1 files changed, 78 insertions, 0 deletions
diff --git a/lib/arel/nodes/window.rb b/lib/arel/nodes/window.rb
new file mode 100644
index 0000000000..b54eb7fe64
--- /dev/null
+++ b/lib/arel/nodes/window.rb
@@ -0,0 +1,78 @@
+module Arel
+  module Nodes
+    class Window < Arel::Nodes::Node
+      include Arel::Expression
+      attr_accessor :orders, :framing
+
+      def initialize
+        @orders = []
+      end
+
+      def order *expr
+        # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+        @orders.concat expr.map { |x|
+          String === x || Symbol === x ? Nodes::SqlLiteral.new(x.to_s) : x
+        }
+        self
+      end
+
+      def frame(expr)
+        raise ArgumentError, "Window frame cannot be set more than once" if @frame
+        @framing = expr
+      end
+
+      def rows(expr = nil)
+        frame(Rows.new(expr))
+      end
+
+      def range(expr = nil)
+        frame(Range.new(expr))
+      end
+
+      def initialize_copy other
+        super
+        @orders = @orders.map { |x| x.clone }
+      end
+    end
+
+    class NamedWindow < Window
+      attr_accessor :name
+
+      def initialize name
+        super()
+        @name = name
+      end
+
+      def initialize_copy other
+        super
+        @name = other.name.clone
+      end
+    end
+
+    class Rows < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Range < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class CurrentRow < Arel::Nodes::Node; end
+
+    class Preceding < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Following < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+  end
+end
+\ No newline at end of file