reflex_copy/reflex/state.py

"""Define the reflex state specification."""
from __future__ import annotations

import asyncio
import contextlib
import copy
import functools
import inspect
import json
import os
import traceback
import urllib.parse
import uuid
from abc import ABC, abstractmethod
from collections import defaultdict
from types import FunctionType, MethodType
from typing import (
    Any,
    AsyncIterator,
    Callable,
    ClassVar,
    Dict,
    List,
    Optional,
    Sequence,
    Set,
    Type,
)

import cloudpickle
import pydantic
import wrapt
from redis.asyncio import Redis

from reflex import constants
from reflex.base import Base
from reflex.event import (
    Event,
    EventHandler,
    EventSpec,
    _no_chain_background_task,
    fix_events,
    window_alert,
)
from reflex.utils import console, format, prerequisites, types
from reflex.utils.exceptions import ImmutableStateError, LockExpiredError
from reflex.utils.serializers import SerializedType, serialize, serializer
from reflex.vars import BaseVar, ComputedVar, Var

Delta = Dict[str, Any]
var = ComputedVar


class HeaderData(Base):
    """An object containing headers data."""

    host: str = ""
    origin: str = ""
    upgrade: str = ""
    connection: str = ""
    pragma: str = ""
    cache_control: str = ""
    user_agent: str = ""
    sec_websocket_version: str = ""
    sec_websocket_key: str = ""
    sec_websocket_extensions: str = ""
    accept_encoding: str = ""
    accept_language: str = ""

    def __init__(self, router_data: Optional[dict] = None):
        """Initalize the HeaderData object based on router_data.

        Args:
            router_data: the router_data dict.
        """
        super().__init__()
        if router_data:
            for k, v in router_data.get(constants.RouteVar.HEADERS, {}).items():
                setattr(self, format.to_snake_case(k), v)


class PageData(Base):
    """An object containing page data."""

    host: str = ""  # repeated with self.headers.origin (remove or keep the duplicate?)
    path: str = ""
    raw_path: str = ""
    full_path: str = ""
    full_raw_path: str = ""
    params: dict = {}

    def __init__(self, router_data: Optional[dict] = None):
        """Initalize the PageData object based on router_data.

        Args:
            router_data: the router_data dict.
        """
        super().__init__()
        if router_data:
            self.host = router_data.get(constants.RouteVar.HEADERS, {}).get("origin")
            self.path = router_data.get(constants.RouteVar.PATH, "")
            self.raw_path = router_data.get(constants.RouteVar.ORIGIN, "")
            self.full_path = f"{self.host}{self.path}"
            self.full_raw_path = f"{self.host}{self.raw_path}"
            self.params = router_data.get(constants.RouteVar.QUERY, {})


class SessionData(Base):
    """An object containing session data."""

    client_token: str = ""
    client_ip: str = ""
    session_id: str = ""

    def __init__(self, router_data: Optional[dict] = None):
        """Initalize the SessionData object based on router_data.

        Args:
            router_data: the router_data dict.
        """
        super().__init__()
        if router_data:
            self.client_token = router_data.get(constants.RouteVar.CLIENT_TOKEN, "")
            self.client_ip = router_data.get(constants.RouteVar.CLIENT_IP, "")
            self.session_id = router_data.get(constants.RouteVar.SESSION_ID, "")


class RouterData(Base):
    """An object containing RouterData."""

    session: SessionData = SessionData()
    headers: HeaderData = HeaderData()
    page: PageData = PageData()

    def __init__(self, router_data: Optional[dict] = None):
        """Initialize the RouterData object.

        Args:
            router_data: the router_data dict.
        """
        super().__init__()
        self.session = SessionData(router_data)
        self.headers = HeaderData(router_data)
        self.page = PageData(router_data)


RESERVED_BACKEND_VAR_NAMES = {
    "_backend_vars",
    "_computed_var_dependencies",
    "_substate_var_dependencies",
    "_always_dirty_computed_vars",
    "_always_dirty_substates",
}


class BaseState(Base, ABC, extra=pydantic.Extra.allow):
    """The state of the app."""

    # A map from the var name to the var.
    vars: ClassVar[Dict[str, Var]] = {}

    # The base vars of the class.
    base_vars: ClassVar[Dict[str, BaseVar]] = {}

    # The computed vars of the class.
    computed_vars: ClassVar[Dict[str, ComputedVar]] = {}

    # Vars inherited by the parent state.
    inherited_vars: ClassVar[Dict[str, Var]] = {}

    # Backend vars that are never sent to the client.
    backend_vars: ClassVar[Dict[str, Any]] = {}

    # Backend vars inherited
    inherited_backend_vars: ClassVar[Dict[str, Any]] = {}

    # The event handlers.
    event_handlers: ClassVar[Dict[str, EventHandler]] = {}

    # A set of subclassses of this class.
    class_subclasses: ClassVar[Set[Type[BaseState]]] = set()

    # Mapping of var name to set of computed variables that depend on it
    _computed_var_dependencies: ClassVar[Dict[str, Set[str]]] = {}

    # Mapping of var name to set of substates that depend on it
    _substate_var_dependencies: ClassVar[Dict[str, Set[str]]] = {}

    # Set of vars which always need to be recomputed
    _always_dirty_computed_vars: ClassVar[Set[str]] = set()

    # Set of substates which always need to be recomputed
    _always_dirty_substates: ClassVar[Set[str]] = set()

    # The parent state.
    parent_state: Optional[BaseState] = None

    # The substates of the state.
    substates: Dict[str, BaseState] = {}

    # The set of dirty vars.
    dirty_vars: Set[str] = set()

    # The set of dirty substates.
    dirty_substates: Set[str] = set()

    # The routing path that triggered the state
    router_data: Dict[str, Any] = {}

    # Per-instance copy of backend variable values
    _backend_vars: Dict[str, Any] = {}

    # The router data for the current page
    router: RouterData = RouterData()

    def __init__(self, *args, parent_state: BaseState | None = None, **kwargs):
        """Initialize the state.

        Args:
            *args: The args to pass to the Pydantic init method.
            parent_state: The parent state.
            **kwargs: The kwargs to pass to the Pydantic init method.

        """
        kwargs["parent_state"] = parent_state
        super().__init__(*args, **kwargs)

        # Setup the substates.
        for substate in self.get_substates():
            self.substates[substate.get_name()] = substate(parent_state=self)
        # Convert the event handlers to functions.
        self._init_event_handlers()

        # Create a fresh copy of the backend variables for this instance
        self._backend_vars = copy.deepcopy(self.backend_vars)

    def _init_event_handlers(self, state: BaseState | None = None):
        """Initialize event handlers.

        Allow event handlers to be called directly on the instance. This is
        called recursively for all parent states.

        Args:
            state: The state to initialize the event handlers on.
        """
        if state is None:
            state = self

        # Convert the event handlers to functions.
        for name, event_handler in state.event_handlers.items():
            if event_handler.is_background:
                fn = _no_chain_background_task(type(state), name, event_handler.fn)
            else:
                fn = functools.partial(event_handler.fn, self)
            fn.__module__ = event_handler.fn.__module__  # type: ignore
            fn.__qualname__ = event_handler.fn.__qualname__  # type: ignore
            setattr(self, name, fn)

        # Also allow direct calling of parent state event handlers
        if state.parent_state is not None:
            self._init_event_handlers(state.parent_state)

    def __repr__(self) -> str:
        """Get the string representation of the state.

        Returns:
            The string representation of the state.
        """
        return f"{self.__class__.__name__}({self.dict()})"

    @classmethod
    def __init_subclass__(cls, **kwargs):
        """Do some magic for the subclass initialization.

        Args:
            **kwargs: The kwargs to pass to the pydantic init_subclass method.

