"""数据库会话与租户上下文。

安全模型（务必理解，否则会写出越权 bug）：

1. 应用进程用 **dadao_app** 角色连库 —— 非 owner、非 superuser、非 bypassrls。
   owner/superuser 会**绕过 RLS**，所以应用绝不使用迁移角色。
2. 每个请求在**同一个事务**里先 `set_config('app.ws_id', ..., true)`
   （true = 事务级，事务结束自动失效，不会污染连接池里的下一条请求）。
3. RLS 策略拿这个变量做过滤。变量没设 → 策略为 false → 一行都查不到。
4. 仓储层强制 ws_id 必填，双保险：即使 RLS 被误关，代码也不会跨租户查。
"""

from __future__ import annotations

import uuid
from collections.abc import AsyncIterator
from typing import Any

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.pool import NullPool

from .config import get_settings
from .errors import AppError, ErrorCode

_settings = get_settings()

_engine_kwargs: dict[str, Any] = {"echo": _settings.db_echo, "pool_pre_ping": True}
if _settings.env == "test":
    # pytest-asyncio 每个用例一个事件循环，连接池跨循环复用会报
    # "attached to a different loop"，测试环境干脆不池化。
    _engine_kwargs["poolclass"] = NullPool
else:
    _engine_kwargs["pool_size"] = _settings.db_pool_size

engine = create_async_engine(_settings.database_url, **_engine_kwargs)
SessionFactory = async_sessionmaker(engine, expire_on_commit=False, autoflush=False)


async def get_session() -> AsyncIterator[AsyncSession]:
    """一个请求 = 一个事务。异常即整体回滚。"""
    async with SessionFactory() as session:
        async with session.begin():
            yield session


async def bind_tenant(session: AsyncSession, ws_id: uuid.UUID, user_id: uuid.UUID | None) -> None:
    """把租户上下文写进当前事务。必须在任何业务查询之前调用。"""
    await session.execute(
        text("SELECT set_config('app.ws_id', :ws, true)"), {"ws": str(ws_id)}
    )
    if user_id is not None:
        await session.execute(
            text("SELECT set_config('app.user_id', :uid, true)"), {"uid": str(user_id)}
        )


async def bind_user(session: AsyncSession, user_id: uuid.UUID) -> None:
    """只绑用户（登录后尚未选定工作区的场景）。"""
    await session.execute(
        text("SELECT set_config('app.user_id', :uid, true)"), {"uid": str(user_id)}
    )


async def current_app_role(session: AsyncSession) -> dict[str, Any]:
    """自检用：确认应用连接的不是特权角色。"""
    row = (
        await session.execute(
            text(
                "SELECT current_user AS role, "
                "pg_has_role(current_user, 'pg_read_all_data', 'member') AS read_all, "
                "(SELECT rolsuper FROM pg_roles WHERE rolname = current_user) AS is_super, "
                "(SELECT rolbypassrls FROM pg_roles WHERE rolname = current_user) AS bypass_rls"
            )
        )
    ).mappings().one()
    return dict(row)


class Repo:
    """仓储基类：ws_id 必填，且没有默认值——不给"忘了传"留余地。"""

    def __init__(self, session: AsyncSession, ws_id: uuid.UUID) -> None:
        if ws_id is None:
            raise AppError(ErrorCode.BAD_REQUEST, "缺少工作区上下文")
        self.session = session
        self.ws_id = ws_id


class UserRepo:
    """全局仓储（app_user 无租户），仅认证流程使用。"""

    def __init__(self, session: AsyncSession) -> None:
        self.session = session