overpass

defmodule Overpass.API do
    @moduledoc """
    Provides the functions to query the Overpass API.

    Don't forget to add the following to your `config/config.exs`:
    ```
    config :overpass, url: "http://overpass-api.de/api/interpreter"
    ```
    """

    require Logger

    @url Application.get_env(:overpass, :url)

    @doc """
    Querys the OverpassAPI with the given query (xml or overpass ql).
    Returns a tuple `{:ok, {:xml, body}}` or `{:ok, {:json, body}}` on success
    or `{:error, error}` on error.
    """
    @spec query(String.t) :: {:ok, {:json, String.t}}
    @spec query(String.t) :: {:ok, {:xml, String.t}}
    @spec query(String.t) :: {:error, String.t}
    def query(query) do
        Logger.debug("Query: #{query}")
        HTTPoison.post(@url, query) |> process_response()
    end

    defp process_response({
        :ok,
        %HTTPoison.Response{
            status_code: 200,
            body: body,
            headers: headers}
    }) do
        Logger.debug("status_code: 200")
        %{"Content-Type" => content_type} = Enum.into(headers, %{})
        case content_type do
            "application/osm3s+xml" -> {:ok, {:xml, body}}
            "application/json" -> {:ok, {:json, body}}
            _ -> {:error, "Unsuported Content-Type"}
        end
    end

    defp process_response({
        :ok,
        %HTTPoison.Response{
            status_code: code,
            body: _body,
            headers: _headers}
    }) do
        Logger.error("status_code: #{code}")
        {:error, "status_code: #{code}"}
    end

    defp process_response({:error, error}) do
        Logger.error(error)
        {:error, error}
    end
end