        Raises:
            ValueError: If a substate class shadows another.
        """
        is_testing_env = constants.PYTEST_CURRENT_TEST in os.environ
        super().__init_subclass__(**kwargs)
        # Event handlers should not shadow builtin state methods.
        cls._check_overridden_methods()

        # Reset subclass tracking for this class.
        cls.class_subclasses = set()

        # Get the parent vars.
        parent_state = cls.get_parent_state()
        if parent_state is not None:
            cls.inherited_vars = parent_state.vars
            cls.inherited_backend_vars = parent_state.backend_vars

            # Check if another substate class with the same name has already been defined.
            if cls.__name__ in set(c.__name__ for c in parent_state.class_subclasses):
                if is_testing_env:
                    # Clear existing subclass with same name when app is reloaded via
                    # utils.prerequisites.get_app(reload=True)
                    parent_state.class_subclasses = set(
                        c
                        for c in parent_state.class_subclasses
                        if c.__name__ != cls.__name__
                    )
                else:
                    # During normal operation, subclasses cannot have the same name, even if they are
                    # defined in different modules.
                    raise ValueError(
                        f"The substate class '{cls.__name__}' has been defined multiple times. "
                        "Shadowing substate classes is not allowed."
                    )
            # Track this new subclass in the parent state's subclasses set.
            parent_state.class_subclasses.add(cls)

        cls.new_backend_vars = {
            name: value
            for name, value in cls.__dict__.items()
            if types.is_backend_variable(name, cls)
            and name not in cls.inherited_backend_vars
            and not isinstance(value, FunctionType)
        }

        cls.backend_vars = {**cls.inherited_backend_vars, **cls.new_backend_vars}

        # Set the base and computed vars.
        cls.base_vars = {
            f.name: BaseVar(_var_name=f.name, _var_type=f.outer_type_)._var_set_state(
                cls
            )
            for f in cls.get_fields().values()
            if f.name not in cls.get_skip_vars()
        }
        cls.computed_vars = {
            v._var_name: v._var_set_state(cls)
            for v in cls.__dict__.values()
            if isinstance(v, ComputedVar)
        }
        cls.vars = {
            **cls.inherited_vars,
            **cls.base_vars,
            **cls.computed_vars,
        }
        cls.event_handlers = {}

        # Setup the base vars at the class level.
        for prop in cls.base_vars.values():
            cls._init_var(prop)

        # Set up the event handlers.
        events = {
            name: fn
            for name, fn in cls.__dict__.items()
            if cls._item_is_event_handler(name, fn)
        }

        for mixin in cls._mixins():
            for name, value in mixin.__dict__.items():
                if isinstance(value, ComputedVar):
                    fget = cls._copy_fn(value.fget)
                    newcv = ComputedVar(fget=fget, _var_name=value._var_name)
                    newcv._var_set_state(cls)
                    setattr(cls, name, newcv)
                    cls.computed_vars[newcv._var_name] = newcv
                    cls.vars[newcv._var_name] = newcv
                    continue
                if events.get(name) is not None:
                    continue
                if not cls._item_is_event_handler(name, value):
                    continue
                if parent_state is not None and parent_state.event_handlers.get(name):
                    continue
                value = cls._copy_fn(value)
                value.__qualname__ = f"{cls.__name__}.{name}"
                events[name] = value

        for name, fn in events.items():
            handler = EventHandler(fn=fn)
            cls.event_handlers[name] = handler
            setattr(cls, name, handler)

        cls._init_var_dependency_dicts()

        for name in cls.new_backend_vars:
            setattr(cls, name, PrivateVarDescriptor())

    @staticmethod
    def _copy_fn(fn: Callable) -> Callable:
        """Copy a function. Used to copy ComputedVars and EventHandlers from mixins.

        Args:
            fn: The function to copy.

        Returns:
            The copied function.
        """
        newfn = FunctionType(
            fn.__code__,
            fn.__globals__,
            name=fn.__name__,
            argdefs=fn.__defaults__,
            closure=fn.__closure__,
        )
        newfn.__annotations__ = fn.__annotations__
        return newfn

    @staticmethod
    def _item_is_event_handler(name: str, value: Any) -> bool:
        """Check if the item is an event handler.

        Args:
            name: The name of the item.
            value: The value of the item.

        Returns:
            Whether the item is an event handler.
        """
        return (
            not name.startswith("_")
            and isinstance(value, Callable)
            and not isinstance(value, EventHandler)
            and hasattr(value, "__code__")
        )

    @classmethod
    def _mixins(cls) -> List[Type]:
        """Get the mixin classes of the state.

        Returns:
            The mixin classes of the state.
        """
        return [
            mixin
            for mixin in cls.__mro__
            if not issubclass(mixin, (BaseState, ABC))
            and mixin not in [pydantic.BaseModel, Base]
        ]

    @classmethod
    def _init_var_dependency_dicts(cls):
        """Initialize the var dependency tracking dicts.

        Allows the state to know which vars each ComputedVar depends on and
        whether a ComputedVar depends on a var in its parent state.

        Additional updates tracking dicts for vars and substates that always
        need to be recomputed.
        """
        # Initialize per-class var dependency tracking.
        cls._computed_var_dependencies = defaultdict(set)
        cls._substate_var_dependencies = defaultdict(set)

        inherited_vars = set(cls.inherited_vars).union(
            set(cls.inherited_backend_vars),
        )
        for cvar_name, cvar in cls.computed_vars.items():
            # Add the dependencies.
            for var in cvar._deps(objclass=cls):
                cls._computed_var_dependencies[var].add(cvar_name)
                if var in inherited_vars:
                    # track that this substate depends on its parent for this var
                    state_name = cls.get_name()
                    parent_state = cls.get_parent_state()
                    while parent_state is not None and var in parent_state.vars:
                        parent_state._substate_var_dependencies[var].add(state_name)
                        state_name, parent_state = (
                            parent_state.get_name(),
                            parent_state.get_parent_state(),
                        )

        # ComputedVar with cache=False always need to be recomputed
        cls._always_dirty_computed_vars = set(
            cvar_name
            for cvar_name, cvar in cls.computed_vars.items()
            if not cvar._cache
        )

        # Any substate containing a ComputedVar with cache=False always needs to be recomputed
        cls._always_dirty_substates = set()
        if cls._always_dirty_computed_vars:
            # Tell parent classes that this substate has always dirty computed vars
            state_name = cls.get_name()
            parent_state = cls.get_parent_state()
            while parent_state is not None:
                parent_state._always_dirty_substates.add(state_name)
                state_name, parent_state = (
                    parent_state.get_name(),
                    parent_state.get_parent_state(),
                )

    @classmethod
    def _check_overridden_methods(cls):
        """Check for shadow methods and raise error if any.

        Raises:
            NameError: When an event handler shadows an inbuilt state method.
        """
        overridden_methods = set()
        state_base_functions = cls._get_base_functions()
        for name, method in inspect.getmembers(cls, inspect.isfunction):
            # Check if the method is overridden and not a dunder method
            if (
                not name.startswith("__")
                and method.__name__ in state_base_functions
                and state_base_functions[method.__name__] != method
            ):
                overridden_methods.add(method.__name__)

        for method_name in overridden_methods:
            raise NameError(
                f"The event handler name `{method_name}` shadows a builtin State method; use a different name instead"
            )

    @classmethod
    def get_skip_vars(cls) -> set[str]:
        """Get the vars to skip when serializing.

        Returns:
            The vars to skip when serializing.
        """
        return (
            set(cls.inherited_vars)
            | {
                "parent_state",
                "substates",
                "dirty_vars",
                "dirty_substates",
                "router_data",
            }
            | RESERVED_BACKEND_VAR_NAMES
        )

    @classmethod
    @functools.lru_cache()
    def get_parent_state(cls) -> Type[BaseState] | None:
        """Get the parent state.

