feat(web): Core Refactor Phase A — extract sampling and cache modules; add adaptive TTL + eviction heuristics, Redis PoC, and metrics wiring. Tests added for TTL, eviction, exports, splash-adaptive, card index, and service worker. Docs+roadmap updated.

code/tests/test_sampling_unit.py

@@ -0,0 +1,54 @@
+import os
+from code.web.services import sampling
+from code.web.services import card_index
+
+
+def setup_module(module):  # ensure deterministic env weights
+    os.environ.setdefault("RARITY_W_MYTHIC", "1.2")
+
+
+def test_rarity_diminishing():
+    # Monkeypatch internal index
+    card_index._CARD_INDEX.clear()  # type: ignore
+    theme = "Test Theme"
+    card_index._CARD_INDEX[theme] = [  # type: ignore
+        {"name": "Mythic One", "tags": [theme], "color_identity": "G", "mana_cost": "G", "rarity": "mythic"},
+        {"name": "Mythic Two", "tags": [theme], "color_identity": "G", "mana_cost": "G", "rarity": "mythic"},
+    ]
+    def no_build():
+        return None
+    sampling.maybe_build_index = no_build  # type: ignore
+    cards = sampling.sample_real_cards_for_theme(theme, 2, None, synergies=[theme], commander=None)
+    rarity_weights = [r for c in cards for r in c["reasons"] if r.startswith("rarity_weight_calibrated")]  # type: ignore
+    assert len(rarity_weights) >= 2
+    v1 = float(rarity_weights[0].split(":")[-1])
+    v2 = float(rarity_weights[1].split(":")[-1])
+    assert v1 > v2  # diminishing returns
+
+
+def test_commander_overlap_monotonic_diminishing():
+    cmd_tags = {"A","B","C","D"}
+    synergy_set = {"A","B","C","D","E"}
+    # Build artificial card tag lists with increasing overlaps
+    bonus1 = sampling.commander_overlap_scale(cmd_tags, ["A"], synergy_set)
+    bonus2 = sampling.commander_overlap_scale(cmd_tags, ["A","B"], synergy_set)
+    bonus3 = sampling.commander_overlap_scale(cmd_tags, ["A","B","C"], synergy_set)
+    assert 0 < bonus1 < bonus2 < bonus3
+    # Diminishing increments: delta shrinks
+    assert (bonus2 - bonus1) > 0
+    assert (bonus3 - bonus2) < (bonus2 - bonus1)
+
+
+def test_splash_off_color_penalty_applied():
+    card_index._CARD_INDEX.clear()  # type: ignore
+    theme = "Splash Theme"
+    # Commander W U B R (4 colors)
+    commander = {"name": "CommanderTest", "tags": [theme], "color_identity": "WUBR", "mana_cost": "", "rarity": "mythic"}
+    # Card with single off-color G (W U B R G)
+    splash_card = {"name": "CardSplash", "tags": [theme], "color_identity": "WUBRG", "mana_cost": "G", "rarity": "rare"}
+    card_index._CARD_INDEX[theme] = [commander, splash_card]  # type: ignore
+    sampling.maybe_build_index = lambda: None  # type: ignore
+    cards = sampling.sample_real_cards_for_theme(theme, 2, None, synergies=[theme], commander="CommanderTest")
+    splash = next((c for c in cards if c["name"] == "CardSplash"), None)
+    assert splash is not None
+    assert any(r.startswith("splash_off_color_penalty") for r in splash["reasons"])  # type: ignore