import struct

class VdesMessageUnpack:
    """VDES消息解包工具类"""
    
    def __init__(self):
        self.message_frames = []
        self.current_message = b''
        self.is_receiving = False
        self.is_unpacked = False        #是否解析到结束帧
        self.MMSI: int
    
    def unpack_tcp_packet(self, packet_data):
        """解包TCP协议报文"""
        # 检查帧头
        if packet_data[:4] != b'####':
            raise ValueError("无效的报文帧头")
            
        # 解析报文类型和长度
        packet_type = struct.unpack('>I', packet_data[4:8])[0]
        packet_length = struct.unpack('>I', packet_data[8:12])[0]
        packet_content = packet_data[12:]
        
        # 处理不同类型的帧
        if packet_type == 10:  # 消息帧
            # print(f"消息帧内容: {packet_content.hex()}")
            frame_type, message = self._process_message_frame(packet_content)
        else:
            print(f"忽略未知报文类型: {packet_type}")
            return None, None
        return frame_type, message
    
    def _process_message_frame(self, content):
        """处理消息帧内容"""
        # 解析帧类型(1字节)
        frame_type = struct.unpack('>B', content[:1])[0]
        # print(f"帧类型: {frame_type}")

        
        if frame_type == 0:  # 起始帧
            self.is_receiving = True
            self.current_message = b''
            # 解析目标MMSI和优先级
            target_mmsi = struct.unpack('>I', content[1:5])[0]
            priority = struct.unpack('>B', content[5:6])[0]
            self.MMSI = target_mmsi
            # print(f"开始接收消息，目标MMSI: {target_mmsi}, 优先级: {priority}")
            
        elif frame_type == 1:  # 中间帧
            if self.is_receiving:
                self.current_message = content[1:]
                # print(f"接收中间帧，{self.current_message}")

                
        elif frame_type == 2:  # 结束帧
            if self.is_receiving:
                self.current_message = b''
                # self.message_frames.append(self.current_message)
                self.is_receiving = False
                # print(f"消息接收完成，总长度: {len(self.current_message)}字节")
                
        else:
            print(f"忽略未知帧类型: {frame_type}")
        return frame_type, self.current_message
    
    def get_unpack_statu(self):
        """获取解包状态"""
        return self.is_receiving


    def get_message_frames(self):
        """获取解包后的消息帧列表"""
        return self.message_frames
    
    def get_mmsi(self):
        """获取解包后的消息帧列表"""
        return self.MMSI