generic HTTP adapter

Gemfile

@@ -10,6 +10,8 @@ end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.2.3'
 gem 'pg', '>= 0.20'
+gem 'schema_plus_enums'
+
 # Use Puma as the app server
 gem 'puma', '~> 3.12'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder

Gemfile.lock

@@ -96,8 +96,10 @@ GEM
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
     interception (0.5)
+    its-it (1.3.0)
     json (2.1.0)
     jwt (2.1.0)
+    key_struct (0.4.2)
     license_finder (5.8.0)
       bundler
       rubyzip
@@ -129,6 +131,8 @@ GEM
       builder
       minitest (>= 5.0)
       ruby-progressbar
+    modware (0.1.3)
+      key_struct (~> 0.4)
     msgpack (1.2.10)
     multi_json (1.13.1)
     multi_xml (0.6.0)
@@ -208,6 +212,17 @@ GEM
     ruby-progressbar (1.10.0)
     rubyzip (1.2.2)
     safe_yaml (1.0.4)
+    schema_monkey (2.1.5)
+      activerecord (>= 4.2)
+      modware (~> 0.1)
+    schema_plus_core (2.2.3)
+      activerecord (~> 5.0)
+      its-it (~> 1.2)
+      schema_monkey (~> 2.1)
+    schema_plus_enums (0.1.8)
+      activerecord (>= 4.2, < 5.3)
+      its-it (~> 1.2)
+      schema_plus_core
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
@@ -288,6 +303,7 @@ DEPENDENCIES
   que-web
   rails (~> 5.2.3)
   responders (~> 2.4.1)
+  schema_plus_enums
   spring
   tzinfo-data
   validate_url
@@ -297,4 +313,4 @@ DEPENDENCIES
   yabeda-rails
 
