feat(api): add difficulty‑segmented solved data to yearly stats

apps/api/src/stats.ts

@@ -10,8 +10,8 @@
  * free to colour it however it likes.
  *
  * `recent`, `attempting` and `year` feed the docs page's LeetCode-style cards
- * (recently solved, the solved ring, the year heatmap). They are additive: the
- * terminal dashboard ignores them.
+ * (recently solved, the solved ring, the heatmap and the submissions chart).
+ * They are additive: the terminal dashboard ignores them.
  */
 import {
   CAMPAIGN_DAYS,
@@ -59,7 +59,7 @@ interface TopicStat {
   temperature: Temperature;
 }
 
-/** Days in the year heatmap: the 365 ending today, like LeetCode's "past one year". */
+/** Days in `year`: the 365 ending today, which always covers the current calendar year to date. */
 const YEAR_DAYS = 365;
 
 /** How many problems `recent` lists. */
@@ -252,38 +252,52 @@ export async function buildStats(db: D1Database, today: string): Promise<object>
     )
     .first<{ n: number }>();
 
-  // Attempts per day over the past year, every day present, plus the three
-  // figures LeetCode prints above its heatmap. `heat` stays campaign-scoped
-  // (the terminal dashboard lays it out by campaign week); this is the
-  // calendar-scoped view of the same table.
+  // The past year, one entry per day (zeros included), split by difficulty two
+  // ways: every logged attempt, and every first solve — the same first-pass
+  // date `recent` uses. `heat` stays campaign-scoped (the terminal dashboard
+  // lays it out by campaign week); this is the calendar-scoped view the docs
+  // heatmap and submissions chart window and bucket for themselves.
   const yearStart = addDays(today, -(YEAR_DAYS - 1));
-  const { results: yearRows } = await db
+  const { results: attemptRows } = await db
     .prepare(
-      `SELECT date,
-              COUNT(*) AS attempts,
-              SUM(CASE WHEN result = 'pass' THEN 1 ELSE 0 END) AS passes
-       FROM attempts WHERE date BETWEEN ?1 AND ?2 GROUP BY date`,
+      `SELECT a.date AS date, p.difficulty AS difficulty,
+              COUNT(*) AS n,
+              SUM(CASE WHEN a.result = 'pass' THEN 1 ELSE 0 END) AS passes
+       FROM attempts a JOIN problems p ON p.lc_number = a.lc_number
+       WHERE a.date BETWEEN ?1 AND ?2
+       GROUP BY a.date, p.difficulty`,
     )
     .bind(yearStart, today)
-    .all<{ date: string; attempts: number; passes: number | null }>();
-  const yearByDate = new Map(yearRows.map((r) => [r.date, r]));
-  const yearDays = Array.from({ length: YEAR_DAYS }, (_, i) => {
-    const date = addDays(yearStart, i);
-    const row = yearByDate.get(date);
-    return { date, attempts: row?.attempts ?? 0, passes: row?.passes ?? 0 };
-  });
-  let run = 0;
-  let maxStreak = 0;
-  for (const d of yearDays) {
-    run = d.attempts > 0 ? run + 1 : 0;
-    maxStreak = Math.max(maxStreak, run);
+    .all<{ date: string; difficulty: string; n: number; passes: number | null }>();
+  const { results: solvedRows } = await db
+    .prepare(
+      `SELECT date, difficulty, COUNT(*) AS n
+       FROM (SELECT MIN(a.date) AS date, p.difficulty AS difficulty
+             FROM attempts a JOIN problems p ON p.lc_number = a.lc_number
+             WHERE a.result = 'pass'
+             GROUP BY p.lc_number)
+       WHERE date BETWEEN ?1 AND ?2
+       GROUP BY date, difficulty`,
+    )
+    .bind(yearStart, today)
+    .all<{ date: string; difficulty: string; n: number }>();
+  const year = Array.from({ length: YEAR_DAYS }, (_, i) => ({
+    date: addDays(yearStart, i),
+    passes: 0,
+    attempts: Object.fromEntries(DIFFICULTIES.map((d) => [d, 0])),
+    solved: Object.fromEntries(DIFFICULTIES.map((d) => [d, 0])),
+  }));
+  const yearIndex = new Map(year.map((d, i) => [d.date, i]));
+  for (const row of attemptRows) {
+    const day = year[yearIndex.get(row.date) ?? -1];
+    if (!day || !(row.difficulty in day.attempts)) continue;
+    day.attempts[row.difficulty] = row.n;
+    day.passes += row.passes ?? 0;
+  }
+  for (const row of solvedRows) {
+    const day = year[yearIndex.get(row.date) ?? -1];
+    if (day && row.difficulty in day.solved) day.solved[row.difficulty] = row.n;
   }
-  const year = {
-    days: yearDays,
-    attempts: yearDays.reduce((n, d) => n + d.attempts, 0),
-    active_days: yearDays.filter((d) => d.attempts > 0).length,
-    max_streak: maxStreak,
-  };
 
   return {
     generated: new Date().toISOString(),