feat(布置作业): 能按知识点点选题目；一个班一天能布置几节课；数据统计认老师布置的课；后台能管布置过的课

- 课堂看板「选题」弹框：左边知识点（加必会题），右边搜题号/题名、点选，按点的先后排；
  只列这次作业的语言能交的题（/problems、/problem-tags 加 ?language=）
- 一天多节课：0040 拿掉 class_lesson (class_name, day) 唯一约束，每次布置一行；
  看板「改」只改当前一节，加「新的一节」；这一节布置超过 100 分钟时先问这节课做哪几道题。
  不带 lessonId/newLesson 的老请求照旧改今天最后一节
- 数据统计「一行一节课」：布置过的课以布置为准（题目和顺序照布置、做完按全班算、标「布置」），
  这些提交不再参与推断切段，也不算零散；详情页「做完」注明是这一天/这节课/这段时间
- 后台「课堂作业」：一节一行，改（班级/日子/时刻/语言/题目）、看统计、删除、补一节；
  看板加「布置过的课」入口。题号校验和「做完」口径抽到 services/lesson.ts，三处共用

⚠️ 机房站点要和服务器一起升级：旧代码布置时 ON CONFLICT (class_name, day) 找不到约束会报错

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

apps/web/src/oj/api.ts

@@ -260,12 +260,16 @@ export function getClassLesson(className?: string) {
   return api.get<ClassLesson>('classroom/lesson', { params: { className } })
 }
 
-/** 给这个班布置今天的题，空数组 = 清掉 */
-export function setClassLesson(className: string, problemDisplayIds: string[], language: LessonLanguage | null) {
+/**
+ * 给这个班布置今天的一节课，空数组 = 清掉这一节。`lessonId` 为 null 是今天新开一节
+ * （一个班一天可以上几节内容不同的课），否则改那一节
+ */
+export function setClassLesson(className: string, problemDisplayIds: string[], language: LessonLanguage | null, lessonId: number | null) {
   return api.put<null>('classroom/lesson', {
     className,
     problemDisplayIds,
     language,
+    ...(lessonId === null ? { newLesson: true } : { lessonId }),
   } satisfies ClassLessonRequest)
 }
 

apps/web/src/oj/classroom/board.vue

@@ -15,6 +15,8 @@ import { parseTime } from 'utils/functions'
 import type { ClassBoard, ClassBoardCell, ClassBoardProblem, ClassBoardStudent } from 'utils/types'
 import ExplainModal, { type ExplainPerson } from './components/ExplainModal.vue'
 import LeaveModal from './components/LeaveModal.vue'
+import AdminLink from 'shared/components/AdminLink.vue'
+import { useBreakpoints } from 'shared/composables/breakpoints'
 import LessonForm from './components/LessonForm.vue'
 import TrailPanel from './components/TrailPanel.vue'
 import { errorKind, type ErrorKind } from 'utils/errorKind'
@@ -41,6 +43,7 @@ const collabStore = useCollabStore()
 const message = useMessage()
 const theme = useThemeVars()
 const tone = useTone()
+const { isDesktop } = useBreakpoints()
 const router = useRouter()
 const route = useRoute()
 const { help, peek } = useTeacherHelp()
@@ -111,13 +114,34 @@ onUnmounted(pause)
 
 // ---------- 这节课的题：上课时当场填 ----------
 
-const editing = ref(false)
+/** 顶上那条布置框开着没有：edit = 改这一节，new = 今天再开一节 */
+const editing = ref<false | 'edit' | 'new'>(false)
 
-/** 还没有题（没布置、今天也推断不出来）：填题号的框就是这页最大的东西 */
-const needLesson = computed(() => !!board.value?.className && !board.value.problems.length)
+/**
+ * 一个班一天可以上几节内容不同的课。打开看板（或换到这个班）时，这一节已经布置了这么久，
+ * 多半是上一节课的 —— 先问这节课做哪几道题，底下能点回去接着看上一节。
+ * 只在第一次看到这一节时判一次：老师一直开着看板时，15 秒一刷不会把表突然换掉
+ */
+const STALE_LESSON_MINUTES = 100
+const staleLessonId = ref<number | null>(null)
+const seenLessonIds = new Set<number>()
+watch(
+  () => board.value?.lessonId ?? null,
+  (lessonId) => {
+    if (lessonId === null || seenLessonIds.has(lessonId)) return
+    seenLessonIds.add(lessonId)
+    const assignedAt = board.value?.assignedAt
+    if (assignedAt && Date.now() - Date.parse(assignedAt) > STALE_LESSON_MINUTES * 60_000) staleLessonId.value = lessonId
+  },
+)
+const staleLesson = computed(() => board.value?.lessonId != null && board.value.lessonId === staleLessonId.value)
+
+/** 还没有题（没布置、今天也推断不出来），或者布置的是上一节课的：填题号的框就是这页最大的东西 */
+const needLesson = computed(() => !!board.value?.className && (!board.value.problems.length || staleLesson.value))
 
