feat: add maintainer day-over-day stat deltas

src/app/(app)/maintainer/page.tsx

@@ -25,7 +25,11 @@ import {
 } from '@/app/actions/maintainer';
 import type { MaintainerInstall } from '@/lib/maintainer/detect';
 import type { MaintainerPrRow } from '@/lib/maintainer/queue';
-import type { MaintainerAnalyticsTrends } from '@/lib/maintainer/analytics';
+import {
+  emptyMaintainerDayOverDayStats,
+  type MaintainerAnalyticsTrends,
+  type MaintainerDayOverDayMetric,
+} from '@/lib/maintainer/analytics';
 import { isOk } from '@/lib/result';
 import RefreshButton from './refresh-button';
 import InviteContributorButton from './invite-contributor-button';
@@ -97,7 +101,12 @@ export default async function MaintainerPage({
   const trendsRes = await getMaintainerAnalyticsTrends({ installationId: activeInstallId });
   const analyticsTrends: MaintainerAnalyticsTrends = isOk(trendsRes)
     ? trendsRes.data
-    : { weekly: [], levelDistribution: [], avgReviewTimeHours: null };
+    : {
+        weekly: [],
+        levelDistribution: [],
+        avgReviewTimeHours: null,
+        dayOverDay: emptyMaintainerDayOverDayStats(),
+      };
   const repoHealthRes = await getRepoHealthOverview({ installationId: activeInstallId });
   const repoHealthRows: RepoHealthRow[] = isOk(repoHealthRes) ? repoHealthRes.data : [];
 
@@ -210,6 +219,37 @@ export default async function MaintainerPage({
           {activeInstall.accountLogin} ({activeInstall.permissionLevel.replace('_', ' ')})
         </p>
         <QueueSettings settings={settings} />
+        <section className="mb-8 grid gap-4 md:grid-cols-2 lg:grid-cols-4">
+          <StatTile
+            label="PRs Opened"
+            value={formatCount(analyticsTrends.dayOverDay.openedPrs.current)}
+            detail="today"
+            delta={analyticsTrends.dayOverDay.openedPrs}
+          />
+          <StatTile
+            label="PRs Merged"
+            value={formatCount(analyticsTrends.dayOverDay.mergedPrs.current)}
+            detail="today"
+            delta={analyticsTrends.dayOverDay.mergedPrs}
+          />
+          <StatTile
+            label="Mentor Reviews"
+            value={formatCount(analyticsTrends.dayOverDay.mentorReviews.current)}
+            detail="today"
+            delta={analyticsTrends.dayOverDay.mentorReviews}
+          />
+          <StatTile
+            label="Average Review Time"
+            value={
+              analyticsTrends.avgReviewTimeHours !== null
+                ? `${analyticsTrends.avgReviewTimeHours.toFixed(1)}h`
+                : '-'
+            }
+            detail="all verified PRs"
+            delta={analyticsTrends.dayOverDay.avgReviewTimeHours}
+            deltaUnit="h"
+          />
+        </section>
         <AnalyticsTrends data={analyticsTrends} />
         {promotionEligible.length > 0 && (
           <section className="mb-8 rounded-2xl border border-emerald-900/60 bg-emerald-950/20 p-5">
@@ -493,6 +533,62 @@ export default async function MaintainerPage({
   );
 }
 
+function StatTile({
+  label,
+  value,
+  detail,
+  delta,
+  deltaUnit,
+}: {
+  label: string;
+  value: string;
+  detail: string;
+  delta: MaintainerDayOverDayMetric;
+  deltaUnit?: 'h';
+}) {
+  return (
+    <section className="rounded-2xl border border-zinc-800 bg-zinc-900 p-5">
+      <div className="flex items-start justify-between gap-3">
+        <h2 className="text-sm font-semibold text-white">{label}</h2>
+        <DeltaBadge metric={delta} unit={deltaUnit} />
+      </div>
+      <div className="mt-4 flex items-baseline gap-2">
+        <span className="text-4xl font-bold text-white">{value}</span>
+        <span className="text-xs text-zinc-500">{detail}</span>
+      </div>
+    </section>
+  );
+}
+
+function DeltaBadge({ metric, unit }: { metric: MaintainerDayOverDayMetric; unit?: 'h' }) {
+  const label = formatDelta(metric, unit);
+  const tone =
+    metric.direction === 'up'
+      ? 'border-emerald-800/70 bg-emerald-950/60 text-emerald-300'
+      : metric.direction === 'down'
+        ? 'border-red-800/70 bg-red-950/60 text-red-300'
+        : 'border-zinc-700 bg-zinc-800/70 text-zinc-400';
+
+  return (
+    <span className={`rounded-full border px-2 py-0.5 text-xs font-medium ${tone}`}>{label}</span>
+  );
+}
+
+function formatCount(value: number | null): string {
+  return value === null ? '-' : value.toLocaleString();
+}
+
+function formatDelta(metric: MaintainerDayOverDayMetric, unit?: 'h'): string {
+  if (metric.delta === null) {
+    return metric.current && metric.current > 0 ? 'new today' : 'no data';
+  }
+  if (metric.delta === 0) return 'no change';
+
+  const sign = metric.delta > 0 ? '+' : '';
+  const value = unit === 'h' ? `${sign}${metric.delta.toFixed(1)}h` : `${sign}${metric.delta}`;
+  return `${value} vs yesterday`;
+}
+
 function FilterPill({ label, href, active }: { label: string; href: string; active: boolean }) {
   return (
     <Link

