feat(课堂看板): 标出谁在线、谁今天没上过线，请假框里没上线的人分在前面一堆

机房有两人共用一台电脑的，同桌只有一个登着，只看「此刻在不在线」会把旁边的人
当成没来。所以每次记在线时按天再记一笔「今天最后一次上线」：
- 看板「在线」列（原「在写」）：开着题的照旧写题号，其余写 在线 / N 分钟前在 / 今天没上线
- 还没交过的人里，今天没上过线的排最前
- 请假框分「今天没上线」「今天上过线」两堆，前一堆可以一键全勾上

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/src/auth/presence.ts

@@ -1,6 +1,7 @@
 import type { ChainableCommander } from "ioredis"
 
 import { redis } from "../redis"
+import { calendarDay } from "../time"
 
 /**
  * 「谁现在在线」。member = userId，score = 最后一次活动的毫秒时间戳。
@@ -18,9 +19,24 @@ const PRESENCE_KEY = "online-users"
  */
 const ONLINE_WINDOW_MS = 5 * 60 * 1000
 
+/**
+ * 「今天谁上过线、最后一次是几点」，一天一个 key，同样是 userId → 毫秒时间戳。
+ *
+ * 课堂看板拿它判断谁今天没来：机房有两人共用一台电脑的，同一时刻只有一个人登着，
+ * 只看「此刻在不在线」会把坐在旁边的同桌当成没来。上过线的人不管现在登没登着都算来过。
+ * 上面那张会被修剪到最近 5 分钟，留不住这个，所以单记一张，放两天自己过期。
+ */
+const seenTodayKey = (day: string) => `online-users:${day}`
+const SEEN_TODAY_TTL_SECONDS = 2 * 24 * 60 * 60
+
 /** 记一笔活动。传 pipeline 而不是自己发命令：调用点都在热路径上 */
 export function markOnline(pipeline: ChainableCommander, userId: number) {
-  pipeline.zadd(PRESENCE_KEY, Date.now(), String(userId))
+  const now = Date.now()
+  const seenKey = seenTodayKey(calendarDay(now))
+  pipeline
+    .zadd(PRESENCE_KEY, now, String(userId))
+    .zadd(seenKey, now, String(userId))
+    .expire(seenKey, SEEN_TODAY_TTL_SECONDS)
 }
 
 /**
@@ -51,3 +67,21 @@ export async function isUserOnline(userId: number) {
   const score = await redis.zscore(PRESENCE_KEY, String(userId))
   return score !== null && Number(score) >= Date.now() - ONLINE_WINDOW_MS
 }
+
+/**
+ * 这批人今天最后一次上线的时刻（毫秒），今天没上过线的不在结果里。
+ * `online` 和 onlineUserIds 同一个窗口
+ */
+export async function seenToday(userIds: number[]) {
+  const seen = new Map<number, { at: number; online: boolean }>()
+  if (!userIds.length) return seen
+  const scores = await redis.zmscore(seenTodayKey(calendarDay()), ...userIds.map(String))
+  const cutoff = Date.now() - ONLINE_WINDOW_MS
+  userIds.forEach((userId, i) => {
+    const score = scores[i]
+    if (score === null || score === undefined) return
+    const at = Number(score)
+    seen.set(userId, { at, online: at >= cutoff })
+  })
+  return seen
+}

apps/api/src/routes/classroom.ts

@@ -17,6 +17,7 @@ import { and, asc, desc, eq, gte, inArray, isNotNull, isNull, lt, sql } from "dr
 import { Hono } from "hono"
 
 import { requireAuth, requireTeacher, type AppEnv } from "../auth/middleware"
+import { seenToday } from "../auth/presence"
 import { getLoginWindow } from "../auth/session"
 import { presenceOf } from "../collab/state"
 import { db, schema } from "../db"
@@ -568,7 +569,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
   // 「来了几次」代码和流程图合起来数：那天只画了流程图的也算来过，和 recentDays 同一个口径
   const recentActivity = activityRows({ since: windowStart, users: userIds })
   const localDay = sql<string>`to_char(${localTime(recentActivity.createTime)}, 'YYYY-MM-DD')`
-  const [cells, lastSubmits, lastDrawn, attendance, drawn, latests] = await Promise.all([
+  const [cells, lastSubmits, lastDrawn, attendance, drawn, latests, seen] = await Promise.all([
     ids.length && userIds.length
       ? db
           .select({
@@ -694,6 +695,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
             desc(schema.submission.createTime),
           )
       : [],
+    seenToday(userIds),
   ])
   const latestByKey = new Map(latests.map((row) => [`${row.userId}:${row.problemId}`, row]))
   const cellByKey = new Map(cells.map((row) => [`${row.userId}:${row.problemId}`, row]))
@@ -757,6 +759,10 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
           drawnToday: drawnTodayUsers.has(student.userId),
           recentAttended: attendedByUser.get(student.userId) ?? 0,
           editing: presenceOf(student.userId)?.problemId ?? null,
+          online: seen.get(student.userId)?.online ?? false,
+          seenAt: seen.has(student.userId)
+            ? new Date(seen.get(student.userId)!.at).toISOString()
+            : null,
         }) satisfies ClassBoardStudent,
     ),
     recentLessons: recentDays.length,