 async function lessonSaved() {
   editing.value = false
+  staleLessonId.value = null
   selectedId.value = null
   await load()
 }
@@ -434,28 +458,36 @@ function lastText(student: ClassBoardStudent) {
         v-if="editing && board && className"
         :board="board"
         :class-name="className"
+        :lesson-id="editing === 'edit' ? board.lessonId : null"
         variant="inline"
         class="lesson-edit"
         @saved="lessonSaved"
         @cancel="editing = false"
       />
-      <div v-else-if="board?.problems.length" class="lesson">
+      <div v-else-if="board?.problems.length && !needLesson" class="lesson">
         <span class="lesson-label">{{ board.source === 'teacher' ? '这节课' : '今天在做' }}</span>
         <span v-if="board.language" class="chip lang">{{ LANGUAGE_SHOW_VALUE[board.language] }}</span>
         <span v-for="problem in board.problems" :key="problem.problemId" class="chip">
           {{ problem.problemDisplayId }}
         </span>
         <span v-if="board.assignedAt" class="assigned"> {{ parseTime(board.assignedAt, 'HH:mm') }} {{ board.assignedBy }} 布置 </span>
-        <n-button text type="primary" class="edit" @click="editing = true">
+        <n-button text type="primary" class="edit" @click="editing = 'edit'">
           <template #icon><Icon icon="ph:pencil-simple" /></template>
           {{ board.source === 'teacher' ? '改' : '布置' }}
         </n-button>
+        <!-- 一天上几节内容不同的课：下一节另开一份，别把上一节的改掉（统计按布置切课） -->
+        <n-button v-if="board.source === 'teacher'" text type="primary" class="edit" @click="editing = 'new'">
+          <template #icon><Icon icon="ph:plus" /></template>
+          新的一节
+        </n-button>
       </div>
 
       <div class="spacer"></div>
       <n-button v-if="board?.className" :type="leaveStudents.length ? 'warning' : 'default'" :secondary="!!leaveStudents.length" @click="leaveDialog = true">
         {{ leaveStudents.length ? `请假 ${leaveStudents.length} 人` : '请假' }}
       </n-button>
+      <!-- 布置过的每一节课：改错了班、隔天想起来补，去后台 -->
+      <AdminLink v-if="isDesktop" :to="{ name: 'admin lesson list', query: className ? { className } : {} }">布置过的课</AdminLink>
       <!-- 看板只管今天；以前几节课的、任意时间段的去统计（带上这个班） -->
       <n-button @click="router.push({ name: 'statistics', query: className ? { className } : {} })"> 回头看 → </n-button>
     </div>
@@ -466,7 +498,12 @@ function lastText(student: ClassBoardStudent) {
       <!-- 刚上课还没有题：填题号的框是这页最大的东西 -->
       <section v-if="needLesson" class="start">
         <div class="start-title">这节课做哪几道题？</div>
-        <LessonForm v-if="className" :board="board" :class-name="className" variant="start" class="start-row" @saved="lessonSaved" />
+        <LessonForm v-if="className" :board="board" :class-name="className" :lesson-id="null" variant="start" class="start-row" @saved="lessonSaved" />
+        <div v-if="staleLesson" class="earlier">
+          <span>上一节 {{ board.assignedAt ? parseTime(board.assignedAt, 'HH:mm') : '' }} {{ board.assignedBy }} 布置</span>
+          <span v-for="problem in board.problems" :key="problem.problemId" class="chip">{{ problem.problemDisplayId }}</span>
+          <n-button text type="primary" class="edit" @click="staleLessonId = null">接着看这一节</n-button>
+        </div>
       </section>
 
