(.module:
  [library
   [lux (#- Type)
    [abstract
     [equivalence (#+ Equivalence)]
     [monad (#+ do)]]
    [control
     ["<>" parser
      ["<.>" xml (#+ Parser)]
      ["<.>" text]]]
    [data
     ["." product]
     ["." text]
     [format
      ["." xml (#+ XML)]]]]]
  ["." /// #_
   ["#." type (#+ Type)]
   ["#." time (#+ Time)]])

(type: #export Version
  {#extension Type
   #value Text
   #updated Time})

(def: #export equivalence
  (Equivalence Version)
  ($_ product.equivalence
      text.equivalence
      text.equivalence
      ///time.equivalence
      ))

(template [<definition> <tag>]
  [(def: <definition> xml.Tag ["" <tag>])]

  [<extension> "extension"]
  [<value> "value"]
  [<updated> "updated"]

  [<snapshot_version> "snapshotVersion"]
  )

(def: (format_text tag value)
  (-> xml.Tag Text XML)
  (|> value #xml.Text list (#xml.Node tag xml.attributes)))

(def: #export (format (^slots [#extension #value #updated]))
  (-> Version XML)
  (<| (#xml.Node ..<snapshot_version> xml.attributes)
      (list (..format_text ..<extension> extension)
            (..format_text ..<value> value)
            (..format_text ..<updated> (///time.format updated)))))

(def: (text tag)
  (-> xml.Tag (Parser Text))
  (<| (<xml>.node tag)
      <xml>.text))

(def: #export parser
  (Parser Version)
  (<| (<xml>.node ..<snapshot_version>)
      ($_ <>.and
          (<xml>.somewhere (..text ..<extension>))
          (<xml>.somewhere (..text ..<value>))
          (<xml>.somewhere (<text>.embed ///time.parser
                                         (..text ..<updated>)))
          )))