# -*- coding: utf-8 -*-

from datetime import datetime
from sqlalchemy import DateTime, String, Integer, Text, ForeignKey
from sqlalchemy.orm import Mapped, mapped_column, DeclarativeBase, declared_attr, relationship
from sqlalchemy.ext.asyncio import AsyncAttrs
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from app.api.v1.module_system.customer.model import CustomerModel
    from app.api.v1.module_system.tenant.model import TenantModel
    from app.api.v1.module_system.user.model import UserModel

from app.utils.common_util import uuid4_str


class MappedBase(AsyncAttrs, DeclarativeBase):
    """
    声明式基类

    `AsyncAttrs <https://docs.sqlalchemy.org/en/20/orm/extensions/asyncio.html#sqlalchemy.ext.asyncio.AsyncAttrs>`__

    `DeclarativeBase <https://docs.sqlalchemy.org/en/20/orm/declarative_config.html>`__

    `mapped_column() <https://docs.sqlalchemy.org/en/20/orm/mapping_api.html#sqlalchemy.orm.mapped_column>`__

    兼容 SQLite、MySQL 和 PostgreSQL
    """

    __abstract__: bool = True


class ModelMixin(MappedBase):
    """
    模型混入类 - 提供通用字段和功能

    基础模型混合类 Mixin: 一种面向对象编程概念, 使结构变得更加清晰
    
    数据隔离设计原则：
    ==================
    
    1. 租户隔离 (tenant_id):
        - 用于实现多租户SaaS架构的核心隔离
        - 系统租户(tenant_id=1): 管理平台级数据
        - 普通租户(tenant_id>1): 各自独立的业务数据
        - 大部分业务表都需要tenant_id字段
    
    2. 客户隔离 (customer_id):
        - 用于租户内部的二级隔离
        - 仅部分表需要,如用户、日志等
        - 客户属于租户,实现租户下的业务单元隔离
    
    3. 数据权限 (created_id/updated_id):
        - 配合角色的data_scope字段实现精细化权限控制
        - 1:仅本人 → WHERE created_id = current_user_id
        - 2:本部门 → WHERE user.dept_id = current_user.dept_id
        - 3:本部门及以下 → WHERE dept.tree_path LIKE 'current_dept_path%'
        - 4:全部数据 → WHERE tenant_id = current_tenant_id
        - 5:自定义 → WHERE dept_id IN (role_depts)
    
    继承规则：
    - 需要租户隔离的业务表继承此类
    - 不需要隔离的表(如租户表本身)只继承MappedBase
    
    SQLAlchemy加载策略说明:
    - select(默认): 延迟加载,访问时单独查询
    - joined: 使用LEFT JOIN预加载
    - selectin: 使用IN查询批量预加载(推荐用于一对多)
    - subquery: 使用子查询预加载
    - raise/raise_on_sql: 禁止加载
    - noload: 不加载,返回None
    - immediate: 立即加载
    - write_only: 只写不读
    - dynamic: 返回查询对象,支持进一步过滤
    """
    __abstract__: bool = True
    
    # 基础字段
    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True, comment='主键ID')
    uuid: Mapped[str] = mapped_column(String(64), default=uuid4_str, nullable=False, unique=True, comment='UUID全局唯一标识')
    status: Mapped[str] = mapped_column(String(10), default='0', nullable=False, comment="是否启用(0:启用 1:禁用)")
    description: Mapped[str | None] = mapped_column(Text, default=None, nullable=True, comment="备注/描述")
    created_time: Mapped[datetime] = mapped_column(DateTime, default=datetime.now, nullable=False, comment='创建时间')
    updated_time: Mapped[datetime] = mapped_column(DateTime, default=datetime.now, onupdate=datetime.now, nullable=False, comment='更新时间')


class UserMixin(MappedBase):
    """
    用户审计字段 Mixin
    
    用于记录数据的创建者和更新者
    用于实现数据权限中的"仅本人数据权限"
    """
    __abstract__: bool = True
    
    created_id: Mapped[int | None] = mapped_column(
        Integer,
        ForeignKey('sys_user.id', ondelete="SET NULL", onupdate="CASCADE"),
        default=None,
        nullable=True,
        index=True,
        comment="创建人ID"
    )
    updated_id: Mapped[int | None] = mapped_column(
        Integer,
        ForeignKey('sys_user.id', ondelete="SET NULL", onupdate="CASCADE"),
        default=None,
        nullable=True,
        index=True,
        comment="更新人ID"
    )

    @declared_attr
    def created_by(cls) -> Mapped["UserModel"]:
        """
        创建人关联关系（延迟加载，避免循环依赖）
        """
        return relationship(
            "UserModel",
            primaryjoin=f"{cls.__name__}.created_id == UserModel.id",
            lazy="selectin",
            foreign_keys=lambda: [cls.created_id],
            viewonly=True,
            uselist=False
        )

    @declared_attr
    def updated_by(cls) -> Mapped["UserModel"]:
        """
        更新人关联关系（延迟加载，避免循环依赖）
        """
        return relationship(
            "UserModel",
            primaryjoin=f"{cls.__name__}.updated_id == UserModel.id",
            lazy="selectin",
            foreign_keys=lambda: [cls.updated_id],
            viewonly=True,
            uselist=False
        )


class TenantMixin(MappedBase):
    """
    租户字段 Mixin
    
    用于实现多租户SaaS架构的核心隔离
    """
    __abstract__: bool = True

    tenant_id: Mapped[int | None] = mapped_column(
        Integer,
        ForeignKey('sys_tenant.id', ondelete="CASCADE", onupdate="CASCADE"),
        nullable=False,
        index=True,
        comment="所属租户ID"
    )

    @declared_attr
    def tenant(cls) -> Mapped["TenantModel"]:
        """
        租户关联关系（延迟加载，避免循环依赖）
        """
        return relationship(
            "TenantModel",
            primaryjoin=f"{cls.__name__}.tenant_id == TenantModel.id",
            lazy="selectin",
            foreign_keys=lambda: [cls.tenant_id],
            viewonly=True,
            uselist=False
        )


class CustomerMixin(MappedBase):
    """
    客户隔离字段 Mixin
    
    用于租户内部的二级数据隔离
    仅部分表需要此字段:
    - 客户用户 (必填)
    - 客户业务数据 (根据业务需求)
    - 客户专属通知/日志 (可选)
    """
    __abstract__: bool = True

    customer_id: Mapped[int | None] = mapped_column(
        Integer,
        ForeignKey('sys_customer.id', ondelete="CASCADE", onupdate="CASCADE"),
        default=None,
        nullable=True,
        index=True,
        comment="所属客户ID(NULL表示租户级数据,>0表示客户级数据)"
    )

    @declared_attr
    def customer(cls) -> Mapped["CustomerModel"]:
        """
        客户关联关系（延迟加载，避免循环依赖）
        """
        return relationship(
            "CustomerModel",
            primaryjoin=f"{cls.__name__}.customer_id == CustomerModel.id",
            lazy="selectin",
            foreign_keys=lambda: [cls.customer_id],
            viewonly=True,
            uselist=False
        )