Model.py

from __future__ import annotations
import logging, re
from typing import Any, Dict, List, Mapping, Optional, Set, Tuple, Union
from common.orm.Database import Database
from common.orm.backend.Tools import key_to_str
from common.orm.fields.ForeignKeyField import ForeignKeyField
from ..Exceptions import ConstraintException, MutexException
from ..fields.Field import Field
from ..fields.PrimaryKeyField import PrimaryKeyField
from .Tools import NoDupOrderedDict

LOGGER = logging.getLogger(__name__)
DEFAULT_PRIMARY_KEY_NAME = 'pk_auto'

class MetaModel(type):
    @classmethod
    def __prepare__(cls, name : str, bases : Tuple[type, ...], **attrs : Any) -> Mapping[str, Any]:
        return NoDupOrderedDict()

    def __new__(cls, name : str, bases : Tuple[type, ...], attrs : NoDupOrderedDict[str, Any]):
        field_names = list()
        pk_field_name = None
        for key, value in attrs.items():
            if not isinstance(value, Field): continue
            value.name = key
            field_names.append(key)
            if not isinstance(value, PrimaryKeyField): continue
            if pk_field_name is None:
                pk_field_name = key
                continue
            raise AttributeError('PrimaryKeyField for Model({:s}) already set to attribute({:s})'.format(
                str(name), str(pk_field_name)))
        if pk_field_name is None:
            if DEFAULT_PRIMARY_KEY_NAME in attrs.keys():
                msg = 'PrimaryKeyField for Model({:s}) not defined and attribute "{:s}" already used. '\
                      'Leave attribute name "{:s}" for automatic PrimaryKeyField, or set a PrimaryKeyField.'
                raise AttributeError(msg.format(str(name), DEFAULT_PRIMARY_KEY_NAME, DEFAULT_PRIMARY_KEY_NAME))
            pk_field_name = DEFAULT_PRIMARY_KEY_NAME
            attrs[pk_field_name] = PrimaryKeyField(name=pk_field_name)
            field_names.append(pk_field_name)
        cls_obj = super().__new__(cls, name, bases, dict(attrs))
        setattr(cls_obj, '_pk_field_name', pk_field_name)
        setattr(cls_obj, '_field_names_list', field_names)
        setattr(cls_obj, '_field_names_set', set(field_names))
        return cls_obj

KEYWORD_INSTANCES  = 'instances'
KEYWORD_LOCK       = 'lock'
KEYWORD_REFERENCES = 'references'
KEYWORD_STORED     = '_stored'

class Model(metaclass=MetaModel):
    @classmethod
    def get_backend_key_instances(cls) -> str:
        return key_to_str(['{:s}'.format(cls.__name__), KEYWORD_INSTANCES])

    @classmethod
    def get_backend_key_instance(cls, primary_key : str) -> str:
        return '{:s}[{:s}]'.format(cls.__name__, primary_key)

    @classmethod
    def get_backend_key_references(cls, primary_key : str) -> str:
        match = re.match(r'^[a-zA-Z0-9\_]+\[([^\]]*)\]', primary_key)
        if not match: primary_key = cls.get_backend_key_instance(primary_key)
        return key_to_str([primary_key, KEYWORD_REFERENCES])

    @staticmethod
    def get_backend_key_lock(backend_key : str) -> str:
        if backend_key.endswith(KEYWORD_LOCK): return backend_key
        return key_to_str([backend_key, KEYWORD_LOCK])

    @staticmethod
    def get_backend_key_locks(backend_keys : List[str]) -> List[str]:
        return [Model.get_backend_key_lock(backend_key) for backend_key in backend_keys]

    @classmethod
    def backend_key__to__instance_key(cls, backend_key : str) -> str:
        class_name = cls.__name__
        if backend_key.startswith(class_name):
            match = re.match(r'^{:s}\[([^\]]*)\]'.format(class_name), backend_key)
            if match: return match.group(1)
        return backend_key

    def __init__(self, database : Database, primary_key : str, auto_load : bool = True) -> None:
        if not isinstance(database, Database):
            str_class_path = '{}.{}'.format(Database.__module__, Database.__name__)
            raise AttributeError('database must inherit from {}'.format(str_class_path))
        self._model_class = type(self)
        self._class_name = self._model_class.__name__
        pk_field_name = self._pk_field_name # pylint: disable=no-member
        pk_field_instance : 'PrimaryKeyField' = getattr(self._model_class, pk_field_name)
        primary_key = pk_field_instance.validate(primary_key)
        primary_key = self.backend_key__to__instance_key(primary_key)
        setattr(self, pk_field_name, primary_key)
        self._database = database
        self._backend = database.backend
        self._instance_key : str = self.get_backend_key_instance(primary_key)
        self._instances_key : str = self.get_backend_key_instances()
        self._references_key : str = self.get_backend_key_references(primary_key)
        self._owner_key : Optional[str] = None
        if auto_load: self.load()

