(.module:
  [lux (#- Name)
   [abstract
    [monad (#+ do)]
    [equivalence (#+ Equivalence)]]
   [control
    ["<>" parser
     ["<.>" xml (#+ Parser)]
     ["<.>" text]]]
   [data
    ["." product]
    ["." text
     ["%" format (#+ format)]]
    [format
     ["." xml (#+ XML)]]
    [collection
     ["." list ("#\." functor)]]]
   [math
    [number
     ["n" nat]]]
   ["." time (#+ Time)
    ["." instant (#+ Instant)]
    ["." date (#+ Date)]
    ["." year]
    ["." month]]]
  ["." /// #_
   ["#." artifact (#+ Group Name Version Artifact)]])

(type: #export Metadata
  {#group Group
   #name Name
   #versions (List Version)
   #last_updated Instant})

(def: (pad value)
  (-> Nat Text)
  (if (n.< 10 value)
    (format "0" (%.nat value))
    (%.nat value)))

(def: (date_format value)
  (%.Format Date)
  (format (|> value date.year year.value .nat %.nat)
          (|> value date.month month.number ..pad)
          (|> value date.day_of_month ..pad)))

(def: (time_format value)
  (%.Format Time)
  (let [(^slots [#time.hour #time.minute #time.second]) (time.clock value)]
    (format (..pad hour)
            (..pad minute)
            (..pad second))))

(def: (instant_format value)
  (%.Format Instant)
  (format (..date_format (instant.date value))
          (..time_format (instant.time value))))

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

  [<group> "groupId"]
  [<name> "artifactId"]
  [<version> "version"]
  [<versioning> "versioning"]
  [<versions> "versions"]
  [<last_updated> "lastUpdated"]
  [<metadata> "metadata"]
  )

(template [<name> <type> <tag> <pre>]
  [(def: <name>
     (-> <type> XML)
     (|>> <pre> #xml.Text list (#xml.Node <tag> xml.attributes)))]

  [write_group Group ..<group> (|>)]
  [write_name Name ..<name> (|>)]
  [write_version Version ..<version> (|>)]
  [write_last_updated Instant ..<last_updated> ..instant_format]
  )

(def: write_versions
  (-> (List Version) XML)
  (|>> (list\map ..write_version) (#xml.Node ..<versions> xml.attributes)))

(def: #export (write value)
  (-> Metadata XML)
  (#xml.Node ..<metadata>
             xml.attributes
             (list (..write_group (get@ #group value))
                   (..write_name (get@ #name value))
                   (#xml.Node ..<versioning>
                              xml.attributes
                              (list (..write_versions (get@ #versions value))
                                    (..write_last_updated (get@ #last_updated value)))))))

(def: (sub tag parser)
  (All [a] (-> xml.Tag (Parser a) (Parser a)))
  (do <>.monad
    [_ (<xml>.node tag)]
    (<xml>.children parser)))

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

(def: date_parser
  (<text>.Parser Date)
  (do <>.monad
    [year (<>.codec n.decimal (<text>.exactly 4 <text>.decimal))
     year (<>.lift (year.year (.int year)))
     month (<>.codec n.decimal (<text>.exactly 2 <text>.decimal))
     month (<>.lift (month.by_number month))
     day_of_month (<>.codec n.decimal (<text>.exactly 2 <text>.decimal))]
    (<>.lift (date.date year month day_of_month))))

(def: time_parser
  (<text>.Parser Time)
  (do <>.monad
    [hour (<>.codec n.decimal (<text>.exactly 2 <text>.decimal))
     minute (<>.codec n.decimal (<text>.exactly 2 <text>.decimal))
     second (<>.codec n.decimal (<text>.exactly 2 <text>.decimal))]
    (<>.lift (time.time
              {#time.hour hour
               #time.minute minute
               #time.second second
               #time.milli_second 0}))))

(def: last_updated_parser
  (Parser Instant)
  (<text>.embed (do <>.monad
                  [date ..date_parser
                   time ..time_parser]
                  (wrap (instant.from_date_time date time)))
                (..text ..<last_updated>)))

(def: #export parser
  (Parser Metadata)
  (<| (..sub ..<metadata>)
      ($_ <>.and
          (<xml>.somewhere (..text ..<group>))
          (<xml>.somewhere (..text ..<name>))
          (<| (..sub ..<versioning>)
              ($_ <>.and
                  (<| <xml>.somewhere
                      (..sub ..<versions>)
                      (<>.many (..text ..<version>)))
                  (<xml>.somewhere ..last_updated_parser)
                  ))
          )))

(def: #export equivalence
  (Equivalence Metadata)
  ($_ product.equivalence
      text.equivalence
      text.equivalence
      (list.equivalence text.equivalence)
      instant.equivalence
      ))