import logging
import time as _time
from collections.abc import Collection
from dataclasses import dataclass, field
from typing import Any

from yuxi.channel.gateway.auth import GatewayAuthResult
from yuxi.channel.gateway.protocol import RpcEvent, marshal_frame
from yuxi.channel.gateway.rbac import ROLE_HIERARCHY, GatewayRole

logger = logging.getLogger(__name__)

DEFAULT_BROADCAST_RATE = 100
DEFAULT_BROADCAST_BURST = 200
DEFAULT_MAX_BUFFERED_FRAMES = 256
DEFAULT_SLOW_CONSUMER_THRESHOLD = 50

PUBLIC_EVENTS: set[str] = {
    "heartbeat",
    "ping",
    "server.shutdown",
    "server.tick",
}

READ_EVENTS: set[str] = PUBLIC_EVENTS | {
    "channel.created",
    "channel.updated",
    "channel.deleted",
    "channel.state_change",
    "channel.message",
    "session.created",
    "session.updated",
    "session.deleted",
    "session.message",
    "session.tool",
    "agent.status",
    "agent.event",
    "cron.status",
}

WRITE_EVENTS: set[str] = READ_EVENTS | {
    "config.changed",
}

ADMIN_EVENTS: set[str] = WRITE_EVENTS | {
    "plugin.installed",
    "plugin.removed",
    "device.pair.requested",
    "device.pair.resolved",
}

EVENT_MIN_ROLE: dict[str, GatewayRole] = {}

for _event in PUBLIC_EVENTS:
    EVENT_MIN_ROLE[_event] = GatewayRole.VIEWER
for _event in READ_EVENTS - PUBLIC_EVENTS:
    EVENT_MIN_ROLE[_event] = GatewayRole.VIEWER
for _event in WRITE_EVENTS - READ_EVENTS:
    EVENT_MIN_ROLE[_event] = GatewayRole.OPERATOR
for _event in ADMIN_EVENTS - WRITE_EVENTS:
    EVENT_MIN_ROLE[_event] = GatewayRole.ADMIN


@dataclass
class _ConnInfo:
    conn_id: str
    user_id: str | None = None
    roles: list[GatewayRole] = field(default_factory=list)
    subscribed_events: set[str] = field(default_factory=set)
    pending_frames: int = 0


@dataclass
class BroadcastFilter:
    conn_ids: Collection[str] | None = None
    user_ids: Collection[str] | None = None
    roles: Collection[GatewayRole] | None = None
    drop_if_slow: bool = True


@dataclass
class BroadcastResult:
    sent: int = 0
    dropped: int = 0
    filtered: int = 0


class TokenBucket:
    def __init__(self, rate: float, burst: float):
        self.rate = rate
        self.burst = burst
        self.tokens = burst
        self.last_refill = _time.monotonic()

    def consume(self, n: float = 1.0) -> bool:
        self._refill()
        if self.tokens >= n:
            self.tokens -= n
            return True
        return False

    def _refill(self):
        now = _time.monotonic()
        elapsed = now - self.last_refill
        self.tokens = min(self.burst, self.tokens + elapsed * self.rate)
        self.last_refill = now


class GatewayBroadcaster:
    def __init__(
        self,
        broadcast_rate: float = DEFAULT_BROADCAST_RATE,
        broadcast_burst: float = DEFAULT_BROADCAST_BURST,
        max_buffered_frames: int = DEFAULT_MAX_BUFFERED_FRAMES,
        slow_consumer_threshold: int = DEFAULT_SLOW_CONSUMER_THRESHOLD,
    ):
        self._connections: dict[str, _ConnInfo] = {}
        self._rate_limiter = TokenBucket(broadcast_rate, broadcast_burst)
        self._max_buffered_frames = max_buffered_frames
        self._slow_consumer_threshold = slow_consumer_threshold
        self._send_func: dict[str, Any] = {}
        self._global_seq = 0

    @property
    def global_seq(self) -> int:
        return self._global_seq

    @property
    def connection_count(self) -> int:
        return len(self._connections)

    def register_connection(
        self,
        conn_id: str,
        auth: GatewayAuthResult,
        send_fn: Any,
    ) -> None:
        info = _ConnInfo(
            conn_id=conn_id,
            user_id=auth.user_id,
            roles=list(auth.roles) if auth.roles else [],
        )
        self._connections[conn_id] = info
        self._send_func[conn_id] = send_fn

    def unregister_connection(self, conn_id: str) -> None:
        self._connections.pop(conn_id, None)
        self._send_func.pop(conn_id, None)

    def subscribe(self, conn_id: str, events: Collection[str]) -> None:
        info = self._connections.get(conn_id)
        if info is None:
            return
        info.subscribed_events.update(events)

    def unsubscribe(self, conn_id: str, events: Collection[str]) -> None:
        info = self._connections.get(conn_id)
        if info is None:
            return
        info.subscribed_events.difference_update(events)
        if not events or "*" in events:
            info.subscribed_events.clear()

    def clear_subscriptions(self, conn_id: str) -> None:
        info = self._connections.get(conn_id)
        if info is None:
            return
        info.subscribed_events.clear()

