# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Allows JSON-serializable collections to be used as SQLAlchemy column types.
"""

import json
from collections import namedtuple

from sqlalchemy import (
    TypeDecorator,
    VARCHAR,
    event
)
from sqlalchemy.ext import mutable
from ..utils.yaml import yaml

from . import exceptions


class _MutableType(TypeDecorator):
    """
    Dict representation of type.
    """
    @property
    def python_type(self):
        raise NotImplementedError

    def process_literal_param(self, value, dialect):
        pass

    impl = VARCHAR

    def process_bind_param(self, value, dialect):
        if value is not None:
            value = json.dumps(value)
        return value

    def process_result_value(self, value, dialect):
        if value is not None:
            value = json.loads(value)
        return value


class Dict(_MutableType):
    """
    JSON-serializable dict type for SQLAlchemy columns.
    """
    @property
    def python_type(self):
        return dict


class List(_MutableType):
    """
    JSON-serializable list type for SQLAlchemy columns.
    """
    @property
    def python_type(self):
        return list


class _StrictDictMixin(object):

    @classmethod
    def coerce(cls, key, value):
        """
        Convert plain dictionaries to MutableDict.
        """
        try:
            if not isinstance(value, cls):
                if isinstance(value, dict):
                    for k, v in value.items():
                        cls._assert_strict_key(k)
                        cls._assert_strict_value(v)
                    return cls(value)
                return mutable.MutableDict.coerce(key, value)
            else:
                return value
        except ValueError as e:
            raise exceptions.ValueFormatException('could not coerce to MutableDict', cause=e)

    def __setitem__(self, key, value):
        self._assert_strict_key(key)
        self._assert_strict_value(value)
        super(_StrictDictMixin, self).__setitem__(key, value)

    def setdefault(self, key, value):
        self._assert_strict_key(key)
        self._assert_strict_value(value)
        super(_StrictDictMixin, self).setdefault(key, value)

    def update(self, *args, **kwargs):
        for k, v in kwargs.items():
            self._assert_strict_key(k)
            self._assert_strict_value(v)
        super(_StrictDictMixin, self).update(*args, **kwargs)

    @classmethod
    def _assert_strict_key(cls, key):
        if cls._key_cls is not None and not isinstance(key, cls._key_cls):
            raise exceptions.ValueFormatException('key type was set strictly to {0}, but was {1}'
                                                  .format(cls._key_cls, type(key)))

    @classmethod
    def _assert_strict_value(cls, value):
        if cls._value_cls is not None and not isinstance(value, cls._value_cls):
            raise exceptions.ValueFormatException('value type was set strictly to {0}, but was {1}'
                                                  .format(cls._value_cls, type(value)))


class _MutableDict(mutable.MutableDict):
    """
    Enables tracking for dict values.
    """

    @classmethod
    def coerce(cls, key, value):
        """
        Convert plain dictionaries to MutableDict.
        """
        try:
            return mutable.MutableDict.coerce(key, value)
        except ValueError as e:
            raise exceptions.ValueFormatException('could not coerce value', cause=e)


class _StrictListMixin(object):

    @classmethod
    def coerce(cls, key, value):
        "Convert plain dictionaries to MutableDict."
        try:
            if not isinstance(value, cls):
                if isinstance(value, list):
                    for item in value:
                        cls._assert_item(item)
                    return cls(value)
                return mutable.MutableList.coerce(key, value)
            else:
                return value
        except ValueError as e:
            raise exceptions.ValueFormatException('could not coerce to MutableDict', cause=e)

    def __setitem__(self, index, value):
        """
        Detect list set events and emit change events.
        """
        self._assert_item(value)
        super(_StrictListMixin, self).__setitem__(index, value)

    def append(self, item):
        self._assert_item(item)
        super(_StrictListMixin, self).append(item)

    def extend(self, item):
        self._assert_item(item)
        super(_StrictListMixin, self).extend(item)

    def insert(self, index, item):
        self._assert_item(item)
        super(_StrictListMixin, self).insert(index, item)

    @classmethod
    def _assert_item(cls, item):
        if cls._item_cls is not None and not isinstance(item, cls._item_cls):
            raise exceptions.ValueFormatException('key type was set strictly to {0}, but was {1}'
                                                  .format(cls._item_cls, type(item)))


class _MutableList(mutable.MutableList):

    @classmethod
    def coerce(cls, key, value):
        """
        Convert plain dictionaries to MutableDict.
        """
        try:
            return mutable.MutableList.coerce(key, value)
        except ValueError as e:
            raise exceptions.ValueFormatException('could not coerce to MutableDict', cause=e)