       <template v-else>
@@ -557,7 +594,8 @@ function lastText(student: ClassBoardStudent) {
         </section>
       </template>
 
-      <div class="table-wrap">
+      <!-- 上一节的表先不摆：一整列都是上一节的题，和上面「这节课做哪几道题」对不上 -->
+      <div v-if="!staleLesson" class="table-wrap">
         <table class="grid">
           <thead>
             <tr>
@@ -815,6 +853,15 @@ function lastText(student: ClassBoardStudent) {
   gap: 10px;
 }
 
+.earlier {
+  display: flex;
+  align-items: center;
+  flex-wrap: wrap;
+  gap: 6px;
+  font-size: 14px;
+  color: v-bind('theme.textColor3');
+}
+
 /* ---------- 题卡片 ---------- */
 
 .cards {

apps/web/src/oj/classroom/components/LessonForm.vue

@@ -4,16 +4,21 @@ import { setClassLesson } from 'oj/api'
 import { errorMessage } from 'utils/api'
 import { LANGUAGE_SHOW_VALUE } from 'utils/constants'
 import type { ClassBoard } from 'utils/types'
+import { Icon } from '@iconify/vue'
+import ProblemPicker from './ProblemPicker.vue'
 
 /**
  * 看板上布置「这节课的题」：题号是上课时当场填的。两种样子 ——
- * - `inline`：顶上一行里点「改 / 布置」展开的那一小条；
+ * - `inline`：顶上一行里点「改 / 新的一节 / 布置」展开的那一小条；
  * - `start`：刚上课还没有题时，这页最大的那个框。
+ *
+ * 一个班一天可以上几节内容不同的课：`lessonId` 是要改的那一节，null = 今天新开一节
  */
 const props = defineProps<{
   board: ClassBoard
   className: string
   variant: 'inline' | 'start'
+  lessonId: number | null
 }>()
 const emit = defineEmits<{ saved: []; cancel: [] }>()
 const message = useMessage()
@@ -31,27 +36,35 @@ const languageOptions = LESSON_LANGUAGES.map((value) => ({
 const lessonInput = ref('')
 const saving = ref(false)
 
+/** 改的是老师布置的这一节：框里是它的题；新开一节是空的 */
+const editingPlanned = computed(() => props.lessonId !== null && props.lessonId === props.board.lessonId)
+
 function resetLessonInput() {
-  lessonInput.value = props.board.source === 'teacher' ? props.board.problems.map((problem) => problem.problemDisplayId).join(' ') : ''
-  lessonLanguage.value = props.board.language ?? props.board.lastLanguage ?? 'Python'
+  lessonInput.value = editingPlanned.value ? props.board.problems.map((problem) => problem.problemDisplayId).join(' ') : ''
+  lessonLanguage.value = (editingPlanned.value ? props.board.language : null) ?? props.board.lastLanguage ?? 'Python'
 }
 
 resetLessonInput()
 // 推断出来的题也带进框里，老师多半只是确认一下
-if (props.variant === 'inline' && !lessonInput.value && props.board.problems.length) {
+if (props.variant === 'inline' && props.board.source === 'inferred' && !lessonInput.value && props.board.problems.length) {
   lessonInput.value = props.board.problems.map((problem) => problem.problemDisplayId).join(' ')
 }
-// 换了班要把输入框换成那个班今天布置的题、布置时选的语言（15 秒一次的刷新不动它们）。
-// 必须写成两个来源：一个 getter 返回数组的话，每次刷新整个 board 换新，数组也是新的，
+// 换了班、换了一节要把输入框换成那一节的题、布置时选的语言（15 秒一次的刷新不动它们）。
+// 必须写成几个单值来源：一个 getter 返回数组的话，每次刷新整个 board 换新，数组也是新的，
 // 回调次次都跑，老师打到一半的题号每 15 秒被清一次
-watch([() => props.board.className, () => props.board.source], resetLessonInput)
+watch([() => props.board.className, () => props.board.source, () => props.lessonId], resetLessonInput)
+
+function inputIds() {
+  return lessonInput.value.split(/[\s,，、;；]+/).filter(Boolean)
+}
 
