"""CacheMW 与缓存 key 公式测试(ARCH §7.5: 防毒化 key、命中重建、静默降级)。"""

import dataclasses
import hashlib
import json

import pytest

from polygateway.backends.memory.cache import InMemoryCache
from polygateway.errors import ResultInvalidError, TransientError
from polygateway.middleware.cache import CacheMW, build_cache_key, digest_messages
from polygateway.middleware.telemetry import TelemetryEmitter
from polygateway.types import ChatRequest, LLMResponse, SourceConfig

_MSGS = [{"role": "user", "content": "hi"}]


def _resp(content="cached", **overrides):
    base = {
        "content": content,
        "thinking": "",
        "model": "m",
        "provider": "p",
        "prompt_tokens": 1,
        "completion_tokens": 2,
        "latency_ms": 30,
        "ttft_ms": 5.0,
        "max_inter_token_ms": 2.0,
        "cache_hit": False,
        "call_id": "orig",
        "source_name": "s1",
        "usage_source": "measured",
    }
    base.update(overrides)
    return LLMResponse(**base)


class TestKeyFormula:
    def test_same_request_same_key(self):
        k1 = build_cache_key("m", _MSGS, "proj", None)
        k2 = build_cache_key("m", _MSGS, "proj", None)
        assert k1 == k2 and k1.startswith("pgw:cache:")

    @pytest.mark.parametrize(
        ("a", "b"),
        [
            (("m1", _MSGS, "proj", None), ("m2", _MSGS, "proj", None)),
            (("m", _MSGS, "proj", None), ("m", _MSGS, "tenant2", None)),
            (("m", _MSGS, "proj", None), ("m", _MSGS, "proj", "epoch2")),
            (("m", _MSGS, "proj", "s1"), ("m", _MSGS, "proj", "s2")),
            (("m", _MSGS, "proj", None), ("m", [{"role": "user", "content": "yo"}], "proj", None)),
        ],
    )
    def test_any_dimension_change_changes_key(self, a, b):
        assert build_cache_key(*a) != build_cache_key(*b)

    def test_empty_sampling_keeps_legacy_key(self):
        """空采样参数时键形逐字不变,存量缓存不被全量作废(issue #4 决策 C)。

        golden 值取自加 sampling 维度之前的实现,不得随实现漂移。
        """
        assert build_cache_key("qwen-max", [{"role": "user", "content": "hi"}], "proj", None) == (
            "pgw:cache:c54544e8672f4c91373b4a72716a88497445b440b89445aa5379b356b228f58b"
        )
        assert build_cache_key("qwen-max", [{"role": "user", "content": "hi"}], "proj", "s1") == (
            "pgw:cache:eed9cd9cc06acc0dedf4f337b74e06ed3482afdc30fa2acedd194f6cc1df33bf"
        )

    def test_differing_seed_changes_key(self):
        """issue #4 的直接回归: 5 个 seed 若共用一个 key,标准差会恒为 0。"""
        k1 = build_cache_key("m", _MSGS, "proj", None, sampling={"seed": 1})
        k2 = build_cache_key("m", _MSGS, "proj", None, sampling={"seed": 2})
        assert k1 != k2

    def test_sampling_key_order_irrelevant(self):
        k1 = build_cache_key("m", _MSGS, "proj", None, sampling={"seed": 1, "temperature": 0})
        k2 = build_cache_key("m", _MSGS, "proj", None, sampling={"temperature": 0, "seed": 1})
        assert k1 == k2

    def test_empty_sampling_equals_omitted(self):
        """空 dict 与不传须同键,否则升级后存量缓存全部 miss。"""
        assert build_cache_key("m", _MSGS, "proj", None, sampling={}) == build_cache_key(
            "m", _MSGS, "proj", None
        )

    def test_multimodal_part_digested_not_inlined(self):
        big_b64 = "data:image/png;base64," + "A" * 1_000_000
        messages = [
            {
                "role": "user",
                "content": [
                    {"type": "image_url", "image_url": {"url": big_b64}},
                    {"type": "text", "text": "describe"},
                ],
            }
        ]
        digested = digest_messages(messages)
        payload = json.dumps(digested, ensure_ascii=False)
        assert len(payload) < 500  # 大图不进 canonical_json
        expected = hashlib.sha256(big_b64.encode()).hexdigest()
        assert expected in payload  # 但字节变化仍改变 key
        # 图像字节变化 → key 变
        messages2 = [
            {
                "role": "user",
                "content": [
                    {"type": "image_url", "image_url": {"url": big_b64[:-1] + "B"}},
                    {"type": "text", "text": "describe"},
                ],
            }
        ]
        assert build_cache_key("m", messages, "p", None) != build_cache_key(
            "m", messages2, "p", None
        )


class _Terminal:
    def __init__(self, response):
        self.response = response
        self.calls = 0

    async def __call__(self, request):
        self.calls += 1
        if isinstance(self.response, Exception):
            raise self.response
        return self.response


