from __future__ import annotations
import copy
from typing import Any, Dict, TYPE_CHECKING
from ...engines._DatabaseEngine import _DatabaseEngine
from .Tools import format_key

if TYPE_CHECKING:
    from ._Entity import _Entity

class EntityAttributes:
    def __init__(self, parent : '_Entity', entity_key : str, validators : Dict, transcoders : Dict = {}):
        self._parent = parent
        self._database_engine : _DatabaseEngine = self._parent.database_engine
        self._entity_key = format_key(entity_key, self._parent)
        self._validators = validators
        self._transcoders = transcoders

    def validate(self, update_attributes, remove_attributes, attribute_name):
        remove_attributes.discard(attribute_name)
        value = update_attributes.pop(attribute_name, None)
        if value is None: return
        validator = self._validators.get(attribute_name)
        if validator is None: return
        if not validator(value): raise AttributeError('{} is invalid'.format(attribute_name))

    def transcode(self, attribute_name, attribute_value):
        transcoder_set = self._transcoders.get(attribute_name, {})
        transcoder = transcoder_set.get(type(attribute_value))
        return attribute_value if transcoder is None else transcoder(attribute_value)

    def get(self, attributes=[]) -> Dict[str, Any]:
        return {
            k:self.transcode(k, v)
            for k,v in self._database_engine.dict_get(self._entity_key, fields=attributes).items()
        }

    def update(self, update_attributes={}, remove_attributes=[]):
        remove_attributes = set(remove_attributes)
        copy_update_attributes = copy.deepcopy(update_attributes)
        copy_remove_attributes = copy.deepcopy(remove_attributes)

        for attribute_name in self._validators.keys():
            self.validate(copy_update_attributes, copy_remove_attributes, attribute_name)
            attribute_value = update_attributes.get(attribute_name)
            if attribute_value is None: continue
            update_attributes[attribute_name] = self.transcode(attribute_name, attribute_value)

        if len(copy_update_attributes) > 0:
            raise AttributeError('Unexpected update_attributes: {}'.format(str(copy_update_attributes)))

        if len(copy_remove_attributes) > 0:
            raise AttributeError('Unexpected remove_attributes: {}'.format(str(copy_remove_attributes)))

        self._database_engine.dict_update(self._entity_key, update_attributes, remove_attributes)
        return self

    def delete(self, attributes=[]):
        self._database_engine.dict_delete(self._entity_key, attributes)