From e73f75c45872a077e64f4247e354de869c06c326 Mon Sep 17 00:00:00 2001
From: Thorsten Eckel <te@znuny.com>
Date: Thu, 30 Nov 2017 13:44:41 +0100
Subject: [PATCH] Introduced Sequencer Unit base class
 Sequencer::Unit::Common::FallbackProvider to handle simple setting fallback
 values of state attributes if not already present.

---
 lib/sequencer/sequence/import/ldap/users.rb   |  1 +
 .../unit/common/fallback_provider.rb          | 29 +++++++++++++++++++
 lib/sequencer/unit/exchange/connection.rb     | 25 +++++++---------
 .../exchange/folder_contacts/folder_ids.rb    | 13 +++------
 lib/sequencer/unit/ldap/config.rb             | 17 +++++++++++
 lib/sequencer/unit/ldap/connection.rb         | 14 +++------
 6 files changed, 65 insertions(+), 34 deletions(-)
 create mode 100644 lib/sequencer/unit/common/fallback_provider.rb
 create mode 100644 lib/sequencer/unit/ldap/config.rb

diff --git a/lib/sequencer/sequence/import/ldap/users.rb b/lib/sequencer/sequence/import/ldap/users.rb
index 0b39bc5fb..549a08f2e 100644
--- a/lib/sequencer/sequence/import/ldap/users.rb
+++ b/lib/sequencer/sequence/import/ldap/users.rb
@@ -9,6 +9,7 @@ class Sequencer
               'Import::Ldap::Users::StaticAttributes',
               'Import::Ldap::Users::DryRun::Flag',
               'Import::Ldap::Users::DryRun::Payload',
+              'Ldap::Config',
               'Ldap::Connection',
               'Import::Ldap::Users::UserRoles',
               'Import::Ldap::Users::Sum',
diff --git a/lib/sequencer/unit/common/fallback_provider.rb b/lib/sequencer/unit/common/fallback_provider.rb
new file mode 100644
index 000000000..20292ef5c
--- /dev/null
+++ b/lib/sequencer/unit/common/fallback_provider.rb
@@ -0,0 +1,29 @@
+class Sequencer
+  class Unit
+    module Common
+      class FallbackProvider < Sequencer::Unit::Base
+
+        def process
+          provides = self.class.provides
+          raise 'Only one provide attribute possible' if provides.size != 1
+
+          attribute = provides.shift
+          return if state.provided?(attribute)
+
+          result = fallback
+
+          # don't store nil values which are default anyway
+          return if result.nil?
+
+          state.provide(attribute, result)
+        end
+
+        private
+
+        def fallback
+          raise 'Missing implementation of fallback method'
+        end
+      end
+    end
+  end
+end
diff --git a/lib/sequencer/unit/exchange/connection.rb b/lib/sequencer/unit/exchange/connection.rb
index 0f96650a7..2c8f2234c 100644
--- a/lib/sequencer/unit/exchange/connection.rb
+++ b/lib/sequencer/unit/exchange/connection.rb
@@ -1,27 +1,22 @@
 class Sequencer
   class Unit
     module Exchange
-      class Connection < Sequencer::Unit::Base
+      class Connection < Sequencer::Unit::Common::FallbackProvider
 
         uses :ews_config
         provides :ews_connection
 
-        def process
-          # check if EWS connection is already given (sub sequence)
-          return if state.provided?(:ews_connection)
-
-          state.provide(:ews_connection) do
-            Viewpoint::EWSClient.new(
-              config[:endpoint],
-              config[:user],
-              config[:password],
-              additional_opts
-            )
-          end
-        end
-
         private
 
+        def fallback
+          Viewpoint::EWSClient.new(
+            config[:endpoint],
+            config[:user],
+            config[:password],
+            additional_opts
+          )
+        end
+
         def config
           @config ||= begin
             ews_config || ::Import::Exchange.config
diff --git a/lib/sequencer/unit/import/exchange/folder_contacts/folder_ids.rb b/lib/sequencer/unit/import/exchange/folder_contacts/folder_ids.rb
index 87e72073d..49ef21099 100644
--- a/lib/sequencer/unit/import/exchange/folder_contacts/folder_ids.rb
+++ b/lib/sequencer/unit/import/exchange/folder_contacts/folder_ids.rb
@@ -3,19 +3,14 @@ class Sequencer
     module Import
       module Exchange
         module FolderContacts
-          class FolderIds < Sequencer::Unit::Base
-            include ::Sequencer::Unit::Exchange::Folders::Mixin::Folder
+          class FolderIds < Sequencer::Unit::Common::FallbackProvider
 
             provides :ews_folder_ids
 
-            def process
-              # check if ids are already processed
-              return if state.provided?(:ews_folder_ids)
+            private
 
-              state.provide(:ews_folder_ids) do
-                config = ::Import::Exchange.config
-                config[:folders]
-              end
+            def fallback
+              ::Import::Exchange.config[:folders]
             end
           end
         end
diff --git a/lib/sequencer/unit/ldap/config.rb b/lib/sequencer/unit/ldap/config.rb
new file mode 100644
index 000000000..77d242753
--- /dev/null
+++ b/lib/sequencer/unit/ldap/config.rb
@@ -0,0 +1,17 @@
+require 'import/ldap'
+
+class Sequencer
+  class Unit
+    module Ldap
+      class Config < Sequencer::Unit::Common::FallbackProvider
+        provides :ldap_config
+
+        private
+
+        def fallback
+          ::Import::Ldap.config
+        end
+      end
+    end
+  end
+end
diff --git a/lib/sequencer/unit/ldap/connection.rb b/lib/sequencer/unit/ldap/connection.rb
index 144113de4..7d03da751 100644
--- a/lib/sequencer/unit/ldap/connection.rb
+++ b/lib/sequencer/unit/ldap/connection.rb
@@ -1,22 +1,16 @@
 require 'ldap'
-require 'import/ldap'
 
 class Sequencer
   class Unit
     module Ldap
-      class Connection < Sequencer::Unit::Base
+      class Connection < Sequencer::Unit::Common::FallbackProvider
         uses :ldap_config
         provides :ldap_connection
 
-        def process
-          return if state.provided?(:ldap_connection)
+        private
 
-          state.provide(:ldap_connection) do
-            config   = ldap_config
-            config ||= ::Import::Ldap.config
-
-            ::Ldap.new(config)
-          end
+        def fallback
+          ::Ldap.new(ldap_config)
         end
       end
     end