        Returns:
            The parent state.
        """
        parent_states = [
            base
            for base in cls.__bases__
            if types._issubclass(base, BaseState) and base is not BaseState
        ]
        assert len(parent_states) < 2, "Only one parent state is allowed."
        return parent_states[0] if len(parent_states) == 1 else None  # type: ignore

    @classmethod
    def get_substates(cls) -> set[Type[BaseState]]:
        """Get the substates of the state.

        Returns:
            The substates of the state.
        """
        return cls.class_subclasses

    @classmethod
    @functools.lru_cache()
    def get_name(cls) -> str:
        """Get the name of the state.

        Returns:
            The name of the state.
        """
        return format.to_snake_case(cls.__name__)

    @classmethod
    @functools.lru_cache()
    def get_full_name(cls) -> str:
        """Get the full name of the state.

        Returns:
            The full name of the state.
        """
        name = cls.get_name()
        parent_state = cls.get_parent_state()
        if parent_state is not None:
            name = ".".join((parent_state.get_full_name(), name))
        return name

    @classmethod
    @functools.lru_cache()
    def get_class_substate(cls, path: Sequence[str]) -> Type[BaseState]:
        """Get the class substate.

        Args:
            path: The path to the substate.

        Returns:
            The class substate.

        Raises:
            ValueError: If the substate is not found.
        """
        if len(path) == 0:
            return cls
        if path[0] == cls.get_name():
            if len(path) == 1:
                return cls
            path = path[1:]
        for substate in cls.get_substates():
            if path[0] == substate.get_name():
                return substate.get_class_substate(path[1:])
        raise ValueError(f"Invalid path: {path}")

    @classmethod
    def get_class_var(cls, path: Sequence[str]) -> Any:
        """Get the class var.

        Args:
            path: The path to the var.

        Returns:
            The class var.

        Raises:
            ValueError: If the path is invalid.
        """
        path, name = path[:-1], path[-1]
        substate = cls.get_class_substate(tuple(path))
        if not hasattr(substate, name):
            raise ValueError(f"Invalid path: {path}")
        return getattr(substate, name)

    @classmethod
    def _init_var(cls, prop: BaseVar):
        """Initialize a variable.

        Args:
            prop: The variable to initialize

        Raises:
            TypeError: if the variable has an incorrect type
        """
        if not types.is_valid_var_type(prop._var_type):
            raise TypeError(
                "State vars must be primitive Python types, "
                "Plotly figures, Pandas dataframes, "
                "or subclasses of rx.Base. "
                f'Found var "{prop._var_name}" with type {prop._var_type}.'
            )
        cls._set_var(prop)
        cls._create_setter(prop)
        cls._set_default_value(prop)

    @classmethod
    def add_var(cls, name: str, type_: Any, default_value: Any = None):
        """Add dynamically a variable to the State.

        The variable added this way can be used in the same way as a variable
        defined statically in the model.

        Args:
            name: The name of the variable
            type_: The type of the variable
            default_value: The default value of the variable

        Raises:
            NameError: if a variable of this name already exists
        """
        if name in cls.__fields__:
            raise NameError(
                f"The variable '{name}' already exist. Use a different name"
            )

        # create the variable based on name and type
        var = BaseVar(_var_name=name, _var_type=type_)
        var._var_set_state(cls)

        # add the pydantic field dynamically (must be done before _init_var)
        cls.add_field(var, default_value)

        cls._init_var(var)

        # update the internal dicts so the new variable is correctly handled
        cls.base_vars.update({name: var})
        cls.vars.update({name: var})

        # let substates know about the new variable
        for substate_class in cls.__subclasses__():
            substate_class.vars.setdefault(name, var)

        # Reinitialize dependency tracking dicts.
        cls._init_var_dependency_dicts()

    @classmethod
    def _set_var(cls, prop: BaseVar):
        """Set the var as a class member.

        Args:
            prop: The var instance to set.
        """
        setattr(cls, prop._var_name, prop)

    @classmethod
    def _create_setter(cls, prop: BaseVar):
        """Create a setter for the var.

        Args:
            prop: The var to create a setter for.
        """
        setter_name = prop.get_setter_name(include_state=False)
        if setter_name not in cls.__dict__:
            event_handler = EventHandler(fn=prop.get_setter())
            cls.event_handlers[setter_name] = event_handler
            setattr(cls, setter_name, event_handler)

    @classmethod
    def _set_default_value(cls, prop: BaseVar):
        """Set the default value for the var.

        Args:
            prop: The var to set the default value for.
        """
        # Get the pydantic field for the var.
        field = cls.get_fields()[prop._var_name]
        if field.required:
            default_value = prop.get_default_value()
            if default_value is not None:
                field.required = False
                field.default = default_value
        if (
            not field.required
            and field.default is None
            and not types.is_optional(prop._var_type)
        ):
            # Ensure frontend uses null coalescing when accessing.
            prop._var_type = Optional[prop._var_type]

    @staticmethod
    def _get_base_functions() -> dict[str, FunctionType]:
        """Get all functions of the state class excluding dunder methods.

        Returns:
            The functions of rx.State class as a dict.
        """
        return {
            func[0]: func[1]
            for func in inspect.getmembers(BaseState, predicate=inspect.isfunction)
            if not func[0].startswith("__")
        }

    def get_token(self) -> str:
        """Return the token of the client associated with this state.

        Returns:
            The token of the client.
        """
        console.deprecate(
            feature_name="get_token",
            reason="replaced by `State.router.session.client_token`",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        return self.router_data.get(constants.RouteVar.CLIENT_TOKEN, "")

    def get_sid(self) -> str:
        """Return the session ID of the client associated with this state.

        Returns:
            The session ID of the client.
        """
        console.deprecate(
            feature_name="get_sid",
            reason="replaced by `State.router.session.session_id`",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        return self.router_data.get(constants.RouteVar.SESSION_ID, "")

    def get_headers(self) -> Dict:
        """Return the headers of the client associated with this state.

        Returns:
            The headers of the client.
        """
        console.deprecate(
            feature_name="get_headers",
            reason="replaced by `State.router.headers`",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        return self.router_data.get(constants.RouteVar.HEADERS, {})

    def get_client_ip(self) -> str:
        """Return the IP of the client associated with this state.

        Returns:
            The IP of the client.
        """
        console.deprecate(
            feature_name="get_client_ip",
            reason="replaced by `State.router.session.client_ip`",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        return self.router_data.get(constants.RouteVar.CLIENT_IP, "")

    def get_current_page(self, origin=False) -> str:
        """Obtain the path of current page from the router data.

        Args:
            origin: whether to return the base route as shown in browser

        Returns:
            The current page.
        """
        console.deprecate(
            feature_name="get_current_page",
            reason="replaced by State.router.page / self.router.page",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )

        return self.router.page.raw_path if origin else self.router.page.path

    def get_query_params(self) -> dict[str, str]:
        """Obtain the query parameters for the queried page.

        The query object contains both the URI parameters and the GET parameters.

        Returns:
            The dict of query parameters.
        """
        console.deprecate(
            feature_name="get_query_params",
            reason="replaced by `State.router.page.params`",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        return self.router_data.get(constants.RouteVar.QUERY, {})

    def get_cookies(self) -> dict[str, str]:
        """Obtain the cookies of the client stored in the browser.

