"""Centralise mutable runtime application state.

Runtime state is kept outside of Starlette's raw ``app.state`` storage and
exposed through a controlled state manager object. This keeps the FastAPI
framework state bag limited to shared infrastructure handles and immutable
configuration while still allowing existing code to access runtime values via
attribute proxying.
"""

from __future__ import annotations

import datetime
from dataclasses import dataclass, field
from typing import TYPE_CHECKING, Any

from starlette.datastructures import State

from app.models.server import ServerStatus

if TYPE_CHECKING:  # pragma: no cover
    from app.models.config import PendingRecovery

ActivationRecord = dict[str, datetime.datetime]

_RUNTIME_ATTRIBUTES: frozenset[str] = frozenset(
    {
        "setup_complete_cached",
        "server_status",
        "pending_recovery",
        "last_activation",
    }
)


@dataclass
class RuntimeState:
    """Mutable runtime state for the current application instance."""

    setup_complete_cached: bool = False
    server_status: ServerStatus = field(default_factory=lambda: ServerStatus(online=False))
    pending_recovery: PendingRecovery | None = None
    last_activation: ActivationRecord | None = None


class ApplicationState(State):
    """Application state wrapper that delegates runtime state access.

    This allows runtime values to be stored in a dedicated
    :class:`RuntimeState` instance while preserving the familiar attribute-based
    ``app.state`` API for the rest of the application.
    """

    def __init__(self, runtime_state: RuntimeState, state: dict[str, Any] | None = None):
        super().__init__(state)
        object.__setattr__(self, "_runtime_state", runtime_state)

    @property
    def runtime_state(self) -> RuntimeState:
        """Return the dedicated runtime state manager."""
        return object.__getattribute__(self, "_runtime_state")

    def __getattr__(self, key: str) -> Any:
        if key in _RUNTIME_ATTRIBUTES:
            return getattr(self.runtime_state, key)
        return super().__getattr__(key)

    def __setattr__(self, key: str, value: Any) -> None:
        if key in _RUNTIME_ATTRIBUTES:
            setattr(self.runtime_state, key, value)
            return
        super().__setattr__(key, value)

    def __delattr__(self, key: str) -> None:
        if key in _RUNTIME_ATTRIBUTES:
            delattr(self.runtime_state, key)
            return
        super().__delattr__(key)


def get_runtime_state(app: Any) -> RuntimeState:
    """Return the runtime state manager for the current FastAPI application."""
    state = getattr(app, "state", None)
    if state is None or not hasattr(state, "runtime_state"):
        raise AttributeError("Runtime state has not been initialised on the application.")
    return state.runtime_state