feat(课堂看板): 「这节课」那排题号后面写上几点布置的，之后改题不变

class_lesson 加 created_at（0034，老数据用 updated_at 回填），「改」只动 updated_at；
清掉再布置算重新开始。

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

apps/api/src/db/0034_add_class_lesson_created_at.sql

@@ -0,0 +1,4 @@
+ALTER TABLE "class_lesson" ADD COLUMN "created_at" timestamp with time zone DEFAULT now();--> statement-breakpoint
+-- 加这一列之前布置的：只剩最后一次改的时刻，拿它当布置时刻
+UPDATE "class_lesson" SET "created_at" = "updated_at";--> statement-breakpoint
+ALTER TABLE "class_lesson" ALTER COLUMN "created_at" SET NOT NULL;

apps/api/src/db/meta/_journal.json

@@ -239,6 +239,13 @@
       "when": 1791823809856,
       "tag": "0033_drop_message",
       "breakpoints": true
+    },
+    {
+      "idx": 34,
+      "version": "7",
+      "when": 1791858070886,
+      "tag": "0034_add_class_lesson_created_at",
+      "breakpoints": true
     }
   ]
 }

apps/api/src/db/schema.ts

@@ -1433,6 +1433,17 @@ export const classLesson = pgTable(
      */
     language: text().$type<LessonLanguage>(),
     createdBy: integer("created_by").notNull(),
+    /**
+     * 这天第一次布置的时刻，之后「改」只动 updatedAt。清掉（删行）再布置算重新开始。
+     * 加这一列之前布置的用 updated_at 回填（0034）。带默认值是给共库的另一个站点：
+     * 机房那套还没升级时，它的旧代码插入不带这一列
+     */
+    createdAt: timestamp("created_at", {
+      withTimezone: true,
+      mode: "string",
+    })
+      .notNull()
+      .defaultNow(),
     updatedAt: timestamp("updated_at", {
       withTimezone: true,
       mode: "string",

apps/api/src/routes/classroom.ts

@@ -185,14 +185,18 @@ async function visibleProblems(ids: number[]) {
   return new Map(rows.map((row) => [row.id, row]))
 }
 
-/** 老师给这个班今天布置的题（problem.id，按输入顺序）和选的语言；没布置为 null */
+/** 老师给这个班今天布置的题（problem.id，按输入顺序）、选的语言和布置时刻；没布置为 null */
 async function lessonPlan(className: string, day: string) {
   const [row] = await db
-    .select({ problemIds: schema.classLesson.problemIds, language: schema.classLesson.language })
+    .select({
+      problemIds: schema.classLesson.problemIds,
+      language: schema.classLesson.language,
+      createdAt: schema.classLesson.createdAt,
+    })
     .from(schema.classLesson)
     .where(and(eq(schema.classLesson.className, className), eq(schema.classLesson.day, day)))
     .limit(1)
-  return row?.problemIds.length ? { problemIds: row.problemIds, language: row.language } : null
+  return row?.problemIds.length ? row : null
 }
 
 /**
@@ -217,6 +221,7 @@ async function classLessonProblems(className: string, lookbackDays: number) {
       source: "teacher" as const,
       day: today,
       language: plan.language ?? null,
+      assignedAt: plan.createdAt,
       problems: planned.flatMap((id) => {
         const problem = problems.get(id)
         if (!problem) return []
@@ -248,6 +253,7 @@ async function classLessonProblems(className: string, lookbackDays: number) {
     day: picked.length ? latest : null,
     // 推断出来的课不知道老师要的是哪种语言，不限
     language: null,
+    assignedAt: null,
     problems: picked.flatMap((row) => {
       const problem = problems.get(row.problemId)
       return problem
@@ -503,6 +509,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
       day,
       source: null,
       language: null,
+      assignedAt: null,
       lastLanguage: null,
       problems: [],
       students: [],
@@ -707,6 +714,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
     day,
     source: lesson.source,
     language: lesson.language,
+    assignedAt: lesson.assignedAt,
     lastLanguage: last?.language ?? null,
     problems: lesson.problems.map((problem) => ({
       problemId: problem.id,
@@ -848,7 +856,15 @@ classroomRoutes.put("/classroom/lesson", requireTeacher, async (c) => {
   const now = new Date().toISOString()
   await db
     .insert(schema.classLesson)
-    .values({ className, day, problemIds, language, createdBy: user.id, updatedAt: now })
+    .values({
+      className,
+      day,
+      problemIds,
+      language,
+      createdBy: user.id,
+      createdAt: now,
+      updatedAt: now,
+    })
     .onConflictDoUpdate({
       target: [schema.classLesson.className, schema.classLesson.day],
       set: { problemIds, language, createdBy: user.id, updatedAt: now },

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

@@ -485,6 +485,9 @@ function shortTitle(title: string, size: number) {
         <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") }} 布置
+        </span>
         <n-button text class="edit" @click="startEdit">
           <template #icon><Icon icon="ph:pencil-simple" /></template>
           {{ board.source === "teacher" ? "改" : "布置" }}
@@ -854,6 +857,14 @@ function shortTitle(title: string, size: number) {
   font-weight: 600;
 }
 
+.assigned {
+  margin-left: 4px;
+  font-size: 14px;
+  font-variant-numeric: tabular-nums;
+  color: v-bind("theme.textColor3");
+  white-space: nowrap;
+}
+
 .edit {
   margin-left: 4px;
   font-size: 14px;

packages/contract/src/classroom.ts

@@ -151,6 +151,8 @@ export const classBoardSchema = z.object({
   source: z.enum(["teacher", "inferred"]).nullable(),
   /** 今天布置的语言（见 lessonLanguageSchema） */
   language: lessonLanguageSchema,
+  /** 今天第一次布置的时刻，之后改题不变；推断出来的课为 null */
+  assignedAt: z.string().nullable(),
   /** 这个班最近一次布置选的语言（含今天），给语言下拉当默认值；从没选过为 null */
   lastLanguage: lessonLanguageSchema,
   problems: z.array(classBoardProblemSchema),