1 files changed, 120 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
new file mode 100644
index 0000000000..b027901f28
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -0,0 +1,120 @@
+require 'active_support/concern'
+require 'active_support/core_ext/hash/indifferent_access'
+require 'active_support/rescuable'
+
+module ActionController
+  class ParameterMissing < IndexError
+    attr_reader :param
+
+    def initialize(param)
+      @param = param
+      super("key not found: #{param}")
+    end
+  end
+
+  class Parameters < ActiveSupport::HashWithIndifferentAccess
+    attr_accessor :permitted
+    alias :permitted? :permitted
+
+    def initialize(attributes = nil)
+      super(attributes)
+      @permitted = false
+    end
+
+    def permit!
+      @permitted = true
+      self
+    end
+
+    def require(key)
+      self[key].presence || raise(ParameterMissing.new(key))
+    end
+
+    alias :required :require
+
+    def permit(*filters)
+      params = self.class.new
+
+      filters.each do |filter|
+        case filter
+        when Symbol, String then
+          params[filter] = self[filter] if has_key?(filter)
+        when Hash then
+          self.slice(*filter.keys).each do |key, value|
+            return unless value
+
+            key = key.to_sym
+
+            params[key] = each_element(value) do |value|
+              # filters are a Hash, so we expect value to be a Hash too
+              next if filter.is_a?(Hash) && !value.is_a?(Hash)
+
+              value = self.class.new(value) if !value.respond_to?(:permit)
+
+              value.permit(*Array.wrap(filter[key]))
+            end
+          end
+        end
+      end
+
+      params.permit!
+    end
+
+    def [](key)
+      convert_hashes_to_parameters(key, super)
+    end
+
+    def fetch(key, *args)
+      convert_hashes_to_parameters(key, super)
+    rescue KeyError
+      raise ActionController::ParameterMissing.new(key)
+    end
+
+    def slice(*keys)
+      self.class.new(super)
+    end
+
+    def dup
+      super.tap do |duplicate|
+        duplicate.instance_variable_set :@permitted, @permitted
+      end
+    end
+
+    private
+      def convert_hashes_to_parameters(key, value)
+        if value.is_a?(Parameters) || !value.is_a?(Hash)
+          value
+        else
+          # Convert to Parameters on first access
+          self[key] = self.class.new(value)
+        end
+      end
+
+      def each_element(object)
+        if object.is_a?(Array)
+          object.map { |el| yield el }.compact
+        else
+          yield object
+        end
+      end
+  end
+
+  module StrongParameters
+    extend ActiveSupport::Concern
+    include ActiveSupport::Rescuable
+
+    included do
+      rescue_from(ActionController::ParameterMissing) do |parameter_missing_exception|
+        render text: "Required parameter missing: #{parameter_missing_exception.param}", status: :bad_request
+      end
+    end
+
+    def params
+      @_params ||= Parameters.new(request.parameters)
+    end
+
+    def params=(val)
+      @_params = val.is_a?(Hash) ? Parameters.new(val) : val
+    end
+  end
+end