#
# Copyright 2005-2016, David Heinemeier Hansson
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#

# This is lifted from rails activesupport (note the copyright above):
# https://github.com/rails/rails/blob/9f84e60ac9d7bf07d6ae1bc94f3941f5b8f1a228/activesupport/lib/active_support/descendants_tracker.rb

class Chef
  module Mixin
    module DescendantsTracker
      @@direct_descendants = {}

      class << self
        def direct_descendants(klass)
          @@direct_descendants[klass] || []
        end

        def descendants(klass)
          arr = []
          accumulate_descendants(klass, arr)
          arr
        end

        def find_descendants_by_name(klass, name)
          descendants(klass).first { |c| c.name == name }
        end

        # This is the only method that is not thread safe, but is only ever called
        # during the eager loading phase.
        def store_inherited(klass, descendant)
          (@@direct_descendants[klass] ||= []) << descendant
        end

        private

        def accumulate_descendants(klass, acc)
          if direct_descendants = @@direct_descendants[klass]
            acc.concat(direct_descendants)
            direct_descendants.each { |direct_descendant| accumulate_descendants(direct_descendant, acc) }
          end
        end
      end

      def inherited(base)
        DescendantsTracker.store_inherited(self, base)
        super
      end

      def direct_descendants
        DescendantsTracker.direct_descendants(self)
      end

      def find_descendants_by_name(name)
        DescendantsTracker.find_descendants_by_name(self, name)
      end

      def descendants
        DescendantsTracker.descendants(self)
      end
    end
  end
end