defmodule AbsintheSortingCodec do
  @moduledoc """
  Convert the JSON output of an introspection query into deterministic JSON with types ordered alphabetically.

  ## Example
  ```
  AbsintheSortingCodec.encode!(Jason.decode!("swapi.json"))
  ```

  Can be used to convert an Absinthe schema to a sorted, deterministic ordering
  by using AbsintheSortingCodec as the JSON encoder.

  ## Example
  ```bash
  mix absinthe.schema.json --schema MySchema --json-codec AbsintheSortingCodec --pretty true
  ```

  """

  @doc """
  Generates a JSON GraphQL schema in a deterministic format, with lists of objects sorted by their `name` property,
  if they have one.

  `schema` is the Elixir representation of the JSON result of an introspection query (as generated by Absinthe).

  Uses [Jason](https://github.com/michalmuskala/jason) for encoding into JSON.
  """

  def encode(schema, opts \\ []) do
    schema
    |> sorted_objects()
    |> Jason.encode(opts)
  end

  def encode!(schema, opts \\ []) do
    case encode(schema, opts) do
      {:ok, content} -> content
      {:error, reason} -> raise reason
    end
  end

  defp sorted_objects(value)

  defp sorted_objects(map) when is_map(map) do
    for {key, val} <- map, into: %{}, do: {key, sorted_objects(val)}
  end

  defp sorted_objects(list) when is_list(list) do
    list
    |> Enum.sort_by(&list_sorting_value/1)
    |> Enum.map(&sorted_objects/1)
  end

  defp sorted_objects(value), do: value

  defp list_sorting_value(%{name: name}), do: name
  defp list_sorting_value(%{"name" => name}), do: name
  defp list_sorting_value(value), do: value
end