"""
数据库模型定义
"""

from datetime import datetime
from flask_sqlalchemy import SQLAlchemy
from werkzeug.security import generate_password_hash, check_password_hash
import hashlib

db = SQLAlchemy()

# ==================== 用户模型 ====================
class User(db.Model):
    """用户表"""
    __tablename__ = 'users'
    
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    password_hash = db.Column(db.String(256), nullable=False)
    
    # 用户类型: guest, free, vip_basic, vip_pro, vip_enterprise, admin
    user_type = db.Column(db.String(20), default='free')
    
    # 会员信息
    membership_expire = db.Column(db.DateTime, nullable=True)  # 会员到期时间
    
    # 使用统计
    daily_count = db.Column(db.Integer, default=0)      # 今日翻译次数
    total_count = db.Column(db.Integer, default=0)      # 总翻译次数
    last_translate_date = db.Column(db.Date, nullable=True)  # 最后翻译日期
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    # 状态
    is_active = db.Column(db.Boolean, default=True)     # 是否启用
    is_admin = db.Column(db.Boolean, default=False)     # 是否管理员
    
    # 余额
    balance = db.Column(db.Float, default=0.0)          # 账户余额（元）
    
    # 关系
    translations = db.relationship('Translation', backref='user', lazy=True)
    recharges = db.relationship('UserRecharge', backref='user', lazy=True)
    refunds = db.relationship('UserRefund', backref='user', lazy=True)
    
    def set_password(self, password):
        self.password_hash = generate_password_hash(password)
    
    def check_password(self, password):
        return check_password_hash(self.password_hash, password)
    
    def is_vip(self):
        """检查是否为付费会员"""
        if self.user_type.startswith('vip'):
            if self.membership_expire and self.membership_expire > datetime.utcnow():
                return True
            # 过期则降级为免费用户
            self.user_type = 'free'
            self.membership_expire = None
            db.session.commit()
        return False
    
    def can_translate(self, pages, config):
        """检查是否可以翻译（次数、页数限制）"""
        limits = config['USER_LIMITS'].get(self.user_type, config['USER_LIMITS']['free'])
        
        # 检查页数限制
        max_pages = limits['max_pages']
        if max_pages > 0 and pages > max_pages:
            return False, f"PDF页数超出限制（最大{max_pages}页）"
        
        # 检查每日次数限制 - 使用上海时间（UTC+8）
        from datetime import timezone, timedelta
        shanghai_tz = timezone(timedelta(hours=8))
        today = datetime.now(shanghai_tz).date()
        if self.last_translate_date != today:
            self.daily_count = 0
            self.last_translate_date = today
        
        daily_limit = limits['daily_translations']
        if daily_limit > 0 and self.daily_count >= daily_limit:
            return False, f"今日翻译次数已达上限（{daily_limit}次）"
        
        return True, "OK"
    
    def increment_count(self):
        """增加翻译计数"""
        from datetime import timezone, timedelta
        shanghai_tz = timezone(timedelta(hours=8))
        today = datetime.now(shanghai_tz).date()
        if self.last_translate_date != today:
            self.daily_count = 0
            self.last_translate_date = today
        self.daily_count += 1
        self.total_count += 1
        db.session.commit()
    
    def to_dict(self):
        return {
            'id': self.id,
            'username': self.username,
            'email': self.email,
            'user_type': self.user_type,
            'is_vip': self.is_vip(),
            'is_admin': self.is_admin,
            'is_active': self.is_active,
            'balance': self.balance,
            'daily_count': self.daily_count,
            'total_count': self.total_count,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'membership_expire': self.membership_expire.isoformat() if self.membership_expire else None,
        }


# ==================== 翻译记录模型 ====================
class Translation(db.Model):
    """翻译记录表"""
    __tablename__ = 'translations'
    
    id = db.Column(db.Integer, primary_key=True)
    
    # 用户关联
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=True)  # guest可为null
    
    # 文件信息
    file_hash = db.Column(db.String(64), nullable=False)  # 文件MD5哈希
    original_filename = db.Column(db.String(255), nullable=False)
    file_size = db.Column(db.Integer, nullable=False)
    page_count = db.Column(db.Integer, nullable=False)
    
    # 翻译信息
    source_language = db.Column(db.String(10), default='en')
    target_language = db.Column(db.String(10), default='zh')
    translate_params = db.Column(db.Text, nullable=True)  # JSON格式的翻译参数
    
    # 状态
    status = db.Column(db.String(20), default='pending')  # pending, processing, completed, failed
    progress = db.Column(db.Integer, default=0)           # 翻译进度 0-100
    error_message = db.Column(db.Text, nullable=True)
    