        Returns:
                The dict of cookies.
        """
        console.deprecate(
            feature_name=f"rx.get_cookies",
            reason="and has been replaced by rx.Cookie, which can be used as a state var",
            deprecation_version="0.3.0",
            removal_version="0.5.0",
        )
        cookie_dict = {}
        cookies = self.get_headers().get(constants.RouteVar.COOKIE, "").split(";")

        cookie_pairs = [cookie.split("=") for cookie in cookies if cookie]

        for pair in cookie_pairs:
            key, value = pair[0].strip(), urllib.parse.unquote(pair[1].strip())
            try:
                # cast non-string values to the actual types.
                value = json.loads(value)
            except json.JSONDecodeError:
                pass
            finally:
                cookie_dict[key] = value
        return cookie_dict

    @classmethod
    def setup_dynamic_args(cls, args: dict[str, str]):
        """Set up args for easy access in renderer.

        Args:
            args: a dict of args
        """

        def argsingle_factory(param):
            @ComputedVar
            def inner_func(self) -> str:
                return self.router.page.params.get(param, "")

            return inner_func

        def arglist_factory(param):
            @ComputedVar
            def inner_func(self) -> List:
                return self.router.page.params.get(param, [])

            return inner_func

        for param, value in args.items():
            if value == constants.RouteArgType.SINGLE:
                func = argsingle_factory(param)
            elif value == constants.RouteArgType.LIST:
                func = arglist_factory(param)
            else:
                continue
            # to allow passing as a prop
            func._var_name = param
            cls.vars[param] = cls.computed_vars[param] = func._var_set_state(cls)  # type: ignore
            setattr(cls, param, func)

            # Reinitialize dependency tracking dicts.
            cls._init_var_dependency_dicts()

    def __getattribute__(self, name: str) -> Any:
        """Get the state var.

        If the var is inherited, get the var from the parent state.

        Args:
            name: The name of the var.

        Returns:
            The value of the var.
        """
        # If the state hasn't been initialized yet, return the default value.
        if not super().__getattribute__("__dict__"):
            return super().__getattribute__(name)

        inherited_vars = {
            **super().__getattribute__("inherited_vars"),
            **super().__getattribute__("inherited_backend_vars"),
        }
        if name in inherited_vars:
            return getattr(super().__getattribute__("parent_state"), name)

        backend_vars = super().__getattribute__("_backend_vars")
        if name in backend_vars:
            value = backend_vars[name]
        else:
            value = super().__getattribute__(name)

        if isinstance(value, MutableProxy.__mutable_types__) and (
            name in super().__getattribute__("base_vars") or name in backend_vars
        ):
            # track changes in mutable containers (list, dict, set, etc)
            return MutableProxy(wrapped=value, state=self, field_name=name)

        return value

    def __setattr__(self, name: str, value: Any):
        """Set the attribute.

        If the attribute is inherited, set the attribute on the parent state.

        Args:
            name: The name of the attribute.
            value: The value of the attribute.
        """
        if isinstance(value, MutableProxy):
            # unwrap proxy objects when assigning back to the state
            value = value.__wrapped__

        # Set the var on the parent state.
        inherited_vars = {**self.inherited_vars, **self.inherited_backend_vars}
        if name in inherited_vars:
            setattr(self.parent_state, name, value)
            return

        if (
            types.is_backend_variable(name, self.__class__)
            and name not in RESERVED_BACKEND_VAR_NAMES
        ):
            self._backend_vars.__setitem__(name, value)
            self.dirty_vars.add(name)
            self._mark_dirty()
            return

        # Set the attribute.
        super().__setattr__(name, value)

        # Add the var to the dirty list.
        if name in self.vars or name in self._computed_var_dependencies:
            self.dirty_vars.add(name)
            self._mark_dirty()

        # For now, handle router_data updates as a special case
        if name == constants.ROUTER_DATA:
            self.dirty_vars.add(name)
            self._mark_dirty()
            # propagate router_data updates down the state tree
            for substate in self.substates.values():
                setattr(substate, name, value)

    def reset(self):
        """Reset all the base vars to their default values."""
        # Reset the base vars.
        fields = self.get_fields()
        for prop_name in self.base_vars:
            if prop_name == constants.ROUTER:
                continue  # never reset the router data
            setattr(self, prop_name, copy.deepcopy(fields[prop_name].default))

        # Recursively reset the substates.
        for substate in self.substates.values():
            substate.reset()

    def _reset_client_storage(self):
        """Reset client storage base vars to their default values."""
        # Client-side storage is reset during hydrate so that clearing cookies
        # on the browser also resets the values on the backend.
        fields = self.get_fields()
        for prop_name in self.base_vars:
            field = fields[prop_name]
            if isinstance(field.default, ClientStorageBase) or (
                isinstance(field.type_, type)
                and issubclass(field.type_, ClientStorageBase)
            ):
                setattr(self, prop_name, copy.deepcopy(field.default))

        # Recursively reset the substate client storage.
        for substate in self.substates.values():
            substate._reset_client_storage()

    def get_substate(self, path: Sequence[str]) -> BaseState | None:
        """Get the substate.

        Args:
            path: The path to the substate.

        Returns:
            The substate.

        Raises:
            ValueError: If the substate is not found.
        """
        if len(path) == 0:
            return self
        if path[0] == self.get_name():
            if len(path) == 1:
                return self
            path = path[1:]
        if path[0] not in self.substates:
            raise ValueError(f"Invalid path: {path}")
        return self.substates[path[0]].get_substate(path[1:])

    def _get_event_handler(
        self, event: Event
    ) -> tuple[BaseState | StateProxy, EventHandler]:
        """Get the event handler for the given event.

        Args:
            event: The event to get the handler for.


        Returns:
            The event handler.

        Raises:
            ValueError: If the event handler or substate is not found.
        """
        # Get the event handler.
        path = event.name.split(".")
        path, name = path[:-1], path[-1]
        substate = self.get_substate(path)
        if not substate:
            raise ValueError(
                "The value of state cannot be None when processing an event."
            )
        handler = substate.event_handlers[name]

        # For background tasks, proxy the state
        if handler.is_background:
            substate = StateProxy(substate)

        return substate, handler

    async def _process(self, event: Event) -> AsyncIterator[StateUpdate]:
        """Obtain event info and process event.

        Args:
            event: The event to process.

        Yields:
            The state update after processing the event.
        """
        # Get the event handler.
        substate, handler = self._get_event_handler(event)

        # Run the event generator and yield state updates.
        async for update in self._process_event(
            handler=handler,
            state=substate,
            payload=event.payload,
        ):
            yield update

    def _check_valid(self, handler: EventHandler, events: Any) -> Any:
        """Check if the events yielded are valid. They must be EventHandlers or EventSpecs.

        Args:
            handler: EventHandler.
            events: The events to be checked.

        Raises:
            TypeError: If any of the events are not valid.

        Returns:
            The events as they are if valid.
        """

        def _is_valid_type(events: Any) -> bool:
            return isinstance(events, (Event, EventHandler, EventSpec))

        if events is None or _is_valid_type(events):
            return events
        try:
            if all(_is_valid_type(e) for e in events):
                return events
        except TypeError:
            pass

        raise TypeError(
            f"Your handler {handler.fn.__qualname__} must only return/yield: None, Events or other EventHandlers referenced by their class (not using `self`)"
        )

    def _as_state_update(
        self,
        handler: EventHandler,
        events: EventSpec | list[EventSpec] | None,
        final: bool,
    ) -> StateUpdate:
        """Convert the events to a StateUpdate.

        Fixes the events and checks for validity before converting.

        Args:
            handler: The handler where the events originated from.
            events: The events to queue with the update.
            final: Whether the handler is done processing.

        Returns:
            The valid StateUpdate containing the events and final flag.
        """
        # get the delta from the root of the state tree
        state = self
        while state.parent_state is not None:
            state = state.parent_state

        token = self.router.session.client_token

        # Convert valid EventHandler and EventSpec into Event
        fixed_events = fix_events(self._check_valid(handler, events), token)

        # Get the delta after processing the event.
        delta = state.get_delta()
        state._clean()

        return StateUpdate(
            delta=delta,
            events=fixed_events,
            final=final if not handler.is_background else True,
        )

    async def _process_event(
        self, handler: EventHandler, state: BaseState | StateProxy, payload: Dict
    ) -> AsyncIterator[StateUpdate]:
        """Process event.

