fix: make sure we detect content type and set properly or allow it to…

… pass through if set

lib/request_cache/plug.ex

@@ -16,6 +16,8 @@ defmodule RequestCache.Plug do
  # This is compile time so we can check quicker
  @graphql_paths RequestCache.Config.graphql_paths()
  @request_cache_header "rc-cache-status"
+ @json_regex ~r/^(\[|\{)(.*|\n)*(\]|\})$/
+ @html_regex ~r/<!DOCTYPE\s+html>/i
 
  @impl Plug
  def init(opts), do: opts
@@ -95,10 +97,23 @@ defmodule RequestCache.Plug do
  conn
  |> Plug.Conn.halt()
  |> Plug.Conn.put_resp_header(@request_cache_header, "HIT")
- |> Plug.Conn.put_resp_content_type("application/json")
+ |> maybe_put_content_type(result)
  |> Plug.Conn.send_resp(200, result)
  end
 
+ defp maybe_put_content_type(conn, result) do
+ case Plug.Conn.get_resp_header(conn, "content-type") do
+ [_ | _] -> conn
+ [] ->
+ cond do
+ result =~ @json_regex -> Plug.Conn.put_resp_content_type(conn, "application/json")
+ result =~ @html_regex -> Plug.Conn.put_resp_content_type(conn, "text/html")
+
+ true -> conn
+ end
+ end
+ end
+
  defp rest_cache_key(%Plug.Conn{request_path: path, query_string: query_string}) do
  Util.create_key(path, query_string)
  end