    # 输出
    output_path = db.Column(db.String(255), nullable=True)  # 翻译结果文件路径
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    completed_at = db.Column(db.DateTime, nullable=True)
    
    # 是否来自缓存
    from_cache = db.Column(db.Boolean, default=False)
    
    # 重译信息
    retranslate_request = db.Column(db.Text, nullable=True)  # 重译要求
    parent_id = db.Column(db.Integer, db.ForeignKey('translations.id'), nullable=True)  # 原翻译ID
    
    def to_dict(self):
        return {
            'id': self.id,
            'filename': self.original_filename,
            'pages': self.page_count,
            'status': self.status,
            'progress': self.progress,
            'from_cache': self.from_cache,
            'file_size': self.file_size,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'completed_at': self.completed_at.isoformat() if self.completed_at else None,
            'user_id': self.user_id,
        }


# ==================== 翻译缓存模型 ====================
class TranslationCache(db.Model):
    """翻译缓存表"""
    __tablename__ = 'translation_cache'
    
    id = db.Column(db.Integer, primary_key=True)
    
    # 文件哈希
    file_hash = db.Column(db.String(64), unique=True, nullable=False)
    
    # 缓存信息
    cache_path = db.Column(db.String(255), nullable=False)  # 缓存文件路径
    page_count = db.Column(db.Integer, nullable=False)
    file_size = db.Column(db.Integer, default=0)
    
    # 统计
    hit_count = db.Column(db.Integer, default=0)  # 缓存命中次数
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    expires_at = db.Column(db.DateTime, nullable=True)
    
    def increment_hit(self):
        self.hit_count += 1
        db.session.commit()
    
    @staticmethod
    def compute_hash(file_content):
        """计算文件哈希"""
        return hashlib.md5(file_content).hexdigest()


# ==================== 访客翻译记录 ====================
class GuestTranslation(db.Model):
    """访客翻译记录（基于IP或Session）"""
    __tablename__ = 'guest_translations'
    
    id = db.Column(db.Integer, primary_key=True)
    
    # 访客标识
    session_id = db.Column(db.String(64), nullable=False)  # Session ID
    ip_address = db.Column(db.String(45), nullable=True)
    
    # 统计
    daily_count = db.Column(db.Integer, default=0)
    total_count = db.Column(db.Integer, default=0)
    last_translate_date = db.Column(db.Date, nullable=True)
    
    created_at = db.Column(db.DateTime, default=datetime.utcnow)


# ==================== 系统配置模型 ====================
class SystemConfig(db.Model):
    """系统配置表"""
    __tablename__ = 'system_config'
    
    id = db.Column(db.Integer, primary_key=True)
    key = db.Column(db.String(100), unique=True, nullable=False)
    value = db.Column(db.Text, nullable=True)
    description = db.Column(db.String(255), nullable=True)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    @staticmethod
    def get(key, default=None):
        config = SystemConfig.query.filter_by(key=key).first()
        return config.value if config else default
    
    @staticmethod
    def set(key, value, description=None):
        config = SystemConfig.query.filter_by(key=key).first()
        if config:
            config.value = value
        else:
            config = SystemConfig(key=key, value=value, description=description)
            db.session.add(config)
        db.session.commit()


# ==================== 操作日志模型 ====================
class OperationLog(db.Model):
    """操作日志表"""
    __tablename__ = 'operation_logs'
    
    id = db.Column(db.Integer, primary_key=True)
    
    # 操作者
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=True)
    username = db.Column(db.String(80), nullable=True)
    
    # 操作信息
    action = db.Column(db.String(50), nullable=False)  # login, translate, register, etc.
    target = db.Column(db.String(100), nullable=True)  # 操作对象
    detail = db.Column(db.Text, nullable=True)         # 详细信息(JSON)
    
    # IP地址
    ip_address = db.Column(db.String(45), nullable=True)
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    def to_dict(self):
        return {
            'id': self.id,
            'username': self.username,
            'action': self.action,
            'target': self.target,
            'ip_address': self.ip_address,
            'created_at': self.created_at.isoformat() if self.created_at else None,
        }


# ==================== 数据包套餐模型 ====================
class DataPackage(db.Model):
    """数据包购买套餐"""
    __tablename__ = 'data_packages'
    
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), nullable=False)           # 套餐名称
    description = db.Column(db.String(255), nullable=True)     # 描述
    
