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+# Problem Yearly AC Rate — Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add `GET /api/problem/yearly_ac` endpoint returning per-year AC stats for a single problem, and display results as a line chart below the existing pie chart on the problem info page.
+
+**Architecture:** Backend adds `ProblemYearlyACRateAPI` to `problem/views/oj.py` using Django ORM `ExtractYear` + `Count(filter=...)` aggregation, cached in Redis. Frontend adds a `ProblemYearlyChart.vue` Line chart component and wires it into `ProblemInfo.vue`.
+
+**Tech Stack:** Django 6, PostgreSQL, Redis, `django.db.models.functions.ExtractYear`; Vue 3, TypeScript, vue-chartjs, chart.js
+
+---
+
+### Task 1: Add CacheKey constant and write failing test
+
+**Files:**
+- Modify: `OnlineJudge/utils/constants.py`
+- Create: `OnlineJudge/problem/tests.py`
+
+- [ ] **Step 1: Add `problem_yearly_ac` to `CacheKey`**
+
+In `OnlineJudge/utils/constants.py`, add one line to `CacheKey`:
+
+```python
+class CacheKey:
+    waiting_queue = "waiting_queue"
+    contest_rank_cache = "contest_rank_cache"
+    website_config = "website_config"
+    problem_authors = "problem_authors"
+    problem_tags = "problem_tags"
+    comment_stats = "comment_stats"
+    user_activity_rank = "user_activity_rank"
+    problem_yearly_ac = "problem_yearly_ac"   # ← add this line
+```
+
+- [ ] **Step 2: Write failing tests**
+
+Create `OnlineJudge/problem/tests.py`:
+
+```python
+from datetime import datetime, UTC
+
+from django.contrib.auth import get_user_model
+from django.test import Client, TestCase
+
+from problem.models import Problem, ProblemRuleType
+from submission.models import JudgeStatus, Submission
+from utils.constants import Difficulty
+
+User = get_user_model()
+
+
+def make_user():
+    return User.objects.create_user(
+        username="testuser",
+        email="test@example.com",
+        password="pass",
+    )
+
+
+def make_problem(user, _id="P001"):
+    return Problem.objects.create(
+        _id=_id,
+        title="Test Problem",
+        description="",
+        input_description="",
+        output_description="",
+        samples=[],
+        test_case_id="abc123",
+        test_case_score=[],
+        languages=["Python3"],
+        template={},
+        created_by=user,
+        time_limit=1000,
+        memory_limit=256,
+        rule_type=ProblemRuleType.ACM,
+        difficulty=Difficulty.LOW,
+    )
+
+
+def make_submission(problem, result, year):
+    sub = Submission.objects.create(
+        problem=problem,
+        user_id=1,
+        username="testuser",
+        code="print(1)",
+        result=result,
+        language="Python3",
+    )
+    # auto_now_add cannot be passed to create(); update afterward
+    Submission.objects.filter(id=sub.id).update(
+        create_time=datetime(year, 6, 1, tzinfo=UTC)
+    )
+    return sub
+
+
+class ProblemYearlyACRateAPITest(TestCase):
+    def setUp(self):
+        self.client = Client()
+        self.user = make_user()
+        self.problem = make_problem(self.user)
+        # 2023: 3 judged, 1 AC  → ac_rate = 33.33
+        make_submission(self.problem, JudgeStatus.ACCEPTED, 2023)
+        make_submission(self.problem, JudgeStatus.WRONG_ANSWER, 2023)
+        make_submission(self.problem, JudgeStatus.WRONG_ANSWER, 2023)
+        # 2024: 2 judged, 2 AC  → ac_rate = 100.0
+        make_submission(self.problem, JudgeStatus.ACCEPTED, 2024)