 async function saveLesson() {
-  const ids = lessonInput.value.split(/[\s,，、;；]+/).filter(Boolean)
+  const ids = inputIds()
   saving.value = true
   try {
-    await setClassLesson(props.className, ids, ids.length ? lessonLanguage.value : null)
+    await setClassLesson(props.className, ids, ids.length ? lessonLanguage.value : null, props.lessonId)
     message.success(ids.length ? '已布置，学生首页会显示这几道题' : '已清掉')
+    picking.value = false
     emit('saved')
   } catch (error) {
     message.error(errorMessage(error))
@@ -59,19 +72,43 @@ async function saveLesson() {
     saving.value = false
   }
 }
+
+// ---- 选题弹框：不用记题号，按知识点挑。框里已经敲了的题号带进去，题名能对上的带上题名 ----
+const picking = ref(false)
+const pickerInitial = ref<{ id: string; title?: string }[]>([])
+function openPicker() {
+  const titles = new Map(props.board.problems.map((p) => [p.problemDisplayId.toLowerCase(), p.title]))
+  pickerInitial.value = inputIds().map((id) => ({ id, title: titles.get(id.toLowerCase()) }))
+  picking.value = true
+}
+function pickerConfirm(ids: string[]) {
+  lessonInput.value = ids.join(' ')
+  saveLesson()
+}
 </script>
 
 <template>
   <div v-if="variant === 'inline'">
     <n-select v-model:value="lessonLanguage" :options="languageOptions" aria-label="用什么语言做" class="lang-select" />
     <n-input v-model:value="lessonInput" placeholder="这节课的题号，用空格隔开" clearable autofocus @keyup.enter="saveLesson" />
+    <n-button @click="openPicker">
+      <template #icon><Icon icon="ph:list-checks" /></template>
+      选题
+    </n-button>
     <n-button type="primary" :loading="saving" @click="saveLesson">布置</n-button>
     <n-button @click="emit('cancel')">取消</n-button>
+    <!-- 弹层挂在 body 下，放在根节点里面：两个根会让看板传进来的 class 落空 -->
+    <ProblemPicker v-model:show="picking" v-model:language="lessonLanguage" :initial="pickerInitial" :saving="saving" @confirm="pickerConfirm" />
   </div>
   <div v-else>
     <n-select v-model:value="lessonLanguage" :options="languageOptions" aria-label="用什么语言做" size="large" class="lang-select" />
     <n-input v-model:value="lessonInput" size="large" placeholder="输入题号，用空格隔开" class="start-input" @keyup.enter="saveLesson" />
+    <n-button size="large" @click="openPicker">
+      <template #icon><Icon icon="ph:list-checks" /></template>
+      选题
+    </n-button>
     <n-button type="primary" size="large" :loading="saving" @click="saveLesson">布置</n-button>
+    <ProblemPicker v-model:show="picking" v-model:language="lessonLanguage" :initial="pickerInitial" :saving="saving" @confirm="pickerConfirm" />
   </div>
 </template>
 