    # 翻译次数
    translation_count = db.Column(db.Integer, default=0)       # 翻译次数（-1表示无限）
    
    # 价格
    price = db.Column(db.Float, default=0)                     # 价格
    original_price = db.Column(db.Float, nullable=True)        # 原价（用于显示折扣）
    
    # 有效期
    valid_days = db.Column(db.Integer, default=30)             # 有效天数（0表示永久）
    
    # 排序和状态
    sort_order = db.Column(db.Integer, default=0)              # 排序
    is_active = db.Column(db.Boolean, default=True)            # 是否上架
    is_recommended = db.Column(db.Boolean, default=False)      # 是否推荐
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    def to_dict(self):
        return {
            'id': self.id,
            'name': self.name,
            'description': self.description,
            'translation_count': self.translation_count,
            'price': self.price,
            'original_price': self.original_price,
            'valid_days': self.valid_days,
            'is_active': self.is_active,
            'is_recommended': self.is_recommended,
        }


# ==================== 用户数据包购买记录 ====================
class UserPackage(db.Model):
    """用户购买的数据包"""
    __tablename__ = 'user_packages'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    package_id = db.Column(db.Integer, db.ForeignKey('data_packages.id'), nullable=False)
    
    # 套餐信息快照
    package_name = db.Column(db.String(100), nullable=False)
    translation_count = db.Column(db.Integer, default=0)       # 总次数
    remaining_count = db.Column(db.Integer, default=0)         # 剩余次数
    
    # 有效期
    expire_at = db.Column(db.DateTime, nullable=True)          # 过期时间（None表示永久）
    
    # 购买信息
    price_paid = db.Column(db.Float, default=0)                # 实付金额
    payment_method = db.Column(db.String(20), nullable=True)   # 支付方式
    payment_status = db.Column(db.String(20), default='pending')  # pending, paid, refunded
    
    # 时间
    purchased_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    # 关系
    user = db.relationship('User', backref=db.backref('packages', lazy=True))
    package = db.relationship('DataPackage', backref=db.backref('purchases', lazy=True))
    
    def is_valid(self):
        """检查数据包是否有效"""
        if self.remaining_count <= 0:
            return False
        if self.expire_at and self.expire_at < datetime.utcnow():
            return False
        return True


# ==================== 系统配置（动态） ====================
class DynamicConfig(db.Model):
    """动态系统配置（可在页面修改）"""
    __tablename__ = 'dynamic_config'
    
    id = db.Column(db.Integer, primary_key=True)
    category = db.Column(db.String(50), default='general')      # 分类: general, user_limits, membership
    key = db.Column(db.String(100), unique=True, nullable=False)
    value = db.Column(db.Text, nullable=True)
    value_type = db.Column(db.String(20), default='string')    # string, int, float, bool, json
    description = db.Column(db.String(255), nullable=True)
    
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    updated_by = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=True)
    
    @staticmethod
    def get(key, default=None):
        config = DynamicConfig.query.filter_by(key=key).first()
        if not config:
            return default
        
        # 类型转换
        if config.value_type == 'int':
            return int(config.value) if config.value else 0
        elif config.value_type == 'float':
            return float(config.value) if config.value else 0.0
        elif config.value_type == 'bool':
            return config.value.lower() in ('true', '1', 'yes')
        elif config.value_type == 'json':
            import json
            return json.loads(config.value) if config.value else {}
        return config.value
    
    @staticmethod
    def set(key, value, category='general', value_type='string', description=None, user_id=None):
        config = DynamicConfig.query.filter_by(key=key).first()
        
        # 类型转换
        if value_type == 'json':
            import json
            value = json.dumps(value, ensure_ascii=False)
        elif value_type == 'bool':
            value = 'true' if value else 'false'
        else:
            value = str(value) if value is not None else None
        
        if config:
            config.value = value
            config.value_type = value_type
            config.updated_by = user_id
        else:
            config = DynamicConfig(
                category=category,
                key=key,
                value=value,
                value_type=value_type,
                description=description,
                updated_by=user_id
            )
            db.session.add(config)
        
        db.session.commit()
        return config


# ==================== 用户类型配置（动态增删） ====================
class UserTypeConfig(db.Model):
    """用户类型配置表 - 支持动态增删"""
    __tablename__ = 'user_type_config'
    
    id = db.Column(db.Integer, primary_key=True)
    type_key = db.Column(db.String(50), unique=True, nullable=False)  # 类型标识: guest, free, vip_basic, etc.
    display_name = db.Column(db.String(100), nullable=False)          # 显示名称: 访客, 免费用户, 基础会员
    