        Args:
            handler: EventHandler to process.
            state: State to process the handler.
            payload: The event payload.

        Yields:
            StateUpdate object
        """
        # Get the function to process the event.
        fn = functools.partial(handler.fn, state)

        # Wrap the function in a try/except block.
        try:
            # Handle async functions.
            if asyncio.iscoroutinefunction(fn.func):
                events = await fn(**payload)

            # Handle regular functions.
            else:
                events = fn(**payload)
            # Handle async generators.
            if inspect.isasyncgen(events):
                async for event in events:
                    yield state._as_state_update(handler, event, final=False)
                yield state._as_state_update(handler, events=None, final=True)

            # Handle regular generators.
            elif inspect.isgenerator(events):
                try:
                    while True:
                        yield state._as_state_update(handler, next(events), final=False)
                except StopIteration as si:
                    # the "return" value of the generator is not available
                    # in the loop, we must catch StopIteration to access it
                    if si.value is not None:
                        yield state._as_state_update(handler, si.value, final=False)
                yield state._as_state_update(handler, events=None, final=True)

            # Handle regular event chains.
            else:
                yield state._as_state_update(handler, events, final=True)

        # If an error occurs, throw a window alert.
        except Exception:
            error = traceback.format_exc()
            print(error)
            yield state._as_state_update(
                handler,
                window_alert("An error occurred. See logs for details."),
                final=True,
            )

    def _mark_dirty_computed_vars(self) -> None:
        """Mark ComputedVars that need to be recalculated based on dirty_vars."""
        dirty_vars = self.dirty_vars
        while dirty_vars:
            calc_vars, dirty_vars = dirty_vars, set()
            for cvar in self._dirty_computed_vars(from_vars=calc_vars):
                self.dirty_vars.add(cvar)
                dirty_vars.add(cvar)
                actual_var = self.computed_vars.get(cvar)
                if actual_var is not None:
                    actual_var.mark_dirty(instance=self)

    def _dirty_computed_vars(self, from_vars: set[str] | None = None) -> set[str]:
        """Determine ComputedVars that need to be recalculated based on the given vars.

        Args:
            from_vars: find ComputedVar that depend on this set of vars. If unspecified, will use the dirty_vars.

        Returns:
            Set of computed vars to include in the delta.
        """
        return set(
            cvar
            for dirty_var in from_vars or self.dirty_vars
            for cvar in self._computed_var_dependencies[dirty_var]
        )

    def get_delta(self) -> Delta:
        """Get the delta for the state.

        Returns:
            The delta for the state.
        """
        delta = {}

        # Apply dirty variables down into substates
        self.dirty_vars.update(self._always_dirty_computed_vars)
        self._mark_dirty()

        # Return the dirty vars for this instance, any cached/dependent computed vars,
        # and always dirty computed vars (cache=False)
        delta_vars = (
            self.dirty_vars.intersection(self.base_vars)
            .union(self._dirty_computed_vars())
            .union(self._always_dirty_computed_vars)
        )

        subdelta = {
            prop: getattr(self, prop)
            for prop in delta_vars
            if not types.is_backend_variable(prop, self.__class__)
        }
        if len(subdelta) > 0:
            delta[self.get_full_name()] = subdelta

        # Recursively find the substate deltas.
        substates = self.substates
        for substate in self.dirty_substates.union(self._always_dirty_substates):
            delta.update(substates[substate].get_delta())

        # Format the delta.
        delta = format.format_state(delta)

        # Return the delta.
        return delta

    def _mark_dirty(self):
        """Mark the substate and all parent states as dirty."""
        state_name = self.get_name()
        if (
            self.parent_state is not None
            and state_name not in self.parent_state.dirty_substates
        ):
            self.parent_state.dirty_substates.add(self.get_name())
            self.parent_state._mark_dirty()

        # have to mark computed vars dirty to allow access to newly computed
        # values within the same ComputedVar function
        self._mark_dirty_computed_vars()

        # Propagate dirty var / computed var status into substates
        substates = self.substates
        for var in self.dirty_vars:
            for substate_name in self._substate_var_dependencies[var]:
                self.dirty_substates.add(substate_name)
                substate = substates[substate_name]
                substate.dirty_vars.add(var)
                substate._mark_dirty()

    def _clean(self):
        """Reset the dirty vars."""
        # Recursively clean the substates.
        for substate in self.dirty_substates:
            self.substates[substate]._clean()

        # Clean this state.
        self.dirty_vars = set()
        self.dirty_substates = set()

    def get_value(self, key: str) -> Any:
        """Get the value of a field (without proxying).

        The returned value will NOT track dirty state updates.

        Args:
            key: The key of the field.

        Returns:
            The value of the field.
        """
        if isinstance(key, MutableProxy):
            return super().get_value(key.__wrapped__)
        return super().get_value(key)

    def dict(self, include_computed: bool = True, **kwargs) -> dict[str, Any]:
        """Convert the object to a dictionary.

        Args:
            include_computed: Whether to include computed vars.
            **kwargs: Kwargs to pass to the pydantic dict method.

        Returns:
            The object as a dictionary.
        """
        if include_computed:
            # Apply dirty variables down into substates to allow never-cached ComputedVar to
            # trigger recalculation of dependent vars
            self.dirty_vars.update(self._always_dirty_computed_vars)
            self._mark_dirty()

        base_vars = {
            prop_name: self.get_value(getattr(self, prop_name))
            for prop_name in self.base_vars
        }
        computed_vars = (
            {
                # Include the computed vars.
                prop_name: self.get_value(getattr(self, prop_name))
                for prop_name in self.computed_vars
            }
            if include_computed
            else {}
        )
        variables = {**base_vars, **computed_vars}
        d = {
            self.get_full_name(): {k: variables[k] for k in sorted(variables)},
        }
        for substate_d in [
            v.dict(include_computed=include_computed, **kwargs)
            for v in self.substates.values()
        ]:
            d.update(substate_d)
        return d

    async def __aenter__(self) -> BaseState:
        """Enter the async context manager protocol.

        This should not be used for the State class, but exists for
        type-compatibility with StateProxy.

        Raises:
            TypeError: always, because async contextmanager protocol is only supported for background task.
        """
        raise TypeError(
            "Only background task should use `async with self` to modify state."
        )

    async def __aexit__(self, *exc_info: Any) -> None:
        """Exit the async context manager protocol.

        This should not be used for the State class, but exists for
        type-compatibility with StateProxy.

        Args:
            exc_info: The exception info tuple.
        """
        pass


class State(BaseState):
    """The app Base State."""

    # The hydrated bool.
    is_hydrated: bool = False

    def on_load_internal(self) -> list[Event | EventSpec] | None:
        """Queue on_load handlers for the current page.

        Returns:
            The list of events to queue for on load handling.
        """
        # Do not app.compile_()!  It should be already compiled by now.
        app = getattr(prerequisites.get_app(), constants.CompileVars.APP)
        load_events = app.get_load_events(self.router.page.path)
        if not load_events and self.is_hydrated:
            return  # Fast path for page-to-page navigation
        self.is_hydrated = False
        return [
            *fix_events(
                load_events,
                self.router.session.client_token,
                router_data=self.router_data,
            ),
            type(self).set_is_hydrated(True),  # type: ignore
        ]

    def update_vars_internal(self, vars: dict[str, Any]) -> None:
        """Apply updates to fully qualified state vars.

        The keys in `vars` should be in the form of `{state.get_full_name()}.{var_name}`,
        and each value will be set on the appropriate substate instance.

