Merge branch 'features/apc2s-pagination' into 'develop'

Fix AP C2S pagination

Closes #866 and #751

See merge request pleroma/pleroma!2491

1 files changed, 40 insertions, 23 deletions

diff --git a/lib/pleroma/web/controller_helper.ex b/lib/pleroma/web/controller_helper.ex
index c9a3a2585..1e0491a96 100644
--- a/lib/pleroma/web/controller_helper.ex
+++ b/lib/pleroma/web/controller_helper.ex
@@ -5,7 +5,9 @@
 defmodule Pleroma.Web.ControllerHelper do
   use Pleroma.Web, :controller
 
-  # As in MastoAPI, per https://api.rubyonrails.org/classes/ActiveModel/Type/Boolean.html
+  alias Pleroma.Pagination
+
+  # As in Mastodon API, per https://api.rubyonrails.org/classes/ActiveModel/Type/Boolean.html
   @falsy_param_values [false, 0, "0", "f", "F", "false", "False", "FALSE", "off", "OFF"]
   def truthy_param?(blank_value) when blank_value in [nil, ""], do: nil
   def truthy_param?(value), do: value not in @falsy_param_values
@@ -34,38 +36,53 @@ defmodule Pleroma.Web.ControllerHelper do
 
   defp param_to_integer(_, default), do: default
 
-  def add_link_headers(conn, activities, extra_params \\ %{}) do
+  def add_link_headers(conn, activities, extra_params \\ %{})
+
+  def add_link_headers(%{assigns: %{skip_link_headers: true}} = conn, _activities, _extra_params),
+    do: conn
+
+  def add_link_headers(conn, activities, extra_params) do
+    case get_pagination_fields(conn, activities, extra_params) do
+      %{"next" => next_url, "prev" => prev_url} ->
+        put_resp_header(conn, "link", "<#{next_url}>; rel=\"next\", <#{prev_url}>; rel=\"prev\"")
+
+      _ ->
+        conn
+    end
+  end
+
+  def get_pagination_fields(conn, activities, extra_params \\ %{}) do
     case List.last(activities) do
       %{id: max_id} ->
         params =
           conn.params
           |> Map.drop(Map.keys(conn.path_params))
-          |> Map.drop(["since_id", "max_id", "min_id"])
           |> Map.merge(extra_params)
-
-        limit =
-          params
-          |> Map.get("limit", "20")
-          |> String.to_integer()
+          |> Map.drop(Pagination.page_keys() -- ["limit", "order"])
 
         min_id =
-          if length(activities) <= limit do
-            activities
-            |> List.first()
-            |> Map.get(:id)
-          else
-            activities
-            |> Enum.at(limit * -1)
-            |> Map.get(:id)
-          end
-
-        next_url = current_url(conn, Map.merge(params, %{max_id: max_id}))
-        prev_url = current_url(conn, Map.merge(params, %{min_id: min_id}))
-
-        put_resp_header(conn, "link", "<#{next_url}>; rel=\"next\", <#{prev_url}>; rel=\"prev\"")
+          activities
+          |> List.first()
+          |> Map.get(:id)
+
+        fields = %{
+          "next" => current_url(conn, Map.put(params, :max_id, max_id)),
+          "prev" => current_url(conn, Map.put(params, :min_id, min_id))
+        }
+
+        #  Generating an `id` without already present pagination keys would
+        # need a query-restriction with an `q.id >= ^id` or `q.id <= ^id`
+        # instead of the `q.id > ^min_id` and `q.id < ^max_id`.
+        #  This is because we only have ids present inside of the page, while
+        # `min_id`, `since_id` and `max_id` requires to know one outside of it.
+        if Map.take(conn.params, Pagination.page_keys() -- ["limit", "order"]) != [] do
+          Map.put(fields, "id", current_url(conn, conn.params))
+        else
+          fields
+        end
 
       _ ->
-        conn
+        %{}
     end
   end