#
# Author:: Seth Chisamore <schisamo@chef.io>
# Copyright:: 2011-2018, Chef Software, Inc <legal@chef.io>
#
# 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.
#

class Chef
  class Resource
    class ChefHandler < Chef::Resource
      resource_name :chef_handler
      provides(:chef_handler) { true }

      description "Use the chef_handler resource to install or uninstall Chef reporting/exception handlers."
      introduced "14.0"

      property :class_name, String,
               description: "The name of the handler class (can be module name-spaced).",
               name_property: true

      property :source, String,
               description: "The full path to the handler file. Can also be a gem path if the handler ships as part of a Ruby gem."

      property :arguments, [Array, Hash],
               description: "Arguments to pass the handler's class initializer.",
               default: lazy { [] }

      property :type, Hash,
               description: "The type of Chef Handler to register as, i.e. :report, :exception or both.",
               default: { report: true, exception: true }

      # supports means a different thing in chef-land so we renamed it but
      # wanted to make sure we didn't break the world
      alias_method :supports, :type

      # This action needs to find an rb file that presumably contains the indicated class in it and the
      # load that file. It then instantiates that class by name and registers it as a handler.
      action :enable do
        description "Enables the Chef handler for the current Chef run on the current node"

        class_name = new_resource.class_name
        new_resource.type.each do |type, enable|
          next unless enable

          unregister_handler(type, class_name)
        end

        handler = nil

        require new_resource.source unless new_resource.source.nil?

        _, klass = get_class(class_name)
        handler = klass.send(:new, *collect_args(new_resource.arguments))

        new_resource.type.each do |type, enable|
          next unless enable
          register_handler(type, handler)
        end
      end

      action :disable do
        description "Disables the Chef handler for the current Chef run on the current node"

        new_resource.type.each_key do |type|
          unregister_handler(type, new_resource.class_name)
        end
      end

      action_class do
        # Registers a handler in Chef::Config.
        #
        # @param handler_type [Symbol] such as :report or :exception.
        # @param handler [Chef::Handler] handler to register.
        def register_handler(handler_type, handler)
          Chef::Log.info("Enabling #{handler.class.name} as a #{handler_type} handler.")
          Chef::Config.send("#{handler_type}_handlers") << handler
        end

        # Removes all handlers that match the given class name in Chef::Config.
        #
        # @param handler_type [Symbol] such as :report or :exception.
        # @param class_full_name [String] such as 'Chef::Handler::ErrorReport'.
        def unregister_handler(handler_type, class_full_name)
          Chef::Config.send("#{handler_type}_handlers").delete_if do |v|
            # avoid a bit of log spam
            if v.class.name == class_full_name
              Chef::Log.info("Disabling #{class_full_name} as a #{handler_type} handler.")
              true
            end
          end
        end

        # Walks down the namespace heirarchy to return the class object for the given class name.
        # If the class is not available, NameError is thrown.
        #
        # @param class_full_name [String] full class name such as 'Chef::Handler::Foo' or 'MyHandler'.
        # @return [Array] parent class and child class.
        def get_class(class_full_name)
          ancestors = class_full_name.split("::")
          class_name = ancestors.pop

          # We need to search the ancestors only for the first/uppermost namespace of the class, so we
          # need to enable the #const_get inherit paramenter only when we are searching in Kernel scope
          # (see COOK-4117).
          parent = ancestors.inject(Kernel) { |scope, const_name| scope.const_get(const_name, scope === Kernel) }
          child = parent.const_get(class_name, parent === Kernel)
          [parent, child]
        end

        def collect_args(resource_args = [])
          if resource_args.is_a? Array
            resource_args
          else
            [resource_args]
          end
        end
      end
    end
  end
end