feat: 用 SSE 替代 SWR 轮询，实现房间状态实时推送

SSE 断连时自动降级为 2s 轮询，重连后切回 SSE。

src/lib/buildRoomStatus.ts

@@ -0,0 +1,69 @@
+import { getRoomData } from "./store";
+import type { RoomStatus, MatchType } from "@/types";
+
+export async function buildRoomStatus(
+  roomId: string,
+): Promise<RoomStatus | null> {
+  const data = await getRoomData(roomId);
+  if (!data) return null;
+
+  const total = data.restaurants.length;
+  const allFinished =
+    data.users.length > 0 &&
+    data.users.every((u) => (data.swipeCounts[u] ?? 0) >= total);
+
+  let match = data.match;
+  let matchType: MatchType = null;
+  let matchLikes = 0;
+  let runnerUps: { id: string; likes: number }[] = [];
+
+  if (match) {
+    matchType = "unanimous";
+    matchLikes = data.users.length;
+  } else if (allFinished && data.restaurants.length > 0) {
+    const ranked = rankRestaurants(data.likes, data.restaurants);
+    if (ranked[0].likes > 0) {
+      match = ranked[0].id;
+      matchType = "best";
+      matchLikes = ranked[0].likes;
+      runnerUps = ranked.slice(1, 3).filter((r) => r.likes > 0);
+    } else {
+      match = ranked[0].id;
+      matchType = "no_match";
+      matchLikes = 0;
+    }
+  }
+
+  const likeCounts: Record<string, number> = {};
+  for (const [rid, users] of Object.entries(data.likes)) {
+    if (users.length > 0) {
+      likeCounts[rid] = users.length;
+    }
+  }
+
+  return {
+    roomId,
+    userCount: data.users.length,
+    match,
+    matchType,
+    matchLikes,
+    runnerUps,
+    likeCounts,
+    swipeCounts: data.swipeCounts,
+    restaurants: data.restaurants,
+  };
+}
+
+function rankRestaurants(
+  likes: Record<string, string[]>,
+  restaurants: { id: string; rating: number }[],
+): { id: string; likes: number }[] {
+  return restaurants
+    .map((r) => ({
+      id: r.id,
+      likes: likes[r.id]?.length ?? 0,
+      rating: r.rating,
+    }))
+    .sort((a, b) => b.likes - a.likes || b.rating - a.rating)
+    .map(({ id, likes: l }) => ({ id, likes: l }));
+}

src/lib/roomEvents.ts

@@ -0,0 +1,23 @@
+type Listener = () => void;
+
+const listeners = new Map<string, Set<Listener>>();
+
+export function subscribe(roomId: string, listener: Listener): () => void {
+  if (!listeners.has(roomId)) {
+    listeners.set(roomId, new Set());
+  }
+  const set = listeners.get(roomId)!;
+  set.add(listener);
+
+  return () => {
+    set.delete(listener);
+    if (set.size === 0) listeners.delete(roomId);
+  };
+}
+
+export function notify(roomId: string) {
+  const set = listeners.get(roomId);
+  if (set) {
+    for (const fn of set) fn();
+  }
+}