refactors into uri construction

as proposed by @asaaki

lib/contentful/query.ex

@@ -190,11 +190,17 @@ defmodule Contentful.Query do
         env,
         api_key
       ) do
-    url = [
-      space |> Delivery.url(env),
-      queryable.endpoint(),
-      parameters |> Request.collection_query_params()
-    ]
+    params = parameters |> Request.collection_query_params()
+
+    url =
+      [
+        space |> Delivery.url(env),
+        queryable.endpoint()
+      ]
+      |> Enum.join()
+      |> URI.parse()
+      |> add_query_params(params)
+      |> to_string()
 
     {url, api_key |> Request.headers()}
     |> Delivery.send_request()
@@ -439,4 +445,12 @@ defmodule Contentful.Query do
   def allowed_filter_modifiers do
     @allowed_filter_modifiers
   end
+
+  defp add_query_params(uri, []) do
+    uri
+  end
+
+  defp add_query_params(%URI{} = uri, params) do
+    uri |> Map.put(:query, URI.encode_query(params))
+  end
 end

lib/contentful/request.ex

@@ -18,24 +18,21 @@ defmodule Contentful.Request do
     accept: "application/json"
   ]
 
-  def collection_query_params([]) do
-    ""
-  end
+  def collection_query_params([]), do: []
 
   @doc """
   parses the options for retrieving a collection, usually triggered by a `Contentful.Query.fetch_all/4`.
   It will drop any option that is not in an allowed set of parameter options.
 
   ## Examples
 
-      "?limit=50&skip=25&order=foobar"
+      [limit: 50, skip: 25, order: "foobar"]
         = collection_query_params(limit: 50, baz: "foo", skip: 25, order: "foobar", bar: 42)
 
   Also provides support for mapping out some of the API specific syntax in field handling.
 
   ## Examples
-
-      "?sys.id[ne]=foobar" = collection_query_params(select_params: [id: [ne: "foobar"]])
+      [{:"sys.id[ne]", "foobar"}] = collection_query_params(select_params: [id: [ne: "foobar"]])
 
   """
   @spec collection_query_params(
@@ -45,21 +42,17 @@ defmodule Contentful.Request do
           content_type: String.t(),
           query: String.t(),
           select_params: map()
-        ) :: String.t()
+        ) :: list()
   def collection_query_params(options) do
     filters =
       options
       |> Keyword.get(:select_params)
       |> fallback([])
       |> deconstruct_filters()
 
-    params =
-      options
-      |> Keyword.take([:limit, :skip, :include, :content_type, :query])
-      |> Keyword.merge(filters)
-      |> URI.encode_query()
-
-    "?#{params}"
+    options
+    |> Keyword.take([:limit, :skip, :include, :content_type, :query])
+    |> Keyword.merge(filters)
   end
 
   @doc """

lib/contentful_delivery/delivery.ex

@@ -214,7 +214,7 @@ defmodule Contentful.Delivery do
   @doc """
   Sends a request against the CDA. It's really just a wrapper around `HTTPoison.get/2`
   """
-  @spec send_request(tuple()) :: {:ok, Response.t()}
+  @spec send_request({binary(), any()}) :: {:error, HTTPoison.Error.t()} | {:ok, Response.t()}
   def send_request({url, headers}) do
     get(url, headers)
   end

test/contentful_delivery/request_test.exs

@@ -18,7 +18,7 @@ defmodule Contentful.RequestTest do
 
   describe "collection_query_params/1" do
     test "omits arbitrary keywords" do
-      "?limit=1&skip=2" = Request.collection_query_params(limit: 1, skip: 2)
+      [limit: 1, skip: 2] = Request.collection_query_params(limit: 1, skip: 2)
     end
 
     test "raises an error for unknown modifiers" do
@@ -28,16 +28,16 @@ defmodule Contentful.RequestTest do
     end
 
     test "translates id into sys.id" do
-      "?sys.id=foo" = Request.collection_query_params(select_params: [id: "foo"])
+      [{:"sys.id", "foo"}] = Request.collection_query_params(select_params: [id: "foo"])
     end
 
     test "supports modifiers" do
-      "?fields.name%5Bne%5D=bar" =
+      [{:"fields.name[ne]", "bar"}] =
         Request.collection_query_params(select_params: [name: [ne: "bar"]])
     end
 
     test "supports translation of array properties" do
-      "?fields.tags%5Bnin%5D=foo%2Cbar%2Cbarfoo" =
+      [{:"fields.tags[nin]", "foo,bar,barfoo"}] =
         Request.collection_query_params(select_params: [tags: [nin: ["foo", "bar", "barfoo"]]])
     end
   end