Share per-date game cache across dailyArchive users (R1)

judgeDay and hasMissedGameDayBetween re-ran the same listByDate query for
every user in an archive run (U× amplification for the archived date plus
its look-back window). Introduce a memoizing GameDayCache and thread one
instance through the whole runDailyArchive pass so each distinct date is
read from Firestore once. Off-day detection is naturally memoized via the
cached query results. Standalone callers (statsService) keep their prior
behavior via a per-call default cache. No change to judgment results.

src/repositories/gameRepository.ts

@@ -35,3 +35,29 @@ export async function listByDate(date: DateString): Promise<GameWithId[]> {
     .get();
   return snap.docs.map((d) => ({ gameId: d.id, ...(d.data() as Game) }));
 }
+
+/**
+ * 동일 날짜의 `listByDate` 결과를 메모이즈하는 캐시.
+ *
+ * `dailyArchive`처럼 한 번의 run에서 여러 유저를 처리하며 같은 날짜의 `games`를
+ * 반복 조회하는 경로에서, 날짜당 Firestore read를 1회로 줄이기 위해 쓴다.
+ * Promise를 캐싱하므로 동시 호출도 단일 쿼리로 합쳐진다.
+ */
+export interface GameDayCache {
+  listByDate(date: DateString): Promise<GameWithId[]>;
+}
+
+/** 새 `GameDayCache`를 생성한다. 캐시는 인스턴스 수명 동안만 유효하다. */
+export function createGameDayCache(): GameDayCache {
+  const cache = new Map<DateString, Promise<GameWithId[]>>();
+  return {
+    listByDate(date: DateString): Promise<GameWithId[]> {
+      let p = cache.get(date);
+      if (!p) {
+        p = listByDate(date);
+        cache.set(date, p);
+      }
+      return p;
+    },
+  };
+}

src/scheduled/dailyArchive.ts

@@ -9,7 +9,7 @@ import {
   snapshotRankForUser,
 } from "../services/rankSnapshotService";
 import { todayKst } from "../types/dateString";
-import { getGame } from "../repositories/gameRepository";
+import { getGame, createGameDayCache } from "../repositories/gameRepository";
 import { deleteUserVoteGame } from "../repositories/voteRepository";
 import { processGameEndWithGame } from "../services/gameResultService";
 import type { VoteHistoryDoc } from "../types/panit";
@@ -92,6 +92,9 @@ export async function runDailyArchive(
 
     let archived = 0;
     const judgedUids: string[] = [];
+    // 같은 날짜(및 결석 판정용 직전 날짜들)의 games를 유저마다 재조회하지 않도록
+    // run 전체에서 1개의 날짜별 캐시를 공유한다. 날짜당 Firestore read 1회로 수렴.
+    const gameCache = createGameDayCache();
   try {
     const snap = await rtdb.ref("/userVotes").get();
     if (!snap.exists()) {
@@ -136,7 +139,7 @@ export async function runDailyArchive(
         logger.error(`snapshotRank failed uid=${uid} date=${date}`, err);
       }
       try {
-        await judgeDay(uid, date, { data });
+        await judgeDay(uid, date, { data }, gameCache);
       } catch (err) {
         logger.error(`judgeDay failed uid=${uid} date=${date}`, err);
       }

src/services/judgmentService.ts

@@ -1,5 +1,8 @@
 import { logger } from "firebase-functions";
-import { listByDate } from "../repositories/gameRepository";
+import {
+  createGameDayCache,
+  type GameDayCache,
+} from "../repositories/gameRepository";
 import { getRange, setDay } from "../repositories/voteHistoryRepository";
 import {
   applyDailyJudgmentTx,
@@ -26,12 +29,14 @@ import { addDaysKst, tuesdayOf, type DateString } from "../types/dateString";
  */
 export async function hasMissedGameDayBetween(
   lastJudged: DateString,
-  upTo: DateString
+  upTo: DateString,
+  gameCache?: GameDayCache
 ): Promise<boolean> {
+  const fetch = gameCache ?? createGameDayCache();
   const MAX_LOOKBACK = 14;
   let cursor = addDaysKst(upTo, -1);
   for (let i = 0; i < MAX_LOOKBACK && cursor > lastJudged; i++) {
-    const games = await listByDate(cursor);
+    const games = await fetch.listByDate(cursor);
     const completed = games.filter((g) => g.status === "completed").length;
     if (thresholdsFor(completed) !== "skip") return true;
     cursor = addDaysKst(cursor, -1);
@@ -53,9 +58,11 @@ export async function hasMissedGameDayBetween(
 export async function judgeDay(
   uid: string,
   date: DateString,
-  voteDoc: VoteHistoryDoc
+  voteDoc: VoteHistoryDoc,
+  gameCache?: GameDayCache
 ): Promise<void> {
-  const games = await listByDate(date);
+  const fetch = gameCache ?? createGameDayCache();
+  const games = await fetch.listByDate(date);
   const completedCount = games.filter((g) => g.status === "completed").length;
   const threshold = thresholdsFor(completedCount);
 
@@ -76,7 +83,7 @@ export async function judgeDay(
   const streakBrokenIn =
     lastJudgedPre != null &&
     lastJudgedPre < addDaysKst(date, -1) &&
-    (await hasMissedGameDayBetween(lastJudgedPre, date));
+    (await hasMissedGameDayBetween(lastJudgedPre, date, fetch));
 
   const tx = await applyDailyJudgmentTx(uid, date, {
     judgment,