"""yuxi.storage.transactions 单元测试。

覆盖 ``SqlAlchemyTransactionContext`` / ``SqlAlchemyTransactionAdapter`` /
``with_session`` 与四个事务异常类，使用 ``MagicMock`` / ``AsyncMock`` 模拟
``AsyncSession`` 与事务对象，不连接真实 DB。
"""

from __future__ import annotations

from unittest.mock import AsyncMock, MagicMock

import pytest
from yuxi.storage.transactions import (
    SqlAlchemyTransactionContext,
    TransactionBeginError,
    TransactionCommitError,
    TransactionInactiveError,
    TransactionRollbackError,
    with_session,
)

pytestmark = pytest.mark.unit


def _make_session() -> MagicMock:
    """构造 AsyncSession 桩。

    默认 ``in_transaction`` 返回 False（无隐式事务），模拟干净 session。
    ``begin_nested`` 返回一个 ``AsyncMock``，可作为 async context manager。
    """
    session = MagicMock()
    session.begin = AsyncMock()
    session.in_transaction = MagicMock(return_value=False)
    session.commit = AsyncMock()
    session.close = AsyncMock()
    # AsyncMock 实例自身支持 async context manager 协议（__aenter__/__aexit__）
    session.begin_nested = MagicMock(return_value=AsyncMock())
    return session


def _make_txn() -> MagicMock:
    """构造事务对象桩。"""
    txn = MagicMock()
    txn.commit = AsyncMock()
    txn.rollback = AsyncMock()
    txn.is_active = True
    return txn


# ─── __aenter__：autobegin 隐式事务处理 ─────────────────────────────────────


class TestAenterHandlesAutobegin:
    async def test_begin_handles_autobegin_implicit_transaction(self):
        """SQLAlchemy 2.0 autobegin 语义：前置 SELECT 触发隐式事务，
        ``__aenter__`` 应先提交隐式事务再开启显式事务，避免
        ``InvalidRequestError: A transaction is already begun``。
        """
        # Arrange
        session = _make_session()
        session.in_transaction = MagicMock(return_value=True)
        txn = _make_txn()
        session.begin = AsyncMock(return_value=txn)
        ctx = SqlAlchemyTransactionContext(session)

        # Act
        result = await ctx.__aenter__()

        # Assert
        assert result is ctx
        session.commit.assert_awaited_once()  # 先提交隐式事务
        session.begin.assert_awaited_once()  # 再开启显式事务
        assert ctx._txn is txn


# ─── __aexit__：is_active 检查避免 ResourceClosedError ─────────────────────


class TestAexitChecksIsActive:
    async def test_aexit_checks_is_active_avoids_resource_closed_error(self):
        """事务已被 SQLAlchemy 内部关闭（``is_active=False``，如 flush 失败）
        时，``__aexit__`` 应跳过 commit/rollback，避免 ``ResourceClosedError``。
        """
        # Arrange
        session = _make_session()
        txn = _make_txn()
        txn.is_active = False
        session.begin = AsyncMock(return_value=txn)
        ctx = SqlAlchemyTransactionContext(session)
        await ctx.__aenter__()

        # Act
        await ctx.__aexit__(None, None, None)

        # Assert
        txn.commit.assert_not_awaited()
        txn.rollback.assert_not_awaited()
        assert ctx._txn is None


# ─── commit / rollback 幂等 ────────────────────────────────────────────────


class TestCommitIdempotent:
    async def test_commit_is_idempotent(self):
        """多次调用 ``commit()`` 仅首次生效，后续 no-op。"""
        # Arrange
        session = _make_session()
        txn = _make_txn()
        session.begin = AsyncMock(return_value=txn)
        ctx = SqlAlchemyTransactionContext(session)
        await ctx.__aenter__()

        # Act
        await ctx.commit()
        await ctx.commit()

        # Assert
        txn.commit.assert_awaited_once()
        assert ctx._txn is None


class TestRollbackIdempotent:
    async def test_rollback_is_idempotent(self):
        """多次调用 ``rollback()`` 仅首次生效，后续 no-op。"""
        # Arrange
        session = _make_session()
        txn = _make_txn()
        session.begin = AsyncMock(return_value=txn)
        ctx = SqlAlchemyTransactionContext(session)
        await ctx.__aenter__()

        # Act
        await ctx.rollback()
        await ctx.rollback()

        # Assert
        txn.rollback.assert_awaited_once()
        assert ctx._txn is None


# ─── savepoint ─────────────────────────────────────────────────────────────


class TestSavepoint:
    async def test_savepoint_rolls_back_on_exception(self):
        """``savepoint()`` 在异常时回滚到 SAVEPOINT，外层事务不受污染：
        SAVEPOINT 的 ``__aexit__`` 收到异常，外层 ``_txn`` 仍可正常提交。
        """
        # Arrange
        session = _make_session()
        txn = _make_txn()
        session.begin = AsyncMock(return_value=txn)
        sp_cm = session.begin_nested.return_value  # AsyncMock
        ctx = SqlAlchemyTransactionContext(session)
        await ctx.__aenter__()