+        make_submission(self.problem, JudgeStatus.ACCEPTED, 2024)
+
+    def test_missing_problem_id_returns_error(self):
+        res = self.client.get("/api/problem/yearly_ac")
+        self.assertEqual(res.status_code, 200)
+        self.assertEqual(res.json()["error"], "error")
+
+    def test_nonexistent_problem_returns_error(self):
+        res = self.client.get("/api/problem/yearly_ac?problem_id=NOPE")
+        self.assertEqual(res.json()["error"], "error")
+
+    def test_returns_yearly_data_sorted_by_year(self):
+        res = self.client.get(f"/api/problem/yearly_ac?problem_id={self.problem._id}")
+        body = res.json()
+        self.assertIsNone(body["error"])
+        rows = body["data"]
+        self.assertEqual(len(rows), 2)
+        self.assertEqual(rows[0]["year"], 2023)
+        self.assertEqual(rows[0]["total"], 3)
+        self.assertEqual(rows[0]["accepted"], 1)
+        self.assertAlmostEqual(rows[0]["ac_rate"], 33.33, places=1)
+        self.assertEqual(rows[1]["year"], 2024)
+        self.assertEqual(rows[1]["total"], 2)
+        self.assertEqual(rows[1]["accepted"], 2)
+        self.assertAlmostEqual(rows[1]["ac_rate"], 100.0)
+
+    def test_excludes_pending_and_judging(self):
+        make_submission(self.problem, JudgeStatus.PENDING, 2023)
+        make_submission(self.problem, JudgeStatus.JUDGING, 2023)
+        res = self.client.get(f"/api/problem/yearly_ac?problem_id={self.problem._id}")
+        rows = res.json()["data"]
+        # 2023 total must stay 3 (pending/judging excluded)
+        self.assertEqual(rows[0]["total"], 3)
+```
+
+- [ ] **Step 3: Run test to confirm it fails**
+
+```bash
+cd OnlineJudge && python manage.py test problem.tests.ProblemYearlyACRateAPITest -v 2
+```
+
+Expected: Failure with `404` or `ImportError` — endpoint does not exist yet.
+
+---
+
+### Task 2: Implement view and register URL
+
+**Files:**
+- Modify: `OnlineJudge/problem/views/oj.py`
+- Modify: `OnlineJudge/problem/urls/oj.py`
+
+- [ ] **Step 1: Add `ExtractYear` import to `problem/views/oj.py`**
+
+At the top of `OnlineJudge/problem/views/oj.py`, the existing imports already include `from django.db.models import Count, Q`. Add one more:
+
+```python
+from django.db.models.functions import ExtractYear
+```
+
+Also confirm `from utils.constants import CacheKey` is present (it is, via existing cache usage).
+
+- [ ] **Step 2: Add `ProblemYearlyACRateAPI` class at end of file**
+
+Append to `OnlineJudge/problem/views/oj.py`:
+
+```python
+class ProblemYearlyACRateAPI(APIView):
+    def get(self, request):
+        problem_id = request.GET.get("problem_id")
+        if not problem_id:
+            return self.error("problem_id is required")
+
+        cache_key = f"{CacheKey.problem_yearly_ac}:{problem_id}"
+        cached = cache.get(cache_key)
+        if cached is not None:
+            return self.success(cached)
+
+        try:
+            problem = Problem.objects.get(
+                _id=problem_id, contest_id__isnull=True, visible=True
+            )
+        except Problem.DoesNotExist:
+            return self.error("Problem does not exist")
+
+        rows = (
+            Submission.objects.filter(
+                problem_id=problem.id,
+                contest_id__isnull=True,
+            )
+            .exclude(result__in=[JudgeStatus.PENDING, JudgeStatus.JUDGING])
+            .annotate(year=ExtractYear("create_time"))
+            .values("year")
+            .annotate(
+                total=Count("id"),