apps/web/src/oj/classroom/components/ProblemPicker.vue

@@ -0,0 +1,522 @@
+<script setup lang="ts">
+import { Icon } from '@iconify/vue'
+import type { LessonLanguage, Tag } from '@oj2/contract'
+import { useThemeVars } from 'naive-ui'
+import { getProblemList, getProblemTagList } from 'shared/api'
+import { useTone } from 'shared/composables/tone'
+import { LANGUAGE_SHOW_VALUE } from 'utils/constants'
+import type { ProblemRow } from 'utils/types'
+import ProblemTypeTag from 'oj/problem/components/ProblemTypeTag.vue'
+
+/**
+ * 看板布置作业的「选题」弹框：左边按知识点分，右边勾题，底下按勾的先后排成这节课的顺序。
+ * 只列能用这次作业的语言交的题（左栏题数也按这个语言数），不用再一个个记题号。
+ * 点「布置」直接存，和在输入框里敲题号回车是一回事
+ */
+const props = defineProps<{
+  /** 打开时已经在框里的题（题号 + 知道的话带上题名） */
+  initial: { id: string; title?: string }[]
+  saving: boolean
+  /** pick = 只把选好的题交回去（后台改一节时用），不直接布置 */
+  mode?: 'assign' | 'pick'
+}>()
+const show = defineModel<boolean>('show', { required: true })
+const language = defineModel<LessonLanguage>('language', { required: true })
+const emit = defineEmits<{ confirm: [ids: string[]] }>()
+
+const theme = useThemeVars()
+const tone = useTone()
+
+const LESSON_LANGUAGES: LessonLanguage[] = ['Python', 'C', 'C++', 'SQL']
+const languageOptions = LESSON_LANGUAGES.map((value) => ({ label: LANGUAGE_SHOW_VALUE[value], value }))
+const SORTS = [
+  { label: '最新出的', value: '' },
+  { label: '做过的人最多', value: '-submission_number' },
+]
+const PAGE_SIZE = 100
+/** 老师挑的题，必会题是按课堂用得最多挑出来的，放在知识点前面 */
+const MUST_DO = '必会题'
+
+const tags = ref<Tag[]>([])
+const tag = ref('')
+const keyword = ref('')
+const sort = ref('')
+const page = ref(1)
+const rows = ref<ProblemRow[]>([])
+const total = ref(0)
+const loading = ref(false)
+
+/** 勾的先后就是这节课的顺序 */
+const picked = ref<{ id: string; title?: string }[]>([])
+const pickedIndex = computed(() => new Map(picked.value.map((p, i) => [p.id.toLowerCase(), i])))
+
+const knowledge = computed(() => tags.value.filter((t) => t.category === 'knowledge').sort((a, b) => b.problemCount - a.problemCount))
+const mustDo = computed(() => tags.value.find((t) => t.name === MUST_DO) ?? null)
+const allCount = ref(0)
+
+async function loadTags() {
+  const list = await getProblemTagList(language.value)
+  tags.value = list
+  // 换了语言，原来选的知识点在这个语言下可能一道都没有
+  if (tag.value && !list.some((t) => t.name === tag.value)) tag.value = ''
+}
+
+let seq = 0
+async function loadRows() {
+  const mine = ++seq
+  loading.value = true
+  try {
+    const res = await getProblemList((page.value - 1) * PAGE_SIZE, PAGE_SIZE, {
+      tag: tag.value,
+      keyword: keyword.value.trim(),
+      sort: sort.value,
+      language: language.value,
+    })
+    if (mine !== seq) return
+    rows.value = res.results
+    total.value = res.total
+    if (!tag.value && !keyword.value.trim()) allCount.value = res.total
+  } finally {
+    if (mine === seq) loading.value = false
+  }
+}
+
+const listRef = ref<HTMLElement | null>(null)
+function reload() {
+  page.value = 1
+  listRef.value?.scrollTo({ top: 0 })
+  loadRows()
+}
+
+watch(show, (open) => {
+  if (!open) return
+  picked.value = props.initial.map((p) => ({ ...p }))
+  keyword.value = ''
+  loadTags()
+  reload()
+})
+watch(language, () => {
+  if (!show.value) return
+  loadTags()
+  reload()
+})
+// 搜题号多半是记得那道题、不知道它在哪个知识点下，所以搜的是整个题库；点了知识点就不再搜
+function pickTag(name: string) {
+  keyword.value = ''
+  tag.value = name
+}
+watch(keyword, (text) => {
+  if (text.trim()) tag.value = ''
+})
+watch([tag, sort], reload)
+watchDebounced(keyword, reload, { debounce: 300 })
+watch(page, () => {
+  listRef.value?.scrollTo({ top: 0 })
+  loadRows()
+})
+
+function toggle(row: ProblemRow) {
+  const key = row._id.toLowerCase()
+  if (pickedIndex.value.has(key)) picked.value = picked.value.filter((p) => p.id.toLowerCase() !== key)
+  else picked.value = [...picked.value, { id: row._id, title: row.title }]
+}
+
+function remove(id: string) {
+  picked.value = picked.value.filter((p) => p.id !== id)
+}
+
+const DIFFICULTY_TONE = { 简单: 'success', 中等: 'warning', 困难: 'error' } as const
+function difficultyStyle(row: ProblemRow) {
+  if (!row.difficulty) return {}
+  const t = tone(DIFFICULTY_TONE[row.difficulty])
+  return { color: t.color, background: t.background }
+}
+
+// n-modal 把内容挂到 body 下，<style> 里的 v-bind() 传不进去，颜色走根节点的内联变量