    def get_subscriptions(self, conn_id: str) -> set[str]:
        info = self._connections.get(conn_id)
        if info is None:
            return set()
        return set(info.subscribed_events)

    async def broadcast(
        self,
        event: str,
        data: dict | None = None,
        filter_: BroadcastFilter | None = None,
    ) -> BroadcastResult:
        return await self._broadcast_internal(event, data, filter_)

    async def broadcast_to_conn_ids(
        self,
        event: str,
        data: dict | None,
        conn_ids: Collection[str],
    ) -> BroadcastResult:
        return await self._broadcast_internal(event, data, BroadcastFilter(conn_ids=conn_ids))

    async def broadcast_to_user(
        self,
        event: str,
        data: dict | None,
        user_id: str,
    ) -> BroadcastResult:
        return await self._broadcast_internal(event, data, BroadcastFilter(user_ids={user_id}))

    async def broadcast_to_role(
        self,
        event: str,
        data: dict | None,
        role: GatewayRole,
    ) -> BroadcastResult:
        return await self._broadcast_internal(event, data, BroadcastFilter(roles={role}))

    async def send_event(
        self,
        conn_id: str,
        event: str,
        data: dict | None = None,
    ) -> bool:
        send_fn = self._send_func.get(conn_id)
        if send_fn is None:
            return False
        self._global_seq += 1
        rpc_event = RpcEvent(
            event=event,
            data=data,
            seq=self._global_seq,
            state_version=self._resolve_state_version(event),
        )
        try:
            await send_fn(marshal_frame(rpc_event))
            return True
        except Exception:
            return False

    async def _broadcast_internal(
        self,
        event: str,
        data: dict | None,
        filter_: BroadcastFilter | None,
    ) -> BroadcastResult:

        result = BroadcastResult()

        if not self._connections:
            return result

        candidates = [
            conn_id
            for conn_id, info in self._connections.items()
            if self._passes_filter(info, event, filter_) and self._has_event_scope(info, event)
        ]
        candidate_count = len(candidates)
        result.filtered = len(self._connections) - candidate_count

        if not candidates:
            return result

        if not self._rate_limiter.consume(candidate_count):
            logger.warning("Broadcast rate limited: event=%s candidates=%d", event, candidate_count)
            return result

        self._global_seq += 1
        rpc_event = RpcEvent(
            event=event,
            data=data,
            seq=self._global_seq,
            state_version=self._resolve_state_version(event),
        )
        frame = marshal_frame(rpc_event)

        for conn_id in candidates:
            info = self._connections.get(conn_id)
            if info is None:
                continue

            info.pending_frames += 1
            is_slow = info.pending_frames > self._slow_consumer_threshold
            drop = filter_ is not None and filter_.drop_if_slow

            if is_slow and drop:
                info.pending_frames = max(0, info.pending_frames - 1)
                result.dropped += 1
                continue

            if info.pending_frames > self._max_buffered_frames:
                logger.warning(
                    "Slow consumer exceeded max buffer: %s (event=%s pending=%d)",
                    conn_id,
                    event,
                    info.pending_frames,
                )
                info.pending_frames = max(0, info.pending_frames - 1)
                result.dropped += 1
                continue

            send_fn = self._send_func.get(conn_id)
            if send_fn is None:
                continue

            try:
                await send_fn(frame)
                info.pending_frames = max(0, info.pending_frames - 1)
                result.sent += 1
            except Exception:
                logger.debug("Failed to send event %s to %s", event, conn_id)

        return result

    def _passes_filter(
        self,
        info: _ConnInfo,
        event: str,
        filter_: BroadcastFilter | None,
    ) -> bool:
        if info.subscribed_events:
            if event not in info.subscribed_events and "*" not in info.subscribed_events:
                return False

        if filter_ is None:
            return True

        if filter_.conn_ids is not None and info.conn_id not in filter_.conn_ids:
            return False
        if filter_.user_ids is not None and info.user_id not in filter_.user_ids:
            return False
        if filter_.roles is not None:
            user_has_role = any(r in filter_.roles for r in info.roles)
            if not user_has_role:
                return False

        return True

    @staticmethod
    def _has_event_scope(info: _ConnInfo, event: str) -> bool:
        min_role = EVENT_MIN_ROLE.get(event)
        if min_role is None:
            return True

        if not info.roles:
            return min_role == GatewayRole.VIEWER

        max_level = max(ROLE_HIERARCHY.get(r, 0) for r in info.roles)
        required_level = ROLE_HIERARCHY.get(min_role, 0)
        return max_level >= required_level

    def pending_frame_count(self, conn_id: str) -> int:
        info = self._connections.get(conn_id)
        if info is None:
            return 0
        return info.pending_frames

    def _resolve_state_version(self, event: str) -> int | None:
        versioned_events = {
            "channel.state_change",
            "config.changed",
            "plugin.installed",
            "plugin.removed",
        }
        if event in versioned_events:
            return self._global_seq
        return None


gateway_broadcaster = GatewayBroadcaster()