[RFC-039] chef handler dsl

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/chef/event_dispatch/dsl.rb b/lib/chef/event_dispatch/dsl.rb
new file mode 100644
index 0000000000..f61ea90580
--- /dev/null
+++ b/lib/chef/event_dispatch/dsl.rb
@@ -0,0 +1,46 @@
+#
+# Author:: Ranjib Dey (<ranjib@linux.com>)
+# Copyright:: Copyright (c) 2015 Ranjib Dey
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+require 'chef/event_dispatch/base'
+require 'chef/exceptions'
+require 'chef/config'
+
+class Chef
+  module EventDispatch
+    class DSL
+      # Adds a new event handler derived from base handler
+      # with user defined block against a chef event
+      #
+      # @return [Chef::EventDispatch::Base] a base handler object
+      def on(event_type, &block)
+        validate!(event_type)
+        handler = Chef::EventDispatch::Base.new
+        handler.define_singleton_method(event_type) do |*args|
+          block.call(args)
+        end
+        Chef::Config[:event_handlers] << handler
+        handler
+      end
+
+      private
+      def validate!(event_type)
+        all_event_types = (Chef::EventDispatch::Base.instance_methods - Object.instance_methods)
+        raise Chef::Exceptions::UnknownEventType unless all_event_types.include?(event_type)
+      end
+    end
+  end
+end