"""事件聚合器 (MVP-1 / P5 简化版)

时间窗口去重: 对同一 ``(source_id, event_type, track_id_or_bbox_hash)``
在配置窗口内只保留一条预警事件，重复命中时更新 ``last_seen``
与 ``occurrence_count``，避免预警刷屏。

后续 MVP-2 会扩展空间邻近合并、置信度加权融合等能力。
"""

from __future__ import annotations

import logging
import time
from collections import OrderedDict
from typing import Dict, List, Optional, Tuple

from models.event_schemas import AlertEvent, UnifiedDetection

logger = logging.getLogger(__name__)


_AggKey = Tuple[Optional[str], str, str]


class EventAggregator:
    """基于时间窗口的预警去重 / 聚合器。

    Args:
        dedup_window_seconds: 去重窗口 (秒)，同 key 在窗口内不会重复产出
        max_active_events: 内存中最大活跃事件数，超过时按 LRU 淘汰
    """

    def __init__(
        self,
        dedup_window_seconds: float = 30.0,
        max_active_events: int = 1000,
    ) -> None:
        self.dedup_window_seconds = max(0.0, dedup_window_seconds)
        self.max_active_events = max(1, max_active_events)
        # 按插入顺序保存以便 LRU 淘汰
        self._active: "OrderedDict[_AggKey, AlertEvent]" = OrderedDict()

    # ------------------------------------------------------------------
    # 主入口
    # ------------------------------------------------------------------

    def aggregate(self, alerts: List[AlertEvent]) -> List[AlertEvent]:
        """聚合一批预警事件，返回去重后真正应当对外发出的事件。"""

        now = time.time()
        self._evict_expired(now)

        emitted: List[AlertEvent] = []
        for alert in alerts:
            key = self._make_key(alert)
            existing = self._active.get(key)
            if existing is None:
                self._active[key] = alert
                self._active.move_to_end(key)
                emitted.append(alert)
                if len(self._active) > self.max_active_events:
                    dropped_key, _ = self._active.popitem(last=False)
                    logger.debug("聚合器 LRU 淘汰事件: %s", dropped_key)
            else:
                # 窗口内重复：仅更新统计
                existing.last_seen = now
                existing.occurrence_count += 1
                if alert.confidence > existing.confidence:
                    existing.confidence = alert.confidence
                self._active.move_to_end(key)
        return emitted

    # ------------------------------------------------------------------
    # 内部
    # ------------------------------------------------------------------

    @staticmethod
    def _make_key(alert: AlertEvent) -> _AggKey:
        if alert.detections:
            target_id = EventAggregator._target_identity(alert.detections[0])
        else:
            target_id = "no_target"
        return (alert.source_id, alert.event_type.value, target_id)

    @staticmethod
    def _target_identity(det: UnifiedDetection) -> str:
        """构造目标稳定标识：优先 track_id，否则用 bbox 网格哈希。"""

        if det.track_id is not None:
            return f"t{det.track_id}"
        # 按 50px 栅格归一，避免微小抖动导致漏聚合
        cx, cy = det.bbox.center
        return f"g{int(cx) // 50}_{int(cy) // 50}_{det.class_name}"

    def _evict_expired(self, now: float) -> None:
        if self.dedup_window_seconds <= 0:
            self._active.clear()
            return
        # 基于 first_seen 判断窗口过期：保证 "同一目标 30 秒内只产生 1 条事件"，
        # 同时窗口到期后允许再次触发 (而不会因为不断收到同类检测而无限延期)。
        expired_keys = [
            key
            for key, alert in self._active.items()
            if now - alert.first_seen > self.dedup_window_seconds
        ]
        for key in expired_keys:
            self._active.pop(key, None)

    # ------------------------------------------------------------------
    # 自省
    # ------------------------------------------------------------------

    @property
    def active_count(self) -> int:
        return len(self._active)

    def snapshot(self) -> Dict[str, AlertEvent]:
        """返回当前活跃事件的快照 (用于调试 / 监控)。"""

        return {f"{k[0]}|{k[1]}|{k[2]}": v for k, v in self._active.items()}


__all__ = ["EventAggregator"]