+const vars = computed(() => ({
+  // 宽度也写在这里：n-modal 的 preset card 上 scoped 的 class 宽度不生效
+  width: 'min(1040px, calc(100vw - 32px))',
+  '--text2': theme.value.textColor2,
+  '--text3': theme.value.textColor3,
+  '--divider': theme.value.dividerColor,
+  '--hover': theme.value.hoverColor,
+  '--action': theme.value.actionColor,
+  '--primary': theme.value.primaryColor,
+  '--on-bg': tone('success').background,
+  '--on-text': tone('success').color,
+}))
+</script>
+
+<template>
+  <n-modal v-model:show="show" preset="card" :style="vars" :bordered="false" :auto-focus="false" title="选题">
+    <template #header-extra>
+      <div class="head-extra">
+        <span class="muted">用</span>
+        <n-select v-model:value="language" :options="languageOptions" aria-label="用什么语言做" size="small" class="lang" />
+        <span class="muted">做</span>
+      </div>
+    </template>
+
+    <div class="body">
+      <nav class="tags">
+        <button class="tag" :class="{ on: tag === '' && !keyword.trim() }" @click="pickTag('')">
+          <span>全部</span><span class="count">{{ allCount || '' }}</span>
+        </button>
+        <button v-if="mustDo" class="tag" :class="{ on: tag === MUST_DO }" @click="pickTag(MUST_DO)">
+          <span>{{ MUST_DO }}</span
+          ><span class="count">{{ mustDo.problemCount }}</span>
+        </button>
+        <div class="tag-head">知识点</div>
+        <button v-for="t in knowledge" :key="t.id" class="tag" :class="{ on: tag === t.name }" @click="pickTag(t.name)">
+          <span>{{ t.name }}</span
+          ><span class="count">{{ t.problemCount }}</span>
+        </button>
+      </nav>
+
+      <section class="main">
+        <div class="filters">
+          <n-input v-model:value="keyword" placeholder="搜题号或题目名" clearable class="search">
+            <template #prefix><Icon icon="ph:magnifying-glass" /></template>
+          </n-input>
+          <n-select v-model:value="sort" :options="SORTS" class="sort" />
+        </div>
+
+        <div ref="listRef" class="list">
+          <n-spin :show="loading" class="spin">
+            <n-empty v-if="!loading && !rows.length" :description="`没有能用 ${LANGUAGE_SHOW_VALUE[language]} 做的题`" class="empty" />
+            <button v-for="row in rows" :key="row.id" type="button" class="row" :class="{ on: pickedIndex.has(row._id.toLowerCase()) }" @click="toggle(row)">
+              <span class="check">
+                <template v-if="pickedIndex.has(row._id.toLowerCase())">{{ pickedIndex.get(row._id.toLowerCase())! + 1 }}</template>
+              </span>
+              <span class="pid">{{ row._id }}</span>
+              <span class="title">
+                <span class="title-text">{{ row.title }}</span>
+                <ProblemTypeTag v-if="row.allowFlowchart" kind="flowchart" />
+                <ProblemTypeTag v-if="row.hasAstRules" kind="ast" />
+              </span>
+              <span class="diff" :style="difficultyStyle(row)">{{ row.difficulty ?? '' }}</span>
+              <span class="people">{{ row.solvedUsers }}/{{ row.triedUsers }}</span>
+            </button>
+          </n-spin>
+        </div>
+        <div v-if="total > PAGE_SIZE" class="pager">
+          <n-pagination v-model:page="page" :page-size="PAGE_SIZE" :item-count="total" simple />
+        </div>
+      </section>
+    </div>
+
+    <template #footer>
+      <div class="foot">
+        <div class="picked">
+          <span v-if="!picked.length" class="muted">还没选题</span>
+          <span v-for="(p, i) in picked" :key="p.id" class="pick">
+            <b>{{ i + 1 }}</b>
+            <span>{{ p.id }}</span>
+            <span v-if="p.title" class="pick-title">{{ p.title }}</span>
+            <button type="button" class="x" :aria-label="`去掉 ${p.id}`" @click="remove(p.id)"><Icon icon="ph:x-bold" /></button>
+          </span>
+        </div>
+        <n-button @click="show = false">取消</n-button>
+        <n-button
+          type="primary"
+          :disabled="!picked.length && (mode === 'pick' || !initial.length)"
+          :loading="saving"
+          @click="
+            emit(
+              'confirm',
+              picked.map((p) => p.id),
+            )
+          "
+        >
