feat: add source selectors and cooldown memo

tests/unit/test_sources.py

@@ -0,0 +1,58 @@
+"""sources.py 选源策略与冷却备忘测试(蓝本 CHS app/providers/selector.py:20,36)。"""
+
+from polygateway.sources import LeastInflightSelector, RoundRobinSelector, SourceCooldownMemo
+from polygateway.types import SourceConfig, SourceStats
+
+
+def _src(name):
+    return SourceConfig(
+        name=name, provider="openai", base_url="https://gw.example/v1",
+        api_key="sk", model="m", timeout_s=10.0,
+    )
+
+
+class TestRoundRobin:
+    def test_rotation_advances_each_call(self):
+        sources = [_src("a"), _src("b"), _src("c")]
+        sel = RoundRobinSelector()
+        orders = [tuple(s.name for s in sel.order(sources, {})) for _ in range(4)]
+        assert orders == [("a", "b", "c"), ("b", "c", "a"), ("c", "a", "b"), ("a", "b", "c")]
+
+    def test_single_source_stable(self):
+        sources = [_src("only")]
+        sel = RoundRobinSelector()
+        assert [s.name for s in sel.order(sources, {})] == ["only"]
+        assert [s.name for s in sel.order(sources, {})] == ["only"]
+
+
+class TestLeastInflight:
+    def test_orders_by_inflight_ascending(self):
+        sources = [_src("a"), _src("b"), _src("c")]
+        stats = {"a": SourceStats(5, 0, 0), "b": SourceStats(1, 0, 0), "c": SourceStats(3, 0, 0)}
+        sel = LeastInflightSelector()
+        assert [s.name for s in sel.order(sources, stats)] == ["b", "c", "a"]
+
+    def test_stable_on_ties(self):
+        sources = [_src("a"), _src("b")]
+        stats = {"a": SourceStats(2, 0, 0), "b": SourceStats(2, 0, 0)}
+        assert [s.name for s in LeastInflightSelector().order(sources, stats)] == ["a", "b"]
+
+
+class TestCooldownMemo:
+    def test_active_until_expiry(self):
+        t = {"now": 100.0}
+        memo = SourceCooldownMemo(now=lambda: t["now"])
+        assert not memo.active("a")
+        memo.set_until("a", 130.0)
+        assert memo.active("a")
+        assert memo.remaining("a") == 30.0
+        t["now"] = 131.0
+        assert not memo.active("a")
+        assert memo.remaining("a") == 0.0
+
+    def test_extend_after_wait_hint(self):
+        t = {"now": 0.0}
+        memo = SourceCooldownMemo(now=lambda: t["now"])
+        memo.set_until("a", 10.0)
+        memo.set_until("a", 5.0)  # 更早的截止不回退已有备忘
+        assert memo.remaining("a") == 10.0