        This function is primarily used to apply cookie and local storage
        updates from the frontend to the appropriate substate.

        Args:
            vars: The fully qualified vars and values to update.
        """
        for var, value in vars.items():
            state_name, _, var_name = var.rpartition(".")
            var_state = self.get_substate(state_name.split("."))
            setattr(var_state, var_name, value)


class StateProxy(wrapt.ObjectProxy):
    """Proxy of a state instance to control mutability of vars for a background task.

    Since a background task runs against a state instance without holding the
    state_manager lock for the token, the reference may become stale if the same
    state is modified by another event handler.

    The proxy object ensures that writes to the state are blocked unless
    explicitly entering a context which refreshes the state from state_manager
    and holds the lock for the token until exiting the context. After exiting
    the context, a StateUpdate may be emitted to the frontend to notify the
    client of the state change.

    A background task will be passed the `StateProxy` as `self`, so mutability
    can be safely performed inside an `async with self` block.

        class State(rx.State):
            counter: int = 0

            @rx.background
            async def bg_increment(self):
                await asyncio.sleep(1)
                async with self:
                    self.counter += 1
    """

    def __init__(self, state_instance):
        """Create a proxy for a state instance.

        Args:
            state_instance: The state instance to proxy.
        """
        super().__init__(state_instance)
        # compile is not relevant to backend logic
        self._self_app = getattr(prerequisites.get_app(), constants.CompileVars.APP)
        self._self_substate_path = state_instance.get_full_name().split(".")
        self._self_actx = None
        self._self_mutable = False

    async def __aenter__(self) -> StateProxy:
        """Enter the async context manager protocol.

        Sets mutability to True and enters the `App.modify_state` async context,
        which refreshes the state from state_manager and holds the lock for the
        given state token until exiting the context.

        Background tasks should avoid blocking calls while inside the context.

        Returns:
            This StateProxy instance in mutable mode.
        """
        self._self_actx = self._self_app.modify_state(
            self.__wrapped__.router.session.client_token
        )
        mutable_state = await self._self_actx.__aenter__()
        super().__setattr__(
            "__wrapped__", mutable_state.get_substate(self._self_substate_path)
        )
        self._self_mutable = True
        return self

    async def __aexit__(self, *exc_info: Any) -> None:
        """Exit the async context manager protocol.

        Sets proxy mutability to False and persists any state changes.

        Args:
            exc_info: The exception info tuple.
        """
        if self._self_actx is None:
            return
        self._self_mutable = False
        await self._self_actx.__aexit__(*exc_info)
        self._self_actx = None

    def __enter__(self):
        """Enter the regular context manager protocol.

        This is not supported for background tasks, and exists only to raise a more useful exception
        when the StateProxy is used incorrectly.

        Raises:
            TypeError: always, because only async contextmanager protocol is supported.
        """
        raise TypeError("Background task must use `async with self` to modify state.")

    def __exit__(self, *exc_info: Any) -> None:
        """Exit the regular context manager protocol.

        Args:
            exc_info: The exception info tuple.
        """
        pass

    def __getattr__(self, name: str) -> Any:
        """Get the attribute from the underlying state instance.

        Args:
            name: The name of the attribute.

        Returns:
            The value of the attribute.
        """
        value = super().__getattr__(name)
        if not name.startswith("_self_") and isinstance(value, MutableProxy):
            # ensure mutations to these containers are blocked unless proxy is _mutable
            return ImmutableMutableProxy(
                wrapped=value.__wrapped__,
                state=self,  # type: ignore
                field_name=value._self_field_name,
            )
        if isinstance(value, functools.partial) and value.args[0] is self.__wrapped__:
            # Rebind event handler to the proxy instance
            value = functools.partial(
                value.func,
                self,
                *value.args[1:],
                **value.keywords,
            )
        if isinstance(value, MethodType) and value.__self__ is self.__wrapped__:
            # Rebind methods to the proxy instance
            value = type(value)(value.__func__, self)  # type: ignore
        return value

    def __setattr__(self, name: str, value: Any) -> None:
        """Set the attribute on the underlying state instance.

        If the attribute is internal, set it on the proxy instance instead.

        Args:
            name: The name of the attribute.
            value: The value of the attribute.

        Raises:
            ImmutableStateError: If the state is not in mutable mode.
        """
        if (
            name.startswith("_self_")  # wrapper attribute
            or self._self_mutable  # lock held
            # non-persisted state attribute
            or name in self.__wrapped__.get_skip_vars()
        ):
            super().__setattr__(name, value)
            return

        raise ImmutableStateError(
            "Background task StateProxy is immutable outside of a context "
            "manager. Use `async with self` to modify state."
        )


class StateUpdate(Base):
    """A state update sent to the frontend."""

    # The state delta.
    delta: Delta = {}

    # Events to be added to the event queue.
    events: List[Event] = []

    # Whether this is the final state update for the event.
    final: bool = True


class StateManager(Base, ABC):
    """A class to manage many client states."""

    # The state class to use.
    state: Type[BaseState]

    @classmethod
    def create(cls, state: Type[BaseState]):
        """Create a new state manager.

        Args:
            state: The state class to use.

        Returns:
            The state manager (either memory or redis).
        """
        redis = prerequisites.get_redis()
        if redis is not None:
            return StateManagerRedis(state=state, redis=redis)
        return StateManagerMemory(state=state)

    @abstractmethod
    async def get_state(self, token: str) -> BaseState:
        """Get the state for a token.

        Args:
            token: The token to get the state for.

        Returns:
            The state for the token.
        """
        pass

    @abstractmethod
    async def set_state(self, token: str, state: BaseState):
        """Set the state for a token.

        Args:
            token: The token to set the state for.
            state: The state to set.
        """
        pass

    @abstractmethod
    @contextlib.asynccontextmanager
    async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
        """Modify the state for a token while holding exclusive lock.

        Args:
            token: The token to modify the state for.

        Yields:
            The state for the token.
        """
        yield self.state()


class StateManagerMemory(StateManager):
    """A state manager that stores states in memory."""

    # The mapping of client ids to states.
    states: Dict[str, BaseState] = {}

    # The mutex ensures the dict of mutexes is updated exclusively
    _state_manager_lock = asyncio.Lock()

    # The dict of mutexes for each client
    _states_locks: Dict[str, asyncio.Lock] = pydantic.PrivateAttr({})

    class Config:
        """The Pydantic config."""

        fields = {
            "_states_locks": {"exclude": True},
        }

    async def get_state(self, token: str) -> BaseState:
        """Get the state for a token.

        Args:
            token: The token to get the state for.

        Returns:
            The state for the token.
        """
        if token not in self.states:
            self.states[token] = self.state()
        return self.states[token]

    async def set_state(self, token: str, state: BaseState):
        """Set the state for a token.

        Args:
            token: The token to set the state for.
            state: The state to set.
        """
        pass

    @contextlib.asynccontextmanager
    async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
        """Modify the state for a token while holding exclusive lock.

        Args:
            token: The token to modify the state for.

        Yields:
            The state for the token.
        """
        if token not in self._states_locks:
            async with self._state_manager_lock:
                if token not in self._states_locks:
                    self._states_locks[token] = asyncio.Lock()

        async with self._states_locks[token]:
            state = await self.get_state(token)
            yield state
            await self.set_state(token, state)


class StateManagerRedis(StateManager):
    """A state manager that stores states in redis."""

    # The redis client to use.
    redis: Redis

    # The token expiration time (s).
    token_expiration: int = constants.Expiration.TOKEN

    # The maximum time to hold a lock (ms).
    lock_expiration: int = constants.Expiration.LOCK

    # The keyspace subscription string when redis is waiting for lock to be released
    _redis_notify_keyspace_events: str = (
        "K"  # Enable keyspace notifications (target a particular key)
        "g"  # For generic commands (DEL, EXPIRE, etc)
        "x"  # For expired events
        "e"  # For evicted events (i.e. maxmemory exceeded)
    )

    # These events indicate that a lock is no longer held
    _redis_keyspace_lock_release_events: Set[bytes] = {
        b"del",
        b"expire",
        b"expired",
        b"evicted",
    }

    async def get_state(self, token: str) -> BaseState:
        """Get the state for a token.