+          <template v-if="mode === 'pick'">{{ picked.length ? `用这 ${picked.length} 道` : '选好了' }}</template>
+          <template v-else>{{ picked.length ? `布置这 ${picked.length} 道` : initial.length ? '清掉' : '布置' }}</template>
+        </n-button>
+      </div>
+    </template>
+  </n-modal>
+</template>
+
+<style scoped>
+.head-extra {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.lang {
+  width: 110px;
+}
+
+.muted {
+  color: var(--text3);
+}
+
+.body {
+  display: flex;
+  gap: 16px;
+  height: min(560px, calc(100vh - 260px));
+}
+
+/* ---- 左栏：知识点 ---- */
+.tags {
+  flex: 0 0 168px;
+  overflow-y: auto;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  padding-right: 12px;
+  border-right: 1px solid var(--divider);
+}
+
+.tag-head {
+  margin: 10px 10px 4px;
+  font-size: 13px;
+  color: var(--text3);
+}
+
+.tag {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  gap: 8px;
+  height: 36px;
+  padding: 0 10px;
+  border: 0;
+  border-radius: 6px;
+  background: none;
+  color: inherit;
+  font: inherit;
+  font-size: 15px;
+  text-align: left;
+  cursor: pointer;
+  flex-shrink: 0;
+}
+
+.tag:hover {
+  background: var(--hover);
+}
+
+.tag.on {
+  background: var(--on-bg);
+  color: var(--on-text);
+  font-weight: 600;
+}
+
+.count {
+  font-size: 13px;
+  color: var(--text3);
+  font-variant-numeric: tabular-nums;
+}
+
+.tag.on .count {
+  color: inherit;
+}
+
+/* ---- 右边：题 ---- */
+.main {
+  flex: 1 1 0;
+  min-width: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+
+.filters {
+  display: flex;
+  gap: 8px;
+}
+
+.search {
+  flex: 1 1 0;
+}
+
+.sort {
+  width: 150px;
+}
+
+.list {
+  flex: 1 1 0;
+  overflow-y: auto;
+}
+
+.spin {
+  min-height: 100%;
+}
+
+.empty {
+  padding: 60px 0;
+}
+
+.row {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  width: 100%;
+  height: 44px;
+  padding: 0 10px;
+  border: 0;
+  border-bottom: 1px solid var(--divider);
+  background: none;
+  color: inherit;
+  font: inherit;
+  font-size: 15px;
+  text-align: left;
+  cursor: pointer;
+}
+
+.row:hover {
+  background: var(--hover);
+}
+
+.row.on {
+  background: var(--on-bg);
+}
+
+.check {
+  flex: 0 0 22px;
+  height: 22px;
+  border: 1.5px solid var(--text3);
+  border-radius: 5px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 13px;
+  font-weight: 700;
+  color: #fff;
+}
+
+.row.on .check {
+  border-color: var(--primary);
+  background: var(--primary);
+}
+
+.pid {
+  flex: 0 0 56px;
+  font-variant-numeric: tabular-nums;
+  color: var(--text2);
+}
+
+.title {
+  flex: 1 1 0;
+  min-width: 0;
+  display: flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.title-text {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.diff {
+  flex: 0 0 auto;
+  padding: 1px 8px;
+  border-radius: 4px;
+  font-size: 13px;
+}
+
+.people {
+  flex: 0 0 76px;
+  text-align: right;
+  font-size: 14px;
+  color: var(--text3);
+  font-variant-numeric: tabular-nums;
+}
+
+.pager {
+  display: flex;
+  justify-content: flex-end;
+}
+
+/* ---- 底下：选好的，按先后 ---- */
+.foot {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.picked {
+  flex: 1 1 0;
+  min-width: 0;
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+}
+
+.pick {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  height: 30px;
+  padding: 0 4px 0 10px;
+  border-radius: 6px;
+  background: var(--action);
+  font-size: 14px;
+  font-variant-numeric: tabular-nums;
+  max-width: 260px;
+}
+
+.pick b {
+  color: var(--text3);
+}
+
+.pick-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  color: var(--text2);
+}
+
+.x {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 22px;
+  height: 22px;
+  border: 0;
+  border-radius: 4px;
+  background: none;
+  color: var(--text3);
+  cursor: pointer;
+  flex-shrink: 0;
+}
+
+.x:hover {
+  background: var(--hover);
+  color: inherit;
+}
+
+@media (max-width: 768px) {
+  .body {
+    flex-direction: column;
+    height: calc(100vh - 280px);
+  }
+
+  .tags {
+    flex: 0 0 auto;
+    flex-direction: row;
+    overflow-x: auto;
+    padding: 0 0 8px;
+    border-right: 0;
+    border-bottom: 1px solid var(--divider);
+  }
+
+  .tag-head {
+    display: none;
+  }
+
+  .people {
+    display: none;
+  }
+
+  .foot {
+    flex-wrap: wrap;
+  }
+
+  .picked {
+    flex-basis: 100%;
+  }
+}
+</style>

