"""
文本上下文构造器
"""

def build_context_text(openpilot_data, prev_action=None, prev_tta=None, 
                       is_extended=False, use_belief_token=False):
    """
    构造VLM的文本上下文
    
    Args:
        ...
        use_belief_token: bool - 是否在末尾添加<BELIEF> token
    """
    action_names = ["silent", "observe", "alert"]
    
    # 基础车辆状态
    text = f"""Vehicle State:
- Speed: {openpilot_data.get('speed', 0):.1f} km/h
- ACC: {'ON' if openpilot_data.get('acc', False) else 'OFF'}
- LKA: {'ON' if openpilot_data.get('lka', False) else 'OFF'}
- Lane confidence: L={openpilot_data.get('lane_left_prob', 0.5):.2f}, R={openpilot_data.get('lane_right_prob', 0.5):.2f}
- Path plan confidence: {openpilot_data.get('path_confidence', 0.5):.2f}
- Lateral offset: {openpilot_data.get('lateral_offset', 0.0):.2f}m

Environment:
- Weather: {openpilot_data.get('weather', 'unknown')}
- Time: {openpilot_data.get('time_of_day', 'unknown')}
"""
    
    # 历史信息
    if prev_action is not None and prev_tta is not None:
        text += f"""
Previous State:
- Action taken: {action_names[prev_action]}
- TTA estimate: {prev_tta:.2f}s
"""
    
    # OBSERVE提示
    if is_extended:
        text += "\n[Note: Extended temporal window (3s) with focused spatial attention]"
    
    # 任务描述
    text += "\n\nTask: Estimate time-to-accident (TTA) from multimodal observations."
    
    # BELIEF token（如果启用）
    if use_belief_token:
        text += " <BELIEF>"
    
    return text