scaffolder: add filesystem access helpers

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/scaffolder/src/lib/filesystem/WebFileSystemAccess.ts

@@ -0,0 +1,105 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * 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 {
+  TemplateFileSystemAccess,
+  TemplateDirectoryAccess,
+  TemplateFileAccess,
+} from './types';
+
+type WritableFileHandle = FileSystemFileHandle & {
+  createWritable(): Promise<{
+    write(data: string | Blob | BufferSource): Promise<void>;
+    close(): Promise<void>;
+  }>;
+};
+
+// A nicer type than the one from the TS lib
+interface IterableDirectoryHandle extends FileSystemDirectoryHandle {
+  values(): AsyncIterable<
+    | ({ kind: 'file' } & WritableFileHandle)
+    | ({ kind: 'directory' } & IterableDirectoryHandle)
+  >;
+}
+
+const showDirectoryPicker = (window as any).showDirectoryPicker as
+  | (() => Promise<IterableDirectoryHandle>)
+  | undefined;
+
+class WebFileAccess implements TemplateFileAccess {
+  constructor(
+    readonly path: string,
+    private readonly handle: WritableFileHandle,
+  ) {}
+
+  file(): Promise<File> {
+    return this.handle.getFile();
+  }
+
+  async save(data: string | Blob | BufferSource): Promise<void> {
+    const writable = await this.handle.createWritable();
+    await writable.write(data);
+    await writable.close();
+  }
+}
+
+class WebDirectoryAccess implements TemplateDirectoryAccess {
+  constructor(private readonly handle: IterableDirectoryHandle) {}
+
+  async listFiles(): Promise<TemplateFileAccess[]> {
+    const content = [];
+    for await (const entry of this.listDirectoryContents(this.handle)) {
+      content.push(entry);
+    }
+    return content;
+  }
+
+  private async *listDirectoryContents(
+    dirHandle: IterableDirectoryHandle,
+    basePath: string[] = [],
+  ): AsyncIterable<TemplateFileAccess> {
+    for await (const handle of dirHandle.values()) {
+      if (handle.kind === 'file') {
+        yield new WebFileAccess([...basePath, handle.name].join('/'), handle);
+      } else if (handle.kind === 'directory') {
+        yield* this.listDirectoryContents(handle, [...basePath, handle.name]);
+      }
+    }
+  }
+}
+
+/** @internal */
+export class WebFileSystemAccess implements TemplateFileSystemAccess {
+  private static instance = new WebFileSystemAccess();
+
+  static get(): TemplateFileSystemAccess {
+    return this.instance;
+  }
+
+  static isSupported(): boolean {
+    return Boolean(showDirectoryPicker);
+  }
+
+  private constructor() {}
+
+  async requestDirectoryAccess(): Promise<TemplateDirectoryAccess> {
+    if (!showDirectoryPicker) {
+      throw new Error('File system access is not supported');
+    }
+    const handle = await showDirectoryPicker();
+    return new WebDirectoryAccess(handle);
+  }
+}

plugins/scaffolder/src/lib/filesystem/helpers.ts

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * 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.
+ */
+
+export async function blobToBase64(file: Blob) {
+  const reader = new FileReader();
+  reader.readAsDataURL(file);
+  return new Promise<string>((resolve, reject) => {
+    reader.onload = () => {
+      const uri = reader.result as string;
+      resolve(uri.slice(uri.indexOf(',') + 1));
+    };
+    reader.onerror = reject;
+  });
+}

plugins/scaffolder/src/lib/filesystem/index.ts

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * 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.
+ */
+
+export type {
+  TemplateFileAccess,
+  TemplateDirectoryAccess,
+  TemplateFileSystemAccess,
+} from './types';
+export { blobToBase64 } from './helpers';
+export { WebFileSystemAccess } from './WebFileSystemAccess';

plugins/scaffolder/src/lib/filesystem/types.ts

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * 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.
+ */
+
+export interface TemplateFileAccess {
+  path: string;
+  file(): Promise<File>;
+  save(data: string | BufferSource | Blob): Promise<void>;
+}
+
+export interface TemplateDirectoryAccess {
+  listFiles(): Promise<Array<TemplateFileAccess>>;
+}
+
+export interface TemplateFileSystemAccess {
+  requestDirectoryAccess(): Promise<TemplateDirectoryAccess>;
+}