    # 权限配置
    daily_translations = db.Column(db.Integer, default=10)            # 每日翻译次数 (-1=无限)
    max_pages = db.Column(db.Integer, default=50)                     # 最大页数 (-1=无限)
    max_file_size = db.Column(db.Integer, default=30*1024*1024)       # 最大文件大小(bytes)
    
    # 功能列表(JSON)
    features = db.Column(db.Text, default='[]')                        # JSON数组: ["basic_translate", "history"]
    
    # 排序和状态
    sort_order = db.Column(db.Integer, default=0)                     # 排序权重
    is_active = db.Column(db.Boolean, default=True)                   # 是否启用
    is_system = db.Column(db.Boolean, default=False)                  # 是否系统内置(不可删除)
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    def get_features(self):
        """获取功能列表"""
        import json
        try:
            return json.loads(self.features) if self.features else []
        except:
            return []
    
    def set_features(self, feature_list):
        """设置功能列表"""
        import json
        self.features = json.dumps(feature_list, ensure_ascii=False)
    
    def to_dict(self):
        return {
            'id': self.id,
            'type_key': self.type_key,
            'display_name': self.display_name,
            'daily_translations': self.daily_translations,
            'max_pages': self.max_pages,
            'max_file_size': self.max_file_size,
            'features': self.get_features(),
            'sort_order': self.sort_order,
            'is_active': self.is_active,
            'is_system': self.is_system,
        }


# ==================== 会员套餐配置（动态增删） ====================
class MembershipPlanConfig(db.Model):
    """会员套餐配置表 - 支持动态增删"""
    __tablename__ = 'membership_plan_config'
    
    id = db.Column(db.Integer, primary_key=True)
    plan_key = db.Column(db.String(50), unique=True, nullable=False)  # 套餐标识: vip_basic, vip_pro, etc.
    display_name = db.Column(db.String(100), nullable=False)          # 显示名称: 基础会员
    
    # 价格配置
    price = db.Column(db.Float, default=0)                            # 价格
    original_price = db.Column(db.Float, nullable=True)               # 原价(用于折扣显示)
    period = db.Column(db.String(20), default='month')                # 周期: month, quarter, year
    period_days = db.Column(db.Integer, default=30)                   # 周期天数
    
    # 描述
    description = db.Column(db.String(255), nullable=True)            # 套餐描述
    
    # 对应的用户类型
    user_type_key = db.Column(db.String(50), nullable=True)           # 购买后升级到的用户类型
    
    # 排序和状态
    sort_order = db.Column(db.Integer, default=0)
    is_active = db.Column(db.Boolean, default=True)
    is_recommended = db.Column(db.Boolean, default=False)             # 是否推荐
    is_system = db.Column(db.Boolean, default=False)                  # 是否系统内置(不可删除)
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    def to_dict(self):
        return {
            'id': self.id,
            'plan_key': self.plan_key,
            'display_name': self.display_name,
            'price': self.price,
            'original_price': self.original_price,
            'period': self.period,
            'period_days': self.period_days,
            'description': self.description,
            'user_type_key': self.user_type_key,
            'sort_order': self.sort_order,
            'is_active': self.is_active,
            'is_recommended': self.is_recommended,
            'is_system': self.is_system,
        }


# ==================== 用户充值记录 ====================
class UserRecharge(db.Model):
    """用户充值记录"""
    __tablename__ = 'user_recharges'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    
    # 充值信息
    amount = db.Column(db.Float, nullable=False)               # 充值金额
    balance_before = db.Column(db.Float, default=0)            # 充值前余额
    balance_after = db.Column(db.Float, default=0)             # 充值后余额
    
    # 支付方式
    payment_method = db.Column(db.String(20), default='balance')  # balance, alipay, wechat, manual
    
    # 状态
    status = db.Column(db.String(20), default='pending')      # pending, completed, failed, cancelled
    order_no = db.Column(db.String(64), unique=True, nullable=True)  # 订单号
    
    # 备注
    remark = db.Column(db.String(255), nullable=True)         # 管理员备注
    operator_id = db.Column(db.Integer, nullable=True)        # 操作管理员ID
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    completed_at = db.Column(db.DateTime, nullable=True)
    
    def to_dict(self):
        return {
            'id': self.id,
            'user_id': self.user_id,
            'amount': self.amount,
            'balance_before': self.balance_before,
            'balance_after': self.balance_after,
            'payment_method': self.payment_method,
            'status': self.status,
            'order_no': self.order_no,
            'remark': self.remark,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'completed_at': self.completed_at.isoformat() if self.completed_at else None,
        }


