list all municipalities of brazil by state

municipalities.ex

defmodule CEP.Municipalities do
  @moduledoc """
  Documentation for `CEP.Municipalities`.
  """

  alias CEP.{Utils, Municipalities}

  defstruct has_municipalities?: false,
            states:              %{},
            municipalities:      [],
            timeout:             900,
            cache:               nil

  @municipalities_url "https://sidra.ibge.gov.br/Territorio/Unidades?nivel=6"

  @doc """
  Get municipalities
  """

  def get(
    %CEP{all?: all?, municipalities?: municipalities?} = options
  ) when all? and not municipalities? do
    options
  end

  @doc """
  Get municipalities
  """

  def get(%CEP{
    all?: all?,
    municipalities?: municipalities?,
    cache_exists?: cache_exists?,
    cache: cache,
    timeout: timeout
  } = options) when all? or municipalities? do
    sections = if cache_exists?, do: Utils.list_sections(cache), else: []

    load_municipalities_from_cache(%Municipalities{
      timeout: timeout,
      cache: cache,
      has_municipalities?: municipalities? and Enum.member?(sections, "municipalities")
    })
    |> get_municipalities
    |> IO.inspect

    options
  end

  def get_municipalities(
    %Municipalities{has_municipalities?: has_municipalities?, cache: cache, timeout: timeout} = struct
  ) when not has_municipalities? do
    case HTTPoison.get(@municipalities_url, [], timeout: 15_000, recv_timeout: timeout * 1_000) do
      {:ok, %{status_code: 200, body: body}} ->
        Utils.write_cache(body, cache, :municipalities)
        |> Poison.decode
        |> parse_municipalities(struct)

      {:ok, %{status_code: status}} ->
        exit {:error, "something went wrong, http code ##{status}"}

      {:error, %{reason: reason}} ->
        exit {:error, "something else went really wrong, reason: #{reason}"}
    end

  end

  def load_municipalities_from_cache(
    %Municipalities{has_municipalities?: has_municipalities?} = struct
  ) when not has_municipalities? do
    struct
  end

  def load_municipalities_from_cache(
    %Municipalities{has_municipalities?: has_municipalities?, cache: cache} = struct
  ) when has_municipalities? do
    Utils.read_cache(cache, :municipalities) |> parse_municipalities(struct)
  end

  def parse_municipalities(
    [municipality | m_tail], [state | s_tail], %{municipalities: municipalities} = struct, s_cache \\ []
  ) do
    parse_municipalities(
      m_tail,
      s_tail,
      %Municipalities{struct | municipalities: ["#{municipality}_#{state}" | municipalities] },
      [ %{state: state, municipality: municipality} | s_cache ]
    ) 
  end

  def parse_municipalities [], [], %{municipalities: municipalities, states: states} = struct, s_cache do
    %Municipalities{struct | municipalities: municipalities, states: Enum.group_by(s_cache, & &1[:state])}
  end

  def parse_municipalities({:ok, %{"Nivel"=>%{"Id"=>6}, "Nomes"=>names, "SiglasUF"=>ufs}}, struct) do
    parse_municipalities names, ufs, struct
  end
end