"""middleware/rate_limit.py 请求限流中间件单元测试。"""

from contextlib import asynccontextmanager

import fakeredis.aioredis
from fastapi import FastAPI
from fastapi.testclient import TestClient

import middleware.rate_limit as rate_limit_module
from middleware.rate_limit import rate_limit_middleware


def _make_app():
    @asynccontextmanager
    async def lifespan(app):
        # 在应用运行的事件循环内创建 FakeRedis，避免跨循环绑定问题
        app.state.redis = fakeredis.aioredis.FakeRedis(decode_responses=True)
        yield
        await app.state.redis.aclose()

    app = FastAPI(lifespan=lifespan)

    @app.get("/")
    async def home():
        return {"ok": True}

    app.middleware("http")(rate_limit_middleware)

    return app


def test_rate_limit_disabled_passes(monkeypatch):
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_ENABLED", False)
    with TestClient(_make_app()) as client:
        for _ in range(5):
            r = client.get("/")
            assert r.status_code == 200
            assert r.json()["ok"] is True


async def _fake_sliding_window(redis, current_key, prev_key, window_seconds, window_index, now):
    """fakeredis 不支持 Lua eval，用等价实现打桩滑动窗口计数/加权语义。"""
    cur = await redis.incr(current_key)
    if cur == 1:
        await redis.expire(current_key, window_seconds)
    prev = int(await redis.get(prev_key) or 0)
    elapsed = now - window_index * window_seconds
    f = elapsed / window_seconds
    f = max(0.0, min(1.0, f))
    return prev * (1 - f) + cur


def test_rate_limit_exceeds_returns_business_error(monkeypatch):
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_ENABLED", True)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_LIMIT", 3)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_WINDOW_SECONDS", 60)
    monkeypatch.setattr(rate_limit_module, "sliding_window_incr", _fake_sliding_window)
    with TestClient(_make_app()) as client:
        for _ in range(3):
            r = client.get("/")
            assert r.status_code == 200
            assert r.json()["ok"] is True
        r = client.get("/")
        assert r.status_code == 200
        assert r.json()["code"] == 1
        assert "过于频繁" in r.json()["msg"]


def test_rate_limit_window_accepts_after_reset(monkeypatch):
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_ENABLED", True)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_LIMIT", 2)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_WINDOW_SECONDS", 60)
    monkeypatch.setattr(rate_limit_module, "sliding_window_incr", _fake_sliding_window)
    with TestClient(_make_app()) as client:
        for _ in range(2):
            r = client.get("/")
            assert r.json()["ok"] is True
        r = client.get("/")
        assert r.json()["code"] == 1
        # 同一窗口内持续限流，不会因后续请求解除
        r = client.get("/")
        assert r.json()["code"] == 1


def test_rate_limit_sliding_window_prevents_boundary_burst(monkeypatch):
    """窗口边界处请求数按时间加权，不发生固定窗口的 2× 突发。"""
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_ENABLED", True)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_LIMIT", 3)
    monkeypatch.setattr(rate_limit_module, "RATE_LIMIT_WINDOW_SECONDS", 100)
    monkeypatch.setattr(rate_limit_module, "sliding_window_incr", _fake_sliding_window)

    clock = {"t": 50.0}
    monkeypatch.setattr(rate_limit_module.time, "time", lambda: clock["t"])

    with TestClient(_make_app()) as client:
        # 窗口0（t=50）：2 个请求，配额充足，放行
        for _ in range(2):
            assert client.get("/").json()["ok"] is True
        # 进入窗口1（t=150，f=0.5）：上一窗口 2 个请求加权计入
        clock["t"] = 150.0
        # effective: 2*0.5+1=2 放行；2*0.5+2=3 放行；2*0.5+3=4 > 3 拒绝
        for _ in range(2):
            assert client.get("/").json()["ok"] is True
        r = client.get("/")
        assert r.json()["code"] == 1