+                accepted=Count("id", filter=Q(result=JudgeStatus.ACCEPTED)),
+            )
+            .order_by("year")
+        )
+
+        data = [
+            {
+                "year": row["year"],
+                "total": row["total"],
+                "accepted": row["accepted"],
+                "ac_rate": round(row["accepted"] / row["total"] * 100, 2)
+                if row["total"] > 0
+                else 0.0,
+            }
+            for row in rows
+        ]
+
+        cache.set(cache_key, data, 3600)
+        return self.success(data)
+```
+
+- [ ] **Step 3: Register URL in `problem/urls/oj.py`**
+
+Replace the full contents of `OnlineJudge/problem/urls/oj.py` with:
+
+```python
+from django.urls import path
+
+from ..views.oj import (
+    ContestProblemAPI,
+    PickOneAPI,
+    ProblemAPI,
+    ProblemAuthorAPI,
+    ProblemSolvedPeopleCount,
+    ProblemTagAPI,
+    ProblemYearlyACRateAPI,
+    SimilarProblemAPI,
+)
+
+urlpatterns = [
+    path("problem/tags", ProblemTagAPI.as_view()),
+    path("problem", ProblemAPI.as_view()),
+    path("problem/beat_count", ProblemSolvedPeopleCount.as_view()),
+    path("problem/similar", SimilarProblemAPI.as_view()),
+    path("problem/author", ProblemAuthorAPI.as_view()),
+    path("problem/yearly_ac", ProblemYearlyACRateAPI.as_view()),
+    path("pickone", PickOneAPI.as_view()),
+    path("contest/problem", ContestProblemAPI.as_view()),
+]
+```
+
+- [ ] **Step 4: Run tests — expect all 4 to pass**
+
+```bash
+cd OnlineJudge && python manage.py test problem.tests.ProblemYearlyACRateAPITest -v 2
+```
+
+Expected output:
+```
+test_excludes_pending_and_judging ... ok
+test_missing_problem_id_returns_error ... ok
+test_nonexistent_problem_returns_error ... ok
+test_returns_yearly_data_sorted_by_year ... ok
+
+Ran 4 tests in ...s
+
+OK
+```
+
+- [ ] **Step 5: Commit**
+
+```bash
+git -C OnlineJudge add utils/constants.py problem/views/oj.py problem/urls/oj.py problem/tests.py
+git -C OnlineJudge commit -m "feat: add problem yearly AC rate API endpoint"
+```
+
+---
+
+### Task 3: Frontend — add API function
+
+**Files:**
+- Modify: `ojnext/src/oj/api.ts`
+
+- [ ] **Step 1: Add `YearlyACData` type and `getProblemYearlyAC` function**
+
+In `ojnext/src/oj/api.ts`, add after the `getSimilarProblems` function (near the `// ==================== 相似题目推荐 ====================` section):
+
+```typescript
+export interface YearlyACData {
+  year: number
+  total: number
+  accepted: number
+  ac_rate: number
+}
+
+export function getProblemYearlyAC(problemId: string) {
+  return http.get<YearlyACData[]>("problem/yearly_ac", {
+    params: { problem_id: problemId },
+  })
+}
+```
+
+- [ ] **Step 2: Commit**
+
+```bash
+git -C ojnext add src/oj/api.ts
+git -C ojnext commit -m "feat: add getProblemYearlyAC API function"
+```
+
+---
+
+### Task 4: Frontend — create `ProblemYearlyChart.vue`
+
+**Files:**
+- Create: `ojnext/src/oj/problem/components/ProblemYearlyChart.vue`
+
+- [ ] **Step 1: Create the component**
+
+Create `ojnext/src/oj/problem/components/ProblemYearlyChart.vue` with the following content:
+
+```vue
+<template>
+  <div class="yearly-chart" v-if="props.data.length > 1">
+    <Line :data="chartData" :options="chartOptions" />
+  </div>
+</template>
+
+<script setup lang="ts">
+import { Line } from "vue-chartjs"
+import {
+  Chart as ChartJS,
+  CategoryScale,
+  Filler,
+  LinearScale,
+  LineElement,
+  PointElement,
+  Title,
+  Tooltip,
+} from "chart.js"
