nginx: refactor upstream generation

lib.nix

@@ -17,4 +17,64 @@ rec {
     l = firstListenerOfType r w.settings.worker_listeners;
   in connectionInfo l;
 
+  mapWorkersToUpstreamsByType = workerInstances:
+    lib.pipe workerInstances [
+      lib.attrValues
+
+      # Index by worker type
+      (lib.foldl (acc: worker: acc // {
+        ${worker.type} = (acc.${worker.type} or [ ]) ++ [ worker ];
+      }) { })
+
+      # Subindex by resource names, listener types, and convert to upstreams
+      (lib.mapAttrs (_: workers: lib.pipe workers [
+        (lib.concatMap (worker: worker.settings.worker_listeners))
+        lib.flatten
+        mapListenersToUpstreamsByType
+      ]))
+    ];
+
+    mapListenersToUpstreamsByType = listenerInstances:
+      lib.pipe listenerInstances [
+        # Index by resource names
+        (lib.concatMap (listener: lib.pipe listener [
+          (listener: let
+            allResourceNames = lib.pipe listener.resources [
+              (map (resource: resource.names))
+              lib.flatten
+              lib.unique
+            ];
+          in if allResourceNames == [ ]
+            then { "empty" = listener; }
+            else lib.genAttrs allResourceNames (_: listener))
+          lib.attrsToList
+        ]))
+
+        (lib.foldl (acc: listener: acc // {
+          ${listener.name} = (acc.${listener.name} or [ ]) ++ [ listener.value ];
+        }) { })
+
+        # Index by listener type
+        (lib.mapAttrs (_:
+          (lib.foldl (acc: listener: acc // {
+            ${listener.type} = (acc.${listener.type} or [ ]) ++ [ listener ];
+          }) { })
+        ))
+
+        # Convert listeners to upstream URIs
+        (lib.mapAttrs (_:
+          (lib.mapAttrs (_: listeners:
+            lib.pipe listeners [
+              (lib.concatMap (listener:
+                if listener.path != null
+                  then [ "unix:${listener.path}" ]
+                  else (map (addr: "${addr}:${toString listener.port}") listener.bind_addresses)
+              ))
+              # NOTE: Adding ` = { }` to every upstream might seem unnecessary in isolation,
+              #       but it makes it easier to set upstreams in the nginx module.
+              (uris: lib.genAttrs uris (_: { }))
+            ]
+          ))
+        ))
+      ];
 }