First pass for Ecto -> Json API - WIP

json_api.ex

defmodule JsonApi do
  def filter_struct(obj) do
    is_struct?(obj) or (is_list(obj) && is_struct?(Enum.at(obj,0)))
  end
  def is_struct?(obj) do
    is_map(obj) && Map.get(obj, :__struct__) != nil
    #      ( obj.__struct__ == Ecto.Association.NotLoaded || 
  end

  def json_api(obj) do
    if is_list(obj) do
      data = Enum.map(obj, &json_api_data(&1))
      %{ data: data }
    else
      json_api_data(obj)
    end
  end

  def json_api_data(obj, filter \\ []) do

    # Go one level deep while splitting out the structs
    # If it's a struct, it should be under relationships and includes
    {structures, attributes} =
       Map.drop(obj, [:__meta__, :__struct__])
       |> Enum.partition( fn{k,v} ->
           filter_struct(v)
          end)

    attributes = attributes |> Enum.into(%{})

    # Parse the structures to give some relationships
    relationships =
      structures
      |> Enum.map( fn{k,v} ->
           if ! is_list(v), do: v = [v]
           data = Enum.reduce(v, [], fn(x, acc) ->
             id = Map.get(x,:id)
             if id, do: acc = acc ++ [%{"type": to_string(k), "id": id}]
           end)
           data
         end)
     |> List.flatten
     |> Enum.reject(&is_nil(&1))

     # Ugly, but go over the included set from the structures one more time
     included =
       structures
       |> Enum.map( fn{k,v} ->
           if ! is_list(v), do: v = [v]
           data = Enum.reduce(v, [], fn(x, acc) ->
             id = Map.get(x,:id)
             # find everything that isn't a struct and put it into a map
             attributes=
               x
               |> Map.drop([:__meta__, :__struct__])
               |> Enum.reject(fn{k,v} ->
                    filter_struct(v)
                  end)
               |> Enum.into(%{})


             if id, do: acc = acc ++ [%{"type": x.__meta__.source, "id": id, "attributes": attributes}]
           end)
           data
        end)
     |> List.flatten
     |> Enum.reject(&is_nil(&1))

    # Generate first level object
    %{
       type: obj.__meta__.source,
       id: attributes[:id],
       attributes: attributes,
       links: %{ "self": "something" },
       relationships: relationships,
       included: included
     }
  end
end