        Args:
            token: The token to get the state for.

        Returns:
            The state for the token.
        """
        redis_state = await self.redis.get(token)
        if redis_state is None:
            await self.set_state(token, self.state())
            return await self.get_state(token)
        return cloudpickle.loads(redis_state)

    async def set_state(
        self, token: str, state: BaseState, lock_id: bytes | None = None
    ):
        """Set the state for a token.

        Args:
            token: The token to set the state for.
            state: The state to set.
            lock_id: If provided, the lock_key must be set to this value to set the state.

        Raises:
            LockExpiredError: If lock_id is provided and the lock for the token is not held by that ID.
        """
        # check that we're holding the lock
        if (
            lock_id is not None
            and await self.redis.get(self._lock_key(token)) != lock_id
        ):
            raise LockExpiredError(
                f"Lock expired for token {token} while processing. Consider increasing "
                f"`app.state_manager.lock_expiration` (currently {self.lock_expiration}) "
                "or use `@rx.background` decorator for long-running tasks."
            )
        await self.redis.set(token, cloudpickle.dumps(state), ex=self.token_expiration)

    @contextlib.asynccontextmanager
    async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
        """Modify the state for a token while holding exclusive lock.

        Args:
            token: The token to modify the state for.

        Yields:
            The state for the token.
        """
        async with self._lock(token) as lock_id:
            state = await self.get_state(token)
            yield state
            await self.set_state(token, state, lock_id)

    @staticmethod
    def _lock_key(token: str) -> bytes:
        """Get the redis key for a token's lock.

        Args:
            token: The token to get the lock key for.

        Returns:
            The redis lock key for the token.
        """
        return f"{token}_lock".encode()

    async def _try_get_lock(self, lock_key: bytes, lock_id: bytes) -> bool | None:
        """Try to get a redis lock for a token.

        Args:
            lock_key: The redis key for the lock.
            lock_id: The ID of the lock.

        Returns:
            True if the lock was obtained.
        """
        return await self.redis.set(
            lock_key,
            lock_id,
            px=self.lock_expiration,
            nx=True,  # only set if it doesn't exist
        )

    async def _wait_lock(self, lock_key: bytes, lock_id: bytes) -> None:
        """Wait for a redis lock to be released via pubsub.

        Coroutine will not return until the lock is obtained.

        Args:
            lock_key: The redis key for the lock.
            lock_id: The ID of the lock.
        """
        state_is_locked = False
        lock_key_channel = f"__keyspace@0__:{lock_key.decode()}"
        # Enable keyspace notifications for the lock key, so we know when it is available.
        await self.redis.config_set(
            "notify-keyspace-events", self._redis_notify_keyspace_events
        )
        async with self.redis.pubsub() as pubsub:
            await pubsub.psubscribe(lock_key_channel)
            while not state_is_locked:
                # wait for the lock to be released
                while True:
                    if not await self.redis.exists(lock_key):
                        break  # key was removed, try to get the lock again
                    message = await pubsub.get_message(
                        ignore_subscribe_messages=True,
                        timeout=self.lock_expiration / 1000.0,
                    )
                    if message is None:
                        continue
                    if message["data"] in self._redis_keyspace_lock_release_events:
                        break
                state_is_locked = await self._try_get_lock(lock_key, lock_id)

    @contextlib.asynccontextmanager
    async def _lock(self, token: str):
        """Obtain a redis lock for a token.

        Args:
            token: The token to obtain a lock for.

        Yields:
            The ID of the lock (to be passed to set_state).

        Raises:
            LockExpiredError: If the lock has expired while processing the event.
        """
        lock_key = self._lock_key(token)
        lock_id = uuid.uuid4().hex.encode()

        if not await self._try_get_lock(lock_key, lock_id):
            # Missed the fast-path to get lock, subscribe for lock delete/expire events
            await self._wait_lock(lock_key, lock_id)
        state_is_locked = True

        try:
            yield lock_id
        except LockExpiredError:
            state_is_locked = False
            raise
        finally:
            if state_is_locked:
                # only delete our lock
                await self.redis.delete(lock_key)

    async def close(self):
        """Explicitly close the redis connection and connection_pool.

        It is necessary in testing scenarios to close between asyncio test cases
        to avoid having lingering redis connections associated with event loops
        that will be closed (each test case uses its own event loop).

        Note: Connections will be automatically reopened when needed.
        """
        await self.redis.close(close_connection_pool=True)


class ClientStorageBase:
    """Base class for client-side storage."""

    def options(self) -> dict[str, Any]:
        """Get the options for the storage.

        Returns:
            All set options for the storage (not None).
        """
        return {
            format.to_camel_case(k): v for k, v in vars(self).items() if v is not None
        }


class Cookie(ClientStorageBase, str):
    """Represents a state Var that is stored as a cookie in the browser."""

    name: str | None
    path: str
    max_age: int | None
    domain: str | None
    secure: bool | None
    same_site: str

    def __new__(
        cls,
        object: Any = "",
        encoding: str | None = None,
        errors: str | None = None,
        /,
        name: str | None = None,
        path: str = "/",
        max_age: int | None = None,
        domain: str | None = None,
        secure: bool | None = None,
        same_site: str = "lax",
    ):
        """Create a client-side Cookie (str).

        Args:
            object: The initial object.
            encoding: The encoding to use.
            errors: The error handling scheme to use.
            name: The name of the cookie on the client side.
            path: Cookie path. Use / as the path if the cookie should be accessible on all pages.
            max_age: Relative max age of the cookie in seconds from when the client receives it.
            domain: Domain for the cookie (sub.domain.com or .allsubdomains.com).
            secure: Is the cookie only accessible through HTTPS?
            same_site: Whether the cookie is sent with third party requests.
                One of (true|false|none|lax|strict)

        Returns:
            The client-side Cookie object.

        Note: expires (absolute Date) is not supported at this time.
        """
        if encoding or errors:
            inst = super().__new__(cls, object, encoding or "utf-8", errors or "strict")
        else:
            inst = super().__new__(cls, object)
        inst.name = name
        inst.path = path
        inst.max_age = max_age
        inst.domain = domain
        inst.secure = secure
        inst.same_site = same_site
        return inst


class LocalStorage(ClientStorageBase, str):
    """Represents a state Var that is stored in localStorage in the browser."""

    name: str | None
    sync: bool = False

    def __new__(
        cls,
        object: Any = "",
        encoding: str | None = None,
        errors: str | None = None,
        /,
        name: str | None = None,
        sync: bool = False,
    ) -> "LocalStorage":
        """Create a client-side localStorage (str).

        Args:
            object: The initial object.
            encoding: The encoding to use.
            errors: The error handling scheme to use.
            name: The name of the storage key on the client side.
            sync: Whether changes should be propagated to other tabs.

        Returns:
            The client-side localStorage object.
        """
        if encoding or errors:
            inst = super().__new__(cls, object, encoding or "utf-8", errors or "strict")
        else:
            inst = super().__new__(cls, object)
        inst.name = name
        inst.sync = sync
        return inst


class MutableProxy(wrapt.ObjectProxy):
    """A proxy for a mutable object that tracks changes."""

