check-purchases.rb

require 'google/api_client' # version 0.7.1

# Set purchase data hash
data = {
  token: 'gldfdkfjpnnhmnclekpndgph.AO-J1OwXKIzAKUzprnFnNTClSoe7AYx4kF6_d5IujRI7jiTUIHMwQq0oV_fXyjMXf3sUzpCaS0lUWXvqpraR5Pp5Fmk4MvN7CbGDU0lgAg_kqvKDgT1A9y6C3mpBjYBLPN64plT78M-V',
  productId: 'chebucks18',
  packageName: 'com.snegoffon.corruption'
}

# Initialize client
client = Google::APIClient.new

# Build method for request
method = client.discovered_api('androidpublisher', 'v1.1').inapppurchases.get

# Load key from Google Developers Console
key = Google::APIClient::KeyUtils.load_from_pkcs12('config/google-api-privatekey.p12', 'notasecret')

# Build authorization object
client.authorization = Signet::OAuth2::Client.new(
  :token_credential_uri => 'https://accounts.google.com/o/oauth2/token',
  :audience => 'https://accounts.google.com/o/oauth2/token',
  :scope => 'https://www.googleapis.com/auth/androidpublisher',
  :issuer => '694168420610-sh9dpuvldpeu8obmnujs3l4ari16q5h5@developer.gserviceaccount.com',
  :signing_key => key)

# Get access_token
client.authorization.fetch_access_token!

# Until this moment everything is fine: access_token was successfully fetched

# Do the query to Purchase Status API
client.execute(api_method: method, parameters: data)

# => 403
# {
#   "error" => 
#     {
#       "errors" => 
#         {
#           "domain"=>"global",
#           "reason"=>"forbidden",
#           "message"=>"Forbidden"
#         }
#     }
# }