's say we have three classes which use joined table inheritance
    TextItem, Article and BlogPost. Article and BlogPost inherit TextItem.

    ::

        get_tables(Article)  # [Table('article', ...), Table('text_item')]

        get_tables(Article())

        get_tables(Article.__mapper__)


    .. versionadded: 0.26.0

    :param mixed:
        SQLAlchemy Mapper / Declarative class or a SA Alias object wrapping
        any of these objects.
    """
    if isinstance(mixed, sa.orm.util.AliasedClass):
        mapper = sa.inspect(mixed).mapper
    else:
        if not isclass(mixed):
            mixed = mixed.__class__
        mapper = sa.inspect(mixed)
    return mapper.tables


def get_columns(mixed):
    """
    Return a collection of all Column objects for given SQLAlchemy
    object.

    The type of the collection depends on the type of the object to return the
    columns from.

    ::

        get_columns(User)

        get_columns(User())

        get_columns(User.__table__)

        get_columns(User.__mapper__)

        get_columns(sa.orm.aliased(User))

        get_columns(sa.orm.alised(User.__table__))


    :param mixed:
        SA Table object, SA Mapper, SA declarative class, SA declarative class
        instance or an alias of any of these objects
    """
    if isinstance(mixed, sa.Table):
        return mixed.c
    if isinstance(mixed, sa.orm.util.AliasedClass):
        return sa.inspect(mixed).mapper.columns
    if isinstance(mixed, sa.sql.selectable.Alias):
        return mixed.c
    if isinstance(mixed, sa.orm.Mapper):
        return mixed.columns
    if not isclass(mixed):
        mixed = mixed.__class__
    return sa.inspect(mixed).columns


def table_name(obj):
    """
    Return table name of given target, declarative class or the
    table name where the declarative attribute is bound to.
    """
    class_ = getattr(obj, 'class_', obj)

    try:
        return class_.__tablename__
    except AttributeError:
        pass

    try:
        return class_.__table__.name
    except AttributeError:
        pass


def getattrs(obj, attrs):
    return map(partial(getattr, obj), attrs)


def local_values(prop, entity):
    return tuple(getattrs(entity, local_column_names(prop)))


def list_local_values(prop, entities):
    return map(partial(local_values, prop), entities)


def remote_values(prop, entity):
    return tuple(getattrs(entity, remote_column_names(prop)))


def local_remote_expr(prop, entity):
    return sa.and_(
        *[
            getattr(remote(prop), r.name)
            ==
            getattr(entity, l.name)
            for l, r in prop.local_remote_pairs
            if r in remote_column_names(prop)
        ]
    )


def list_local_remote_exprs(prop, entities):
    return map(partial(local_remote_expr, prop), entities)


def remote(prop):
    try:
        return prop.secondary.c
    except AttributeError:
        return prop.mapper.class_


def local_column_names(prop):
    if not hasattr(prop, 'secondary'):
        yield prop._discriminator_col.key
        for id_col in prop._id_cols:
            yield id_col.key
    elif prop.secondary is None:
        for local, _ in prop.local_remote_pairs:
            yield local.name
    else:
        if prop.secondary is not None:
            for local, remote in prop.local_remote_pairs:
                for fk in remote.foreign_keys:
                    if fk.column.table in prop.parent.tables:
                        yield local.name


def remote_column_names(prop):
    if not hasattr(prop, 'secondary'):
        yield '__tablename__'
        yield 'id'
    elif prop.secondary is None:
        for _, remote in prop.local_remote_pairs:
            yield remote.name
    else:
        for _, remote in prop.local_remote_pairs:
            for fk in remote.foreign_keys:
                if fk.column.table in prop.parent.tables:
                    yield remote.name


def query_labels(query):
    """
    Return all labels for given SQLAlchemy query object.

    Example::


        query = session.query(
            Category,
            db.func.count(Article.id).label('articles')
        )

        query_labels(query)  # ('articles', )

    :param query: SQLAlchemy Query object
    """
    for entity in query._entities:
        if isinstance(entity, _ColumnEntity) and entity._label_name:
            yield entity._label_name


def query_entities(query):
    """
    Return a generator that iterates through all entities for given SQLAlchemy
    query object.

    Examples::


        query = session.query(Category)

        query_entities(query)  # <Category>


        query = session.query(Category.id)

        query_entities(query)  # <Category>


    This function also supports queries with joins.