src/app/actions/maintainer/analytics.ts

@@ -9,6 +9,11 @@ import { profiles, xpEvents, pullRequests } from '@/lib/db/schema';
 import { eq, inArray, sum, desc, and, count } from 'drizzle-orm';
 import { cacheGet, cacheSet } from '@/lib/cache';
 import type { MaintainerAnalyticsTrends } from '@/lib/maintainer/analytics';
+import {
+  buildDayOverDayStats,
+  buildMaintainerAnalyticsTrends,
+  emptyMaintainerDayOverDayStats,
+} from '@/lib/maintainer/analytics';
 import {
   comparePrRows,
   validateFilters,
@@ -182,57 +187,91 @@ export async function getMaintainerAnalyticsTrends(args: {
 
   const repos = await listMaintainerRepos(user.id, args.installationId);
   if (repos.length === 0) {
-    return ok({ weekly: [], levelDistribution: [], avgReviewTimeHours: null });
+    return ok({
+      weekly: [],
+      levelDistribution: [],
+      avgReviewTimeHours: null,
+      dayOverDay: emptyMaintainerDayOverDayStats(),
+    });
   }
 
   const cacheKey = `maint:analytics-trends:${user.id}:${args.installationId}`;
   const cached = await cacheGet<MaintainerAnalyticsTrends>(cacheKey);
-  if (cached) return ok(cached);
+  if (cached?.dayOverDay) return ok(cached);
 
   const { data, error } = await service.rpc('maintainer_analytics_trends', {
     repo_names: repos,
   });
 
   if (error) return err('query_failed', error.message);
 
-  // Fetch average review time from pull_requests
+  const yesterdayStart = new Date();
+  yesterdayStart.setDate(yesterdayStart.getDate() - 1);
+
+  // Fetch review stats and day-over-day deltas from timestamped PR rows.
   const { data: prs } = await service
     .from('pull_requests')
-    .select('github_created_at, mentor_review_at')
+    .select('github_created_at, merged_at, mentor_review_at')
     .in('repo_full_name', repos)
     .eq('mentor_verified', true)
-    .not('mentor_review_at', 'is', null);
+    .not('github_created_at', 'is', null)
+    .gte('github_created_at', yesterdayStart.toISOString());
 
   let avgReviewTimeHours = null;
-  if (prs && prs.length > 0) {
+  const reviewRows = (
+    (prs ?? []) as {
+      github_created_at: string;
+      merged_at: string | null;
+      mentor_review_at: string | null;
+    }[]
+  ).filter((pr) => pr.mentor_review_at);
+
+  if (reviewRows.length > 0) {
     const totalSeconds = (
-      prs as { github_created_at: string; mentor_review_at: string | null }[]
+      reviewRows as { github_created_at: string; mentor_review_at: string | null }[]
     ).reduce((sum: number, pr) => {
       const created = new Date(pr.github_created_at).getTime();
       const reviewed = new Date(pr.mentor_review_at!).getTime();
       return sum + (reviewed - created) / 1000;
     }, 0);
-    avgReviewTimeHours = totalSeconds / prs.length / 3600;
+    avgReviewTimeHours = totalSeconds / reviewRows.length / 3600;
   }
 
-  const trends = normaliseAnalyticsTrends(data, avgReviewTimeHours);
+  const dayOverDay = buildDayOverDayStats(
+    new Date(),
+    (
+      (prs ?? []) as {
+        github_created_at: string | null;
+        merged_at: string | null;
+        mentor_review_at: string | null;
+      }[]
+    ).map((pr) => ({
+      githubCreatedAt: pr.github_created_at,
+      mergedAt: pr.merged_at,
+      mentorReviewAt: pr.mentor_review_at,
+    })),
+  );
+
+  const trends = normaliseAnalyticsTrends(data, avgReviewTimeHours, dayOverDay);
   await cacheSet(cacheKey, trends, 30 * 60);
   return ok(trends);
 }
 
