"""数据看板：后台定时聚合、内存快照、SSE 版本通知。"""

from __future__ import annotations

import asyncio
import json
import os
from collections.abc import AsyncIterator, Awaitable, Callable
from typing import Any

from hub_dashboard import DASHBOARD_POLL_INTERVAL_SEC

HUB_DASHBOARD_SSE_HEARTBEAT_SEC = float(os.getenv("HUB_DASHBOARD_SSE_HEARTBEAT_SEC", "25"))

BuildFn = Callable[[], Awaitable[dict[str, Any]]]


class DashboardStore:
    def __init__(self) -> None:
        self._lock = asyncio.Lock()
        self.version = 0
        self.payload: dict[str, Any] | None = None
        self.aggregating = False
        self.last_error: str | None = None
        self._subscribers: list[asyncio.Queue[str | None]] = []
        self._task: asyncio.Task | None = None
        self._stop = asyncio.Event()
        self._refresh = asyncio.Event()
        self._build_fn: BuildFn | None = None

    async def start(self, build_fn: BuildFn) -> None:
        if self._task and not self._task.done():
            return
        self._build_fn = build_fn
        self._stop.clear()
        self._task = asyncio.create_task(self._loop(), name="hub-dashboard-poll")

    async def stop(self) -> None:
        self._stop.set()
        self._refresh.set()
        if self._task:
            self._task.cancel()
            try:
                await self._task
            except asyncio.CancelledError:
                pass
            self._task = None
        self._broadcast(close=True)

    def request_refresh(self) -> None:
        self._refresh.set()

    def snapshot_dict(self) -> dict[str, Any]:
        p = dict(self.payload or {})
        if not p:
            return {
                "ok": False,
                "dashboard_version": self.version,
                "aggregating": self.aggregating,
                "error": self.last_error,
                "poll_interval_sec": DASHBOARD_POLL_INTERVAL_SEC,
            }
        return {
            **p,
            "dashboard_version": self.version,
            "aggregating": self.aggregating,
            "error": self.last_error or p.get("error"),
            "poll_interval_sec": DASHBOARD_POLL_INTERVAL_SEC,
        }

    def event_dict(self) -> dict[str, Any]:
        p = self.payload or {}
        return {
            "dashboard_version": self.version,
            "updated_at": p.get("updated_at"),
            "aggregating": self.aggregating,
            "ok": p.get("ok", True) if self.payload else False,
            "error": self.last_error or p.get("error"),
        }

    async def _loop(self) -> None:
        assert self._build_fn is not None
        while not self._stop.is_set():
            await self._aggregate_once(self._build_fn)
            if self._stop.is_set():
                break
            self._refresh.clear()
            sleep_task = asyncio.create_task(asyncio.sleep(DASHBOARD_POLL_INTERVAL_SEC))
            refresh_task = asyncio.create_task(self._refresh.wait())
            done, pending = await asyncio.wait(
                {sleep_task, refresh_task},
                return_when=asyncio.FIRST_COMPLETED,
            )
            for t in pending:
                t.cancel()

    async def _aggregate_once(self, build_fn: BuildFn) -> None:
        async with self._lock:
            self.aggregating = True
        self._broadcast()
        try:
            result = await build_fn()
            if not isinstance(result, dict):
                result = {"ok": False, "msg": "聚合返回无效"}
        except Exception as e:
            result = {"ok": False, "msg": str(e), "error": "aggregate_failed"}
        async with self._lock:
            self.version += 1
            prev = self.payload if isinstance(self.payload, dict) else None
            if result.get("ok") is False and prev and prev.get("ok"):
                self.payload = prev
                self.last_error = str(result.get("msg") or result.get("error") or "aggregate_failed")
            else:
                self.payload = result
                self.last_error = None if result.get("ok") is not False else (
                    str(result.get("msg") or result.get("error") or "aggregate_failed")
                )
            self.aggregating = False
        self._broadcast()

    def _broadcast(self, *, close: bool = False) -> None:
        dead: list[asyncio.Queue[str | None]] = []
        for q in self._subscribers:
            try:
                q.put_nowait(None if close else json.dumps(self.event_dict(), ensure_ascii=False))
            except asyncio.QueueFull:
                try:
                    q.get_nowait()
                except asyncio.QueueEmpty:
                    pass
                try:
                    q.put_nowait(json.dumps(self.event_dict(), ensure_ascii=False))
                except asyncio.QueueFull:
                    dead.append(q)
            except Exception:
                dead.append(q)
        for q in dead:
            if q in self._subscribers:
                self._subscribers.remove(q)

    async def iter_sse(self) -> AsyncIterator[str]:
        q: asyncio.Queue[str | None] = asyncio.Queue(maxsize=32)
        self._subscribers.append(q)
        try:
            yield _sse_frame(self.event_dict())
            while True:
                try:
                    raw = await asyncio.wait_for(q.get(), timeout=HUB_DASHBOARD_SSE_HEARTBEAT_SEC)
                except asyncio.TimeoutError:
                    yield ": heartbeat\n\n"
                    continue
                if raw is None:
                    break
                try:
                    data = json.loads(raw)
                except Exception:
                    data = self.event_dict()
                yield _sse_frame(data)
        finally:
            if q in self._subscribers:
                self._subscribers.remove(q)


def _sse_frame(data: dict[str, Any]) -> str:
    body = json.dumps(data, ensure_ascii=False)
    return f"event: dashboard\ndata: {body}\n\n"


dashboard_store = DashboardStore()