(.module:
  lux
  (lux (data [text]
             (coll [list "list/" Fold<List>]
                   (dictionary ["dict" unordered #+ Dict])))))

(type: #export Influences (Dict Text (List Text)))

(def: #export (track to from)
  (-> Text Text Influences Influences)
  (|>> (dict.update~ from (list) (|>> (#.Cons to)))
       (dict.update~ to (list) id)))

(def: (effluents module influences)
  (-> Text Influences (Maybe (List Text)))
  (dict.get module influences))

(def: #export (untrack module influences)
  (-> Text Influences Influences)
  (case (effluents module influences)
    (#.Some effluents)
    (list/fold untrack (dict.remove module influences) effluents)

    #.None
    influences))

(def: #export empty Influences (dict.new text.Hash<Text>))