GoogleAPIをRubyでPostで叩いてトークンとか取得する

GoogleAPI_post.rb

require 'sinatra'
require 'sinatra/reloader'
require 'net/http'
require 'uri'
require 'json'

#この方法だと1人しか管理できない

client_id     = 'XXX.googleusercontent.comみたいなclient_id'
client_secret = "client_secret"
redirect_uri  = 'http://localhost:4567/redirect'#リダイレクト先
scope         = 'https://www.googleapis.com/auth/calendar'

access_token  = ''
refresh_token = ''
token_type    = ''

get '/login' do
    if refresh_token != ""
        "既に認証しています"
    else
        oauth_url = "https://accounts.google.com/o/oauth2/auth?client_id=#{client_id}&redirect_uri=#{redirect_uri}&scope=#{scope}&response_type=code&approval_prompt=force&access_type=offline"
        redirect oauth_url.to_s
    end

end

get '/redirect' do
    uri = URI.parse('https://accounts.google.com/o/oauth2/token')

    response = nil

    request = Net::HTTP::Post.new(uri.request_uri)

    request.body = "client_secret=#{client_secret}&grant_type=authorization_code&redirect_uri=#{redirect_uri}&client_id=#{client_id}&code=#{params['code']}"

    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE

    res = http.start do
        http.request(request)
    end

    if res.code == '200'
        json = JSON.parse(res.body)
        access_token = json['access_token']
        refresh_token = json['refresh_token']
        token_type = json['token_type']
    else
        puts "Error #{res.code} #{res.message}"
        "エラー"
    end
    "認証完了"
end

get '/refreshtoken' do
    if refresh_token != ""
        uri = URI.parse('https://accounts.google.com/o/oauth2/token')

        response = nil

        request = Net::HTTP::Post.new(uri.request_uri)

        request.body = "client_secret=#{client_secret}&client_id=#{client_id}&refresh_token=#{refresh_token}&grant_type=refresh_token"
        print request.body

        http = Net::HTTP.new(uri.host, uri.port)
        http.use_ssl = true
        http.verify_mode = OpenSSL::SSL::VERIFY_NONE

        res = http.start do
            http.request(request)
        end

        if res.code == '200'
            json = JSON.parse(res.body)
            access_token = json['access_token']
            token_type = json['token_type']
        else
            puts "Error #{res.code} #{res.message}"
            "エラー"
        end
        "認証更新完了"
    else
        "認証されていません"
    end
end

#カレンダーのポストについて

# https://www.googleapis.com/calendar/v3/calendars/#{カレンダーID}/events?key=#{APIキー}
# に対して
# Authorization: #{token_type} #{access_token}
#                            ↑のスペース重要！
# のヘッダーを付けて
# https://developers.google.com/google-apps/calendar/v3/reference/events/insert#try-it
# を参考にしてPOSTのbodyを作って
# POSTすればカレンダーをいじれる