        # Act / Assert：savepoint 内抛异常，被捕获后外层仍能正常退出
        with pytest.raises(ValueError, match="boom"):
            async with ctx.savepoint():
                raise ValueError("boom")

        # SAVEPOINT 的 __aexit__ 收到异常
        sp_cm.__aexit__.assert_awaited_once()
        exc_type_arg = sp_cm.__aexit__.await_args.args[0]
        assert exc_type_arg is ValueError
        # 外层事务未被污染：rollback 未触发
        txn.rollback.assert_not_awaited()

        # 外层正常退出 → commit
        await ctx.__aexit__(None, None, None)
        txn.commit.assert_awaited_once()

    async def test_savepoint_commits_on_success(self):
        """``savepoint()`` 在正常退出时释放 SAVEPOINT（``__aexit__`` 收到 None）。"""
        # Arrange
        session = _make_session()
        sp_cm = session.begin_nested.return_value
        ctx = SqlAlchemyTransactionContext(session)

        # Act
        async with ctx.savepoint():
            pass

        # Assert
        sp_cm.__aexit__.assert_awaited_once()
        args = sp_cm.__aexit__.await_args.args
        assert args == (None, None, None)


# ─── get_session / transaction_id ──────────────────────────────────────────


class TestGetSession:
    def test_get_session_returns_shared_session(self):
        """``get_session()`` 返回构造时传入的 session（C-I1 透传）。"""
        # Arrange
        session = _make_session()
        ctx = SqlAlchemyTransactionContext(session)

        # Act / Assert
        assert ctx.get_session() is session


class TestTransactionId:
    def test_transaction_id_generated(self):
        """``__init__`` 生成 ``tx_`` 前缀的唯一 transaction_id。"""
        # Arrange
        session = _make_session()

        # Act
        ctx1 = SqlAlchemyTransactionContext(session)
        ctx2 = SqlAlchemyTransactionContext(session)

        # Assert
        assert ctx1.transaction_id.startswith("tx_")
        assert ctx2.transaction_id.startswith("tx_")
        assert ctx1.transaction_id != ctx2.transaction_id


# ─── 异常链与 UnifiedError 协议 ─────────────────────────────────────────────


class TestExceptionTraceback:
    async def test_exception_preserves_original_traceback(self):
        """``raise ... from exc`` 保留原始异常链（``__cause__``）。"""
        # Arrange
        session = _make_session()
        txn = _make_txn()
        original = RuntimeError("db connection lost")
        txn.commit = AsyncMock(side_effect=original)
        session.begin = AsyncMock(return_value=txn)
        ctx = SqlAlchemyTransactionContext(session)
        await ctx.__aenter__()

        # Act / Assert
        with pytest.raises(TransactionCommitError) as exc_info:
            await ctx.commit()
        assert exc_info.value.__cause__ is original


class TestUnifiedErrorProtocol:
    def test_exception_implements_unified_error_protocol(self):
        """四个异常类提供 status_code / error_code / message / details / trace_id。"""
        cases = [
            (TransactionBeginError, "TX_BEGIN_ERROR"),
            (TransactionCommitError, "TX_COMMIT_ERROR"),
            (TransactionRollbackError, "TX_ROLLBACK_ERROR"),
            (TransactionInactiveError, "TX_INACTIVE_ERROR"),
        ]
        for exc_cls, code in cases:
            # Act
            exc = exc_cls(
                "msg",
                transaction_id="tx1",
                session_state="active",
                trace_id="t1",
            )

            # Assert：UnifiedError 协议字段
            assert exc.error_code == code
            assert exc.message == "msg"
            assert exc.trace_id == "t1"
            # 四个 TX_* 错误码未注册到状态码映射表，基类查表返回 500
            assert exc.status_code == 500
            # details 自动包含诊断字段（to_dict 排除 error_code/message/trace_id）
            details = exc.details
            assert details["transaction_id"] == "tx1"
            assert details["session_state"] == "active"


# ─── with_session 辅助方法 ─────────────────────────────────────────────────


class TestWithSession:
    async def test_with_session_creates_and_closes_temporary_session(self):
        """``with_session`` 创建临时 session 并在退出时关闭。"""
        # Arrange
        session = _make_session()
        factory = MagicMock(return_value=session)

        # Act
        async with with_session(factory) as s:
            # Assert：yield 的是 factory 创建的 session
            assert s is session

        # Assert：factory 调用一次，session 关闭一次
        factory.assert_called_once_with()
        session.close.assert_awaited_once()