    ::


        query = session.query(Category).join(Article)

        query_entities(query)  # (<Category>, <Article>)


    :param query: SQLAlchemy Query object
    """
    for entity in query._entities:
        if entity.entity_zero:
            yield entity.entity_zero.class_

    for entity in query._join_entities:
        if isinstance(entity, Mapper):
            yield entity.class_
        else:
            yield entity


def get_query_entity_by_alias(query, alias):
    entities = query_entities(query)
    if not alias:
        return list(entities)[0]

    for entity in entities:
        if isinstance(entity, AliasedInsp):
            name = entity.name
        else:
            name = entity.__table__.name

        if name == alias:
            return entity


def get_attrs(expr):
    if isinstance(expr, AliasedInsp):
        return expr.mapper.attrs
    else:
        return inspect(expr).attrs


def get_hybrid_properties(class_):
    for prop in sa.inspect(class_).all_orm_descriptors:
        if isinstance(prop, hybrid_property):
            yield prop


def get_expr_attr(expr, attr_name):
    if isinstance(expr, AliasedInsp):
        return getattr(expr.selectable.c, attr_name)
    else:
        return getattr(expr, attr_name)


def get_declarative_base(model):
    """
    Returns the declarative base for given model class.

    :param model: SQLAlchemy declarative model
    """
    for parent in model.__bases__:
        try:
            parent.metadata
            return get_declarative_base(parent)
        except AttributeError:
            pass
    return model


def getdotattr(obj_or_class, dot_path):
    """
    Allow dot-notated strings to be passed to `getattr`.

    ::

        getdotattr(SubSection, 'section.document')

        getdotattr(subsection, 'section.document')


    :param obj_or_class: Any object or class
    :param dot_path: Attribute path with dot mark as separator
    """
    last = obj_or_class
    # Coerce object style paths to strings.
    path = str(dot_path)

    for path in dot_path.split('.'):
        getter = attrgetter(path)
        if isinstance(last, list):
            tmp = []
            for el in last:
                if isinstance(el, list):
                    tmp.extend(map(getter, el))
                else:
                    tmp.append(getter(el))
            last = tmp
        elif isinstance(last, InstrumentedAttribute):
            last = getter(last.property.mapper.class_)
        elif last is None:
            return None
        else:
            last = getter(last)
    return last


def has_changes(obj, attr):
    """
    Simple shortcut function for checking if given attribute of given
    declarative model object has changed during the transaction.


    ::


        from sqlalchemy_utils import has_changes


        user = User()

        has_changes(user, 'name')  # False

        user.name = u'someone'

        has_changes(user, 'name')  # True


    :param obj: SQLAlchemy declarative model object
    :param attr: Name of the attribute
    """
    return (
        sa.inspect(obj)
        .attrs
        .get(attr)
        .history
        .has_changes()
    )


def identity(obj_or_class):
    """
    Return the identity of given sqlalchemy declarative model class or instance
    as a tuple. This differs from obj._sa_instance_state.identity in a way that
    it always returns the identity even if object is still in transient state (
    new object that is not yet persisted into database). Also for classes it
    returns the identity attributes.

    ::

        from sqlalchemy import inspect
        from sqlalchemy_utils import identity


        user = User(name=u'John Matrix')
        session.add(user)
        identity(user)  # None
        inspect(user).identity  # None

        session.flush()  # User now has id but is still in transient state

        identity(user)  # (1,)
        inspect(user).identity  # None

        session.commit()

        identity(user)  # (1,)
        inspect(user).identity  # (1, )


    You can also use identity for classes::


        identity(User)  # (User.id, )

    .. versionadded: 0.21.0

    :param obj: SQLAlchemy declarative model object
    """
    return tuple(
        getattr(obj_or_class, column_key)
        for column_key in get_primary_keys(obj_or_class).keys()
    )


def naturally_equivalent(obj, obj2):
    """
    Returns whether or not two given SQLAlchemy declarative instances are
    naturally equivalent (all their non primary key properties are equivalent).


    ::

        from sqlalchemy_utils import naturally_equivalent


        user = User(name=u'someone')
        user2 = User(name=u'someone')

        user == user2  # False

        naturally_equivalent(user, user2)  # True


    :param obj: SQLAlchemy declarative model object
    :param obj2: SQLAlchemy declarative model object to compare with `obj`
    """
    for prop in sa.inspect(obj.__class__).iterate_properties:
        if not isinstance(prop, sa.orm.ColumnProperty):
            continue

        if prop.columns[0].primary_key:
            continue

        if not (getattr(obj, prop.key) == getattr(obj2, prop.key)):
            return False
    return True