"""In-process event bus for real-time dashboard updates (SSE)."""

from __future__ import annotations

import asyncio
import json
import time
from collections import deque
from typing import Any


class EventBus:
    def __init__(self, history: int = 200):
        self._subs: set[asyncio.Queue] = set()
        self._history: deque[dict] = deque(maxlen=history)
        self._seq = 0

    def publish(self, kind: str, data: Any) -> None:
        self._seq += 1
        ev = {"seq": self._seq, "ts": time.time(), "type": kind, "data": data}
        self._history.append(ev)
        dead = []
        for q in self._subs:
            try:
                q.put_nowait(ev)
            except asyncio.QueueFull:
                dead.append(q)
        for q in dead:
            self._subs.discard(q)

    def subscribe(self) -> asyncio.Queue:
        q: asyncio.Queue = asyncio.Queue(maxsize=500)
        self._subs.add(q)
        return q

    def unsubscribe(self, q: asyncio.Queue) -> None:
        self._subs.discard(q)

    def recent(self, kinds: set[str] | None = None, limit: int = 50) -> list[dict]:
        evs = [e for e in self._history if not kinds or e["type"] in kinds]
        return evs[-limit:]

    @staticmethod
    def format_sse(ev: dict) -> str:
        return f"id: {ev['seq']}\nevent: {ev['type']}\ndata: {json.dumps(ev, ensure_ascii=False)}\n\n"


bus = EventBus()