Support Constraints for Feature Flags

lib/unleash/strategy.ex

@@ -16,6 +16,7 @@ defmodule Unleash.Strategy do
   require Logger
 
   alias Unleash.Config
+  alias Unleash.Strategy.Constraint
 
   defmacro __using__(opts) do
     name = opts[:name]
@@ -49,7 +50,7 @@ defmodule Unleash.Strategy do
 
   * `parameters` - A map of paramters returned from the Unleash server. This
     can be whatever you like, such as a configured list of `userIds`.
-  * `context` - The context passed into `Unleash.enabled?/3`. 
+  * `context` - The context passed into `Unleash.enabled?/3`.
 
 
   ## Examples
@@ -72,7 +73,7 @@ defmodule Unleash.Strategy do
       Config.strategies()
       |> Enum.find(fn {n, _mod} -> n == name end)
 
-    module.check_enabled(strategy["parameters"], context)
+    check_constraints(strategy, context) and module.check_enabled(strategy["parameters"], context)
   end
 
   def enabled?(_strat, _context), do: false
@@ -97,4 +98,9 @@ defmodule Unleash.Strategy do
 
     result
   end
+
+  defp check_constraints(%{"constraints" => constraints}, context),
+    do: Constraint.verify_all(constraints, context)
+
+  defp check_constraints(_strategy, _context), do: true
 end

lib/unleash/strategy/constraint.ex

@@ -0,0 +1,35 @@
+defmodule Unleash.Strategy.Constraint do
+  @moduledoc """
+  Module that is used to verify
+  [constraints](https://www.unleash-hosted.com/docs/strategy-constraints/) are
+  met.
+
+  These constraints allow for very complex and specifc strategies to be
+  enacted by allowing users to specify context values to include or exclude.
+  """
+
+  def verify_all(constraints, context) do
+    Enum.all?(constraints, &verify(&1, context))
+  end
+
+  defp verify(%{"contextName" => name, "operator" => op, "values" => values}, context) do
+    context
+    |> find_value(name)
+    |> check(op, values)
+  end
+
+  defp verify(%{}, _context), do: false
+
+  defp check(value, "IN", values), do: value in values
+  defp check(value, "NOT_IN", values), do: value not in values
+
+  defp find_value(nil, _name), do: nil
+
+  defp find_value(ctx, name) do
+    Map.get(
+      ctx,
+      String.to_atom(Recase.to_snake(name)),
+      find_value(Map.get(ctx, :properties), name)
+    )
+  end
+end

mix.exs

@@ -60,7 +60,7 @@ defmodule Unleash.MixProject do
       {:stream_data, "~> 0.4.3", only: [:test, :dev]},
       {:excoveralls, "~> 0.8", only: :test},
       {:mox, "~> 0.5.1", only: :test},
-      {:recase, "~> 0.6.0", only: :test},
+      {:recase, "~> 0.6.0"},
       {:murmur, "~> 1.0"},
       {:mojito, "~> 0.5.0"},
       {:jason, "~> 1.1"},

test/unleash/client_specification_test.exs

@@ -42,12 +42,6 @@ defmodule Unleash.ClientSpecificationTest do
         @expected expected
 
         @tag capture_log: true
-        if String.starts_with?(name, "09-strategy-constraints") do
-          @tag skip: true
-        else
-          @tag skip: false
-        end
-
         test t do
           context = entity_from_file(@context)
 
@@ -76,7 +70,11 @@ defmodule Unleash.ClientSpecificationTest do
 
   defp entity_from_file(e) do
     e
-    |> Enum.map(fn {k, v} -> {String.to_atom(Recase.to_snake(k)), v} end)
+    |> Enum.map(fn
+      {"payload", v} -> {:payload, v}
+      {k, v} when is_map(v) -> {String.to_atom(Recase.to_snake(k)), entity_from_file(v)}
+      {k, v} -> {String.to_atom(Recase.to_snake(k)), v}
+    end)
     |> Enum.into(%{})
   end
 end