1 files changed, 55 insertions, 0 deletions
diff --git a/activerecord/lib/arel/nodes/case.rb b/activerecord/lib/arel/nodes/case.rb
new file mode 100644
index 0000000000..654a54825e
--- /dev/null
+++ b/activerecord/lib/arel/nodes/case.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Case < Arel::Nodes::Node
+      attr_accessor :case, :conditions, :default
+
+      def initialize(expression = nil, default = nil)
+        @case = expression
+        @conditions = []
+        @default = default
+      end
+
+      def when(condition, expression = nil)
+        @conditions << When.new(Nodes.build_quoted(condition), expression)
+        self
+      end
+
+      def then(expression)
+        @conditions.last.right = Nodes.build_quoted(expression)
+        self
+      end
+
+      def else(expression)
+        @default = Else.new Nodes.build_quoted(expression)
+        self
+      end
+
+      def initialize_copy(other)
+        super
+        @case = @case.clone if @case
+        @conditions = @conditions.map { |x| x.clone }
+        @default = @default.clone if @default
+      end
+
+      def hash
+        [@case, @conditions, @default].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.case == other.case &&
+          self.conditions == other.conditions &&
+          self.default == other.default
+      end
+      alias :== :eql?
+    end
+
+    class When < Binary # :nodoc:
+    end
+
+    class Else < Unary # :nodoc:
+    end
+  end
+end