Add download file API

Summary: Changelog: Expose "downloadFile" API to Flipper plugins. Allow them to download files form the web to Flipper Server.

Reviewed By: mweststrate

Differential Revision: D32950685

fbshipit-source-id: 7b7f666e165ff7bf209230cdc96078272ede3616

desktop/flipper-server-core/src/FlipperServerImpl.tsx

@@ -45,6 +45,7 @@ import {
 } from './fb-stubs/internRequests';
 import {commandNodeApiExec} from './commands/NodeApiExec';
 import {access, copyFile, mkdir, unlink} from 'fs/promises';
+import {commandDownloadFileStartFactory} from './commands/DownloadFile';
 
 export const SERVICE_FLIPPER = 'flipper.oAuthToken';
 
@@ -228,6 +229,11 @@ export class FlipperServerImpl implements FlipperServer {
     'node-api-fs-unlink': unlink,
     'node-api-fs-mkdir': mkdir,
     'node-api-fs-copyFile': copyFile,
+    // TODO: Unit tests
+    // TODO: Do we need API to cancel an active download?
+    'download-file-start': commandDownloadFileStartFactory(
+      this.emit.bind(this),
+    ),
     'get-config': async () => this.config,
     'get-changelog': getChangelog,
     'device-list': async () => {

desktop/flipper-server-core/src/commands/DownloadFile.tsx

@@ -0,0 +1,106 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {FlipperServerCommands, FlipperServerEvents} from 'flipper-common';
+import {pathExists} from 'fs-extra';
+import {promises, createWriteStream, ReadStream} from 'fs';
+import axios from 'axios';
+import {v4 as uuid} from 'uuid';
+
+const {unlink} = promises;
+
+// Adapter which forces node.js implementation for axios instead of browser implementation
+// used by default in Electron. Node.js implementation is better, because it
+// supports streams which can be used for direct downloading to disk.
+const axiosHttpAdapter = require('axios/lib/adapters/http'); // eslint-disable-line import/no-commonjs
+
+export const commandDownloadFileStartFactory =
+  (
+    emit: (
+      event: 'download-file-update',
+      payload: FlipperServerEvents['download-file-update'],
+    ) => void,
+  ): FlipperServerCommands['download-file-start'] =>
+  async (
+    url,
+    dest,
+    {method = 'GET', timeout, maxRedirects, headers, overwrite} = {},
+  ) => {
+    const destExists = await pathExists(dest);
+
+    if (destExists) {
+      if (!overwrite) {
+        throw new Error(
+          'FlipperServerImpl -> executing "download-file" -> path already exists and overwrite set to false',
+        );
+      }
+
+      await unlink(dest);
+    }
+
+    const downloadId = uuid();
+
+    const response = await axios.request<ReadStream>({
+      method,
+      url,
+      responseType: 'stream',
+      adapter: axiosHttpAdapter,
+      timeout,
+      maxRedirects,
+      headers,
+    });
+    const totalSize = response.headers['content-length'] ?? 0;
+
+    const writeStream = response.data.pipe(
+      createWriteStream(dest, {autoClose: true}),
+    );
+    let downloaded = 0;
+    response.data.on('data', (data: any) => {
+      downloaded += Buffer.byteLength(data);
+      emit('download-file-update', {
+        id: downloadId,
+        downloaded,
+        totalSize,
+        status: 'downloading',
+      });
+    });
+
+    response.data.on('error', (e: Error) => {
+      writeStream.destroy(e);
+    });
+
+    writeStream.on('finish', () => {
+      emit('download-file-update', {
+        id: downloadId,
+        downloaded,
+        totalSize,
+        status: 'success',
+      });
+    });
+
+    writeStream.on('error', (e: Error) => {
+      response.data.destroy();
+      emit('download-file-update', {
+        id: downloadId,
+        downloaded,
+        totalSize,
+        status: 'error',
+        message: e.message,
+        stack: e.stack,
+      });
+    });
+
+    return {
+      id: downloadId,
+      headers: response.headers,
+      status: response.status,
+      statusText: response.statusText,
+      totalSize,
+    };
+  };