Add constraints phase

lib/constraints.ex

@@ -0,0 +1,11 @@
+defmodule AbsintheHelpers.Constraint do
+  @moduledoc false
+
+  alias Absinthe.Blueprint.Input
+
+  @type error_reason :: atom()
+  @type error_details :: map()
+
+  @callback call(Input.Value.t(), tuple()) ::
+              {:ok, Input.Value.t()} | {:error, error_reason(), error_details()}
+end

lib/constraints/max.ex

@@ -0,0 +1,27 @@
+defmodule AbsintheHelpers.Constraints.Max do
+  @moduledoc false
+
+  @behaviour AbsintheHelpers.Constraint
+
+  def call(node = %{items: _items}, {:max, _min}) do
+    {:ok, node}
+  end
+
+  def call(node = %{data: data = %Decimal{}}, {:max, max}) do
+    if is_integer(max) and Decimal.gt?(data, max),
+      do: {:error, :max_exceeded, %{max: max, value: data}},
+      else: {:ok, node}
+  end
+
+  def call(node = %{data: data}, {:max, max}) when is_binary(data) do
+    if String.length(data) > max,
+      do: {:error, :max_exceeded, %{max: max, value: data}},
+      else: {:ok, node}
+  end
+
+  def call(node = %{data: data}, {:max, max}) do
+    if data > max,
+      do: {:error, :max_exceeded, %{max: max, value: data}},
+      else: {:ok, node}
+  end
+end

lib/constraints/max_items.ex

@@ -0,0 +1,17 @@
+defmodule AbsintheHelpers.Constraints.MaxItems do
+  @moduledoc false
+
+  @behaviour AbsintheHelpers.Constraint
+
+  def call(node = %{items: items}, {:max_items, max_items}) do
+    if Enum.count(items) > max_items do
+      {:error, :max_items_exceeded, %{max_items: max_items, items: Enum.map(items, & &1.data)}}
+    else
+      {:ok, node}
+    end
+  end
+
+  def call(node, {:max_items, _max_items}) do
+    {:ok, node}
+  end
+end

lib/constraints/min.ex

@@ -0,0 +1,27 @@
+defmodule AbsintheHelpers.Constraints.Min do
+  @moduledoc false
+
+  @behaviour AbsintheHelpers.Constraint
+
+  def call(node = %{items: _items}, {:min, _min}) do
+    {:ok, node}
+  end
+
+  def call(node = %{data: data = %Decimal{}}, {:min, min}) do
+    if is_integer(min) and Decimal.lt?(data, min),
+      do: {:error, :min_not_met, %{min: min, value: data}},
+      else: {:ok, node}
+  end
+
+  def call(node = %{data: data}, {:min, min}) when is_binary(data) do
+    if String.length(data) < min,
+      do: {:error, :min_not_met, %{min: min, value: data}},
+      else: {:ok, node}
+  end
+
+  def call(node = %{data: data}, {:min, min}) do
+    if data < min,
+      do: {:error, :min_not_met, %{min: min, value: data}},
+      else: {:ok, node}
+  end
+end

lib/constraints/min_items.ex

@@ -0,0 +1,17 @@
+defmodule AbsintheHelpers.Constraints.MinItems do
+  @moduledoc false
+
+  @behaviour AbsintheHelpers.Constraint
+
+  def call(node = %{items: items}, {:min_items, min_items}) do
+    if Enum.count(items) < min_items do
+      {:error, :min_items_not_met, %{min_items: min_items, items: Enum.map(items, & &1.data)}}
+    else
+      {:ok, node}
+    end
+  end
+
+  def call(node, {:min_items, _min_items}) do
+    {:ok, node}
+  end
+end

