Future createClient()

in example/main.dart [39:73]

• 15 lines of code
• 2 McCabe index (conditional complexity)

Future<oauth2.Client> createClient() async {
  var exists = await credentialsFile.exists();

  // If the OAuth2 credentials have already been saved from a previous run, we
  // just want to reload them.
  if (exists) {
    var credentials =
        oauth2.Credentials.fromJson(await credentialsFile.readAsString());
    return oauth2.Client(credentials, identifier: identifier, secret: secret);
  }

  // If we don't have OAuth2 credentials yet, we need to get the resource owner
  // to authorize us. We're assuming here that we're a command-line application.
  var grant = oauth2.AuthorizationCodeGrant(
      identifier, authorizationEndpoint, tokenEndpoint,
      secret: secret);

  // A URL on the authorization server (authorizationEndpoint with some additional
  // query parameters). Scopes and state can optionally be passed into this method.
  var authorizationUrl = grant.getAuthorizationUrl(redirectUrl);

  // Redirect the resource owner to the authorization URL. Once the resource
  // owner has authorized, they'll be redirected to `redirectUrl` with an
  // authorization code. The `redirect` should cause the browser to redirect to
  // another URL which should also have a listener.
  //
  // `redirect` and `listen` are not shown implemented here.
  await redirect(authorizationUrl);
  var responseUrl = await listen(redirectUrl);

  // Once the user is redirected to `redirectUrl`, pass the query parameters to
  // the AuthorizationCodeGrant. It will validate them and extract the
  // authorization code to create a new Client.
  return await grant.handleAuthorizationResponse(responseUrl.queryParameters);
}