    @property
    def database(self) -> Database: return self._database

    @property
    def instance_key(self) -> str: return self._instance_key

    def lock(self, extra_keys : List[List[str]] = []):
        lock_keys = Model.get_backend_key_locks(
            [self._instance_key, self._instances_key, self._references_key] + extra_keys)
        acquired,self._owner_key = self._backend.lock(lock_keys, owner_key=self._owner_key)
        if acquired: return
        raise MutexException('Unable to lock keys {:s} using owner_key {:s}'.format(
            str(lock_keys), str(self._owner_key)))

    def unlock(self, extra_keys : List[List[str]] = []):
        lock_keys = Model.get_backend_key_locks(
            [self._instance_key, self._instances_key, self._references_key] + extra_keys)
        released = self._backend.unlock(lock_keys, self._owner_key)
        if released: return
        raise MutexException('Unable to unlock keys {:s} using owner_key {:s}'.format(
            str(lock_keys), str(self._owner_key)))

    def load(self) -> bool:
        pk_field_name = self._pk_field_name # pylint: disable=no-member

        try:
            self.lock()

            attributes = self._backend.dict_get(self._instance_key)
            if attributes is None or len(attributes) == 0: return False
            for field_name in self._field_names_list: # pylint: disable=no-member
                if field_name == pk_field_name: continue
                if field_name not in attributes: continue
                raw_field_value = attributes[field_name]
                field_instance : 'Field' = getattr(self._model_class, field_name)
                field_value = field_instance.deserialize(raw_field_value)
                if isinstance(field_instance, ForeignKeyField):
                    setattr(self, field_name + KEYWORD_STORED, field_value)
                    field_value = field_instance.foreign_model(self._database, field_value, auto_load=True)
                setattr(self, field_name, field_value)
            return True
        finally:
            self.unlock()

    def save(self) -> None:
        attributes : Dict[str, Any] = dict()
        required_keys : Set[str] = set()
        foreign_additions : Dict[str, str] = dict()
        foreign_removals : Dict[str, str] = dict()
        for field_name in self._field_names_list: # pylint: disable=no-member
            field_value = getattr(self, field_name)
            field_instance : 'Field' = getattr(self._model_class, field_name)
            serialized_field_value = field_instance.serialize(field_value)
            if (serialized_field_value is None) and (not field_instance.required): continue
            if isinstance(field_instance, ForeignKeyField):
                foreign_reference = '{:s}:{:s}'.format(self._instance_key, field_name)
                field_value_stored = getattr(self, field_name + KEYWORD_STORED, None)
                if field_value_stored is not None:
                    foreign_removals[self.get_backend_key_references(field_value_stored)] = foreign_reference
                foreign_additions[self.get_backend_key_references(serialized_field_value)] = foreign_reference
                required_keys.add(serialized_field_value)
            attributes[field_name] = serialized_field_value

        extra_keys = []
        extra_keys.extend(list(foreign_removals.keys()))
        extra_keys.extend(list(foreign_additions.keys()))

        try:
            self.lock(extra_keys=extra_keys)

            not_exists = [
                str(required_key)
                for required_key in required_keys
                if not self._backend.exists(required_key)]
            if len(not_exists) > 0:
                raise ConstraintException('Required Keys ({:s}) does not exist'.format(', '.join(sorted(not_exists))))

            self._backend.dict_update(self._instance_key, attributes)
            self._backend.set_add(self._instances_key, self._instance_key)

            for serialized_field_value,foreign_reference in foreign_removals.items():
                self._backend.set_remove(serialized_field_value, foreign_reference)

            for serialized_field_value,foreign_reference in foreign_additions.items():
                self._backend.set_add(serialized_field_value, foreign_reference)
        finally:
            self.unlock(extra_keys=extra_keys)

