fix(intrusion): 修复代码质量问题 - 空值检查和常量提取

修复内容：
1. 添加 state_start_time 空值检查（CONFIRMING_INTRUSION 和 CONFIRMING_CLEAR 状态）
2. 移除 get_state() 未使用的 roi_id 参数
3. get_state() 接受 current_time 参数，避免直接调用 datetime.now()
4. 提取魔法数字：ALARM_LEVEL_INTRUSION = 3

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

algorithms.py

@@ -389,6 +389,9 @@ class IntrusionAlgorithm:
     STATE_ALARMED = "ALARMED"                        # 已告警（等待入侵消失）
     STATE_CONFIRMING_CLEAR = "CONFIRMING_CLEAR"      # 入侵消失确认中
 
+    # 告警级别常量
+    ALARM_LEVEL_INTRUSION = 3
+
     def __init__(
         self,
         cooldown_seconds: int = 300,
@@ -472,41 +475,46 @@ class IntrusionAlgorithm:
 
         elif self.state == self.STATE_CONFIRMING_INTRUSION:
             # 入侵确认中：需要持续检测到人
-            elapsed = (current_time - self.state_start_time).total_seconds()
-
-            if not roi_has_person:
-                # 人消失了，回到IDLE
+            if self.state_start_time is None:
+                # 防御性编程：如果状态时间为空，重置到IDLE
                 self.state = self.STATE_IDLE
-                self.state_start_time = None
-                logger.debug(f"ROI {roi_id}: CONFIRMING_INTRUSION → IDLE (人消失)")
-            elif elapsed >= self.confirm_seconds:
-                # 入侵确认成功，检查冷却期
-                cooldown_key = f"{camera_id}_{roi_id}"
-                if cooldown_key not in self.alert_cooldowns or \
-                   (current_time - self.alert_cooldowns[cooldown_key]).total_seconds() > self.cooldown_seconds:
+                logger.error(f"ROI {roi_id}: CONFIRMING_INTRUSION 状态异常，state_start_time为None，重置到IDLE")
+            else:
+                elapsed = (current_time - self.state_start_time).total_seconds()
 
-                    bbox = self._get_latest_bbox(tracks, roi_id)
-                    self._intrusion_start_time = self.state_start_time  # 记录入侵开始时间
-
-                    alerts.append({
-                        "roi_id": roi_id,
-                        "camera_id": camera_id,
-                        "bbox": bbox,
-                        "alert_type": "intrusion",
-                        "alarm_level": 3,
-                        "message": "检测到周界入侵",
-                        "first_frame_time": self._intrusion_start_time.strftime('%Y-%m-%d %H:%M:%S'),
-                    })
-
-                    self.alert_cooldowns[cooldown_key] = current_time
-                    self.state = self.STATE_ALARMED
-                    # _last_alarm_id 由 main.py 通过 set_last_alarm_id() 回填
-                    logger.warning(f"ROI {roi_id}: CONFIRMING_INTRUSION → ALARMED (告警触发)")
-                else:
-                    # 冷却期内，回到IDLE
+                if not roi_has_person:
+                    # 人消失了，回到IDLE
                     self.state = self.STATE_IDLE
                     self.state_start_time = None
-                    logger.debug(f"ROI {roi_id}: CONFIRMING_INTRUSION → IDLE (冷却期内)")
+                    logger.debug(f"ROI {roi_id}: CONFIRMING_INTRUSION → IDLE (人消失)")
+                elif elapsed >= self.confirm_seconds:
+                    # 入侵确认成功，检查冷却期
+                    cooldown_key = f"{camera_id}_{roi_id}"
+                    if cooldown_key not in self.alert_cooldowns or \
+                       (current_time - self.alert_cooldowns[cooldown_key]).total_seconds() > self.cooldown_seconds:
+
+                        bbox = self._get_latest_bbox(tracks, roi_id)
+                        self._intrusion_start_time = self.state_start_time  # 记录入侵开始时间
+
+                        alerts.append({
+                            "roi_id": roi_id,
+                            "camera_id": camera_id,
+                            "bbox": bbox,
+                            "alert_type": "intrusion",
+                            "alarm_level": self.ALARM_LEVEL_INTRUSION,
+                            "message": "检测到周界入侵",
+                            "first_frame_time": self._intrusion_start_time.strftime('%Y-%m-%d %H:%M:%S'),
+                        })
+
+                        self.alert_cooldowns[cooldown_key] = current_time
+                        self.state = self.STATE_ALARMED
+                        # _last_alarm_id 由 main.py 通过 set_last_alarm_id() 回填
+                        logger.warning(f"ROI {roi_id}: CONFIRMING_INTRUSION → ALARMED (告警触发)")
+                    else:
+                        # 冷却期内，回到IDLE
+                        self.state = self.STATE_IDLE
+                        self.state_start_time = None
+                        logger.debug(f"ROI {roi_id}: CONFIRMING_INTRUSION → IDLE (冷却期内)")
 
