How to refresh Google token

user.rb

require 'google/api_client'
require 'google/api_client/client_secrets'
require 'google/api_client/auth/installed_app'

class User < ActiveRecord::Base
 

  def save_google_credentials(omniauth, params)
    if omniauth["credentials"]["refresh_token"]
      self.google_access_token = omniauth["credentials"]["token"]
      self.google_refresh_token = omniauth["credentials"]["refresh_token"]
      self.google_token_expires_at = Time.now.to_i + 3600
      save
    end
  end

  def refresh_token
    data = {
      :client_id => ENV['GOOGLE_CLIENT_ID'],
      :client_secret => ENV['GOOGLE_SECRET'],
      :refresh_token => google_refresh_token,
      :grant_type => "refresh_token"
    }
    @response = ActiveSupport::JSON.decode(RestClient.post "https://accounts.google.com/o/oauth2/token", data)
    if @response["access_token"].present?
      self.google_token_expires_at = Time.now.to_i + 3600
      self.google_access_token = @response["access_token"]
      save
    else
      # No Token
      puts "No Token :("
    end
  rescue RestClient::BadRequest => e
    # Bad request
    puts "Error: bad request :("
  end

  def revoke_google_token
    @response = RestClient.get "https://accounts.google.com/o/oauth2/revoke?token=#{google_refresh_token}"
    self.google_refresh_token = nil
    self.google_access_token = nil
    self.google_token_expires_at = nil
    save
  rescue RestClient::BadRequest => e
    # Bad request
    puts "Error: bad request :("
  end

  def access_token_expired?
    google_token_expires_at.to_i <= Time.now.to_i
  end

  def get_calendar(start_date = Date.today)
    refresh_token if access_token_expired?
    if google_access_token
      client = Google::APIClient.new(:application_name => 'My App', :application_version => '1.0.0')
      calendar = client.discovered_api('calendar', 'v3')
      client_secrets = Google::APIClient::ClientSecrets.load(ENV['GOOGLE_SECRET_FILE'])
      client.authorization = client_secrets.to_authorization
      client.authorization.scope = 'https://www.googleapis.com/auth/calendar'
      auth = client.authorization
      auth.access_token = google_access_token
      auth.refresh_token = google_refresh_token
      min_time= start_date.at_beginning_of_week.to_time.utc.iso8601
      max_time= start_date.at_end_of_week.to_time.utc.iso8601
      result = client.execute(
        :api_method => calendar.events.list,
        :parameters => {'calendarId' => 'primary', 'singleEvents' => true, "timeMin" => min_time, "timeMax" => max_time, "fields" => "items(start,end,transparency)"},
        :authorization => auth
      )
      self.google_calendars = {"items" => result.data["items"].to_json}
      save
    end
  rescue
    Rails.logger.info "Error"
  end

  def google_events
    JSON.parse(google_calendars["items"]) rescue []
  end

  def google_busy_time(tz=nil)
    Time.zone = tz || timezone
    #google_events.map{|e| Time.zone.parse(e["start"]["dateTime"]).strftime("%Y-%m-%d %H:00")} rescue []
    # transparency = transparent if available
    google_events.map{|e|
      e["transparency"].nil? ?
      [
        e["start"]["dateTime"] != nil ? Time.zone.parse(e["start"]["dateTime"]).strftime("%Y-%m-%d %H:%M").to_time.to_i : Time.zone.parse(e["start"]["date"]).strftime("%Y-%m-%d %H:%M").to_time.to_i,
        e["end"]["dateTime"] != nil ? Time.zone.parse(e["end"]["dateTime"]).strftime("%Y-%m-%d %H:%M").to_time.to_i : Time.zone.parse(e["end"]["date"]).strftime("%Y-%m-%d %H:%M").to_time.to_i
        ] : [0,0]
    }
  rescue
    []
  end
  
  def google_debug_time
    google_busy_time.map {|e| [Time.at(e[0]), Time.at(e[1])]} 
  end

  def debug_busy_time
    existing_bookings_time.map {|e| [Time.at(e[0]), Time.at(e[1])]} 
  end
end