In-house redirect handler for mediaproxy with Hackney adapter

Also ensure we always pass an absolute URL to Hackney when parsing a redirect response

(cherry picked from commit 00ac6bce8d244eec7e2460358296619e5cacba6b)

changelog.d/hackney-mediaproxy.change

@@ -0,0 +1 @@
+Use a custom redirect handler to ensure MediaProxy redirects are followed with Hackney

lib/pleroma/reverse_proxy/client/hackney.ex

@@ -5,6 +5,20 @@
 defmodule Pleroma.ReverseProxy.Client.Hackney do
   @behaviour Pleroma.ReverseProxy.Client
 
+  # redirect handler from Pleb, slightly modified to work with Hackney
+  # https://declin.eu/objects/d4f38e62-5429-4614-86d1-e8fc16e6bf33
+  # https://github.com/benoitc/hackney/issues/273
+  @redirect_statuses [301, 302, 303, 307, 308]
+  defp absolute_redirect_url(original_url, resp_headers) do
+    location =
+      Enum.find(resp_headers, fn {header, _location} ->
+        String.downcase(header) == "location"
+      end)
+
+    URI.merge(original_url, elem(location, 1))
+    |> URI.to_string()
+  end
+
   @impl true
   def request(method, url, headers, body, opts \\ []) do
     opts =
@@ -12,7 +26,35 @@ defmodule Pleroma.ReverseProxy.Client.Hackney do
         path
       end)
 
-    :hackney.request(method, url, headers, body, opts)
+    if opts[:follow_redirect] != false do
+      {_state, req_opts} = Access.get_and_update(opts, :follow_redirect, fn a -> {a, false} end)
+      res = :hackney.request(method, url, headers, body, req_opts)
+
+      case res do
+        {:ok, code, resp_headers, _client} when code in @redirect_statuses ->
+          :hackney.request(
+            method,
+            absolute_redirect_url(url, resp_headers),
+            headers,
+            body,
+            req_opts
+          )
+
+        {:ok, code, resp_headers} when code in @redirect_statuses ->
+          :hackney.request(
+            method,
+            absolute_redirect_url(url, resp_headers),
+            headers,
+            body,
+            req_opts
+          )
+
+        _ ->
+          res
+      end
+    else
+      :hackney.request(method, url, headers, body, opts)
+    end
   end
 
   @impl true