Convert a elixir json-decoded object to a map no matter how deep

json_map_builder.ex

defmodule JSONMapBuilder do
  def to_map(list) when is_list(list) and length(list) > 0 do
    case list |> List.first do
      {_, _} ->
        Enum.reduce(list, %{}, fn(tuple, acc) ->
          {key, value} = tuple
          Map.put(acc, binary_to_atom(key), to_map(value))
        end)
      _ ->
        list
    end
  end

  def to_map(tuple) when is_tuple(tuple) do
    {key, value} = tuple
    Enum.into([{binary_to_atom(key), to_map(value)}], %{})
  end

  def to_map(value), do: value
end

json_map_test.exs

defmodule JSONMapTest do
  use ExUnit.Case
  alias JSONMapBuilder, as: JS

  @simple_tuple [{"key", "value"}]
  @simple_map %{key: "value"}

  @deep_tuple [{"key1", {"key2", "value2"}}]
  @deep_map %{key1: %{key2: "value2"}}

  @multiple_deep_tuple [
    {"key1",
      [{"key2", "value2"},
      {"key3", "value3"}]
    },
    {"another_key",
      {"another_key2",
        {"another_value", "another_values_value"}
      }
    }
  ]

  @multiple_deep_map %{key1: %{key2: "value2", key3: "value3"}, another_key: %{another_key2: %{another_value: "another_values_value"}}}

  test "converts tuple to map with one level deep" do
    assert JS.to_map(@simple_tuple) == @simple_map
  end

  test "converts tuple to map with two levels" do
    assert JS.to_map(@deep_tuple) == @deep_map
  end

  test "converts tuple with multiple values and keys with multiple levels" do
    assert JS.to_map(@multiple_deep_tuple) == @multiple_deep_map
  end

  test "doesn't convert an empty list into a map when converting" do
    assert JS.to_map([{"key", []}]) == %{key: []}
  end

  test "doesn't convert an list of non-tuples into a map when converting" do
    assert JS.to_map([{"key", [1, 2, 3]}]) == %{key: [1, 2, 3]}
  end
end