1 files changed, 126 insertions, 0 deletions
diff --git a/activerecord/lib/arel/nodes/window.rb b/activerecord/lib/arel/nodes/window.rb
new file mode 100644
index 0000000000..4916fc7fbe
--- /dev/null
+++ b/activerecord/lib/arel/nodes/window.rb
@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Window < Arel::Nodes::Node
+      attr_accessor :orders, :framing, :partitions
+
+      def initialize
+        @orders = []
+        @partitions = []
+        @framing = nil
+      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 partition(*expr)
+        # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+        @partitions.concat expr.map { |x|
+          String === x || Symbol === x ? Nodes::SqlLiteral.new(x.to_s) : x
+        }
+        self
+      end
+
+      def frame(expr)
+        @framing = expr
+      end
+
+      def rows(expr = nil)
+        if @framing
+          Rows.new(expr)
+        else
+          frame(Rows.new(expr))
+        end
+      end
+
+      def range(expr = nil)
+        if @framing
+          Range.new(expr)
+        else
+          frame(Range.new(expr))
+        end
+      end
+
+      def initialize_copy(other)
+        super
+        @orders = @orders.map { |x| x.clone }
+      end
+
+      def hash
+        [@orders, @framing].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.orders == other.orders &&
+          self.framing == other.framing &&
+          self.partitions == other.partitions
+      end
+      alias :== :eql?
+    end
+
+    class NamedWindow < Window
+      attr_accessor :name
+
+      def initialize(name)
+        super()
+        @name = name
+      end
+
+      def initialize_copy(other)
+        super
+        @name = other.name.clone
+      end
+
+      def hash
+        super ^ @name.hash
+      end
+
+      def eql?(other)
+        super && self.name == other.name
+      end
+      alias :== :eql?
+    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 < Node
+      def hash
+        self.class.hash
+      end
+
+      def eql?(other)
+        self.class == other.class
+      end
+      alias :== :eql?
+    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