import numpy as np
from typing import Tuple

class SeatbeltMisuseDetector:
    """
    安全带误用检测器
    
    Euro NCAP 2026 三种误用场景:
    1. Buckle only: 扣入但未绕身体
    2. Lap only: 对角部分在背后
    3. Fully behind back: 整条在背后
    """
    
    def __init__(self):
        self.misuse_types = {
            'buckle_only': {'points': 2, 'description': '扣入但未绕身体'},
            'lap_only': {'points': 2, 'description': '对角部分在背后'},
            'behind_back': {'points': 1, 'description': '整条在背后'}
        }
        self.alert_duration = 0
        self.alert_triggered = False
        
    def detect(
        self,
        buckle_engaged: bool,      # 扣锁是否扣入
        belt_visible_chest: float,  # 胸前安全带可见度 (0-1)
        belt_visible_lap: float,    # 腰部安全带可见度
        belt_visible_shoulder: float, # 肩部可见度
        person_present: bool
    ) -> dict:
        """检测安全带误用"""
        
        if not person_present:
            return {'status': 'EMPTY', 'alert': False}
        
        if not buckle_engaged:
            return {'status': 'UNBUCKLED', 'alert': True, 'alert_type': 'unbuckled'}
        
        # 三种误用检测
        if buckle_engaged and belt_visible_chest < 0.2 and belt_visible_lap < 0.2:
            # 扣入但安全带不可见 = buckle only
            return self._trigger_alert('buckle_only')
        
        if buckle_engaged and belt_visible_lap > 0.5 and belt_visible_shoulder < 0.3:
            # 腰带可见但对角不可见 = lap only
            return self._trigger_alert('lap_only')
        
        if buckle_engaged and belt_visible_chest < 0.1:
            # 胸前完全不可见 = behind back
            return self._trigger_alert('behind_back')
        
        # 正确佩戴
        self.alert_duration = 0
        self.alert_triggered = False
        return {'status': 'CORRECT', 'alert': False}
    
    def _trigger_alert(self, misuse_type: str) -> dict:
        self.alert_duration += 1
        # 30秒内触发
        if self.alert_duration >= 30:
            self.alert_triggered = True
        
        return {
            'status': 'MISUSE',
            'misuse_type': misuse_type,
            'description': self.misuse_types[misuse_type]['description'],
            'points_at_risk': self.misuse_types[misuse_type]['points'],
            'alert': self.alert_triggered,
            'alert_duration_sec': self.alert_duration,
            'visual_alert': True,  # 视觉持续
            'audio_alert': self.alert_triggered  # 听觉30秒后
        }


if __name__ == "__main__":
    detector = SeatbeltMisuseDetector()
    
    # 测试三种误用
    tests = [
        ("正确佩戴", True, 0.8, 0.7, 0.8, True),
        ("Buckle only", True, 0.1, 0.1, 0.1, True),
        ("Lap only", True, 0.1, 0.7, 0.2, True),
        ("Behind back", True, 0.05, 0.05, 0.05, True),
        ("未扣", False, 0, 0, 0, True),
    ]
    
    for name, buckle, chest, lap, shoulder, present in tests:
        for _ in range(31):  # 模拟30秒
            result = detector.detect(buckle, chest, lap, shoulder, present)
        print(f"{name}: {result['status']}", end="")
        if 'misuse_type' in result:
            print(f" ({result['misuse_type']}, 风险{result['points_at_risk']}分)", end="")
        print(f" 告警: {result['alert']}")