PayrollManagementSystem/backend/tests/unit/test_param_snapshot.py

"""参数快照（时点化取值）测试。

守的是：覆盖链与兜底 —— 一旦取错维度（如企业户取到市政阈值行）
或漏兜底，核算会用错口径或直接崩溃；同日多次变更必须取最新留痕。
仓储 SQL 的排序语义（同日取 id 最大）在集成测试中覆盖。
"""

from dataclasses import FrozenInstanceError
from datetime import date
from fractions import Fraction

import pytest

from app.services.param_service import ParamSnapshot


def _snap(rows: list[tuple[str, str, str]]) -> ParamSnapshot:
    """构造快照。rows 须模拟仓储输出：同一 (code, dim) 的最新值在前。"""
    # 仓储实际返回 4 元组（含生效日期）；单测关注覆盖链，统一补同一个日期
    return ParamSnapshot.from_rows(
        date(2026, 10, 1), [(code, dim, value, date(2026, 1, 1)) for code, dim, value in rows]
    )


class TestCoverChain:
    """覆盖链：角色维度 > 产品类别维度 > 默认行（''）。"""

    def test_产品类别维度优先于默认行(self) -> None:
        snap = _snap([("enterprise.rate", "", "3"), ("enterprise.rate", "municipal_water", "2")])
        assert snap.get("enterprise.rate", product_category="municipal_water") == "2"

    def test_无匹配维度时落默认行(self) -> None:
        snap = _snap([("enterprise.rate", "", "3"), ("enterprise.rate", "municipal_water", "2")])
        assert snap.get("enterprise.rate", product_category="rail_transit") == "3"

    def test_角色维度优先于产品类别维度(self) -> None:
        snap = _snap([("some.param", "municipal_water", "A"), ("some.param", "salesperson", "B")])
        got = snap.get("some.param", role_code="salesperson", product_category="municipal_water")
        assert got == "B"

    def test_无任何维度匹配且无默认行_回退注册表默认值(self) -> None:
        snap = _snap([("enterprise.rate", "municipal_water", "2")])
        # 轨交无行、无默认行 → 回退注册表 default_value（3）
        assert snap.fraction("enterprise.rate", product_category="rail_transit") == Fraction(3)


class TestFallback:
    """注册表默认值兜底（种子缺失时的安全网）。"""

    def test_未定义参数按注册表默认值兜底(self) -> None:
        snap = _snap([])
        assert snap.fraction("prepay.rate") == Fraction(10)

    def test_未注册编码抛ValueError_属代码缺陷(self) -> None:
        snap = _snap([])
        with pytest.raises(ValueError):
            snap.fraction("not.registered.code")


class TestSameDayChanges:
    """同日多次变更：仓储 SQL 已按 (effective_date, id) 倒序，快照取先出现者。"""

    def test_同日多次变更取最新一条(self) -> None:
        snap = _snap([("enterprise.rate", "", "3"), ("enterprise.rate", "", "2")])
        assert snap.fraction("enterprise.rate") == Fraction(3)


class TestTypedGetters:
    """类型化取值：Fraction 精确解析、整数、布尔、文本。"""

    def test_fraction精确解析分数式(self) -> None:
        snap = _snap([("salesperson.rate.slope", "salesperson", "4/360")])
        assert snap.fraction("salesperson.rate.slope", role_code="salesperson") == Fraction(1, 90)

    def test_integer(self) -> None:
        snap = _snap([("salesperson.days.boundary", "salesperson", "360")])
        assert snap.integer("salesperson.days.boundary", role_code="salesperson") == 360

    def test_text返回枚举原文(self) -> None:
        snap = _snap([("payment.weight.mode", "", "FULL")])
        assert snap.text("payment.weight.mode") == "FULL"

    def test_boolean(self) -> None:
        snap = _snap([("some.flag", "", "1")])
        assert snap.boolean("some.flag") is True
        assert snap.boolean("some.flag") is not False


class TestImmutability:
    """快照冻结：解析结果不得被调用方改写（核算期间一致性）。"""

    def test_字段不可赋值(self) -> None:
        snap = _snap([])
        with pytest.raises(FrozenInstanceError):
            snap.biz_date = date(2026, 1, 1)  # type: ignore[misc]