+import type { YearlyACData } from "oj/api"
+
+ChartJS.register(
+  CategoryScale,
+  Filler,
+  LinearScale,
+  LineElement,
+  PointElement,
+  Title,
+  Tooltip,
+)
+
+const props = defineProps<{ data: YearlyACData[] }>()
+
+const chartData = computed(() => ({
+  labels: props.data.map((d) => String(d.year)),
+  datasets: [
+    {
+      label: "AC 率",
+      data: props.data.map((d) => d.ac_rate),
+      fill: true,
+      tension: 0.3,
+      backgroundColor: "rgba(99, 179, 237, 0.2)",
+      borderColor: "rgba(99, 179, 237, 1)",
+      pointBackgroundColor: "rgba(99, 179, 237, 1)",
+    },
+  ],
+}))
+
+const chartOptions = computed(() => ({
+  responsive: true,
+  maintainAspectRatio: false,
+  plugins: {
+    title: {
+      display: true,
+      text: "历年 AC 率",
+      font: { size: 20 },
+    },
+    tooltip: {
+      callbacks: {
+        label: (context: any) => {
+          const d = props.data[context.dataIndex]
+          return [`AC 率: ${d.ac_rate}%`, `通过: ${d.accepted} / ${d.total}`]
+        },
+      },
+    },
+  },
+  scales: {
+    y: {
+      min: 0,
+      max: 100,
+      ticks: {
+        callback: (value: any) => `${value}%`,
+      },
+    },
+  },
+}))
+</script>
+
+<style scoped>
+.yearly-chart {
+  width: 100%;
+  max-width: 500px;
+  height: 250px;
+  margin: 24px auto;
+}
+</style>
+```
+
+- [ ] **Step 2: Commit**
+
+```bash
+git -C ojnext add src/oj/problem/components/ProblemYearlyChart.vue
+git -C ojnext commit -m "feat: add ProblemYearlyChart component"
+```
+
+---
+
+### Task 5: Frontend — integrate chart into `ProblemInfo.vue`
+
+**Files:**
+- Modify: `ojnext/src/oj/problem/components/ProblemInfo.vue`
+
+- [ ] **Step 1: Add imports**
+
+In the `<script setup lang="ts">` block, add two imports alongside the existing ones:
+
+```typescript
+import { getProblemYearlyAC, type YearlyACData } from "oj/api"
+import ProblemYearlyChart from "./ProblemYearlyChart.vue"
+```
+
+- [ ] **Step 2: Add reactive data and fetch function**
+
+After `const beatRate = ref("0")`, add:
+
+```typescript
+const yearlyACData = ref<YearlyACData[]>([])
+```
+
+Add a new async function:
+
+```typescript
+async function getYearlyAC() {
+  const res = await getProblemYearlyAC(problem.value!._id)
+  yearlyACData.value = res.data
+}
+```
+
+- [ ] **Step 3: Replace `onMounted` call**
+
+Replace the existing:
+
+```typescript
+onMounted(getBeatRate)
+```
+
+With:
+
+```typescript
+onMounted(() => {
+  getBeatRate()
+  getYearlyAC()
+})
+```
+
+- [ ] **Step 4: Add chart to template**
+
+In the `<template>`, after the existing `.pie` div, add `<ProblemYearlyChart>`:
+
+```html
+  <div class="pie" v-if="problem && problem.submission_number > 0">
+    <Pie :data="data" :options="options" />
+  </div>
+  <ProblemYearlyChart :data="yearlyACData" />
+</template>
+```
+
+- [ ] **Step 5: Start dev server and verify manually**
+
+```bash
+cd ojnext && npm start
+```
+
+Open a problem page and navigate to the info/stats tab. Verify:
+
+1. A problem with submissions spanning **multiple years**: line chart appears below the pie chart, Y-axis shows 0–100%, hovering shows "AC 率: X%" and "通过: Y / Z"
+2. A problem with submissions only in **one year** (or zero): chart is hidden (`v-if="props.data.length > 1"`)
+3. No console errors in the browser devtools
+
+- [ ] **Step 6: Commit**
+
+```bash
+git -C ojnext add src/oj/problem/components/ProblemInfo.vue
+git -C ojnext commit -m "feat: show yearly AC rate chart on problem info page"
+```