add operator implementation

lib/parameter/operator.ex

@@ -0,0 +1,148 @@
+defmodule Parameter.Operator do
+  alias Parameter.Field
+  alias Parameter.Schema
+
+  @type t :: %__MODULE__{
+          schema: module() | nil,
+          valid?: boolean(),
+          data: map(),
+          changes: map(),
+          errors: map(),
+          cast_fields: list(atom())
+        }
+
+  defstruct schema: nil,
+            valid?: false,
+            data: nil,
+            changes: %{},
+            errors: %{},
+            cast_fields: []
+
+  @spec cast(module() | list(Field.t()), map(), list(atom())) :: t()
+  def cast(schema, params, cast_fields) do
+    %__MODULE__{
+      schema: schema,
+      data: params,
+      cast_fields: cast_fields
+    }
+  end
+
+  @spec cast(module() | list(Field.t()), map()) :: t()
+  def cast(schema, params) do
+    schema_fields = Schema.fields(schema)
+
+    %__MODULE__{
+      schema: schema,
+      data: params,
+      cast_fields: infer_cast_fields(schema_fields)
+    }
+  end
+
+  def load(
+        %__MODULE__{
+          schema: schema,
+          data: data,
+          cast_fields: cast_fields
+        } = operator,
+        opts \\ []
+      ) do
+    schema_fields = Schema.fields(schema)
+
+    fields_to_exclude =
+      schema_fields
+      |> Enum.map(& &1.name)
+      |> Enum.reject(fn field -> field in cast_fields end)
+
+    opts_with_fields_to_exclude = Keyword.merge(opts, exclude: fields_to_exclude)
+
+    case Parameter.load(schema, data, opts_with_fields_to_exclude) do
+      {:ok, loaded} ->
+        %__MODULE__{operator | valid?: true, changes: loaded}
+        |> load_assoc(opts)
+
+      {:error, errors} ->
+        %__MODULE__{operator | valid?: false, errors: errors}
+        |> load_assoc(opts)
+    end
+  end
+
+  def load_assoc(%__MODULE__{schema: schema, data: data} = operator, opts \\ []) do
+    schema_fields = Schema.fields(schema)
+    assoc_fields = Schema.assoc_fields(schema)
+
+    Enum.reduce(assoc_fields, operator, fn assoc_field, operator ->
+      %Field{name: name, key: key, type: {assoc_type, schema}} =
+        Enum.find(schema_fields, &(&1.name == assoc_field.name))
+
+      opts =
+        if assoc_type == :array do
+          Keyword.merge(opts, many: true)
+        else
+          opts
+        end
+
+      case schema |> cast(Map.get(data, key)) |> load(opts) do
+        %__MODULE__{valid?: true} = result ->
+          %__MODULE__{operator | changes: Map.put(operator.changes, name, result)}
+
+        %__MODULE__{valid?: false} = result ->
+          %__MODULE__{operator | valid?: false, changes: Map.put(operator.changes, name, result)}
+      end
+    end)
+  end
+
+  defp infer_cast_fields(fields) do
+    fields
+    |> Enum.filter(fn
+      %Parameter.Field{type: {:map, _nested}} -> false
+      %Parameter.Field{type: {:array, _nested}} -> false
+      _ -> true
+    end)
+    |> Enum.map(& &1.name)
+  end
+end
+
+defimpl Inspect, for: Parameter.Operator do
+  import Inspect.Algebra
+
+  def inspect(operator, opts) do
+    list =
+      for attr <- [:schema, :cast_fields, :changes, :errors, :data, :valid?] do
+        {attr, Map.get(operator, attr)}
+      end
+
+    container_doc("#Parameter.Operator<", list, ">", opts, fn
+      {:schema, schema}, opts ->
+        concat("schema: ", schema_field(schema, opts))
+
+      {:cast_fields, cast_fields}, opts ->
+        concat("cast_fields: ", to_doc(cast_fields, opts))
+
+      {:changes, changes}, opts ->
+        concat("changes: ", to_doc(changes, opts))
+
+      {:data, data}, _opts ->
+        concat("data: ", to_doc(data, opts))
+
+      {:errors, errors}, opts ->
+        concat("errors: ", to_doc(errors, opts))
+
+      {:valid?, valid?}, opts ->
+        concat("valid?: ", to_doc(valid?, opts))
+    end)
+  end
+
+  # defp to_struct(%{__struct__: struct}, _opts), do: "#" <> Kernel.inspect(struct) <> "<>"
+  # defp to_struct(other, opts), do: to_doc(other, opts)
+
+  defp schema_field(fields, opts) when is_list(fields) do
+    Enum.reduce(fields, [], fn %Parameter.Field{name: name}, acc ->
+      [name | acc]
+    end)
+    |> to_doc(opts)
+  end
+
+  defp schema_field(module, opts) do
+    to_doc(module, opts)
+  end
+end

lib/parameter/schema.ex

@@ -372,6 +372,16 @@ defmodule Parameter.Schema do
     fields
   end
 
+  def assoc_fields(module_or_fields) do
+    module_or_fields
+    |> fields()
+    |> Enum.filter(fn
+      %Field{type: {:array, _schema}} -> true
+      %Field{type: {:map, _schema}} -> true
+      _ -> false
+    end)
+  end
+
   def field_keys(module) when is_atom(module) do
     module.__param__(:field_keys)
   end