(.module:
  [lux (#- Name Type)
   ["." host (#+ import:)]
   [abstract
    [monad (#+ do)]
    ["." equivalence (#+ Equivalence)]
    ["." hash (#+ Hash)]]
   [control
    ["." io (#+ IO)]
    ["." try (#+ Try)]
    ["." exception (#+ Exception exception:)]
    ["<>" parser
     ["<xml>" xml (#+ Parser)]]]
   [data
    ["." binary (#+ Binary)]
    ["." name]
    ["." maybe]
    ["." text
     ["%" format (#+ format)]
     ["." encoding]]
    [number
     ["." i64]
     ["n" nat]]
    [format
     ["." xml (#+ Tag XML)]]
    [collection
     ["." dictionary (#+ Dictionary)]]]
   [world
    [net (#+ URL)
     ["." uri]]]]
  ["." // #_
   ["#." extension]
   ["#." artifact (#+ Artifact)]
   ["#." hash]])

(type: #export Repository
  URL)

## https://maven.apache.org/ref/3.6.3/maven-core/artifact-handlers.html
(type: #export Type
  Text)

(type: #export Dependency
  {#artifact Artifact
   #type ..Type})

(def: #export equivalence
  (Equivalence Dependency)
  ($_ equivalence.product
      //artifact.equivalence
      text.equivalence
      ))

(def: #export hash
  (Hash Dependency)
  ($_ hash.product
      //artifact.hash
      text.hash
      ))

(template [<type> <name>]
  [(def: #export <name>
     Type
     <type>)]

  ["tar" lux-library]
  ["jar" jvm-library]
  ["pom" pom]
  )

(import: java/lang/String)

(import: java/lang/AutoCloseable
  (close [] #io #try void))

(import: java/io/InputStream)

(import: java/net/URL
  (new [java/lang/String])
  (openStream [] #io #try java/io/InputStream))

(import: java/io/BufferedInputStream
  (new [java/io/InputStream])
  (read [[byte] int int] #io #try int))

(def: buffer-size
  (n.* 512 1,024))

(def: (download url)
  (-> URL (IO (Try Binary)))
  (do {@ (try.with io.monad)}
    [input (|> (java/net/URL::new url)
               java/net/URL::openStream
               (:: @ map (|>> java/io/BufferedInputStream::new)))
     #let [buffer (binary.create ..buffer-size)]]
    (loop [output (:: binary.monoid identity)]
      (do @
        [bytes-read (java/io/BufferedInputStream::read buffer +0 (.int ..buffer-size) input)]
        (case bytes-read
          -1 (do @
               [_ (java/lang/AutoCloseable::close input)]
               (wrap output))
          _ (if (n.= ..buffer-size bytes-read)
              (recur (:: binary.monoid compose output buffer))
              (do @
                [chunk (:: io.monad wrap (binary.slice 0 (.nat bytes-read) buffer))]
                (recur (:: binary.monoid compose output chunk)))))))))

(def: hex-per-byte
  2)

(def: hex-per-nat
  (n.* hex-per-byte i64.bytes-per-i64))

(type: Hash-Reader
  (-> Binary (Try //hash.Hash)))

(def: (sha1 input)
  Hash-Reader
  (do try.monad
    [input (encoding.from-utf8 input)
     [left input] (try.from-maybe (text.split ..hex-per-nat input))
     [middle right] (try.from-maybe (text.split ..hex-per-nat input))
     #let [output (:: binary.monoid identity)]
     left (:: n.hex decode left)
     output (binary.write/64 0 left output)
     middle (:: n.hex decode middle)
     output (binary.write/64 i64.bytes-per-i64 middle output)
     right (:: n.hex decode right)]
    (binary.write/64 (n.* 2 i64.bytes-per-i64) right output)))

(def: (md5 input)
  Hash-Reader
  (do try.monad
    [input (encoding.from-utf8 input)
     [left right] (try.from-maybe (text.split ..hex-per-nat input))
     #let [output (:: binary.monoid identity)]
     left (:: n.hex decode left)
     output (binary.write/64 0 left output)
     right (:: n.hex decode right)]
    (binary.write/64 i64.bytes-per-i64 right output)))

(template [<name>]
  [(exception: #export (<name> {dependency Dependency} {hash Text})
     (let [artifact (get@ #artifact dependency)
           type (get@ #type dependency)]
       (exception.report
        ["Artifact" (format (get@ #//artifact.group artifact)
                            " " (get@ #//artifact.name artifact)
                            " " (get@ #//artifact.version artifact))]
        ["Type" (%.text type)]
        ["Hash" (%.text hash)])))]

