Add expression support to Flipper UI

Author: blumhardts

examples/ui/basic.ru

@@ -48,6 +48,8 @@ Flipper::UI.configure do |config|
   end
 
   config.application_href = "https://example.com"
+
+  config.expressions_enabled = true
 end
 
 # You can uncomment these to get some default data:

lib/flipper/expression.rb

@@ -45,6 +45,10 @@ def evaluate(context = {})
       end
     end
 
+    def in_words
+      function.in_words(*args)
+    end
+
     def eql?(other)
       other.is_a?(self.class) && @function == other.function && @args == other.args
     end

lib/flipper/expression/constant.rb

@@ -16,6 +16,14 @@ def evaluate(_ = nil)
         value
       end
 
+      def in_words
+        value
+      end
+
+      def name
+        'Constant'
+      end
+
       def eql?(other)
         other.is_a?(self.class) && other.value == value
       end

lib/flipper/expressions/all.rb

@@ -4,6 +4,13 @@ class All
       def self.call(*args)
         args.all?
       end
+
+      def self.in_words(*args)
+        count = args.length
+        return args[0].in_words if count == 1
+
+        "all #{count} conditions"
+      end
     end
   end
 end

lib/flipper/expressions/any.rb

@@ -4,6 +4,13 @@ class Any
       def self.call(*args)
         args.any?
       end
+
+      def self.in_words(*args)
+        count = args.length
+        return args[0].in_words if count == 1
+
+        "any #{count} conditions"
+      end
     end
   end
 end

lib/flipper/expressions/boolean.rb

@@ -4,6 +4,10 @@ class Boolean
       def self.call(value)
         Flipper::Typecast.to_boolean(value)
       end
+
+      def self.in_words(arg)
+        self.call(arg.value)
+      end
     end
   end
 end

lib/flipper/expressions/comparable.rb

@@ -8,6 +8,14 @@ def self.operator
       def self.call(left, right)
         left.respond_to?(operator) && right.respond_to?(operator) && left.public_send(operator, right)
       end
+
+      def self.in_words(left, right)
+        "#{left.in_words} is #{operator_in_words} #{right.in_words}"
+      end
+
+      def self.operator_in_words
+        raise NotImplementedError
+      end
     end
   end
 end

lib/flipper/expressions/duration.rb

@@ -23,6 +23,11 @@ def self.call(scalar, unit = 'second')
 
         scalar * SECONDS_PER[unit]
       end
+
+      def self.in_words(*args)
+        return "#{args.first.in_words} seconds" if args.size == 1
+        args.map(&:in_words).join(' ')
+      end
     end
   end
 end

lib/flipper/expressions/equal.rb

@@ -4,6 +4,10 @@ class Equal < Comparable
       def self.operator
         :==
       end
+
+      def self.operator_in_words
+        'equal to'
+      end
     end
   end
 end

lib/flipper/expressions/greater_than.rb

@@ -4,6 +4,10 @@ class GreaterThan < Comparable
       def self.operator
         :>
       end
+
+      def self.operator_in_words
+        'greater than'
+      end
     end
   end
 end