(.module:
  [lux (#- Name)
   [abstract
    ["." monad (#+ do)]
    ["." equivalence (#+ Equivalence)]]
   [control
    ["." try (#+ Try)]
    ["." exception (#+ exception:)]]
   [data
    ["." text
     ["%" format (#+ format)]]
    [collection
     ["." dictionary (#+ Dictionary)]
     ["." set (#+ Set)]
     ["." list ("#@." fold)]]]]
  ["." // #_
   ["#" profile (#+ Name Profile)]])

(type: #export Project
  (Dictionary Name Profile))

(def: #export empty
  (dictionary.from-list text.hash (list [//.default (:: //.monoid identity)])))

(def: #export equivalence
  (Equivalence Project)
  (dictionary.equivalence //.equivalence))

(exception: #export (unknown-profile {name Name})
  (exception.report
   ["Name" (%.text name)]))

(exception: #export (circular-dependency {dependee Name} {dependent Name})
  (exception.report
   ["Dependent" (%.text dependent)]
   ["Dependee" (%.text dependee)]))

(def: (profile' lineage project name)
  (-> (Set Name) Project Name (Try Profile))
  (case (dictionary.get name project)
    (#.Some profile)
    (case (list.find (set.member? lineage)
                     (get@ #//.parents profile))
      (#.Some ouroboros)
      (exception.throw ..circular-dependency [ouroboros name])
      
      #.None
      (do {@ try.monad}
        [parents (monad.map @ (profile' (set.add name lineage) project)
                            (get@ #//.parents profile))]
        (wrap (list@fold (function (_ parent child)
                           (:: //.monoid compose child parent))
                         profile
                         parents))))
    
    #.None
    (exception.throw ..unknown-profile [name])))

(def: #export (profile project name)
  (-> Project Name (Try Profile))
  (profile' (set.new text.hash) project name))