Implement regex constraint for String fields (#9)

* Implement regex constraint for Strings

* Add a test case for regex match on string field

* Update README with regex example

* Bump patch version to 0.1.9

README.md

@@ -59,6 +59,7 @@ defmodule MyApp.Schema do
     arg(:max, :integer, description: "Maximum value allowed")
     arg(:min_items, :integer, description: "Minimum number of items allowed in a list")
     arg(:max_items, :integer, description: "Maximum number of items allowed in a list")
+    arg(:regex, :string, description: "Pattern to match for a string")
   end
 
   query do
@@ -101,7 +102,7 @@ field :my_list, list_of(:integer) do
 end
 
 field :my_field, :integer do
-  arg :my_arg, non_null(:string), directives: [constraints: [min: 10]]
+  arg :my_arg, non_null(:string), directives: [constraints: [min: 10, regex: "^[a-zA-Z]+$"]]
 
   resolve(&MyResolver.resolve/3)
 end

lib/constraints/max.ex

@@ -3,7 +3,7 @@ defmodule AbsintheHelpers.Constraints.Max do
 
   @behaviour AbsintheHelpers.Constraint
 
-  def call(node = %{items: _items}, {:max, _min}) do
+  def call(node = %{items: _items}, {:max, _max}) do
     {:ok, node}
   end
 

lib/constraints/regex.ex

@@ -0,0 +1,15 @@
+defmodule AbsintheHelpers.Constraints.Regex do
+  @moduledoc """
+  Applies regex constraint on node data. This constraint can only be applied to String types.
+  """
+
+  @behaviour AbsintheHelpers.Constraint
+
+  def call(node = %{data: data}, {:regex, regex}) do
+    if data =~ Regex.compile!(regex) do
+      {:ok, node}
+    else
+      {:error, :invalid_format, %{regex: regex}}
+    end
+  end
+end

lib/directives/constraints.ex

@@ -5,11 +5,12 @@ defmodule AbsintheHelpers.Directives.Constraints do
   Supports:
   - `:min`, `:max`: For numbers and string lengths
   - `:min_items`, `:max_items`: For lists
+  - `:regex`: For strings
 
   Applicable to scalars (:string, :integer, :float, :decimal) and lists.
 
   Example:
-      field :username, :string, directives: [constraints: [min: 3, max: 20]]
+      field :username, :string, directives: [constraints: [min: 3, max: 20, regex: "^[a-zA-Z]+$"]]
       arg :tags, list_of(:string), directives: [constraints: [max_items: 5, max: 10]]
 
   Constraints are automatically enforced during query execution.
@@ -20,7 +21,7 @@ defmodule AbsintheHelpers.Directives.Constraints do
   alias Absinthe.Blueprint.TypeReference.{List, NonNull}
 
   @constraints %{
-    string: [:min, :max],
+    string: [:min, :max, :regex],
     number: [:min, :max],
     list: [:min, :max, :min_items, :max_items]
   }
@@ -30,9 +31,12 @@ defmodule AbsintheHelpers.Directives.Constraints do
 
     arg(:min, :integer, description: "Minimum value allowed")
     arg(:max, :integer, description: "Maximum value allowed")
+
     arg(:min_items, :integer, description: "Minimum number of items allowed in a list")
     arg(:max_items, :integer, description: "Maximum number of items allowed in a list")
 
+    arg(:regex, :string, description: "Pattern to match for a string")
+
     expand(&__MODULE__.expand_constraints/2)
   end
 

mix.exs

@@ -4,7 +4,7 @@ defmodule AbsintheHelpers.MixProject do
   def project do
     [
       app: :absinthe_helpers,
-      version: "0.1.8",
+      version: "0.1.9",
       elixir: "~> 1.16",
       start_permanent: Mix.env() == :prod,
       deps: deps(),

test/absinthe_helpers/constraints/regex_test.exs

@@ -0,0 +1,17 @@
+defmodule AbsintheHelpers.Constraints.RegexTest do
+  use ExUnit.Case, async: true
+
+  alias AbsintheHelpers.Constraints.Regex
+
+  test "returns :ok tuple on regex match" do
+    input = %{data: "username"}
+
+    assert {:ok, %{data: "username"}} = Regex.call(input, {:regex, "^[a-z]*$"})
+  end
+
+  test "returns invalid_format error on regex match failure" do
+    input = %{data: "user.name"}
+
+    assert {:error, :invalid_format, %{regex: "^[a-z]*$"}} = Regex.call(input, {:regex, "^[a-z]*$"})
+  end
+end

test/absinthe_helpers/phases/apply_constraints_test.exs

@@ -31,7 +31,7 @@ defmodule AbsintheHelpers.Phases.ApplyConstraintsTest do
         field(:cost, :decimal, directives: [constraints: [min: 10, max: 1000]])
 
         field(:description, :string) do
-          directive(:constraints, min: 5, max: 50)
+          directive(:constraints, regex: "^[a-zA-Z\s]+$", min: 5, max: 50)
         end
 
         field(:override_ids, non_null(list_of(non_null(:integer)))) do
@@ -112,5 +112,32 @@ defmodule AbsintheHelpers.Phases.ApplyConstraintsTest do
                 ]
               }} = TestSchema.run_query(query)
     end
+
+    test "returns invalid_format on strings that do not match regex pattern" do
+      query = """
+      mutation {
+        create_booking(
+          customer_id: 1,
+          service: {
+            cost: "150.75",
+            description: "invalid-description",
+            override_ids: [6, 7, 8],
+            location_ids: [8, 9, 10],
+            commission_ids: []
+          }
+        )
+      }
+      """
+
+      assert {:ok,
+              %{
+                errors: [
+                  %{
+                    message: :invalid_format,
+                    details: %{field: "description", regex: "^[a-zA-Z\s]+$"}
+                  }
+                ]
+              }} = TestSchema.run_query(query)
+    end
   end
 end