Add support for loading files from Google Drive

#vibecoded

src/datasource/google_drive.ts

@@ -0,0 +1,93 @@
+import {TopolaData} from '../util/gedcom_util';
+import {DataSource, DataSourceEnum, SourceSelection} from './data_source';
+import {
+  GOOGLE_DRIVE_CACHE_KEY_PREFIX,
+  googleDriveService,
+} from './google_drive_service';
+import {loadAndPrepareFile} from './load_data';
+
+/** Specification for Google Drive data source. */
+export interface GoogleDriveSourceSpec {
+  source: DataSourceEnum.GOOGLE_DRIVE;
+  /** The unique ID of the file in Google Drive. */
+  fileId: string;
+}
+
+/** Error thrown when Google Drive authentication or authorization fails or is missing. */
+export class GoogleDriveAuthError extends Error {
+  constructor(message?: string) {
+    super(message);
+    this.name = 'GoogleDriveAuthError';
+    // Set the prototype explicitly.
+    Object.setPrototypeOf(this, GoogleDriveAuthError.prototype);
+  }
+}
+
+/** Data source representing family tree data loaded from Google Drive. */
+export class GoogleDriveDataSource implements DataSource<GoogleDriveSourceSpec> {
+  isNewData(
+    newSource: SourceSelection<GoogleDriveSourceSpec>,
+    oldSource: SourceSelection<GoogleDriveSourceSpec>,
+    _data?: TopolaData,
+  ): boolean {
+    return newSource.spec.fileId !== oldSource.spec.fileId;
+  }
+
+  async loadData(
+    source: SourceSelection<GoogleDriveSourceSpec>,
+  ): Promise<TopolaData> {
+    const fileId = source.spec.fileId;
+    const cacheKey = `${GOOGLE_DRIVE_CACHE_KEY_PREFIX}${fileId}`;
+
+    // 1. Check sessionStorage cache
+    try {
+      const cachedData = sessionStorage.getItem(cacheKey);
+      if (cachedData) {
+        return JSON.parse(cachedData);
+      }
+    } catch (e) {
+      console.warn('Failed to load data from session storage: ' + e);
+    }
+
+    // 2. Get the active access token
+    const token = googleDriveService.getAccessToken();
+    if (!token) {
+      throw new GoogleDriveAuthError(
+        'No active Google Drive access token found.',
+      );
+    }
+
+    // 3. Fetch file content from Google Drive API
+    const response = await window
+      .fetch(`https://www.googleapis.com/drive/v3/files/${fileId}?alt=media`, {
+        headers: {
+          Authorization: `Bearer ${token}`,
+        },
+      })
+      .catch((error) => {
+        throw new Error(
+          `Network error fetching file from Google Drive: ${(error as Error).message}`,
+        );
+      });
+
+    // 4. Inspect response status
+    if (
+      response.status === 401 ||
+      response.status === 403 ||
+      response.status === 404
+    ) {
+      throw new GoogleDriveAuthError(
+        `Access denied or file not found (HTTP ${response.status}).`,
+      );
+    }
+    if (response.status !== 200) {
+      throw new Error(
+        `Failed to fetch file from Google Drive (HTTP ${response.status}): ${response.statusText}`,
+      );
+    }
+
+    // 5. Parse and prepare the file content
+    const blob = await response.blob();
+    return loadAndPrepareFile(blob, cacheKey);
+  }
+}