Google task API authentication issue ruby - ruby-on-rails-3

Question

I am having the problem to authenticate a user for google tasks.
At first it authenticates the user and do things perfect. But in the second trip it throws an error.
Signet::AuthorizationError - Authorization failed. Server message:
{
"error" : "invalid_grant"
}:
following is the code:
def api_client code=""
#client ||= (begin
client = Google::APIClient.new
client.authorization.client_id = settings.credentials["client_id"]
client.authorization.client_secret = settings.credentials["client_secret"]
client.authorization.scope = settings.credentials["scope"]
client.authorization.access_token = "" #settings.credentials["access_token"]
client.authorization.redirect_uri = to('/callbackfunction')
client.authorization.code = code
client
end)
end
get '/callbackfunction' do
code = params[:code]
c = api_client code
c.authorization.fetch_access_token!
result = c.execute("tasks.tasklists.list",{"UserId"=>"me"})
unless result.response.status == 401
p "#{JSON.parse(result.body)}"
else
redirect ("/oauth2authorize")
end
end
get '/oauth2authorize' do
redirect api_client.authorization.authorization_uri.to_s, 303
end
What is the problem in performing the second request?
UPDATE:
This is the link and parameters to user consent.
https://accounts.google.com/o/oauth2/auth?
access_type=offline&
approval_prompt=force&
client_id=somevalue&
redirect_uri=http://localhost:4567/oauth2callback&
response_type=code&
scope=https://www.googleapis.com/auth/tasks

Answer 1

The problem is fixed.
Solution:
In the callbackfunction the tokens which are received through the code provided by the user consent are stored in the database.
Then in other functions just retrieve those tokens from the database and use to process whatever you want against the google task API.
get '/callbackfunction' do
code = params[:code]
c = api_client code
c.authorization.fetch_access_token!
# store the tokens in the database.
end
get '/tasklists' do
# Retrieve the codes from the database and create a client
result = client.execute("tasks.tasklists.list",{"UserId"=>"me"})
unless result.response.status == 401
p "#{JSON.parse(result.body)}"
else
redirect "/oauth2authorize"
end
end

Answer 2

I am using rails, and i store the token only inside DB.
then using a script i am setting up new client before calling execute, following is the code.
client = Google::APIClient.new(:application_name => 'my-app', :application_version => '1.0')
client.authorization.scope = 'https://www.googleapis.com/auth/analytics.readonly'
client.authorization.client_id = Settings.ga.app_key
client.authorization.client_secret = Settings.ga.app_secret
client.authorization.access_token = auth.token
client.authorization.refresh_token = true
client.authorization.update_token!({access_token: auth.token})
client.authorization.fetch_access_token!
if client.authorization.refresh_token && client.authorization.expired?
client.authorization.fetch_access_token!
end
puts "Getting accounts list..."
result = client.execute(:api_method => analytics.management.accounts.list)
puts " ===========> #{result.inspect}"
items = JSON.parse(result.response.body)['items']
But,it gives same error you are facing,
/signet-0.4.5/lib/signet/oauth_2/client.rb:875:in `fetch_access_token': Authorization failed. Server message: (Signet::AuthorizationError)
{
"error" : "invalid_grant"
}
from /signet-0.4.5/lib/signet/oauth_2/client.rb:888:in `fetch_access_token!'
Please suggest why it is not able to use the given token? I have used oauth2, so user is already authorized. Now i want to access the api and fetch the data...
===================UPDATE ===================
Ok, two issues were there,
Permission is to be added to devise.rb,
config.omniauth :google_oauth2, Settings.ga.app_key,Settings.ga.app_secret,{
access_type: "offline",
approval_prompt: "" ,
:scope => "userinfo.email, userinfo.profile, plus.me, analytics.readonly"
}
refresh_token must be passed to the API call, otherwise its not able to authorize.
I hope this helps to somebody, facing similar issue.