    # Methods on wrapped objects which should mark the state as dirty.
    __mark_dirty_attrs__ = set(
        [
            "add",
            "append",
            "clear",
            "difference_update",
            "discard",
            "extend",
            "insert",
            "intersection_update",
            "pop",
            "popitem",
            "remove",
            "reverse",
            "setdefault",
            "sort",
            "symmetric_difference_update",
            "update",
        ]
    )
    # Methods on wrapped objects might return mutable objects that should be tracked.
    __wrap_mutable_attrs__ = set(
        [
            "get",
            "setdefault",
        ]
    )

    __mutable_types__ = (list, dict, set, Base)

    def __init__(self, wrapped: Any, state: BaseState, field_name: str):
        """Create a proxy for a mutable object that tracks changes.

        Args:
            wrapped: The object to proxy.
            state: The state to mark dirty when the object is changed.
            field_name: The name of the field on the state associated with the
                wrapped object.
        """
        super().__init__(wrapped)
        self._self_state = state
        self._self_field_name = field_name

    def _mark_dirty(
        self,
        wrapped=None,
        instance=None,
        args=tuple(),
        kwargs=None,
    ) -> Any:
        """Mark the state as dirty, then call a wrapped function.

        Intended for use with `FunctionWrapper` from the `wrapt` library.

        Args:
            wrapped: The wrapped function.
            instance: The instance of the wrapped function.
            args: The args for the wrapped function.
            kwargs: The kwargs for the wrapped function.

        Returns:
            The result of the wrapped function.
        """
        self._self_state.dirty_vars.add(self._self_field_name)
        self._self_state._mark_dirty()
        if wrapped is not None:
            return wrapped(*args, **(kwargs or {}))

    def _wrap_recursive(self, value: Any) -> Any:
        """Wrap a value recursively if it is mutable.

        Args:
            value: The value to wrap.

        Returns:
            The wrapped value.
        """
        if isinstance(value, self.__mutable_types__):
            return type(self)(
                wrapped=value,
                state=self._self_state,
                field_name=self._self_field_name,
            )
        return value

    def _wrap_recursive_decorator(self, wrapped, instance, args, kwargs) -> Any:
        """Wrap a function that returns a possibly mutable value.

        Intended for use with `FunctionWrapper` from the `wrapt` library.

        Args:
            wrapped: The wrapped function.
            instance: The instance of the wrapped function.
            args: The args for the wrapped function.
            kwargs: The kwargs for the wrapped function.

        Returns:
            The result of the wrapped function (possibly wrapped in a MutableProxy).
        """
        return self._wrap_recursive(wrapped(*args, **kwargs))

    def __getattr__(self, __name: str) -> Any:
        """Get the attribute on the proxied object and return a proxy if mutable.

        Args:
            __name: The name of the attribute.

        Returns:
            The attribute value.
        """
        value = super().__getattr__(__name)

        if callable(value):
            if __name in self.__mark_dirty_attrs__:
                # Wrap special callables, like "append", which should mark state dirty.
                value = wrapt.FunctionWrapper(value, self._mark_dirty)

            if __name in self.__wrap_mutable_attrs__:
                # Wrap methods that may return mutable objects tied to the state.
                value = wrapt.FunctionWrapper(
                    value,
                    self._wrap_recursive_decorator,
                )

        if isinstance(value, self.__mutable_types__) and __name not in (
            "__wrapped__",
            "_self_state",
        ):
            # Recursively wrap mutable attribute values retrieved through this proxy.
            return self._wrap_recursive(value)

        return value

    def __getitem__(self, key) -> Any:
        """Get the item on the proxied object and return a proxy if mutable.

        Args:
            key: The key of the item.

        Returns:
            The item value.
        """
        value = super().__getitem__(key)
        # Recursively wrap mutable items retrieved through this proxy.
        return self._wrap_recursive(value)

    def __iter__(self) -> Any:
        """Iterate over the proxied object and return a proxy if mutable.

        Yields:
            Each item value (possibly wrapped in MutableProxy).
        """
        for value in super().__iter__():
            # Recursively wrap mutable items retrieved through this proxy.
            yield self._wrap_recursive(value)

    def __delattr__(self, name):
        """Delete the attribute on the proxied object and mark state dirty.

        Args:
            name: The name of the attribute.
        """
        self._mark_dirty(super().__delattr__, args=(name,))

    def __delitem__(self, key):
        """Delete the item on the proxied object and mark state dirty.

        Args:
            key: The key of the item.
        """
        self._mark_dirty(super().__delitem__, args=(key,))

    def __setitem__(self, key, value):
        """Set the item on the proxied object and mark state dirty.

        Args:
            key: The key of the item.
            value: The value of the item.
        """
        self._mark_dirty(super().__setitem__, args=(key, value))

    def __setattr__(self, name, value):
        """Set the attribute on the proxied object and mark state dirty.

        If the attribute starts with "_self_", then the state is NOT marked
        dirty as these are internal proxy attributes.

        Args:
            name: The name of the attribute.
            value: The value of the attribute.
        """
        if name.startswith("_self_"):
            # Special case attributes of the proxy itself, not applied to the wrapped object.
            super().__setattr__(name, value)
            return
        self._mark_dirty(super().__setattr__, args=(name, value))

    def __copy__(self) -> Any:
        """Return a copy of the proxy.

        Returns:
            A copy of the wrapped object, unconnected to the proxy.
        """
        return copy.copy(self.__wrapped__)

    def __deepcopy__(self, memo=None) -> Any:
        """Return a deepcopy of the proxy.

        Args:
            memo: The memo dict to use for the deepcopy.

        Returns:
            A deepcopy of the wrapped object, unconnected to the proxy.
        """
        return copy.deepcopy(self.__wrapped__, memo=memo)


@serializer
def serialize_mutable_proxy(mp: MutableProxy) -> SerializedType:
    """Serialize the wrapped value of a MutableProxy.

    Args:
        mp: The MutableProxy to serialize.

    Returns:
        The serialized wrapped object.

    Raises:
        ValueError: when the wrapped object is not serializable.
    """
    value = serialize(mp.__wrapped__)
    if value is None:
        raise ValueError(f"Cannot serialize {type(mp.__wrapped__)}")
    return value


class ImmutableMutableProxy(MutableProxy):
    """A proxy for a mutable object that tracks changes.

    This wrapper comes from StateProxy, and will raise an exception if an attempt is made
    to modify the wrapped object when the StateProxy is immutable.
    """

    def _mark_dirty(
        self,
        wrapped=None,
        instance=None,
        args=tuple(),
        kwargs=None,
    ) -> Any:
        """Raise an exception when an attempt is made to modify the object.

        Intended for use with `FunctionWrapper` from the `wrapt` library.

        Args:
            wrapped: The wrapped function.
            instance: The instance of the wrapped function.
            args: The args for the wrapped function.
            kwargs: The kwargs for the wrapped function.

        Returns:
            The result of the wrapped function.

        Raises:
            ImmutableStateError: if the StateProxy is not mutable.
        """
        if not self._self_state._self_mutable:
            raise ImmutableStateError(
                "Background task StateProxy is immutable outside of a context "
                "manager. Use `async with self` to modify state."
            )
        return super()._mark_dirty(
            wrapped=wrapped, instance=instance, args=args, kwargs=kwargs
        )


def code_uses_state_contexts(javascript_code: str) -> bool:
    """Check if the rendered Javascript uses state contexts.

    Args:
        javascript_code: The Javascript code to check.

    Returns:
        True if the code attempts to access a member of StateContexts.
    """
    return bool("useContext(StateContexts" in javascript_code)


class PrivateVarDescriptor:
    """A descriptor to raise error in case private vars is accessed on thr frontend."""

    def __get__(self, *args, **kwargs):
        """Raise error on get value.


        Args:
            *args: The args to pass to the function.
            **kwargs: The kwargs to pass to the function.

        Raises:
            TypeError: if a background variable is used in frontend.
        """
        raise TypeError("Backend Vars cannot be accessed on the frontend.")