feat(revalidate): add type validation and README to revalidate endpoint

Agent-Logs-Url: https://github.com/MobilityData/mobilitydatabase-web/sessions/90eff8fb-c818-4fa7-8edc-49790020ce49

Co-authored-by: Alessandro100 <18631060+Alessandro100@users.noreply.github.com>

Author: Copilot

src/app/api/revalidate/README.md

@@ -0,0 +1,91 @@
+# `/api/revalidate` Endpoint
+
+This endpoint is used by external systems to trigger on-demand Next.js cache revalidation for feed pages. It exposes two HTTP methods:
+
+- **GET** — Used exclusively by the Vercel cron job to revalidate all GBFS feed pages on a schedule.
+- **POST** — Used by external systems to trigger targeted or full-site cache revalidation.
+
+---
+
+## GET
+
+Revalidates all GBFS feed pages. This handler is invoked automatically by Vercel's cron scheduler (configured in `vercel.json`) at 4am UTC Monday–Saturday and 7am UTC Sunday.
+
+### Authentication
+
+Vercel automatically passes an `Authorization: Bearer <CRON_SECRET>` header on every cron invocation. The value must match the `CRON_SECRET` environment variable.
+
+### Response
+
+| Status | Body |
+|--------|------|
+| `200` | `{ "ok": true, "message": "All GBFS feeds revalidated successfully" }` |
+| `401` | `{ "ok": false, "error": "Unauthorized" }` |
+| `500` | `{ "ok": false, "error": "Server misconfigured: CRON_SECRET missing" }` |
+| `500` | `{ "ok": false, "error": "Revalidation failed" }` |
+
+---
+
+## POST
+
+Triggers targeted cache revalidation. The caller controls the scope of revalidation via the request body.
+
+### Authentication
+
+Include the `x-revalidate-secret` header with the value of the `REVALIDATE_SECRET` environment variable.
+
+```
+x-revalidate-secret: <REVALIDATE_SECRET>
+```
+
+### Request Body
+
+```json
+{
+  "type": "<revalidation-type>",
+  "feedIds": ["<feed-id-1>", "<feed-id-2>"]
+}
+```
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `type` | `string` | Yes | The revalidation scope. Must be one of the valid types listed below. |
+| `feedIds` | `string[]` | Only for `specific-feeds` | List of feed IDs to revalidate. Ignored for all other types. |
+
+If the request body is missing or cannot be parsed, the endpoint falls back to the default: `type: "specific-feeds"` with an empty `feedIds` array (no-op).
+
+### Valid `type` Values
+
+| Type | Description |
+|------|-------------|
+| `full` | Revalidates the entire site (all pages and all cache tags). |
+| `all-feeds` | Revalidates all GTFS, GTFS-RT, and GBFS feed detail pages and their shared cache tags. |
+| `all-gtfs-feeds` | Revalidates all GTFS feed detail pages and the `feed-type-gtfs` cache tag. |
+| `all-gtfs-rt-feeds` | Revalidates all GTFS-RT feed detail pages and the `feed-type-gtfs_rt` cache tag. |
+| `all-gbfs-feeds` | Revalidates all GBFS feed detail pages and the `feed-type-gbfs` cache tag. |
+| `specific-feeds` | Revalidates only the pages for the feed IDs listed in `feedIds`. Each feed is revalidated across all feed-type paths (GTFS, GTFS-RT, GBFS) and all locales. |
+
+If an unrecognized or missing `type` is provided, the endpoint returns a `500` error:
+
+```json
+{ "ok": false, "error": "invalid or missing type parameter" }
+```
+
+### Response
+
+| Status | Body |
+|--------|------|
+| `200` | `{ "ok": true, "message": "Revalidation triggered successfully" }` |
+| `401` | `{ "ok": false, "error": "Unauthorized" }` |
+| `500` | `{ "ok": false, "error": "Server misconfigured: REVALIDATE_SECRET missing" }` |
+| `500` | `{ "ok": false, "error": "invalid or missing type parameter" }` |
+| `500` | `{ "ok": false, "error": "Failed to revalidate" }` |
+
+### Example Request
+
+```bash
+curl -X POST https://mobilitydatabase.org/api/revalidate \
+  -H "Content-Type: application/json" \
+  -H "x-revalidate-secret: <REVALIDATE_SECRET>" \
+  -d '{ "type": "specific-feeds", "feedIds": ["feed-abc123", "feed-def456"] }'
+```

src/app/api/revalidate/route.spec.ts

@@ -449,8 +449,31 @@ describe('POST /api/revalidate', () => {
       expect(mockRevalidatePath).toHaveBeenCalledTimes(36);
     });
 
-    it('handles specific-feeds with empty feedIds', async () => {
+    it('returns 500 when type is invalid', async () => {
       const request = new Request('http://localhost:3000/api/revalidate', {
+        method: 'POST',
+        headers: {
+          'x-revalidate-secret': 'test-secret',
+          'content-type': 'application/json',
+        },
+        body: JSON.stringify({
+          type: 'not-a-valid-type',
+        }),
+      });
+
+      const response = await POST(request);
+      const json = await response.json();
+
+      expect(response.status).toBe(500);
+      expect(json).toEqual({
+        ok: false,
+        error: 'invalid or missing type parameter',
+      });
+      expect(mockRevalidatePath).not.toHaveBeenCalled();
+      expect(mockRevalidateTag).not.toHaveBeenCalled();
+    });
+
+    it('handles specific-feeds with empty feedIds', async () => {      const request = new Request('http://localhost:3000/api/revalidate', {
         method: 'POST',
         headers: {
           'x-revalidate-secret': 'test-secret',

src/app/api/revalidate/route.ts

@@ -17,6 +17,15 @@ type RevalidateTypes =
   | 'all-gtfs-feeds'
   | 'specific-feeds';
 
+const VALID_REVALIDATE_TYPES: RevalidateTypes[] = [
+  'full',
+  'all-feeds',
+  'all-gbfs-feeds',
+  'all-gtfs-rt-feeds',
+  'all-gtfs-feeds',
+  'specific-feeds',
+];
+
 interface RevalidateBody {
   feedIds: string[]; // only for 'specific-feeds' revalidation type
   type: RevalidateTypes;
@@ -104,6 +113,13 @@ export async function POST(req: Request): Promise<NextResponse> {
     payload = { ...defaultRevalidateOptions };
   }
 
+  if (!VALID_REVALIDATE_TYPES.includes(payload.type)) {
+    return NextResponse.json(
+      { ok: false, error: 'invalid or missing type parameter' },
+      { status: 500 },
+    );
+  }
+
   // NOTE
   // revalidatePath = triggers revalidation for entire page cache
   // revalidateTag = triggers revalidation for API calls using `unstable_cache` with matching tags (e.g., feed-123, guest-feeds)