"""Runtime event bus for agent state notifications.

This bus is separate from :mod:`nanobot.bus.queue`: message bus events are
user/chat delivery, while runtime events are in-process state notifications
that optional subscribers such as WebUI adapters may render.
"""

from __future__ import annotations

import asyncio
import contextlib
import inspect
from collections.abc import Awaitable, Callable
from dataclasses import dataclass, field
from typing import TYPE_CHECKING, Any

from loguru import logger

from nanobot.bus.events import InboundMessage

if TYPE_CHECKING:
    from nanobot.utils.llm_runtime import LLMRuntime


@dataclass(frozen=True)
class RuntimeEventContext:
    """Routing context common to turn-scoped runtime events."""

    channel: str
    chat_id: str
    session_key: str
    metadata: dict[str, Any] = field(default_factory=dict)
    attributes: dict[str, Any] = field(default_factory=dict)


@dataclass(frozen=True)
class SessionTurnStarted:
    """A user/system turn has loaded its session and is about to build context."""

    context: RuntimeEventContext


@dataclass(frozen=True)
class TurnRuntimeAdmitted:
    """The immutable model runtime selected for one admitted turn."""

    context: RuntimeEventContext
    runtime: LLMRuntime


@dataclass(frozen=True)
class TurnRunStatusChanged:
    """Visible run status changed for a turn."""

    context: RuntimeEventContext
    status: str
    started_at: float | None = None


@dataclass(frozen=True)
class TurnCompleted:
    """A turn has delivered its final user-visible response."""

    context: RuntimeEventContext
    latency_ms: int | None = None
    runtime: LLMRuntime | None = None


@dataclass(frozen=True)
class SessionTurnPersisted:
    """A completed turn has been written to local session storage."""

    context: RuntimeEventContext
    turn_id: str
    sender_id: str


@dataclass(frozen=True)
class GoalStateChanged:
    """A session's sustained-goal state changed."""

    context: RuntimeEventContext
    session_metadata: dict[str, Any] = field(default_factory=dict)


@dataclass(frozen=True)
class RuntimeModelChanged:
    """The active runtime model/preset changed."""

    model: str
    model_preset: str | None


RuntimeEvent = (
    SessionTurnStarted
    | TurnRuntimeAdmitted
    | SessionTurnPersisted
    | TurnRunStatusChanged
    | TurnCompleted
    | GoalStateChanged
    | RuntimeModelChanged
)
RuntimeEventType = (
    type[SessionTurnStarted]
    | type[TurnRuntimeAdmitted]
    | type[SessionTurnPersisted]
    | type[TurnRunStatusChanged]
    | type[TurnCompleted]
    | type[GoalStateChanged]
    | type[RuntimeModelChanged]
)
RuntimeEventHandler = Callable[[Any], Awaitable[None] | None]
_HandlerEntry = tuple[RuntimeEventType | None, RuntimeEventHandler]


class RuntimeEventBus:
    """Small in-process pub/sub bus for runtime state.

    Subscribers run in registration order. ``publish`` awaits async handlers so
    callers can preserve ordering when a runtime event must follow a user
    message. ``publish_nowait`` is available for synchronous call sites.
    """

    def __init__(self) -> None:
        self._handlers: list[_HandlerEntry] = []

    def subscribe(
        self,
        handler: RuntimeEventHandler,
        event_type: RuntimeEventType | None = None,
    ) -> Callable[[], None]:
        entry = (event_type, handler)
        self._handlers.append(entry)

        def _unsubscribe() -> None:
            with contextlib.suppress(ValueError):
                self._handlers.remove(entry)

        return _unsubscribe

    async def publish(self, event: RuntimeEvent) -> None:
        for event_type, handler in list(self._handlers):
            if event_type is not None and not isinstance(event, event_type):
                continue
            try:
                result = handler(event)
                if inspect.isawaitable(result):
                    await result
            except Exception:
                logger.exception("runtime event handler failed for {}", type(event).__name__)

    def publish_nowait(self, event: RuntimeEvent) -> None:
        try:
            loop = asyncio.get_running_loop()
        except RuntimeError:
            logger.debug("dropping runtime event without a running loop: {}", type(event).__name__)
            return
        loop.create_task(self.publish(event))


class RuntimeEventPublisher:
    """Convenience publisher for turn-scoped runtime events.