def _mw(backend, **kwargs):
    defaults = {
        "backend": backend,
        "model_fingerprint": "m",
        "default_namespace": "proj",
        "ttl_s": 3600,
    }
    defaults.update(kwargs)
    return CacheMW(**defaults)


class TestCacheFlow:
    async def test_miss_then_hit_with_fresh_call_id(self):
        backend = InMemoryCache()
        mw = _mw(backend)
        terminal = _Terminal(_resp())
        first = await mw(ChatRequest(messages=_MSGS), terminal)
        assert first.cache_hit is False and terminal.calls == 1
        second = await mw(ChatRequest(messages=_MSGS), terminal)
        assert second.cache_hit is True and second.latency_ms == 0
        assert second.content == "cached"
        assert second.call_id != first.call_id  # 命中生成独立 cache_call_id
        assert terminal.calls == 1  # 未再触达内层

    async def test_differing_sampling_does_not_hit(self):
        """issue #4 的中间件层回归: 逐 rollout 变 seed 必须回源,不得复用响应。"""
        backend = InMemoryCache()
        mw = _mw(backend)
        terminal = _Terminal(_resp())
        await mw(ChatRequest(messages=_MSGS, sampling={"seed": 1}), terminal)
        await mw(ChatRequest(messages=_MSGS, sampling={"seed": 2}), terminal)
        assert terminal.calls == 2  # 两次都回源
        # 同 seed 才命中
        third = await mw(ChatRequest(messages=_MSGS, sampling={"seed": 1}), terminal)
        assert third.cache_hit is True and terminal.calls == 2

    async def test_structured_injection_does_not_pollute_key(self):
        """CacheMW 读 sampling 而非 overlay: 结构化注入不该改变缓存身份。"""
        backend = InMemoryCache()
        mw = _mw(backend)
        terminal = _Terminal(_resp())
        await mw(ChatRequest(messages=_MSGS, sampling={"seed": 1}), terminal)
        polluted = ChatRequest(
            messages=_MSGS,
            sampling={"seed": 1},
            overlay={"seed": 1, "response_format": {"type": "json_object"}},
        )
        assert (await mw(polluted, terminal)).cache_hit is True
        assert terminal.calls == 1

    async def test_per_call_namespace_overrides_default(self):
        backend = InMemoryCache()
        mw = _mw(backend)
        terminal = _Terminal(_resp())
        await mw(ChatRequest(messages=_MSGS, cache_namespace="tenant-a"), terminal)
        # 另一租户不得命中
        await mw(ChatRequest(messages=_MSGS, cache_namespace="tenant-b"), terminal)
        assert terminal.calls == 2

    async def test_failure_not_cached(self):
        backend = InMemoryCache()
        mw = _mw(backend)
        failing = _Terminal(TransientError("boom"))
        with pytest.raises(TransientError):
            await mw(ChatRequest(messages=_MSGS), failing)
        ok = _Terminal(_resp())
        await mw(ChatRequest(messages=_MSGS), ok)
        assert ok.calls == 1  # 失败未被固化,正常回源

    async def test_ttl_expiry(self):
        t = {"now": 0.0}
        backend = InMemoryCache(now=lambda: t["now"])
        mw = _mw(backend, ttl_s=100)
        terminal = _Terminal(_resp())
        await mw(ChatRequest(messages=_MSGS), terminal)
        t["now"] = 101.0
        await mw(ChatRequest(messages=_MSGS), terminal)
        assert terminal.calls == 2


class TestObservabilityFieldsOnHit:
    """issue #3 决策 B1: 命中行原样回放,与 model/prompt_tokens 同一口径。"""

    async def test_fields_replayed_on_hit(self):
        backend = InMemoryCache()
        mw = _mw(backend)
        terminal = _Terminal(
            _resp(cached_prompt_tokens=64, model_reported="MiniMax-Text-01-250321")
        )
        await mw(ChatRequest(messages=_MSGS), terminal)
        hit = await mw(ChatRequest(messages=_MSGS), terminal)
        assert hit.cache_hit is True
        assert hit.cached_prompt_tokens == 64
        assert hit.model_reported == "MiniMax-Text-01-250321"

    async def test_legacy_cache_entry_without_new_keys_rehydrates(self):
        """旧格式条目(无这两个键)必须照常重建为 None,不得抛异常回源。"""
        backend = InMemoryCache()
        mw = _mw(backend)
        key = build_cache_key("m", _MSGS, "proj", None)
        legacy = {
            "content": "legacy",
            "thinking": "",
            "model": "m",
            "provider": "p",
            "prompt_tokens": 1,
            "completion_tokens": 2,
            "latency_ms": 30,
            "ttft_ms": 5.0,
            "max_inter_token_ms": 2.0,
            "cache_hit": False,
            "call_id": "orig",
            "source_name": "s1",
            "cost": None,
            "usage_source": "measured",
        }
        await backend.set(key, json.dumps(legacy), ttl_s=100)
        terminal = _Terminal(_resp())
        hit = await mw(ChatRequest(messages=_MSGS), terminal)
        assert hit.content == "legacy" and terminal.calls == 0  # 真的走了缓存
        assert hit.cached_prompt_tokens is None and hit.model_reported is None