lib/directives/constraints.ex

@@ -0,0 +1,75 @@
+defmodule AbsintheHelpers.Directives.Constraints do
+  @moduledoc """
+  Defines a GraphQL directive for adding constraints to fields and arguments.
+
+  Supports:
+  - `:min`, `:max`: For numbers and string lengths
+  - `:min_items`, `:max_items`: For lists
+
+  Applicable to scalars (:string, :integer, :float, :decimal) and lists.
+
+  Example:
+      field :username, :string, directives: [constraints: [min: 3, max: 20]]
+      arg :tags, list_of(:string), directives: [constraints: [max_items: 5, max: 10]]
+
+  Constraints are automatically enforced during query execution.
+  """
+
+  use Absinthe.Schema.Prototype
+
+  alias Absinthe.Blueprint.TypeReference.{List, NonNull}
+
+  @constraints %{
+    string: [:min, :max],
+    number: [:min, :max],
+    list: [:min, :max, :min_items, :max_items]
+  }
+
+  directive :constraints do
+    on([:argument_definition, :field_definition])
+
+    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")
+
+    expand(&__MODULE__.expand_constraints/2)
+  end
+
+  def expand_constraints(args, node = %{type: type}) do
+    do_expand(args, node, get_args(type))
+  end
+
+  defp get_args(:string), do: @constraints.string
+  defp get_args(type) when type in [:integer, :float, :decimal], do: @constraints.number
+  defp get_args(%List{}), do: @constraints.list
+  defp get_args(%NonNull{of_type: of_type}), do: get_args(of_type)
+  defp get_args(type), do: raise(ArgumentError, "Unsupported type: #{inspect(type)}")
+
+  defp do_expand(args, node, allowed_args) do
+    {valid_args, invalid_args} = Map.split(args, allowed_args)
+    handle_invalid_args(node, invalid_args)
+    update_node(valid_args, node)
+  end
+
+  defp handle_invalid_args(_, args) when map_size(args) == 0, do: :ok
+
+  defp handle_invalid_args(%{type: type, name: name, __reference__: reference}, invalid_args) do
+    args = Map.keys(invalid_args)
+    location_line = get_in(reference, [:location, :line])
+
+    raise Absinthe.Schema.Error,
+      phase_errors: [
+        %Absinthe.Phase.Error{
+          phase: __MODULE__,
+          message:
+            "Invalid constraints for field/arg `#{name}` of type `#{inspect(type)}`: #{inspect(args)}",
+          locations: [%{line: location_line, column: 0}]
+        }
+      ]
+  end
+
+  defp update_node(args, node) do
+    %{node | __private__: Keyword.put(node.__private__, :constraints, args)}
+  end
+end

lib/phases/apply_constraints.ex

@@ -0,0 +1,135 @@
+defmodule AbsintheHelpers.Phases.ApplyConstraints do
+  @moduledoc """
+  Validates input nodes against constraints defined by the `constraints`
+  directive in your Absinthe schema. Constraints can be applied to fields
+  and arguments, enforcing rules such as `min`, `max`, etc. These constraints
+  can be applied to both individual items and lists simultaneously.
+
+  ## Example usage
+
+  Add this phase to your pipeline in your router:
+
+      pipeline =
+        config
+        |> Absinthe.Plug.default_pipeline(opts)
+        |> AbsintheHelpers.Phases.ApplyConstraints.add_to_pipeline(opts)
+
+  Add the constraints directive's prototype schema to your schema:
+
+      defmodule MyApp.Schema do
+        use Absinthe.Schema
+        @prototype_schema AbsintheHelpers.Directives.Constraints
+        # ...
+      end
+
+  Apply constraints to a field or argument:
+
+      field :my_field, :integer, directives: [constraints: [min: 1, max: 10]] do
+        resolve(&MyResolver.resolve/3)
+      end
+
+      arg :my_arg, non_null(:string), directives: [constraints: [min: 10]]
+
+      field :my_list, list_of(:integer), directives: [constraints: [min_items: 2, max_items: 5, min: 1, max: 100]] do
+        resolve(&MyResolver.resolve/3)
+      end
+  """
+
+  use Absinthe.Phase
+
+  alias Absinthe.Blueprint
+  alias Absinthe.Phase
+  alias Blueprint.Input
+
+  def add_to_pipeline(pipeline, opts) do
+    Absinthe.Pipeline.insert_before(
+      pipeline,
+      Phase.Document.Validation.Result,
+      {__MODULE__, opts}
+    )
+  end
+
+  @impl Absinthe.Phase
+  def run(input, _opts \\ []) do
+    {:ok, Blueprint.postwalk(input, &handle_node/1)}
+  end
+
+  defp handle_node(
+         node = %{
+           input_value: %{normalized: normalized},
+           schema_node: %{__private__: private}
+         }
+       ) do
+    if constraints?(private), do: apply_constraints(node, normalized), else: node
+  end
+
+  defp handle_node(node), do: node
+
+  defp apply_constraints(node, list = %Input.List{items: _items}) do
+    with {:ok, _list} <- validate_list(list, node.schema_node.__private__),
+         {:ok, _items} <- validate_items(list.items, node.schema_node.__private__) do
+      node
+    else
+      {:error, reason, details} -> add_custom_error(node, reason, details)
+    end
+  end
+
+  defp apply_constraints(node, %{value: _value}) do
+    case validate_item(node.input_value, node.schema_node.__private__) do
+      {:ok, _validated_value} -> node
+      {:error, reason, details} -> add_custom_error(node, reason, details)
+    end
+  end
+
+  defp apply_constraints(node, _), do: node
+
+  defp validate_list(list, private_tags) do
+    apply_constraints_in_sequence(list, get_constraints(private_tags))
+  end
+
+  defp validate_items(items, private_tags) do
+    Enum.reduce_while(items, {:ok, []}, fn item, {:ok, acc} ->
+      case validate_item(item, private_tags) do
+        {:ok, validated_item} -> {:cont, {:ok, acc ++ [validated_item]}}
+        {:error, reason, details} -> {:halt, {:error, reason, details}}
+      end
+    end)
+  end
+
+  defp validate_item(item, private_tags) do
+    apply_constraints_in_sequence(item, get_constraints(private_tags))
+  end
+
+  defp apply_constraints_in_sequence(item, constraints) do
+    Enum.reduce_while(constraints, {:ok, item}, fn constraint, {:ok, acc} ->
+      case call_constraint(constraint, acc) do
+        {:ok, result} -> {:cont, {:ok, result}}
+        {:error, reason, details} -> {:halt, {:error, reason, details}}
+      end
+    end)
+  end
+
+  defp call_constraint(constraint = {name, _args}, input) do
+    get_constraint_module(name).call(input, constraint)
+  end
+
+  defp get_constraint_module(constraint_name) do
+    String.to_existing_atom(
+      "Elixir.AbsintheHelpers.Constraints.#{Macro.camelize(Atom.to_string(constraint_name))}"
+    )
+  end
+
+  defp get_constraints(private), do: Keyword.get(private, :constraints, [])
+
+  defp constraints?(private), do: private |> get_constraints() |> Enum.any?()
+
+  defp add_custom_error(node, reason, details) do
+    Phase.put_error(node, %Phase.Error{
+      phase: __MODULE__,
+      message: reason,
+      extra: %{
+        details: Map.merge(details, %{field: node.name})
+      }
+    })
+  end
+end

