1 files changed, 124 insertions, 0 deletions
diff --git a/lib/chef/node/common_api.rb b/lib/chef/node/common_api.rb
new file mode 100644
index 0000000000..6f921e15aa
--- /dev/null
+++ b/lib/chef/node/common_api.rb
@@ -0,0 +1,124 @@
+#--
+# Copyright:: Copyright 2016, Chef Software, Inc.
+# 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.
+#
+
+class Chef
+  class Node
+    # shared API between VividMash and ImmutableMash, writer code can be
+    # 'shared' to keep it logically in this file by adding them to the
+    # block list in ImmutableMash.
+    module CommonAPI
+      # method-style access to attributes
+
+      def valid_container?(obj, key)
+        return obj.is_a?(Hash) || (obj.is_a?(Array) && key.is_a?(Fixnum))
+      end
+
+      private :valid_container?
+
+      # - autovivifying / autoreplacing writer
+      # - non-container-ey intermediate objects are replaced with hashes
+      def write(*args, &block)
+        value = block_given? ? yield : args.pop
+        last = args.pop
+        prev_memo = prev_key = nil
+        chain = args.inject(self) do |memo, key|
+          if !valid_container?(memo, key)
+            prev_memo[prev_key] = {}
+            memo = prev_memo[prev_key]
+          end
+          prev_memo = memo
+          prev_key = key
+          memo[key]
+        end
+        if !valid_container?(chain, last)
+          prev_memo[prev_key] = {}
+          chain = prev_memo[prev_key]
+        end
+        chain[last] = value
+      end
+
+      # this autovivifies, but can throw NoSuchAttribute when trying to access #[] on
+      # something that is not a container ("schema violation" issues).
+      #
+      def write!(*args, &block)
+        value = block_given? ? yield : args.pop
+        last = args.pop
+        obj = args.inject(self) do |memo, key|
+          raise Chef::Exceptions::AttributeTypeMismatch unless valid_container?(memo, key)
+          memo[key]
+        end
+        raise Chef::Exceptions::AttributeTypeMismatch unless valid_container?(obj, last)
+        obj[last] = value
+      end
+
+      # FIXME:(?) does anyone need a non-autovivifying writer for attributes that throws exceptions?
+
+      # return true or false based on if the attribute exists
+      def exist?(*path)
+        path.inject(self) do |memo, key|
+          return false unless valid_container?(memo, key)
+          if memo.is_a?(Hash)
+            if memo.key?(key)
+              memo[key]
+            else
+              return false
+            end
+          elsif memo.is_a?(Array)
+            if memo.length > key
+              memo[key]
+            else
+              return false
+            end
+          end
+        end
+        return true
+      end
+
+      # this is a safe non-autovivifying reader that returns nil if the attribute does not exist
+      def read(*path)
+        begin
+          read!(*path)
+        rescue Chef::Exceptions::NoSuchAttribute
+          nil
+        end
+      end
+
+      # non-autovivifying reader that throws an exception if the attribute does not exist
+      def read!(*path)
+        raise Chef::Exceptions::NoSuchAttribute unless exist?(*path)
+        path.inject(self) do |memo, key|
+          memo[key]
+        end
+      end
+
+      # FIXME:(?) does anyone really like the autovivifying reader that we have and wants the same behavior?  readers that write?  ugh...
+
+      def unlink(*path, last)
+        hash = path.empty? ? self : read(*path)
+        return nil unless hash.is_a?(Hash) || hash.is_a?(Array)
+        root.top_level_breadcrumb ||= last
+        hash.delete(last)
+      end
+
+      def unlink!(*path)
+        raise Chef::Exceptions::NoSuchAttribute unless exist?(*path)
+        unlink(*path)
+      end
+
+    end
+  end
+end