移动应用开发新购优惠

def validate_promotion_code(user_id, code):
    # 检查优惠码是否存在且有效
    promotion = Promotion.query.filter_by(code=code).first()
    if not promotion or promotion.is_expired():
        return False, "Invalid or expired promotion code."

    # 检查用户是否已经使用过此优惠码
    if PromotionUsage.query.filter_by(user_id=user_id, promotion_id=promotion.id).first():
        return False, "You have already used this promotion code."

    # 记录优惠码使用情况
    new_usage = PromotionUsage(user_id=user_id, promotion_id=promotion.id)
    db.session.add(new_usage)
    db.session.commit()

    return True, "Promotion code applied successfully."

class Promotion(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    code = db.Column(db.String(50), unique=True, nullable=False)
    discount = db.Column(db.Float, nullable=False)
    expiration_date = db.Column(db.DateTime, nullable=False)

class PromotionUsage(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
    promotion_id = db.Column(db.Integer, db.ForeignKey('promotion.id'), nullable=False)