Improve JSON encoding and decoding

lib/exquickbooks/json_endpoint.ex

@@ -6,6 +6,9 @@ defmodule ExQuickBooks.JSONEndpoint do
     send_request: 1
   ]
 
+  alias ExQuickBooks.Request
+  alias HTTPoison.Response
+
   @json_headers [
     {"Accept", "application/json"},
     {"Content-Type", "application/json"}
@@ -21,12 +24,41 @@ defmodule ExQuickBooks.JSONEndpoint do
     end
   end
 
-  def send_json_request(request) do
+  def send_json_request(request = %Request{}) do
+    new_body = encode_body(request.body)
     new_headers = merge_headers(@json_headers, request.headers)
-    new_request = %{request | headers: new_headers}
 
-    with {:ok, response} <- send_request(new_request) do
-      Poison.Parser.parse(response.body)
+    %{request | body: new_body, headers: new_headers}
+    |> send_request
+    |> parse_response
+  end
+
+  defp encode_body(body) when is_binary(body) do
+    body
+  end
+  defp encode_body(body) do
+    Poison.Encoder.encode(body, [])
+  end
+
+  defp parse_response({ok_error, response = %Response{}}) do
+    is_json =
+      response
+      |> parse_content_type
+      |> String.starts_with?("application/json")
+
+    if is_json do
+      {ok_error, Poison.Parser.parse!(response.body)}
+    else
+      {ok_error, response}
     end
   end
+  defp parse_response(non_response_result) do
+    non_response_result
+  end
+
+  defp parse_content_type(%Response{headers: headers}) do
+    Enum.find_value(headers, "text/plain", fn({header, value}) ->
+      if String.downcase(header) == "content-type", do: value
+    end)
+  end
 end

test/exquickbooks/json_endpoint_test.exs

@@ -30,17 +30,52 @@ defmodule ExQuickBooks.JSONEndpointTest do
     } = take_request()
   end
 
-  test "send_json_request/1 parses the JSON response" do
+  test "send_json_request/1 encodes non-binary request bodies" do
+    request(:get, "path", %{foo: true}) |> send_json_request
+
+    # Note that IO lists are also accepted.
+    assert %{body: body} = take_request()
+    assert to_string(body) == ~S({"foo":true})
+  end
+
+  test "send_json_request/1 doesn't encode binary request bodies" do
+    request(:get, "path", "foo") |> send_json_request
+
+    assert %{
+      body: "foo"
+    } = take_request()
+  end
+
+  test "send_json_request/1 parses JSON responses" do
     send_response %HTTPoison.Response{
       body: ~S({"foo": true}),
       headers: [{"Content-Type", "application/json"}],
       status_code: 200
     }
 
-    result =
-      request(:get, "path")
-      |> send_json_request
+    assert {:ok, %{"foo" => true}} =
+      request(:get, "path") |> send_json_request
+  end
+
+  test "send_json_request/1 parses JSON error responses" do
+    send_response %HTTPoison.Response{
+      body: ~S({"foo": true}),
+      headers: [{"Content-Type", "application/json"}],
+      status_code: 400
+    }
+
+    assert {:error, %{"foo" => true}} =
+      request(:get, "path") |> send_json_request
+  end
+
+  test "send_json_request/1 doesn't parse non-JSON responses" do
+    send_response %HTTPoison.Response{
+      body: "foo",
+      headers: [{"Content-Type", "text/plain"}],
+      status_code: 200
+    }
 
-    assert result == {:ok, %{"foo" => true}}
+    assert {:ok, %HTTPoison.Response{body: "foo"}} =
+      request(:get, "path") |> send_json_request
   end
 end