string_literal.ex

defmodule MyApp.Types.StringLiteral do
  @moduledoc "An ash type for a string that can only take a single value. Used in codegen to create literal values."
  use Ash.Type

  @constraints [
    value: [
      type: :string,
      doc: "The string literal value",
      required: true
    ]
  ]

  @impl true
  def constraints, do: @constraints

  @impl true
  def apply_constraints(_, _), do: :ok

  @impl true
  def storage_type, do: :string

  @impl true
  def cast_input(nil, _), do: {:ok, nil}

  def cast_input(value, constraints) do
    value = to_string(value)

    if value == constraints[:value] do
      {:ok, value}
    else
      :error
    end
  end

  @impl true
  def cast_stored(nil, _), do: {:ok, nil}

  def cast_stored(value, constraints) do
    value = to_string(value)

    if value == constraints[:value] do
      {:ok, value}
    else
      :error
    end
  end

  @impl true
  def dump_to_native(value, _) do
    {:ok, value}
  end
end