    Agent code should decide when state transitions happen; this helper owns
    the mechanics of building event contexts and carrying per-turn metadata.
    """

    def __init__(self, bus: RuntimeEventBus | None = None) -> None:
        self.bus = bus or RuntimeEventBus()
        self._turn_latency_ms: dict[str, int] = {}
        self._turn_runtime: dict[str, LLMRuntime] = {}

    @staticmethod
    def _context(
        *,
        channel: str,
        chat_id: str,
        session_key: str,
        metadata: dict[str, Any] | None,
        attributes: dict[str, Any] | None = None,
    ) -> RuntimeEventContext:
        return RuntimeEventContext(
            channel=channel,
            chat_id=chat_id,
            session_key=session_key,
            metadata=dict(metadata or {}),
            attributes=dict(attributes or {}),
        )

    def record_turn_runtime(self, session_key: str, runtime: LLMRuntime) -> None:
        self._turn_runtime[session_key] = runtime

    def record_turn_latency(self, session_key: str, latency_ms: int | None) -> None:
        if latency_ms is not None:
            self._turn_latency_ms[session_key] = int(latency_ms)

    def clear_turn(self, session_key: str) -> None:
        self._turn_latency_ms.pop(session_key, None)
        self._turn_runtime.pop(session_key, None)

    async def session_turn_started(
        self,
        msg: InboundMessage,
        session_key: str,
    ) -> None:
        await self.bus.publish(
            SessionTurnStarted(
                context=self._context(
                    channel=msg.channel,
                    chat_id=msg.chat_id,
                    session_key=session_key,
                    metadata=msg.metadata,
                )
            )
        )

    async def turn_runtime_admitted(
        self,
        msg: InboundMessage,
        session_key: str,
        runtime: LLMRuntime,
    ) -> None:
        """Record and publish the runtime selected for one turn."""
        self.record_turn_runtime(session_key, runtime)
        await self.bus.publish(
            TurnRuntimeAdmitted(
                context=self._context(
                    channel=msg.channel,
                    chat_id=msg.chat_id,
                    session_key=session_key,
                    metadata=msg.metadata,
                ),
                runtime=runtime,
            )
        )

    async def run_status_changed(
        self,
        msg: InboundMessage,
        session_key: str,
        status: str,
        *,
        started_at: float | None = None,
    ) -> None:
        await self.bus.publish(
            TurnRunStatusChanged(
                context=self._context(
                    channel=msg.channel,
                    chat_id=msg.chat_id,
                    session_key=session_key,
                    metadata=msg.metadata,
                ),
                status=status,
                started_at=started_at,
            )
        )

    async def session_turn_persisted(
        self,
        msg: InboundMessage,
        session_key: str,
        *,
        turn_id: str,
        attributes: dict[str, Any] | None = None,
    ) -> None:
        await self.bus.publish(
            SessionTurnPersisted(
                context=self._context(
                    channel=msg.channel,
                    chat_id=msg.chat_id,
                    session_key=session_key,
                    metadata=msg.metadata,
                    attributes=attributes,
                ),
                turn_id=turn_id,
                sender_id=msg.sender_id,
            )
        )

    async def turn_completed(
        self,
        *,
        channel: str,
        chat_id: str,
        session_key: str,
        metadata: dict[str, Any] | None,
    ) -> None:
        await self.bus.publish(
            TurnCompleted(
                context=self._context(
                    channel=channel,
                    chat_id=chat_id,
                    session_key=session_key,
                    metadata=metadata,
                ),
                latency_ms=self._turn_latency_ms.pop(session_key, None),
                runtime=self._turn_runtime.pop(session_key, None),
            )
        )

    def runtime_model_changed(self, model: str, model_preset: str | None) -> None:
        self.bus.publish_nowait(
            RuntimeModelChanged(model=model, model_preset=model_preset)
        )