feat: health check - can connect to firestore (#97)

src/lib/database.ts

@@ -68,4 +68,36 @@ export class Database {
       completedMissions: updatedMissions,
     });
   }
+
+  /**
+   * Returns true if able to connect to the Firestore instance.
+   * The Firestore API times out a request after 60 seconds. This method
+   * implements a configurable override that defaults to 5 seconds, but there's
+   * no point in setting it higher than 60 seconds.
+   * @param timeout seconds
+   */
+  async isConnected(timeout: number = 5): Promise<boolean> {
+    try {
+      timeout = Math.min(timeout, 60) * 1000;
+      // eslint-disable-next-line no-undef
+      let timerId: NodeJS.Timeout;
+
+      const timer = new Promise<boolean>((resolve) => {
+        timerId = setTimeout(() => resolve(false), timeout);
+      });
+
+      // TODO: research if there's a lighter weight way to status a connection.
+      const connectionCheck = this.db.listCollections();
+
+      return Promise.race([connectionCheck, timer]).then(result => {
+        clearTimeout(timerId);
+        return !!result;
+      });
+
+    } catch (err) {
+      // GoogleError: Total timeout of API google.firestore.v1.Firestore
+      // exceeded 60000 milliseconds before any response was received.
+      return false;
+    }
+  }
 }

src/pages/api/fscheck.ts

@@ -0,0 +1,28 @@
+/**
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import type { NextApiRequest, NextApiResponse } from 'next'
+import { Database } from "../../lib/database";
+
+
+export default async function handler(
+  req: NextApiRequest,
+  res: NextApiResponse,
+) {
+  const fs = new Database();
+  let isConnected = await fs.isConnected();
+  let statusCode = isConnected ? 200 : 503;
+  res.status(statusCode).end();
+}

src/pages/api/user.ts

@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
 import type { NextApiRequest, NextApiResponse } from 'next'
 import { Database } from "../../lib/database";
 import { User } from 'src/models/User';