feat: add activity ring chart with 24-segment SVG arc visualization

src/app/api/metrics/contributions/daily/route.ts

@@ -0,0 +1,86 @@
+import { getServerSession } from "next-auth";
+import { NextRequest } from "next/server";
+import { authOptions } from "@/lib/auth";
+import { GITHUB_API } from "@/lib/github";
+import {
+  isMetricsCacheBypassed,
+  METRICS_CACHE_TTL_SECONDS,
+  metricsCacheKey,
+  withMetricsCache,
+} from "@/lib/metrics-cache";
+
+export const dynamic = "force-dynamic";
+
+interface RepoCommit {
+  repo: string;
+  count: number;
+  url: string;
+}
+
+export async function GET(req: NextRequest) {
+  const session = await getServerSession(authOptions);
+  if (!session?.accessToken || !session.githubLogin) {
+    return Response.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
+  const date = req.nextUrl.searchParams.get("date");
+  if (!date || !/^\d{4}-\d{2}-\d{2}$/.test(date)) {
+    return Response.json({ error: "Missing or invalid date" }, { status: 400 });
+  }
+
+  const bypass = isMetricsCacheBypassed(req);
+  const key = metricsCacheKey(
+    session.githubId ?? session.githubLogin,
+    "contributions",
+    { date }
+  );
+
+  try {
+    const result = await withMetricsCache(
+      {
+        bypass,
+        key,
+        ttlSeconds: METRICS_CACHE_TTL_SECONDS.contributions,
+      },
+      async () => {
+        const searchRes = await fetch(
+          `${GITHUB_API}/search/commits?q=author:${session.githubLogin}+author-date:${date}&per_page=100`,
+          {
+            headers: {
+              Authorization: `Bearer ${session.accessToken}`,
+              Accept: "application/vnd.github+json",
+            },
+            cache: "no-store",
+          }
+        );
+
+        if (!searchRes.ok) throw new Error("GitHub API error");
+
+        const data = (await searchRes.json()) as {
+          items: Array<{
+            repository: { full_name: string; html_url: string };
+          }>;
+        };
+
+        const repoMap: Record<string, { count: number; url: string }> = {};
+        for (const item of data.items) {
+          const { full_name, html_url } = item.repository;
+          if (!repoMap[full_name]) {
+            repoMap[full_name] = { count: 0, url: html_url };
+          }
+          repoMap[full_name].count++;
+        }
+
+        const repos: RepoCommit[] = Object.entries(repoMap).map(
+          ([repo, { count, url }]) => ({ repo, count, url })
+        );
+
+        return { date, repos };
+      }
+    );
+
+    return Response.json(result);
+  } catch {
+    return Response.json({ error: "GitHub API error" }, { status: 502 });
+  }
+}

src/app/api/metrics/contributions/hourly/route.ts

@@ -0,0 +1,82 @@
+import { getServerSession } from "next-auth";
+import { NextRequest } from "next/server";
+import { authOptions } from "@/lib/auth";
+import { GITHUB_API } from "@/lib/github";
+import {
+  isMetricsCacheBypassed,
+  METRICS_CACHE_TTL_SECONDS,
+  metricsCacheKey,
+  withMetricsCache,
+} from "@/lib/metrics-cache";
+
+export const dynamic = "force-dynamic";
+
+export async function GET(req: NextRequest) {
+  const session = await getServerSession(authOptions);
+  if (!session?.accessToken || !session.githubLogin) {
+    return Response.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
+  const days = Number(req.nextUrl.searchParams.get("days")) || 30;
+  const bypass = isMetricsCacheBypassed(req);
+  const key = metricsCacheKey(
+    session.githubId ?? session.githubLogin,
+    "contributions",
+    { days }
+  );
+
+  try {
+    const result = await withMetricsCache(
+      {
+        bypass,
+        key,
+        ttlSeconds: METRICS_CACHE_TTL_SECONDS.contributions,
+      },
+      async () => {
+        const since = new Date();
+        since.setDate(since.getDate() - days);
+        const sinceStr = since.toISOString().slice(0, 10);
+
+        const searchRes = await fetch(
+          `${GITHUB_API}/search/commits?q=author:${session.githubLogin}+author-date:>=${sinceStr}&per_page=100&sort=author-date&order=desc`,
+          {
+            headers: {
+              Authorization: `Bearer ${session.accessToken}`,
+              Accept: "application/vnd.github+json",
+            },
+            cache: "no-store",
+          }
+        );
+
+        if (!searchRes.ok) throw new Error("GitHub API error");
+
+        const data = (await searchRes.json()) as {
+          items: Array<{ commit: { author: { date: string } } }>;
+        };
+
+        // Initialize all 24 hours to 0
+        const hourMap: Record<number, number> = {};
+        for (let i = 0; i < 24; i++) hourMap[i] = 0;
+
+        // NOTE: date.getHours() returns UTC hours from the server,
+        // not the user's local timezone. The client displays these as-is.
+        for (const item of data.items) {
+          const date = new Date(item.commit.author.date);
+          const hour = date.getHours();
+          hourMap[hour]++;
+        }
+
+        const hours = Array.from({ length: 24 }, (_, i) => ({
+          hour: i,
+          commits: hourMap[i],
+        }));
+
+        return { days, hours };
+      }
+    );
+
+    return Response.json(result);
+  } catch {
+    return Response.json({ error: "GitHub API error" }, { status: 502 });
+  }
+}

