[#951] create new route for Virtual Agent JWT proof of concept (#12844)

* [#951] create new route for Virtual Agent JWT proof of concept

[original issue 951](https://github.com/department-of-veterans-affairs/va-virtual-agent/issues/951)
   Co-authored-by: Maurice Okumu <maurice.okumu@thoughtworks.com>

app/controllers/v0/virtual_agent_jwt_token_controller.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require 'erb'
+
+module V0
+  class VirtualAgentJwtTokenController < ApplicationController
+    rescue_from 'V0::VirtualAgentJwtTokenController::ServiceException', with: :service_exception_handler
+    rescue_from Net::HTTPError, with: :service_exception_handler
+
+    def create
+      # on a post request, if the flipper is enabled
+      if Flipper.enabled?(:virtual_agent_fetch_jwt_token, current_user)
+        # create a new jwt token
+        jwt_token = new_jwt_token(current_user)
+        render json: { token: jwt_token }
+      else
+        render json: { token: 'disabled' }
+      end
+    end
+
+    private
+
+    def new_jwt_token(user)
+      url = '/users/v2/session?processRules=true'
+      # get the basic unsigned JWT token
+      token = VAOS::JwtWrapper.new(user).token
+      # request a signed JWT token
+      response = perform(:post, url, token, headers)
+      # raise Common::Exceptions::BackendServiceException.new('VAOS_502', source: self.class) unless body?(response)
+
+      Rails.logger.info('Chatbot JWT session created',
+                        { account_uuid: user.account_uuid, jti: decoded_token(token)['jti'] })
+      response.body
+    end
+
+    def headers
+      { 'Accept' => 'text/plain', 'Content-Type' => 'text/plain', 'Referer' => referrer }
+    end
+
+    def decoded_token(token)
+      JWT.decode(token, nil, false).first
+    end
+
+    def body?(response)
+      response&.body && response.body.present?
+    end
+
+    def referrer
+      if Settings.hostname.ends_with?('.gov')
+        "https://#{Settings.hostname}".gsub('vets', 'va')
+      else
+        'https://review-instance.va.gov' # VAMF rejects Referer that is not valid; such as those of review instances
+      end
+    end
+  end
+end

config/routes.rb

@@ -42,6 +42,7 @@
     resources :education_career_counseling_claims, only: :create
     resources :veteran_readiness_employment_claims, only: :create
     resource :virtual_agent_token, only: [:create], controller: :virtual_agent_token
+    resource :virtual_agent_jwt_token, only: [:create], controller: :virtual_agent_jwt_token
 
     get 'form1095_bs/download_pdf/:tax_year', to: 'form1095_bs#download_pdf'
     get 'form1095_bs/download_txt/:tax_year', to: 'form1095_bs#download_txt'