require:
   .util ->
      ID, CACHE, methods
      tuck, fork-identify

provide:
   Root

;;;;;;;;;;
;; Root ;;
;;;;;;;;;;

class Root:

   constructor{@root, @action = {x} -> x, @idle = false} =
      if not @idle:
         @action{@root}

   [^methods.proxy]{tracks, patch, prevent-dirty-reads} =
      throw E.proxy.not-implemented{"Root instances cannot be proxied."}

   [^methods.iterate-properties]{} =
      id = self[ID]
      {{"root", @root, gen-patch}} where
         gen-patch{patch, new-v} =
            patch.get{id}.root = #update{new-v}
            ;; patch[id] or= {=}
            ;; patch[id].root = #update{new-v}

   [^methods.fork]{dir} =
      rval = Root{dir.acquire{@root}, @action}
      {ID, CACHE} each field ->
         tuck{rval, field, self[field]}
      fork-identify{rval}
      dir.enter{rval, false}
      rval

   [^methods.patch]{patch, dir} =
      match patch.get-for{self}:
         {root => #update{new-root}} ->
            @root = dir.replace{@root, new-root}
            @action{@root}
         else ->
            pass

   [^methods.clobber]{new-root, dir} =
      throw E.clobber.not-implemented{"Cannot clobber a Root."}