from django.core.signing import TimestampSigner, BadSignature, SignatureExpired
from shop.models import WeChatUser
import logging

logger = logging.getLogger(__name__)

def get_current_wechat_user(request):
    """
    根据 Authorization 头获取当前微信用户
    增强逻辑：如果 Token 解析出的 OpenID 对应的用户不存在（可能已被合并删除），
    但该 OpenID 是 Web 虚拟 ID (web_phone)，尝试通过手机号查找现有的主账号。
    """
    auth_header = request.headers.get('Authorization')
    if not auth_header or not auth_header.startswith('Bearer '):
        logger.warning(f"Authentication failed: Missing or invalid Authorization header. Header: {auth_header}")
        return None
    token = auth_header.split(' ')[1]
    signer = TimestampSigner()
    try:
        # 签名包含 openid
        openid = signer.unsign(token, max_age=86400 * 30) # 30天有效
        user = WeChatUser.objects.filter(openid=openid).first()
        
        if user:
            return user
            
        # 如果没找到用户，检查是否是 Web 虚拟 OpenID
        # 场景：Web 用户已被合并到小程序账号，旧 Web Token 依然有效，指向合并后的账号
        logger.info(f"User not found for openid: {openid}, checking for merged account...")
        if openid.startswith('web_'):
            try:
                # 格式: web_13800138000
                parts = openid.split('_', 1)
                if len(parts) == 2:
                    phone = parts[1]
                    # 尝试通过手机号查找（查找合并后的主账号）
                    user = WeChatUser.objects.filter(phone_number=phone).first()
                    if user:
                        logger.info(f"Found merged user {user.id} for phone {phone}")
                        return user
            except Exception as e:
                logger.error(f"Error checking merged account: {e}")
                pass
        
        logger.warning(f"Authentication failed: User not found for openid {openid}")
        return None
    except SignatureExpired:
        logger.warning("Authentication failed: Signature expired")
        return None
    except BadSignature:
        logger.warning("Authentication failed: Bad signature")
        return None
    except Exception as e:
        logger.error(f"Authentication unexpected error: {e}")
        return None