fix: improve the UI for check quota of the user

src/app/api/users/[userId]/token-usage/route.js

@@ -0,0 +1,97 @@
+import { NextResponse } from "next/server";
+import {
+  getUserById,
+  getUserProviderTokenUsageSince,
+  getUserTokenLimits,
+} from "@/lib/db/index.js";
+import { requireAdminUser } from "@/lib/auth/currentUser.js";
+import { getUserTokenLimitWindowStart } from "@/lib/tokenLimitEnforcer.js";
+import {
+  USER_TOKEN_LIMIT_PROVIDER_IDS,
+  USER_TOKEN_LIMIT_WINDOW_IDS,
+} from "open-sse/config/userTokenLimits.js";
+
+export const dynamic = "force-dynamic";
+
+const NO_STORE_HEADERS = { "Cache-Control": "no-store" };
+
+function errorResponse(error) {
+  const message = error?.message || "Request failed";
+  const status = message === "Unauthorized"
+    ? 401
+    : message === "Forbidden"
+      ? 403
+      : message === "User not found"
+        ? 404
+        : 400;
+  return NextResponse.json({ error: message }, { status, headers: NO_STORE_HEADERS });
+}
+
+function buildWindowUsage(limit, used, windowStart) {
+  const normalizedLimit = Math.max(0, Number(limit) || 0);
+  const normalizedUsed = Math.max(0, Number(used) || 0);
+  const remaining = normalizedLimit > 0
+    ? Math.max(0, normalizedLimit - normalizedUsed)
+    : null;
+  const remainingPercentage = normalizedLimit > 0
+    ? Math.round((remaining / normalizedLimit) * 100)
+    : null;
+
+  return {
+    limit: normalizedLimit,
+    used: normalizedUsed,
+    remaining,
+    remainingPercentage,
+    windowStart: windowStart.toISOString(),
+  };
+}
+
+export async function GET(_request, { params }) {
+  try {
+    await requireAdminUser();
+
+    const { userId } = await params;
+    const user = await getUserById(userId);
+    if (!user) throw new Error("User not found");
+    if (user.role !== "user") throw new Error("Token usage only applies to user accounts");
+
+    const now = new Date();
+    const limits = await getUserTokenLimits(user.id);
+    const windows = Object.fromEntries(USER_TOKEN_LIMIT_WINDOW_IDS.map((windowType) => [
+      windowType,
+      getUserTokenLimitWindowStart(windowType, now),
+    ]));
+
+    const usageEntries = await Promise.all(
+      USER_TOKEN_LIMIT_PROVIDER_IDS.flatMap((provider) => (
+        USER_TOKEN_LIMIT_WINDOW_IDS.map(async (windowType) => {
+          const used = await getUserProviderTokenUsageSince(
+            user.id,
+            provider,
+            windows[windowType],
+          );
+          return [provider, windowType, used];
+        })
+      )),
+    );
+
+    const usageByProvider = Object.fromEntries(
+      USER_TOKEN_LIMIT_PROVIDER_IDS.map((provider) => [provider, {}]),
+    );
+    for (const [provider, windowType, used] of usageEntries) {
+      usageByProvider[provider][windowType] = buildWindowUsage(
+        limits[provider]?.[windowType],
+        used,
+        windows[windowType],
+      );
+    }
+
+    return NextResponse.json({
+      userId: user.id,
+      providers: usageByProvider,
+      updatedAt: now.toISOString(),
+    }, { headers: NO_STORE_HEADERS });
+  } catch (error) {
+    return errorResponse(error);
+  }
+}