Firebase Storage REST API

Question

I need very simple static image server for my flutter app. I am thinking about Cloud Storage, because I don't want to worry about own server administrating. I am using experimental Flutter for Desktop as tool for preparation data for mobile app, so I can use only REST API. I found out that Firebase Storage doesn't have own REST API and uses Google Cloud's one. To upload image to Cloud Storage I should make something like this:

curl -X POST --data-binary @[IMAGE_LOCATION] \
-H "Authorization: Bearer [OAUTH2_TOKEN]" \
-H "Content-Type: image/jpeg" \
"https://www.googleapis.com/upload/storage/v1/b/[BUCKET_NAME]/o?uploadType=media&name=[IMAGE_NAME]"

The problem is I can't understand how to get [OAUTH2_TOKEN] (access token) from my Dart code, and how to administrate my images (should I do something with Firebase Admin SDK?)

Could anyone help me, please?

Answer 1

I found answer to this question. First you need to create private key for service account in Firebase settings. Then use it to get access token using dart packages googleapis_auth and http.

var accountCredentials = ServiceAccountCredentials.fromJson({
  "private_key_id": "<please fill in>",
  "private_key": "<please fill in>",
  "client_email": "<please fill in>@developer.gserviceaccount.com",
  "client_id": "<please fill in>.apps.googleusercontent.com",
  "type": "service_account"
});

var scopes = [
  'https://www.googleapis.com/auth/cloud-platform',
];

var client = Client();
AccessCredentials credentials = await obtainAccessCredentialsViaServiceAccount(accountCredentials, scopes, client);
String accessToken = credentials.accessToken.data;

File image = File('path/to/image');
  
var request = Request(
  'POST',
  Uri.parse('https://storage.googleapis.com/upload/storage/v1/b/[BUCKET_NAME]/o?uploadType=media&name=images/$imageName'),
);
request.headers['Authorization'] = "Bearer $accessToken";
request.headers['Content-Type'] = "image/jpeg";
request.bodyBytes = await image.readAsBytes();
  
Response response = await Response.fromStream(await request.send());
print(response.statusCode);
client.close();

Get request you can make the similar way, but you have to encode firebase path to image:

var imagePath = 'images/img.jpg';
var encodedImagePath = Uri.encodeQueryComponent(imagePath);
var request = Request(
  'GET', 
  Uri.parse('https://storage.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/$encodedImagePath?alt=media'),
);
request.headers['Authorization'] = "Bearer $accessToken";

Google Cloud REST API: https://cloud.google.com/storage/docs/downloading-objects