(.module:
  [lux (#- Name)
   ["." host (#+ import:)]
   [abstract
    [codec (#+ Codec)]
    [equivalence (#+ Equivalence)]
    [monad (#+ Monad do)]]
   [control
    ["." try (#+ Try)]
    ["." exception (#+ Exception exception:)]
    ["<>" parser
     ["<.>" xml (#+ Parser)]]
    [concurrency
     ["." promise (#+ Promise)]]]
   [data
    ["." binary (#+ Binary)]
    ["." name]
    ["." maybe]
    [text
     ["%" format (#+ format)]
     ["." encoding]]
    [format
     ["." xml (#+ Tag XML)]]
    [collection
     ["." dictionary (#+ Dictionary)]
     ["." set]]]
   [math
    [number
     ["n" nat]
     ["." i64]]]
   [world
    [net (#+ URL)
     ["." uri]]]]
  ["." // (#+ Dependency)
   ["#." status (#+ Status)]
   ["/#" // #_
    ["/" profile]
    ["#." hash (#+ Hash SHA-1 MD5)]
    ["#." pom]
    ["#." package (#+ Package)]
    ["#." artifact (#+ Artifact)
     ["#/." extension (#+ Extension)]]
    ["#." repository (#+ Repository)
     ["#/." remote (#+ Address)]
     ["#/." origin (#+ Origin)]]]])

(template [<name>]
  [(exception: #export (<name> {artifact Artifact} {extension Extension} {hash Text})
     (exception.report
      ["Artifact" (///artifact.format artifact)]
      ["Extension" (%.text extension)]
      ["Hash" (%.text hash)]))]

  [sha-1_does_not_match]
  [md5_does_not_match]
  )

(def: (verified_hash library repository artifact extension hash codec exception)
  (All [h]
    (-> Binary (Repository Promise) Artifact Extension
        (-> Binary (Hash h)) (Codec Text (Hash h))
        (Exception [Artifact Extension Text])
        (Promise (Try (Hash h)))))
  (do (try.with promise.monad)
    [actual (\ repository download (///repository/remote.uri artifact extension))]
    (\ promise.monad wrap
       (do try.monad
         [output (\ encoding.utf8 decode actual)
          actual (\ codec decode output)
          _ (exception.assert exception [artifact extension output]
                              (\ ///hash.equivalence = (hash library) actual))]
         (wrap actual)))))

(def: (hashed repository artifact extension)
  (-> (Repository Promise) Artifact Extension (Promise (Try [Binary Status])))
  (do (try.with promise.monad)
    [data (\ repository download (///repository/remote.uri artifact extension))
     sha-1 (..verified_hash data
                            repository artifact (format extension ///artifact/extension.sha-1)
                            ///hash.sha-1 ///hash.sha-1_codec ..sha-1_does_not_match)
     md5 (..verified_hash data
                          repository artifact (format extension ///artifact/extension.md5)
                          ///hash.md5 ///hash.md5_codec ..md5_does_not_match)]
    (wrap [data (#//status.Verified sha-1 md5)])))

(def: #export (one repository dependency)
  (-> (Repository Promise) Dependency (Promise (Try Package)))
  (let [[artifact type] dependency
        extension (///artifact/extension.extension type)]
    (do (try.with promise.monad)
      [[pom pom_status] (..hashed repository artifact ///artifact/extension.pom)
       library_&_status (..hashed repository artifact extension)]
      (\ promise.monad wrap
         (do try.monad
           [pom (\ encoding.utf8 decode pom)
            pom (\ xml.codec decode pom)
            profile (<xml>.run ///pom.parser pom)]
           (wrap {#///package.origin (#///repository/origin.Remote "")
                  #///package.library library_&_status
                  #///package.pom [pom pom_status]}))))))

(type: #export Resolution
  (Dictionary Dependency Package))

(def: #export empty
  Resolution
  (dictionary.new //.hash))

(def: #export equivalence
  (Equivalence Resolution)
  (dictionary.equivalence ///package.equivalence))

(exception: #export (cannot_resolve {dependency Dependency})
  (exception.report
   ["Artifact" (%.text (///artifact.format (get@ #//.artifact dependency)))]
   ["Type" (%.text (get@ #//.type dependency))]))

(def: #export (any repositories dependency)
  (-> (List (Repository Promise)) Dependency (Promise (Try Package)))
  (case repositories
    #.Nil
    (|> dependency
        (exception.throw ..cannot_resolve)
        (\ promise.monad wrap))

    (#.Cons repository alternatives)
    (do promise.monad
      [outcome (..one repository dependency)]
      (case outcome
        (#try.Success package)
        (wrap outcome)

        (#try.Failure error)
        (any alternatives dependency)))))

(def: #export (all repositories dependencies resolution)
  (-> (List (Repository Promise)) (List Dependency) Resolution (Promise (Try Resolution)))
  (case dependencies
    #.Nil
    (\ (try.with promise.monad) wrap resolution)

    (#.Cons head tail)
    (do (try.with promise.monad)
      [package (case (dictionary.get head resolution)
                 (#.Some package)
                 (wrap package)

                 #.None
                 (..any repositories head))
       sub_dependencies (\ promise.monad wrap (///package.dependencies package))
       resolution (|> resolution
                      (dictionary.put head package)
                      (all repositories (set.to_list sub_dependencies)))]
      (all repositories tail resolution))))