class _BrokenBackend:
    async def get(self, key):
        raise ConnectionError("redis down")

    async def set(self, key, value, ttl_s):
        raise ConnectionError("redis down")


class TestDegradation:
    async def test_backend_failure_degrades_silently(self):
        mw = _mw(_BrokenBackend())
        terminal = _Terminal(_resp())
        resp = await mw(ChatRequest(messages=_MSGS), terminal)
        assert resp.content == "cached" and terminal.calls == 1  # 读写全降级,调用照常

    async def test_corrupt_cache_value_treated_as_miss(self):
        backend = InMemoryCache()
        mw = _mw(backend)
        key = build_cache_key("m", _MSGS, "proj", None)
        await backend.set(key, "{not json", 3600)
        terminal = _Terminal(_resp())
        resp = await mw(ChatRequest(messages=_MSGS), terminal)
        assert terminal.calls == 1 and resp.cache_hit is False


class _FakeStrategy:
    """fake StructuredOutputStrategy(T2 冻结的 Protocol,不依赖 T11)。"""

    def request_overlay(self, schema):
        return {}

    def parse(self, text):
        data = json.loads(text)  # 简化: 直接 json.loads
        if not isinstance(data, dict):
            raise ResultInvalidError("非对象", raw_text=text)
        return data


class _StrictModel:
    """鸭子型 pydantic 模型: model_validate 要求含 answer 键。"""

    @classmethod
    def model_validate(cls, data):
        if "answer" not in data:
            raise ValueError("missing answer")
        return {"validated": data["answer"]}


class TestStructuredRehydration:
    async def test_hit_rebuilds_structured_data(self):
        backend = InMemoryCache()
        mw = _mw(backend, strategy=_FakeStrategy())
        terminal = _Terminal(_resp(content='{"answer": 42}'))
        req = ChatRequest(messages=_MSGS, structured=_StrictModel)
        await mw(req, terminal)
        hit = await mw(req, terminal)
        assert hit.cache_hit is True
        assert hit.structured_data == {"validated": 42}
        assert terminal.calls == 1

    async def test_schema_change_revalidation_failure_falls_back_to_source(self):
        backend = InMemoryCache()
        mw = _mw(backend, strategy=_FakeStrategy())
        terminal = _Terminal(_resp(content='{"other": 1}'))  # 缓存内容不含 answer
        await mw(ChatRequest(messages=_MSGS), terminal)  # 无 structured 写入
        # 换 schema 读: 重校验失败 → 按未命中回源
        again = await mw(ChatRequest(messages=_MSGS, structured=_StrictModel), terminal)
        assert terminal.calls == 2 and again.cache_hit is False

    async def test_structured_data_not_serialized_into_cache(self):
        backend = InMemoryCache()
        mw = _mw(backend, strategy=_FakeStrategy())
        terminal = _Terminal(
            dataclasses.replace(_resp(content='{"answer": 1}'), structured_data={"x": object()})
        )
        await mw(ChatRequest(messages=_MSGS), terminal)  # 不可 JSON 的 structured_data 不阻塞写缓存
        key = build_cache_key("m", _MSGS, "proj", None)
        raw = await backend.get(key)
        assert raw is not None and "structured_data" not in json.loads(raw)


class TestTelemetryCapDoesNotPoisonTheCacheKey:
    """红线之一(issue #12): 遥测截断绝不能改到缓存 key。

    `digest_messages` 对 content 非 list 的消息**原样透传同一个 dict 对象**
    (本文件上方公式测试依赖的也是这份对象),遥测拿到的与算 key 用的是同一份。
    就地截断会让同一组 messages 在遥测前后算出两个不同的 key——全量 miss、
    且没有任何报错。故这里测的是"截断没有就地改掉调用方的对象",不只是
    "截断函数是纯的"。
    """

    class _Rows:
        def __init__(self):
            self.rows = []

        async def record_llm_call(self, **fields):
            self.rows.append(fields)

    async def test_key_is_byte_identical_across_a_capped_emit(self):
        messages = [
            {"role": "user", "content": "合同正文" * 31},
            {"role": "user", "content": [{"type": "text", "text": "标书正文" * 30}]},
        ]
        before = build_cache_key("m", messages, "proj", None)

        rec = self._Rows()
        await TelemetryEmitter(rec, text_cap=8).emit_attempt(
            request=ChatRequest(messages=messages),
            source=SourceConfig(
                name="s1",
                provider="p",
                base_url="https://gw.example/v1",
                api_key="sk",
                model="m",
                timeout_s=10.0,
            ),
            call_id="c",
            latency_ms=1,
            response=_resp(),
            error=None,
        )
        # 截断确实发生了(否则本用例恒真)
        logged = json.loads(rec.rows[0]["messages"])
        assert "(略 116 字)" in logged[0]["content"]
        assert "(略 112 字)" in logged[1]["content"][0]["text"]

        assert build_cache_key("m", messages, "proj", None) == before