require "multi_auth"

  MultiAuth.config("github", ENV['ID'], ENV['SECRET']) # configuration

  multi_auth = MultiAuth.make(provider, redirect_uri) # initialize engine
  multi_auth.authorize_uri  # URL to provider authentication dialog

  # on http callback, like /multi_auth/github/callback
  user = multi_auth.user(params) # get signed in user

MultiAuth.config("facebook", "facebookClientID", "facebookSecretKey")
MultiAuth.config("google", "googleClientID", "googleSecretKey")

def self.multi_auth(env)
  provider = env.params.url["provider"]
  redirect_uri = "#{Kemal.config.scheme}://#{env.request.host_with_port.as(String)}/multi_auth/#{provider}/callback"
  MultiAuth.make(provider, redirect_uri)
end

get "/multi_auth/:provider" do |env|
  env.redirect(multi_auth(env).authorize_uri)
end

get "/multi_auth/:provider/callback" do |env|
  user = multi_auth(env).user(env.params.query)
  p user.email
  user
end

# config/watch.yml
host: myapp.lvh.me
port: 5000

# config/multi_auth_handler.cr
require "multi_auth"

class MultiAuthHandler
  MultiAuth.config("facebook", "facebookClientID", "facebookSecretKey")
  MultiAuth.config("google", "googleClientID", "googleSecretKey")

  def self.authorize_uri(provider : String)
    MultiAuth.make(provider, "#{Lucky::RouteHelper.settings.base_uri}/oauth/#{provider}/callback").authorize_uri(scope: "email")
  end

  def self.user(provider : String, params : Enumerable({String, String}))
    MultiAuth.make(provider, "#{Lucky::RouteHelper.settings.base_uri}/oauth/#{provider}/callback").user(params)
  end
end

# src/actions/oauth/handler.cr
class OAuth::Handler < BrowserAction
  get "/oauth/:provider" do
    redirect to: MultiAuthHandler.authorize_uri(provider)
  end
end

# src/actions/oauth/handler/callback.cr
class OAuth::Handler::Callback < BrowserAction
  get "/oauth/:provider/callback" do
    user = MultiAuthHandler.user(provider, request.query_params)
    text user.email.to_s
  end
end

# config/initializers/multi_auth.cr
require "multi_auth"

MultiAuth.config("facebook", "facebookClientID", "facebookSecretKey")
MultiAuth.config("google", "googleClientID", "googleSecretKey")

# config/routes.cr
routes :web do
  ...
  get "/multi_auth/:provider", MultiAuthController, :new
  get "/multi_auth/:provider/callback", MultiAuthController, :callback
end

# src/controllers/multi_auth_controller.cr
class MultiAuthController < ApplicationController
  def new
    redirect_to multi_auth.authorize_uri(scope: "email")
  end

  def callback
    multi_auth_user = multi_auth.user(request.query_params)

    if user = User.find_by email: multi_auth_user.email
      login user
    else
      user = User.create!(
        first_name: multi_auth_user.first_name,
        last_name: multi_auth_user.last_name,
        email: multi_auth_user.email
      )
      login user
    end

    redirect_to "/"
  end

  def login(user)
    context.session["user_id"] = user.id
  end

  def provider
    params[:provider]
  end

  def redirect_uri
    "#{Amber.settings.secrets["base_url"]}/multi_auth/#{provider}/callback"
  end

  def multi_auth
    MultiAuth.make(provider, redirect_uri)
  end
end