src/app/dashboard/page.tsx

@@ -1,3 +1,4 @@
+import ActivityRingChart from "@/components/ActivityRingChart";
 import ContributionGraph from "@/components/ContributionGraph";
 import ContributionHeatmap from "@/components/ContributionHeatmap";
 import PRMetrics from "@/components/PRMetrics";
@@ -71,6 +72,10 @@ export default async function DashboardPage() {
         <PRBreakdownChart />
         <CommitTimeChart />
       </div>
+      {/* Row 2b: Activity Ring Chart */}
+      <div className="mt-6">
+        <ActivityRingChart />
+      </div>
 
       <div className="mt-6">
         <PRReviewTrendChart />

src/components/ActivityRingChart.tsx

@@ -0,0 +1,205 @@
+"use client";
+
+import { useEffect, useState, useRef } from "react";
+
+interface HourData {
+  hour: number;
+  commits: number;
+}
+
+function formatHour(hour: number): string {
+  if (hour === 0) return "12am";
+  if (hour < 12) return `${hour}am`;
+  if (hour === 12) return "12pm";
+  return `${hour - 12}pm`;
+}
+
+export default function ActivityRingChart() {
+  const [data, setData] = useState<HourData[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+  const [days, setDays] = useState(30);
+  const [hoveredHour, setHoveredHour] = useState<HourData | null>(null);
+  const [animated, setAnimated] = useState(false);
+  const prefersReduced = useRef(
+    typeof window !== "undefined"
+      ? window.matchMedia("(prefers-reduced-motion: reduce)").matches
+      : false
+  );
+
+  useEffect(() => {
+    setLoading(true);
+    setError(null);
+    setAnimated(false);
+    fetch(`/api/metrics/contributions/hourly?days=${days}`)
+      .then((r) => r.json())
+      .then((res: { hours?: HourData[] }) => {
+        setData(res.hours ?? []);
+        setTimeout(() => setAnimated(true), 50);
+      })
+      .catch(() => setError("Failed to load activity data."))
+      .finally(() => setLoading(false));
+  }, [days]);
+
+  const maxCommits = Math.max(...data.map((d) => d.commits), 1);
+  const peakHour = data.reduce(
+    (a, b) => (b.commits > a.commits ? b : a),
+    { hour: 0, commits: 0 }
+  );
+
+  const cx = 150;
+  const cy = 150;
+  const innerR = 55;
+  const outerMaxR = 120;
+  const segments = 24;
+  const anglePerSegment = (2 * Math.PI) / segments;
+  const gap = 0.04;
+
+  function polarToCartesian(angle: number, r: number) {
+    return {
+      x: cx + r * Math.cos(angle - Math.PI / 2),
+      y: cy + r * Math.sin(angle - Math.PI / 2),
+    };
+  }
+
+  function segmentPath(index: number, outerR: number) {
+    const startAngle = index * anglePerSegment + gap;
+    const endAngle = (index + 1) * anglePerSegment - gap;
+    const o1 = polarToCartesian(startAngle, outerR);
+    const o2 = polarToCartesian(endAngle, outerR);
+    const i1 = polarToCartesian(startAngle, innerR);
+    const i2 = polarToCartesian(endAngle, innerR);
+    const largeArc = endAngle - startAngle > Math.PI ? 1 : 0;
+    return [
+      `M ${i1.x} ${i1.y}`,
+      `L ${o1.x} ${o1.y}`,
+      `A ${outerR} ${outerR} 0 ${largeArc} 1 ${o2.x} ${o2.y}`,
+      `L ${i2.x} ${i2.y}`,
+      `A ${innerR} ${innerR} 0 ${largeArc} 0 ${i1.x} ${i1.y}`,
+      "Z",
+    ].join(" ");
+  }
+
+  return (
+    <div className="rounded-xl border border-[var(--border)] bg-[var(--card)] p-6 shadow-sm flex flex-col h-full">
+      <div className="flex items-center justify-between mb-2">
+        <h2 className="text-lg font-semibold text-[var(--card-foreground)]">
+          Activity Ring
+        </h2>
+        <select
+          value={days}
+          onChange={(e) => setDays(Number(e.target.value))}
+          className="rounded-lg border border-[var(--border)] bg-[var(--card)] px-2 py-1 text-sm text-[var(--card-foreground)] focus:outline-none focus:border-[var(--accent)]"
+        >
+          <option value={7}>Last 7d</option>
+          <option value={30}>Last 30d</option>
+          <option value={90}>Last 90d</option>
+        </select>
+      </div>
+