# ==================== 用户退款记录 ====================
class UserRefund(db.Model):
    """用户退款记录"""
    __tablename__ = 'user_refunds'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    recharge_id = db.Column(db.Integer, db.ForeignKey('user_recharges.id'), nullable=True)  # 关联充值记录
    
    # 退款信息
    amount = db.Column(db.Float, nullable=False)               # 退款金额
    balance_before = db.Column(db.Float, default=0)            # 退款前余额
    balance_after = db.Column(db.Float, default=0)             # 退款后余额
    
    # 原因
    reason = db.Column(db.String(255), nullable=True)         # 退款原因
    reason_type = db.Column(db.String(20), default='user_request')  # user_request, system_error, admin_initiated
    
    # 状态
    status = db.Column(db.String(20), default='pending')      # pending, approved, completed, rejected
    
    # 操作
    operator_id = db.Column(db.Integer, nullable=True)        # 处理管理员ID
    operator_remark = db.Column(db.String(255), nullable=True)  # 管理员处理备注
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    processed_at = db.Column(db.DateTime, nullable=True)
    completed_at = db.Column(db.DateTime, nullable=True)
    
    def to_dict(self):
        return {
            'id': self.id,
            'user_id': self.user_id,
            'recharge_id': self.recharge_id,
            'amount': self.amount,
            'balance_before': self.balance_before,
            'balance_after': self.balance_after,
            'reason': self.reason,
            'reason_type': self.reason_type,
            'status': self.status,
            'operator_remark': self.operator_remark,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'processed_at': self.processed_at.isoformat() if self.processed_at else None,
            'completed_at': self.completed_at.isoformat() if self.completed_at else None,
        }


# ==================== 会员购买记录 ====================
class MembershipPurchase(db.Model):
    """会员购买记录"""
    __tablename__ = 'membership_purchases'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    
    # 套餐信息
    plan_key = db.Column(db.String(50), nullable=False)       # vip_basic, vip_pro, vip_enterprise
    plan_name = db.Column(db.String(100), nullable=False)     # 基础会员, 专业会员
    
    # 价格
    price = db.Column(db.Float, nullable=False)               # 实付金额
    original_price = db.Column(db.Float, nullable=True)       # 原价
    
    # 有效期
    period_days = db.Column(db.Integer, default=30)           # 购买天数
    expire_before = db.Column(db.DateTime, nullable=True)     # 购买前到期时间
    expire_after = db.Column(db.DateTime, nullable=True)      # 购买后到期时间
    
    # 支付方式
    payment_method = db.Column(db.String(20), default='balance')  # balance, alipay, wechat
    
    # 状态
    status = db.Column(db.String(20), default='completed')    # pending, completed, refunded
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    # 关系
    user = db.relationship('User', backref=db.backref('membership_purchases', lazy=True))
    
    def to_dict(self):
        return {
            'id': self.id,
            'user_id': self.user_id,
            'plan_key': self.plan_key,
            'plan_name': self.plan_name,
            'price': self.price,
            'original_price': self.original_price,
            'period_days': self.period_days,
            'expire_after': self.expire_after.isoformat() if self.expire_after else None,
            'payment_method': self.payment_method,
            'status': self.status,
            'created_at': self.created_at.isoformat() if self.created_at else None,
        }


# ==================== 账户流水记录 ====================
class AccountTransaction(db.Model):
    """账户流水记录"""
    __tablename__ = 'account_transactions'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    
    # 流水信息
    transaction_type = db.Column(db.String(20), nullable=False)  # recharge, refund, purchase, consume, refund_purchase
    amount = db.Column(db.Float, nullable=False)                 # 金额（正数加，负数减）
    balance_before = db.Column(db.Float, default=0)              # 操作前余额
    balance_after = db.Column(db.Float, default=0)               # 操作后余额
    
    # 关联
    related_id = db.Column(db.Integer, nullable=True)            # 关联记录ID（充值ID、退款ID等）
    related_type = db.Column(db.String(50), nullable=True)       # 关联类型（recharge, refund, membership_purchase等）
    
    # 描述
    description = db.Column(db.String(255), nullable=True)       # 流水描述
    
    # 时间
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    # 关系
    user = db.relationship('User', backref=db.backref('transactions', lazy=True))
    
    def to_dict(self):
        return {
            'id': self.id,
            'user_id': self.user_id,
            'transaction_type': self.transaction_type,
            'amount': self.amount,
            'balance_before': self.balance_before,
            'balance_after': self.balance_after,
            'related_id': self.related_id,
            'related_type': self.related_type,
            'description': self.description,
            'created_at': self.created_at.isoformat() if self.created_at else None,
        }