 function normaliseAnalyticsTrends(
   value: unknown,
   avgReviewTimeHours: number | null,
+  dayOverDay = emptyMaintainerDayOverDayStats(),
 ): MaintainerAnalyticsTrends {
   if (!value || typeof value !== 'object') {
-    return { weekly: [], levelDistribution: [], avgReviewTimeHours: null };
+    return { weekly: [], levelDistribution: [], avgReviewTimeHours: null, dayOverDay };
   }
 
   const data = value as Partial<MaintainerAnalyticsTrends>;
   return {
     weekly: Array.isArray(data.weekly) ? data.weekly : [],
     levelDistribution: Array.isArray(data.levelDistribution) ? data.levelDistribution : [],
     avgReviewTimeHours,
+    dayOverDay,
   };
 }
 

src/lib/maintainer/analytics.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { buildMaintainerAnalyticsTrends } from './analytics';
+import { buildDayOverDayStats, buildMaintainerAnalyticsTrends } from './analytics';
 
 describe('buildMaintainerAnalyticsTrends', () => {
   it('groups merged PRs and completed XP into the last twelve UTC weeks', () => {
@@ -78,4 +78,109 @@ describe('buildMaintainerAnalyticsTrends', () => {
 
     expect(trends.avgReviewTimeHours).toBe(1.8);
   });
+
+  it('builds day-over-day deltas from UTC PR timestamps', () => {
+    const stats = buildDayOverDayStats(new Date('2026-05-21T12:00:00.000Z'), [
+      {
+        githubCreatedAt: '2026-05-21T02:00:00.000Z',
+        mergedAt: '2026-05-21T03:00:00.000Z',
+        mentorReviewAt: '2026-05-21T06:00:00.000Z',
+      },
+      {
+        githubCreatedAt: '2026-05-21T08:00:00.000Z',
+        mergedAt: '2026-05-21T09:00:00.000Z',
+        mentorReviewAt: '2026-05-21T10:00:00.000Z',
+      },
+      {
+        githubCreatedAt: '2026-05-20T04:00:00.000Z',
+        mergedAt: '2026-05-20T05:00:00.000Z',
+        mentorReviewAt: '2026-05-20T06:00:00.000Z',
+      },
+    ]);
+
+    expect(stats.openedPrs).toMatchObject({
+      current: 2,
+      previous: 1,
+      delta: 1,
+      direction: 'up',
+    });
+    expect(stats.avgReviewTimeHours).toMatchObject({
+      current: 3,
+      previous: 2,
+      delta: 1,
+      direction: 'up',
+    });
+  });
+
+  it('builds day-over-day deltas from UTC PR timestamps', () => {
+    const trends = buildMaintainerAnalyticsTrends({
+      now: new Date('2026-05-21T12:00:00.000Z'),
+      mergedPullRequests: [
+        {
+          githubCreatedAt: '2026-05-21T02:00:00.000Z',
+          mergedAt: '2026-05-21T03:00:00.000Z',
+          mentorReviewAt: '2026-05-21T06:00:00.000Z',
+        },
+        {
+          githubCreatedAt: '2026-05-21T08:00:00.000Z',
+          mergedAt: '2026-05-21T09:00:00.000Z',
+          mentorReviewAt: '2026-05-21T10:00:00.000Z',
+        },
+        {
+          githubCreatedAt: '2026-05-20T04:00:00.000Z',
+          mergedAt: '2026-05-20T05:00:00.000Z',
+          mentorReviewAt: '2026-05-20T06:00:00.000Z',
+        },
+      ],
+      completedRecommendations: [],
+      contributorProfiles: [],
+      levelUps: [],
+    });
+
+    expect(trends.dayOverDay.openedPrs).toMatchObject({
+      current: 2,
+      previous: 1,
+      delta: 1,
+      direction: 'up',
+    });
+    expect(trends.dayOverDay.mergedPrs).toMatchObject({
+      current: 2,
+      previous: 1,
+      delta: 1,
+    });
+    expect(trends.dayOverDay.mentorReviews).toMatchObject({
+      current: 2,
+      previous: 1,
+      delta: 1,
+    });
+    expect(trends.dayOverDay.avgReviewTimeHours).toMatchObject({
+      current: 3,
+      previous: 2,
+      delta: 1,
+      direction: 'up',
+    });
+  });
+
+  it('marks average review time delta as flat when either day has no reviews', () => {
+    const trends = buildMaintainerAnalyticsTrends({
+      now: new Date('2026-05-21T12:00:00.000Z'),
+      mergedPullRequests: [
+        {
+          githubCreatedAt: '2026-05-21T02:00:00.000Z',
+          mergedAt: null,
+          mentorReviewAt: '2026-05-21T06:00:00.000Z',
+        },
+      ],
+      completedRecommendations: [],
+      contributorProfiles: [],
+      levelUps: [],
+    });
+
+    expect(trends.dayOverDay.avgReviewTimeHours).toMatchObject({
+      current: 4,
+      previous: null,
+      delta: null,
+      direction: 'flat',
+    });
+  });
 });