 BUNDLED WITH
-   1.17.1
+   2.0.1

app/adapters/abstract_adapter.rb

@@ -0,0 +1,294 @@
+# frozen_string_literal: true
+
+require 'uri'
+require 'httpclient'
+require 'mutex_m'
+
+# KeycloakAdapter adapter to create/update/delete Clients on using the KeycloakAdapter Client Registration API.
+class AbstractAdapter
+  def self.build_client(*)
+    raise NotImplementedError, __method__
+  end
+
+  attr_reader :endpoint
+
+  def initialize(endpoint, authentication: nil)
+    endpoint = EndpointConfiguration.new(endpoint)
+    @http_client = build_http_client(endpoint)
+    @oidc = OIDC.new(endpoint, http_client)
+    @oidc.access_token = authentication if authentication
+    @endpoint = endpoint.issuer
+  end
+
+  def authentication=(value)
+    oidc.access_token = value
+  end
+
+  def authentication
+    oidc.access_token.token
+  end
+
+  def create_client(_)
+    raise NotImplementedError, __method__
+  end
+
+  def read_client(_)
+    raise NotImplementedError, __method__
+  end
+
+  def update_client(_)
+    raise NotImplementedError, __method__
+  end
+
+  def delete_client(_)
+    raise NotImplementedError, __method__
+  end
+
+  def test
+    raise NotImplementedError, __method__
+  end
+
+  protected
+
+  attr_reader :oidc
+
+  def headers
+    oidc.headers
+  end
+
+  JSON_TYPE = Mime[:json]
+  private_constant :JSON_TYPE
+
+  NULL_TYPE = Mime::Type.lookup(nil)
+
+  attr_reader :http_client
+
+  def build_http_client(endpoint)
+    HTTPClient.new do
+      self.debug_dev = $stderr if ENV.fetch('DEBUG', '0') == '1'
+
+      self.set_auth endpoint, *endpoint.auth
+
+      Rails.application.config.x.http_client.deep_symbolize_keys
+          .slice(:connect_timeout, :send_timeout, :receive_timeout).each do |key, value|
+        self.public_send("#{key}=", value)
+      end
+    end
+  end
+
+  def parse(response)
+    body = self.class.parse_response(response)
+
+    raise InvalidResponseError, { response: response, message: body } unless response.ok?
+
+    params = body.try(:to_h) or return # no need to create client if there are no attributes
+
+    parse_client(params)
+  end
+
+  def parse_client(_)
+    raise NotImplementedError, __method__
+  end
+
+  # TODO: Extract this into Response object to fix :reek:FeatureEnvy
+  def self.parse_response(response)
+    body = response.body
+
+    case Mime::Type.lookup(response.content_type)
+    when JSON_TYPE then JSON.parse(body)
+    when NULL_TYPE then body
+    else raise InvalidResponseError, { response: response, message: 'Unknown Content-Type' }
+    end
+  end
+
+  # Extracts credentials from the endpoint URL.
+  class EndpointConfiguration
+    attr_reader :uri, :client_id, :client_secret
+
+    alias_method :issuer, :uri
+
+    def initialize(endpoint)
+      uri, client_id, client_secret = split_uri(endpoint)
+
+      @uri = normalize_uri(uri).freeze
+      @client_id = client_id.freeze
+      @client_secret = client_secret.freeze
+    end
+
+    def auth
+      [client_id, client_secret]
+    end
+
+    delegate :normalize_uri, :split_uri, to: :class
+
+    def self.normalize_uri(uri)
+      uri.normalize.merge("#{uri.path}/".tr_s('/', '/'))
+    end
+
+    def self.split_uri(endpoint)
+      uri = URI(endpoint)
+      client_id = uri.user
+      client_secret = uri.password
+
+      uri.userinfo = ''
+
+      [ uri, client_id, client_secret ]
+    end
+  end
+
+  # Implements OpenID connect discovery and getting access token.
+  class OIDC
+    include Mutex_m
+
+    def initialize(endpoint, http_client)
+      super()
+
+      @endpoint = endpoint
+      @http_client = http_client
+      @config = nil
+
+      @access_token = AccessToken.new(method(:oauth_client))
+    end
+
+    def well_known_url
+      URI.join(@endpoint.issuer, '.well-known/openid-configuration')
+    end
+
+    def config
+      mu_synchronize do
+        @config ||= fetch_oidc_discovery
+      end
+    end
+
+    # Raised when there is no Access Token to authenticate with.
+    class AuthenticationError < StandardError
+      include Bugsnag::MetaData
+
+      def initialize(error: , endpoint: )
+        self.bugsnag_meta_data = {
+            faraday: { uri: endpoint.to_s }
+        }
+        super(error)
+      end
+    end
+
+    def access_token=(value)
+      @access_token.value = value
+    end
+
+    def token_endpoint
+      config['token_endpoint']
+    end
+
+    def headers
+      { 'Authorization' => "#{authentication_type} #{access_token.token}" }
+    end
+
+    def access_token
+      @access_token.value!
+    rescue => error
+      raise AuthenticationError, error: error, endpoint: @endpoint.issuer
+    end
+
+    protected
+
+    def oauth_client
+      OAuth2::Client.new(@endpoint.client_id, @endpoint.client_secret,
+                         site: @endpoint.uri.dup, token_url: token_endpoint) do |builder|
+        builder.adapter(:httpclient).last.instance_variable_set(:@client, http_client)
+      end
+    end
+
+    attr_reader :http_client
+
+    def fetch_oidc_discovery
+      response = http_client.get(well_known_url)
+      config = AbstractAdapter.parse_response(response)
+
+      case config
+      when ->(obj) { obj.respond_to?(:[]) } then config
+      else raise InvalidOIDCDiscoveryError, response
+      end
+    end
+
+    # Raised when OIDC Discovery is not correct.
+    class InvalidOIDCDiscoveryError < StandardError; end
+
+    # Handles getting and refreshing Access Token for the API access.
+    class AccessToken
+
+      # Breaking :reek:NestedIterators because that is how Faraday expects it.
+      def initialize(oauth_client)
+        @oauth_client = oauth_client
+        @value = Concurrent::IVar.new
+        freeze
+      end
+
+      def value
+        ref = reference or return
+        ref.try_update(&method(:fresh_token))
+
+        ref.value
+      end
+
+      def value=(value)
+        @value.try_set { Concurrent::AtomicReference.new(OAuth2::AccessToken.new(nil, value)) }
+        @value.value
+      end
+
+      def value!
+        value or error
+      end
+
+      def error
+        raise reason
+      end
+
+      protected
+
+      def oauth_client
+        @oauth_client.call
+      end
+
+      delegate :reason, to: :@value
+
+      def reference
+        @value.try_set { Concurrent::AtomicReference.new(get_token) }
+        @value.value
+      end
+
+      def get_token
+        oauth_client.client_credentials.get_token.freeze
+      end
+
+      def fresh_token(access_token)
+        access_token && !access_token.expired? ? access_token : get_token
+      end
+    end
+    private_constant :AccessToken
+
+    def authentication_type
+      'Bearer'
+    end
+  end
+
+  # Raised when unexpected response is returned by the KeycloakAdapter API.
+  class InvalidResponseError < StandardError
+    attr_reader :response
+    include Bugsnag::MetaData
+
+    def initialize(response: , message: )
+      @response = response
+      self.bugsnag_meta_data = {
+          response: {
+              status: status = response.status,
+              reason: reason = response.reason,
+              content_type: response.content_type,
+              body: response.body,
+          },
+          headers: response.headers
+      }
+      super(message.presence || '%s %s' % [ status, reason ])
+    end
+  end
+end