_StrictDictID = namedtuple('_StrictDictID', 'key_cls, value_cls')
_StrictValue = namedtuple('_StrictValue', 'type_cls, listener_cls')

class _StrictDict(object):
    """
    This entire class functions as a factory for strict dicts and their listeners. No type class,
    and no listener type class is created more than once. If a relevant type class exists it is
    returned.
    """
    _strict_map = {}

    def __call__(self, key_cls=None, value_cls=None):
        strict_dict_map_key = _StrictDictID(key_cls=key_cls, value_cls=value_cls)
        if strict_dict_map_key not in self._strict_map:
            key_cls_name = getattr(key_cls, '__name__', str(key_cls))
            value_cls_name = getattr(value_cls, '__name__', str(value_cls))
            # Creating the type class itself. this class would be returned (used by the SQLAlchemy
            # Column).
            strict_dict_cls = type(
                'StrictDict_{0}_{1}'.format(key_cls_name, value_cls_name),
                (Dict, ),
                {}
            )
            # Creating the type listening class.
            # The new class inherits from both the _MutableDict class and the _StrictDictMixin,
            # while setting the necessary _key_cls and _value_cls as class attributes.
            listener_cls = type(
                'StrictMutableDict_{0}_{1}'.format(key_cls_name, value_cls_name),
                (_StrictDictMixin, _MutableDict),
                {'_key_cls': key_cls, '_value_cls': value_cls}
            )
            yaml.representer.RoundTripRepresenter.add_representer(
                listener_cls, yaml.representer.RoundTripRepresenter.represent_list)
            self._strict_map[strict_dict_map_key] = _StrictValue(type_cls=strict_dict_cls,
                                                                 listener_cls=listener_cls)

        return self._strict_map[strict_dict_map_key].type_cls


StrictDict = _StrictDict()
"""
JSON-serializable strict dict type for SQLAlchemy columns.

:param key_cls:
:param value_cls:
"""


class _StrictList(object):
    """
    This entire class functions as a factory for strict lists and their listeners. No type class,
    and no listener type class is created more than once. If a relevant type class exists it is
    returned.
    """
    _strict_map = {}

    def __call__(self, item_cls=None):

        if item_cls not in self._strict_map:
            item_cls_name = getattr(item_cls, '__name__', str(item_cls))
            # Creating the type class itself. this class would be returned (used by the SQLAlchemy
            # Column).
            strict_list_cls = type(
                'StrictList_{0}'.format(item_cls_name),
                (List, ),
                {}
            )
            # Creating the type listening class.
            # The new class inherits from both the _MutableList class and the _StrictListMixin,
            # while setting the necessary _item_cls as class attribute.
            listener_cls = type(
                'StrictMutableList_{0}'.format(item_cls_name),
                (_StrictListMixin, _MutableList),
                {'_item_cls': item_cls}
            )
            yaml.representer.RoundTripRepresenter.add_representer(
                listener_cls, yaml.representer.RoundTripRepresenter.represent_list)
            self._strict_map[item_cls] = _StrictValue(type_cls=strict_list_cls,
                                                      listener_cls=listener_cls)

        return self._strict_map[item_cls].type_cls


StrictList = _StrictList()
"""
JSON-serializable strict list type for SQLAlchemy columns.

:param item_cls:
"""


def _mutable_association_listener(mapper, cls):
    strict_dict_type_to_listener = \
        dict((v.type_cls, v.listener_cls) for v in _StrictDict._strict_map.itervalues())

    strict_list_type_to_listener = \
        dict((v.type_cls, v.listener_cls) for v in _StrictList._strict_map.itervalues())

    for prop in mapper.column_attrs:
        column_type = prop.columns[0].type
        # Dict Listeners
        if type(column_type) in strict_dict_type_to_listener:                                       # pylint: disable=unidiomatic-typecheck
            strict_dict_type_to_listener[type(column_type)].associate_with_attribute(
                getattr(cls, prop.key))
        elif isinstance(column_type, Dict):
            _MutableDict.associate_with_attribute(getattr(cls, prop.key))

        # List Listeners
        if type(column_type) in strict_list_type_to_listener:                                       # pylint: disable=unidiomatic-typecheck
            strict_list_type_to_listener[type(column_type)].associate_with_attribute(
                getattr(cls, prop.key))
        elif isinstance(column_type, List):
            _MutableList.associate_with_attribute(getattr(cls, prop.key))


_LISTENER_ARGS = (mutable.mapper, 'mapper_configured', _mutable_association_listener)


def _register_mutable_association_listener():
    event.listen(*_LISTENER_ARGS)

_register_mutable_association_listener()