lib/phases/apply_transforms.ex

@@ -8,7 +8,7 @@ defmodule AbsintheHelpers.Phases.ApplyTransforms do
   `AbsintheHelpers.Transforms.ToInteger`, or within your own project, as long
   as they implement the same behaviour.
 
-  ## Example Usage
+  ## Example usage
 
   To add this phase to your pipeline, add the following to your router:
 
@@ -73,10 +73,10 @@ defmodule AbsintheHelpers.Phases.ApplyTransforms do
   end
 
   defp handle_node(
-         %{
+         node = %{
            input_value: %{normalized: normalized},
            schema_node: %{__private__: private}
-         } = node
+         }
        ) do
     if transform?(private), do: apply_transforms(node, normalized), else: node
   end

mix.exs

@@ -32,7 +32,8 @@ defmodule AbsintheHelpers.MixProject do
       {:dialyxir, "~> 1.0", only: :dev, runtime: false},
       {:ex_doc, "~> 0.34", only: :dev, runtime: false},
       {:absinthe, "~> 1.0"},
-      {:mimic, "~> 1.10", only: :test}
+      {:mimic, "~> 1.10", only: :test},
+      {:decimal, "~> 1.9"}
     ]
   end
 

mix.lock

@@ -2,6 +2,7 @@
   "absinthe": {:hex, :absinthe, "1.7.8", "43443d12ad2b4fcce60e257ac71caf3081f3d5c4ddd5eac63a02628bcaf5b556", [:mix], [{:dataloader, "~> 1.0.0 or ~> 2.0", [hex: :dataloader, repo: "hexpm", optional: true]}, {:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}, {:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}, {:opentelemetry_process_propagator, "~> 0.2.1 or ~> 0.3", [hex: :opentelemetry_process_propagator, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "c4085df201892a498384f997649aedb37a4ce8a726c170d5b5617ed3bf45d40b"},
   "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
   "credo": {:hex, :credo, "1.7.7", "771445037228f763f9b2afd612b6aa2fd8e28432a95dbbc60d8e03ce71ba4446", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "8bc87496c9aaacdc3f90f01b7b0582467b69b4bd2441fe8aae3109d843cc2f2e"},
+  "decimal": {:hex, :decimal, "1.9.0", "83e8daf59631d632b171faabafb4a9f4242c514b0a06ba3df493951c08f64d07", [:mix], [], "hexpm", "b1f2343568eed6928f3e751cf2dffde95bfaa19dd95d09e8a9ea92ccfd6f7d85"},
   "dialyxir": {:hex, :dialyxir, "1.4.3", "edd0124f358f0b9e95bfe53a9fcf806d615d8f838e2202a9f430d59566b6b53b", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "bf2cfb75cd5c5006bec30141b131663299c661a864ec7fbbc72dfa557487a986"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.41", "ab34711c9dc6212dda44fcd20ecb87ac3f3fce6f0ca2f28d4a00e4154f8cd599", [:mix], [], "hexpm", "a81a04c7e34b6617c2792e291b5a2e57ab316365c2644ddc553bb9ed863ebefa"},
   "erlex": {:hex, :erlex, "0.2.7", "810e8725f96ab74d17aac676e748627a07bc87eb950d2b83acd29dc047a30595", [:mix], [], "hexpm", "3ed95f79d1a844c3f6bf0cea61e0d5612a42ce56da9c03f01df538685365efb0"},