        for serialized_field_value,foreign_reference in foreign_additions.items():
            setattr(self, (foreign_reference.rsplit(':', 1)[-1]) + KEYWORD_STORED, field_value_stored)

    def delete(self) -> None:
        foreign_removals : Dict[str, str] = {}
        for field_name in self._field_names_list: # pylint: disable=no-member
            field_instance : 'Field' = getattr(self._model_class, field_name)
            if not isinstance(field_instance, ForeignKeyField): continue
            foreign_reference = '{:s}:{:s}'.format(self._instance_key, field_name)
            field_value_stored = getattr(self, field_name + KEYWORD_STORED, None)
            if field_value_stored is None: continue
            foreign_removals[self.get_backend_key_references(field_value_stored)] = foreign_reference

        extra_keys = []
        extra_keys.extend(list(foreign_removals.keys()))

        try:
            self.lock(extra_keys=extra_keys)

            if self._backend.exists(self._references_key):
                references = self._backend.set_get_all(self._references_key)
                raise ConstraintException('Instance is used by Keys ({:s})'.format(', '.join(sorted(references))))

            self._backend.delete(self._instance_key)
            self._backend.set_remove(self._instances_key, self._instance_key)

            for serialized_field_value,foreign_reference in foreign_removals.items():
                self._backend.set_remove(serialized_field_value, foreign_reference)
        finally:
            self.unlock(extra_keys=extra_keys)

    @staticmethod
    def get_model_name(model_or_str) -> str:
        if isinstance(model_or_str, str):
            return model_or_str
        if (type(model_or_str).__name__ == 'MetaModel') and issubclass(model_or_str, Model):
            return model_or_str.__name__
        raise Exception()

    def references(
        self, filter_by_models : Optional[Union[type, List[type], Set[type], Tuple[type]]] = None
        ) -> Set[Tuple[str, str]]:

        try:
            self.lock()
            if not self._backend.exists(self._references_key): return {}
            references = self._backend.set_get_all(self._references_key)
            try:
                if filter_by_models is None:
                    pass
                elif isinstance(filter_by_models, str):
                    filter_by_models = {filter_by_models}
                elif isinstance(filter_by_models, (list, set, tuple)):
                    filter_by_models = {Model.get_model_name(model_or_str) for model_or_str in filter_by_models}
                elif (type(filter_by_models).__name__ == 'MetaModel') and issubclass(filter_by_models, Model):
                    filter_by_models = {Model.get_model_name(filter_by_models)}
                else:
                    raise Exception()
            except Exception as e:
                msg = 'filter_by_models({:s}) unsupported. Expected a type or a list/set of types. Optionally, keep '\
                      'it as None to retrieve all the references pointing to this instance.'
                raise AttributeError(msg.format(str(filter_by_models))) from e
            if filter_by_models:
                references = filter(lambda instance_key: instance_key.split('[', 1)[0] in filter_by_models, references)
            return {tuple(reference.rsplit(':', 1)) for reference in references}
        finally:
            self.unlock()

    @classmethod
    def get_primary_keys(cls, database : Database):
        backend = database.backend
        key_model_instances = cls.get_backend_key_instances()
        key_model_instances_lock = cls.get_backend_key_lock(key_model_instances)

        acquired,owner_key = backend.lock(key_model_instances_lock)
        if not acquired:
            raise MutexException('Unable to lock keys {:s}'.format(
                str(key_model_instances_lock)))

        instance_keys = backend.set_get_all(key_model_instances)

        released = backend.unlock(key_model_instances_lock, owner_key)
        if not released:
            raise MutexException('Unable to unlock keys {:s} using owner_key {:s}'.format(
                str(key_model_instances_lock), str(owner_key)))

        return instance_keys

    def dump_id(self) -> Dict:
        raise NotImplementedError()

    def dump(self) -> Dict:
        raise NotImplementedError()

    def __repr__(self) -> str:
        pk_field_name = self._pk_field_name # pylint: disable=no-member
        arguments = ', '.join(
            '{:s}={:s}{:s}'.format(
                name, repr(getattr(self, name)), '(PK)' if name == pk_field_name else '')
            for name in self._field_names_list # pylint: disable=no-member
        )
        return '{:s}({:s})'.format(self._class_name, arguments)