         elif self.state == self.STATE_ALARMED:
             # 已告警状态：等待入侵消失
@@ -518,33 +526,38 @@ class IntrusionAlgorithm:
 
         elif self.state == self.STATE_CONFIRMING_CLEAR:
             # 入侵消失确认中：需要持续未检测到人
-            elapsed = (current_time - self.state_start_time).total_seconds()
-
-            if roi_has_person:
-                # 人又出现了，回到ALARMED
-                self.state = self.STATE_ALARMED
-                self.state_start_time = current_time
-                logger.debug(f"ROI {roi_id}: CONFIRMING_CLEAR → ALARMED (人又出现)")
-            elif elapsed >= self.confirm_seconds:
-                # 消失确认成功，发送resolve事件
-                if self._last_alarm_id and self._intrusion_start_time:
-                    duration_ms = int((current_time - self._intrusion_start_time).total_seconds() * 1000)
-                    alerts.append({
-                        "alert_type": "alarm_resolve",
-                        "resolve_alarm_id": self._last_alarm_id,
-                        "duration_ms": duration_ms,
-                        "last_frame_time": current_time.strftime('%Y-%m-%d %H:%M:%S'),
-                        "resolve_type": "intrusion_cleared",
-                    })
-
-                    logger.info(f"ROI {roi_id}: 告警已解决（入侵消失）")
-
-                # 重置状态
+            if self.state_start_time is None:
+                # 防御性编程：如果状态时间为空，重置到IDLE
                 self.state = self.STATE_IDLE
-                self.state_start_time = None
-                self._last_alarm_id = None
-                self._intrusion_start_time = None
-                logger.debug(f"ROI {roi_id}: CONFIRMING_CLEAR → IDLE (消失确认成功)")
+                logger.error(f"ROI {roi_id}: CONFIRMING_CLEAR 状态异常，state_start_time为None，重置到IDLE")
+            else:
+                elapsed = (current_time - self.state_start_time).total_seconds()
+
+                if roi_has_person:
+                    # 人又出现了，回到ALARMED
+                    self.state = self.STATE_ALARMED
+                    self.state_start_time = current_time
+                    logger.debug(f"ROI {roi_id}: CONFIRMING_CLEAR → ALARMED (人又出现)")
+                elif elapsed >= self.confirm_seconds:
+                    # 消失确认成功，发送resolve事件
+                    if self._last_alarm_id and self._intrusion_start_time:
+                        duration_ms = int((current_time - self._intrusion_start_time).total_seconds() * 1000)
+                        alerts.append({
+                            "alert_type": "alarm_resolve",
+                            "resolve_alarm_id": self._last_alarm_id,
+                            "duration_ms": duration_ms,
+                            "last_frame_time": current_time.strftime('%Y-%m-%d %H:%M:%S'),
+                            "resolve_type": "intrusion_cleared",
+                        })
+
+                        logger.info(f"ROI {roi_id}: 告警已解决（入侵消失）")
+
+                    # 重置状态
+                    self.state = self.STATE_IDLE
+                    self.state_start_time = None
+                    self._last_alarm_id = None
+                    self._intrusion_start_time = None
+                    logger.debug(f"ROI {roi_id}: CONFIRMING_CLEAR → IDLE (消失确认成功)")
 
         return alerts
 
@@ -564,8 +577,10 @@ class IntrusionAlgorithm:
         self.alert_triggered.clear()
         self.detection_start.clear()
 
-    def get_state(self, roi_id: str) -> Dict[str, Any]:
+    def get_state(self, current_time: Optional[datetime] = None) -> Dict[str, Any]:
         """获取当前状态（用于调试和监控）"""
+        current_time = current_time or datetime.now()
+
         state_info = {
             "state": self.state,
             "state_start_time": self.state_start_time.isoformat() if self.state_start_time else None,
@@ -573,7 +588,7 @@ class IntrusionAlgorithm:
 
         # 添加状态特定信息
         if self.state == self.STATE_ALARMED and self._intrusion_start_time:
-            total_intrusion_sec = (datetime.now() - self._intrusion_start_time).total_seconds()
+            total_intrusion_sec = (current_time - self._intrusion_start_time).total_seconds()
             state_info["total_intrusion_sec"] = total_intrusion_sec
             state_info["alarm_id"] = self._last_alarm_id