(core) Adding google drive plugin as a fallback for url plugin

Summary:
When importing from url, user types a url for google spreadsheet,
Grist will switch to Google Drive plugin to allow user to choose file manualy.

Test Plan: Browser tests

Reviewers: paulfitz, dsagal

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2945

app/server/lib/FlexServer.ts

@@ -760,7 +760,7 @@ export class FlexServer implements GristServer {
       // Those keys are eventually visible by the client, but should be usable
       // only from Grist's domains.
       const secrets = {
-        googleClientId : config.googleClientId,
+        googleClientId: config.googleClientId,
       };
       res.set('Content-Type', 'application/javascript');
       res.status(200);

app/server/lib/GoogleImport.ts

@@ -0,0 +1,72 @@
+import {drive} from '@googleapis/drive';
+import {Readable} from 'form-data';
+import {GaxiosError, GaxiosPromise} from 'gaxios';
+import {FetchError, Response as FetchResponse, Headers} from 'node-fetch';
+
+const
+  SPREADSHEETS_MIMETYPE = 'application/vnd.google-apps.spreadsheet',
+  XLSX_MIMETYPE = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
+
+export async function downloadFromGDrive(url: string) {
+  const fileId = fileIdFromUrl(url);
+  const googleDrive = drive("v3");
+  const key = process.env.GOOGLE_API_KEY;
+  if (!key) {
+    throw new Error("Can't download file from Google Drive. Api key is not configured");
+  }
+  if (!fileId) {
+    throw new Error(`Can't download from ${url}. Url is not valid`);
+  }
+  const fileRes = await googleDrive.files.get({
+    key,
+    fileId
+  });
+  if (fileRes.data.mimeType === SPREADSHEETS_MIMETYPE) {
+    return await asFetchResponse(googleDrive.files.export(
+      { key, fileId, alt: 'media', mimeType: XLSX_MIMETYPE },
+      { responseType: 'stream' }
+    ));
+  } else {
+    return await asFetchResponse(googleDrive.files.get(
+      { key, fileId, alt: 'media' },
+      { responseType: 'stream' }
+    ));
+  }
+}
+
+
+async function asFetchResponse(req: GaxiosPromise<Readable>) {
+  try {
+    const res = await req;
+    return new FetchResponse(res.data, {
+      headers: new Headers(res.headers),
+      status: res.status,
+      statusText: res.statusText
+    });
+  } catch (err) {
+    const error: GaxiosError<Readable> = err;
+    if (!error.response) {
+      // Fetch throws exception on network error.
+      // https://github.com/node-fetch/node-fetch/blob/master/docs/ERROR-HANDLING.md
+      throw new FetchError(error.message, "system", error.code || "unknown");
+    } else {
+      // Fetch returns failure response on http error
+      const resInit = error.response ? {
+        status: error.response.status,
+        headers: new Headers(error.response.headers),
+        statusText: error.response.statusText
+      } : undefined;
+      return new FetchResponse(error.response.data, resInit);
+    }
+  }
+}
+
+export function isDriveUrl(url: string) {
+  return !!fileIdFromUrl(url);
+}
+
+function fileIdFromUrl(url: string) {
+  if (!url) { return null; }
+  const match = /^https:\/\/(docs|drive).google.com\/(spreadsheets|file)\/d\/([^/]*)/i.exec(url);
+  return match ? match[3] : null;
+}

app/server/lib/uploads.ts

@@ -5,6 +5,7 @@ import {getAuthorizedUserId, getTransitiveHeaders, getUserId, isSingleUserMode,
         RequestWithLogin} from 'app/server/lib/Authorizer';
 import {expressWrap} from 'app/server/lib/expressWrap';
 import {RequestWithGrist} from 'app/server/lib/FlexServer';
+import {downloadFromGDrive, isDriveUrl} from 'app/server/lib/GoogleImport';
 import {GristServer} from 'app/server/lib/GristServer';
 import {guessExt} from 'app/server/lib/guessExt';
 import * as log from 'app/server/lib/log';
@@ -338,11 +339,16 @@ export async function fetchURL(url: string, accessId: string|null): Promise<Uplo
 async function _fetchURL(url: string, accessId: string|null, fileName: string,
                          headers?: {[key: string]: string}): Promise<UploadResult> {
   try {
-    const response: FetchResponse = await Deps.fetch(url, {
-      redirect: 'follow',
-      follow: 10,
-      headers
-    });
+    let response: FetchResponse;
+    if (isDriveUrl(url)) {
+      response = await downloadFromGDrive(url);
+    } else {
+      response = await Deps.fetch(url, {
+        redirect: 'follow',
+        follow: 10,
+        headers
+      });
+    }
     await _checkForError(response);
     if (fileName === '') {
       const disposition = response.headers.get('content-disposition') || '';