+      <p className="text-sm text-[var(--muted-foreground)] mb-4 h-5">
+        {peakHour.commits > 0 &&
+          `Most active at ${formatHour(peakHour.hour)} (${peakHour.commits} commits)`}
+      </p>
+
+      <div className="flex-1 flex items-center justify-center min-h-[300px]">
+        {loading ? (
+          <div className="h-48 w-48 animate-pulse rounded-full bg-[var(--card-muted)]" />
+        ) : error ? (
+          <p className="text-sm text-[var(--destructive)]">{error}</p>
+        ) : data.every((d) => d.commits === 0) ? (
+          <p className="text-sm text-[var(--muted-foreground)]">
+            No commits in the last {days} days.
+          </p>
+        ) : (
+          <div className="flex flex-col items-center gap-4">
+            <svg width="300" height="300" viewBox="0 0 300 300">
+              {/* Hour labels */}
+              {[0, 6, 12, 18].map((h) => {
+                const angle = h * anglePerSegment - Math.PI / 2;
+                const labelR = outerMaxR + 18;
+                const x = cx + labelR * Math.cos(angle);
+                const y = cy + labelR * Math.sin(angle);
+                return (
+                  <text
+                    key={h}
+                    x={x}
+                    y={y}
+                    textAnchor="middle"
+                    dominantBaseline="middle"
+                    fontSize="10"
+                    fill="var(--muted-foreground)"
+                  >
+                    {formatHour(h)}
+                  </text>
+                );
+              })}
+
+              {/* Segments */}
+              {data.map((d) => {
+                const isPeak = d.hour === peakHour.hour && d.commits > 0;
+                const isHovered = hoveredHour?.hour === d.hour;
+                const ratio = d.commits / maxCommits;
+                const targetR = d.commits === 0
+                  ? innerR + 4
+                  : innerR + (outerMaxR - innerR) * ratio;
+                const currentR =
+                  !prefersReduced.current && !animated ? innerR : targetR;
+
+                return (
+                  <path
+                    key={d.hour}
+                    d={segmentPath(d.hour, currentR)}
+                    fill={
+                      isPeak || isHovered
+                        ? "var(--accent)"
+                        : d.commits === 0
+                        ? "var(--card-muted, #2a2a2a)"
+                        : "var(--accent)"
+                    }
+                    opacity={
+                      d.commits === 0
+                        ? 0.15
+                        : isPeak || isHovered
+                        ? 1
+                        : 0.5 + 0.5 * ratio
+                    }
+                    style={{
+                      transition: prefersReduced.current
+                        ? "none"
+                        : "all 0.6s cubic-bezier(0.34, 1.56, 0.64, 1)",
+                      cursor: d.commits > 0 ? "pointer" : "default",
+                    }}
+                    onMouseEnter={() => setHoveredHour(d)}
+                    onMouseLeave={() => setHoveredHour(null)}
+                  />
+                );
+              })}
+
+              {/* Center label */}
+              <text
+                x={cx}
+                y={cy - 8}
+                textAnchor="middle"
+                fontSize="22"
+                fontWeight="bold"
+                fill="var(--card-foreground)"
+              >
+                {hoveredHour ? hoveredHour.commits : data.reduce((s, d) => s + d.commits, 0)}
+              </text>
+              <text
+                x={cx}
+                y={cy + 14}
+                textAnchor="middle"
+                fontSize="11"
+                fill="var(--muted-foreground)"
+              >
+                {hoveredHour ? formatHour(hoveredHour.hour) : "commits"}
+              </text>
+            </svg>
+          </div>
+        )}
+      </div>
+    </div>
+  );
+}