apps/web/src/oj/statistics/components/Lessons.vue

@@ -79,12 +79,17 @@ function clock(lesson: Lesson) {
   return `${parseTime(lesson.start, 'HH:mm')}–${parseTime(lesson.end, 'HH:mm')}`
 }
 
-/** 23 人来了、花名册却只有 22（有个号不是学生角色）时，不写「23 / 22」 */
+/**
+ * 布置的课知道要做什么，写全班几人做完；推断的课只知道谁交了，写来了几人。
+ * 23 人来了、花名册却只有 22（有个号不是学生角色）时，不写「23 / 22」
+ */
 function attendance(lesson: Lesson) {
+  if (lesson.doneCount !== null) return lesson.classSize ? `做完 ${lesson.doneCount} / ${lesson.classSize}` : `做完 ${lesson.doneCount} 人`
   return lesson.classSize >= lesson.userCount ? `${lesson.userCount} / ${lesson.classSize} 人` : `${lesson.userCount} 人`
 }
 
 function problemText(lesson: Lesson) {
+  if (lesson.assigned) return `布置 ${lesson.problems.length} 道`
   return `${lesson.fromProblemSet ? '题单 ' : ''}${lesson.problems.length} 道`
 }
 
@@ -152,7 +157,7 @@ function percent(value: number, total: number) {
           <span v-if="nowHour !== null" class="now" :style="{ left: axisLeft(nowHour) }"></span>
         </span>
         <b class="c-class">{{ classLabel(lesson.className) }}</b>
-        <span class="c-came">{{ attendance(lesson) }}</span>
+        <span class="c-came" :title="lesson.assigned ? `交过的 ${lesson.userCount} 人` : undefined">{{ attendance(lesson) }}</span>
         <span class="c-probs">{{ problemText(lesson) }}</span>
         <span class="c-rate">
           {{ lesson.total }} 次 ·

apps/web/src/oj/statistics/components/StatisticsView.vue

@@ -65,6 +65,17 @@ const custom = computed<[number, number] | null>(() => {
   return from.value && to.value && Number.isFinite(a) && Number.isFinite(b) ? [a, b] : null
 })
 
+/**
+ * 「做完」只数所选时段之内做对的，和看板、后台「课堂作业」、一行一节课的「做完」不一样
+ * （那几处以前做对的也算）—— 从那边点进来数字会变小，所以写明是哪段时间里做完的
+ */
+const doneLabel = computed(() => {
+  const value = periodValue.value
+  if (value === 'today' || (value === 'custom' && custom.value && custom.value[0] === custom.value[1])) return '这一天做完'
+  if (value === 'lesson' || value === '1h' || value === '2h') return '这节课做完'
+  return '这段时间做完'
+})
+
 const periodValue = computed<Period>(() => {
   // 「那节课」要带着精确的起止时刻，地址栏里缺了就退回默认
   if (period.value === 'lesson') return custom.value ? 'lesson' : DEFAULT_PERIOD
@@ -377,7 +388,7 @@ function resultWidth(value: number) {
           <StatItem label="上了几节课" :value="`${lessons.lessons.length}${lessons.hasMore ? '+' : ''}`" unit="节" />
         </template>
         <template v-if="personCount">
-          <StatItem :label="hasProblems ? '做完' : '做对过题'" :value="`${doneCount} / ${personCount}`" unit="人" tone="success" />
+          <StatItem :label="hasProblems ? doneLabel : '做对过题'" :value="`${doneCount} / ${personCount}`" unit="人" tone="success" />
           <StatItem v-if="hasProblems" label="完成度" :value="`${personCount ? Math.round((doneCount / personCount) * 100) : 0}%`" />
           <StatItem label="一道没交" :value="stats.dataUnaccepted.length" unit="人" tone="error" />
         </template>