(.using
 [library
  [lux "*"
   [abstract
    ["[0]" monad {"+" do}]]
   [control
    ["[0]" try {"+" Try}]
    [concurrency
     ["[0]" async {"+" Async}]]]
   [data
    [collection
     ["[0]" list]
     ["[0]" set]]]
   [world
    [program {"+" Program}]
    [shell {"+" Exit Shell}]
    [console {"+" Console}]
    ["[0]" file
     ["[0]" watch {"+" Watcher}]]]]]
 ["[0]" // "_"
  ["/[1]" // "_"
   [command {"+" Command}]
   ["[1]" profile]
   ["[1][0]" action]
   [dependency
    [resolution {"+" Resolution}]]]])

(def: (targets fs path)
  (-> (file.System Async) file.Path (Async (List file.Path)))
  (let [! async.monad]
    (|> path
        (# fs sub_directories)
        (# ! each (|>> (try.else (list))
                       (monad.each ! (targets fs))))
        (# ! conjoint)
        (# ! each (|>> list.together (list& path))))))

(def: .public delay
  Nat
  1,000)

(def: (pause delay)
  (-> Nat (Async (Try Any)))
  (async.after delay {try.#Success []}))

(def: .public (do! delay watcher command)
  (All (_ a)
    (-> Nat (Watcher Async)
        (-> (Console Async) (Program Async) (file.System Async) (Shell Async) Resolution (Command [Exit a]))
        (-> (Console Async) (Program Async) (file.System Async) (Shell Async) Resolution (Command [Exit Any]))))
  (function (_ console program fs shell resolution)
    (function (_ profile)
      (with_expansions [<call> ((command console program fs shell resolution) profile)]
        (do [! async.monad]
          [targets (|> profile
                       (the ///.#sources)
                       set.list
                       (monad.each ! (..targets fs))
                       (# ! each list.together))]
          (do [! ///action.monad]
            [_ (monad.each ! (# watcher start watch.modification) targets)
             _ <call>]
            (loop [_ []]
              (do !
                [_ (..pause delay)
                 events (# watcher poll [])]
                (case events
                  {.#Item _}
                  (do !
                    [_ <call>]
                    (again []))

                  {.#End}
                  (again []))))))))))