  [sha1-does-not-match]
  [md5-does-not-match]
  )

(type: #export Package
  {#library Binary
   #pom XML
   #dependencies (List Dependency)
   #sha1 Text
   #md5 Text})

(def: (verified-hash dependency library url hash reader exception)
  (-> Dependency Binary URL (-> Binary //hash.Hash) Hash-Reader (Exception [Dependency Text])
      (IO (Try Text)))
  (do (try.with io.monad)
    [#let [reference (hash library)]
     actual (..download url)]
    (:: io.monad wrap
        (do try.monad
          [output (encoding.from-utf8 actual)
           actual (reader actual)
           _ (exception.assert exception [dependency output]
                               (:: binary.equivalence = reference actual))]
          (wrap output)))))

(def: parse-property
  (Parser [Tag Text])
  (do <>.monad
    [property <xml>.tag
     _ (<xml>.node property)
     value (<xml>.children <xml>.text)]
    (wrap [property value])))

(def: parse-dependency
  (Parser Dependency)
  (do {@ <>.monad}
    [properties (:: @ map (dictionary.from-list name.hash)
                    (<xml>.children (<>.some ..parse-property)))]
    (<| <>.lift
        try.from-maybe
        (do maybe.monad
          [group (dictionary.get ["" "groupId"] properties)
           artifact (dictionary.get ["" "artifactId"] properties)
           version (dictionary.get ["" "version"] properties)]
          (wrap {#artifact {#//artifact.group group
                            #//artifact.name artifact
                            #//artifact.version version}
                 #type (|> properties
                           (dictionary.get ["" "type"])
                           (maybe.default ..lux-library))})))))

(def: parse-dependencies
  (Parser (List Dependency))
  (do {@ <>.monad}
    [_ (<xml>.node ["" "dependencies"])]
    (<xml>.children (<>.some ..parse-dependency))))

(def: #export from-pom
  (-> XML (Try (List Dependency)))
  (<xml>.run (do {@ <>.monad}
               [_ (<xml>.node ["" "project"])]
               (<xml>.children (loop [_ []]
                                 (do @
                                   [?dependencies (<>.or ..parse-dependencies
                                                         (<>.maybe <xml>.ignore))]
                                   (case ?dependencies
                                     (#.Left dependencies)
                                     (wrap dependencies)

                                     (#.Right #.None)
                                     (wrap (: (List Dependency)
                                              (list)))

                                     (#.Right (#.Some _))
                                     (recur []))))))))

(def: #export (resolve repository dependency)
  (-> Repository Dependency (IO (Try Package)))
  (let [[artifact type] dependency
        prefix (format repository uri.separator (//artifact.path artifact))]
    (do (try.with io.monad)
      [library (..download (format prefix "." type))
       sha1 (..verified-hash dependency library (format prefix //extension.sha1) //hash.sha1 ..sha1 ..sha1-does-not-match)
       md5 (..verified-hash dependency library (format prefix //extension.md5) //hash.md5 ..md5 ..md5-does-not-match)
       pom (..download (format prefix //extension.pom))]
      (:: io.monad wrap
          (do try.monad
            [pom (encoding.from-utf8 pom)
             pom (:: xml.codec decode pom)
             dependencies (..from-pom pom)]
            (wrap {#library library
                   #pom pom
                   #dependencies dependencies
                   #sha1 sha1
                   #md5 md5}))))))

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

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

(exception: #export (cannot-resolve {dependency Dependency})
  (let [artifact (get@ #artifact dependency)
        type (get@ #type dependency)]
    (exception.report
     ["Artifact" (format (get@ #//artifact.group artifact)
                         " " (get@ #//artifact.name artifact)
                         " " (get@ #//artifact.version artifact))]
     ["Type" (%.text type)])))

(def: (resolve-any repositories dependency)
  (-> (List Repository) Dependency (IO (Try Package)))
  (case repositories
    #.Nil
    (|> dependency
        (exception.throw ..cannot-resolve)
        (:: io.monad wrap))

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

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

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

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

                 #.None
                 (..resolve-any repositories head))
       #let [resolution (dictionary.put head package resolution)]
       resolution (resolve-all repositories (get@ #dependencies package) resolution)]
      (resolve-all repositories tail resolution))))