(.module:
  lux
  (lux (control ["ex" exception #+ exception:]
                pipe
                [monad #+ do])
       (data [bit]
             [maybe]
             ["e" error #+ Error]
             [text "text/" Eq<Text>]
             text/format
             (coll [array]))
       [macro]
       [io #+ IO Process io]
       [host #+ class: interface: object]
       (world [file #+ File]))
  (luxc [lang]
        (lang [".L" variable #+ Register]
              (host [r #+ Expression]))
        [".C" io]))

(template [<name>]
  [(exception: #export (<name> {message Text})
     message)]

  [No-Active-Module-Buffer]
  [Cannot-Execute]

  [No-Anchor]
  )

(host.import: java/lang/Object)

(host.import: java/lang/String
  (getBytes [String] #try [byte]))

(host.import: java/lang/CharSequence)

(host.import: java/lang/Appendable
  (append [CharSequence] Appendable))

(host.import: java/lang/StringBuilder
  (new [])
  (toString [] String))

(host.import: javax/script/ScriptEngine
  (eval [String] #try #? Object))

(host.import: javax/script/ScriptEngineFactory
  (getScriptEngine [] ScriptEngine))

(type: #export Anchor [Text Register])

(type: #export Host
  {#context [Text Nat]
   #anchor (Maybe Anchor)
   #loader (-> Expression (Error Any))
   #interpreter (-> Expression (Error Object))
   #module-buffer (Maybe StringBuilder)
   #program-buffer StringBuilder})

(def: #export init
  (IO Host)
  (io (let [interpreter (|> (undefined)
                            (ScriptEngineFactory::getScriptEngine []))]
        {#context ["" +0]
         #anchor #.None
         #loader (function (_ code)
                   (do e.Monad<Error>
                     [_ (ScriptEngine::eval [(r.expression code)] interpreter)]
                     (wrap [])))
         #interpreter (function (_ code)
                        (do e.Monad<Error>
                          [output (ScriptEngine::eval [(r.expression code)] interpreter)]
                          (wrap (maybe.default (:coerce Object [])
                                               output))))
         #module-buffer #.None
         #program-buffer (StringBuilder::new [])})))

(def: #export r-module-name Text "module.r")

(def: #export init-module-buffer
  (Meta Any)
  (function (_ compiler)
    (#e.Success [(update@ #.host
                          (|>> (:coerce Host)
                               (set@ #module-buffer (#.Some (StringBuilder::new [])))
                               (:coerce Nothing))
                          compiler)
                 []])))

(def: #export (with-sub-context expr)
  (All [a] (-> (Meta a) (Meta [Text a])))
  (function (_ compiler)
    (let [old (:coerce Host (get@ #.host compiler))
          [old-name old-sub] (get@ #context old)
          new-name (format old-name "f___" (%i (.int old-sub)))]
      (case (expr (set@ #.host
                        (:coerce Nothing (set@ #context [new-name +0] old))
                        compiler))
        (#e.Success [compiler' output])
        (#e.Success [(update@ #.host
                              (|>> (:coerce Host)
                                   (set@ #context [old-name (inc old-sub)])
                                   (:coerce Nothing))
                              compiler')
                     [new-name output]])

        (#e.Error error)
        (#e.Error error)))))

(def: #export context
  (Meta Text)
  (function (_ compiler)
    (#e.Success [compiler
                 (|> (get@ #.host compiler)
                     (:coerce Host)
                     (get@ #context)
                     (let> [name sub]
                           name))])))

(def: #export (with-anchor anchor expr)
  (All [a] (-> Anchor (Meta a) (Meta a)))
  (function (_ compiler)
    (let [old (:coerce Host (get@ #.host compiler))]
      (case (expr (set@ #.host
                        (:coerce Nothing (set@ #anchor (#.Some anchor) old))
                        compiler))
        (#e.Success [compiler' output])
        (#e.Success [(update@ #.host
                              (|>> (:coerce Host)
                                   (set@ #anchor (get@ #anchor old))
                                   (:coerce Nothing))
                              compiler')
                     output])

        (#e.Error error)
        (#e.Error error)))))

(def: #export anchor
  (Meta Anchor)
  (function (_ compiler)
    (case (|> compiler (get@ #.host) (:coerce Host) (get@ #anchor))
      (#.Some anchor)
      (#e.Success [compiler anchor])

      #.None
      ((lang.throw No-Anchor "") compiler))))

(def: #export module-buffer
  (Meta StringBuilder)
  (function (_ compiler)
    (case (|> compiler (get@ #.host) (:coerce Host) (get@ #module-buffer))
      #.None
      ((lang.throw No-Active-Module-Buffer "") compiler)
      
      (#.Some module-buffer)
      (#e.Success [compiler module-buffer]))))

(def: #export program-buffer
  (Meta StringBuilder)
  (function (_ compiler)
    (#e.Success [compiler (|> compiler (get@ #.host) (:coerce Host) (get@ #program-buffer))])))

(template [<name> <field> <outputT>]
  [(def: (<name> code)
     (-> Expression (Meta <outputT>))
     (function (_ compiler)
       (let [runner (|> compiler (get@ #.host) (:coerce Host) (get@ <field>))]
         (case (runner code)
           (#e.Error error)
           ((lang.throw Cannot-Execute error) compiler)
           
           (#e.Success output)
           (#e.Success [compiler output])))))]

  [load!     #loader      Any]
  [interpret #interpreter Object]
  )

(def: #export variant-tag-field "luxVT")
(def: #export variant-flag-field "luxVF")
(def: #export variant-value-field "luxVV")

(def: #export int-high-field "luxIH")
(def: #export int-low-field "luxIL")

(def: #export unit Text "")

(def: #export (definition-name [module name])
  (-> Name Text)
  (lang.normalize-name (format module "$" name)))

(def: #export (save code)
  (-> Expression (Meta Any))
  (do macro.Monad<Meta>
    [module-buffer module-buffer
     #let [_ (Appendable::append [(:coerce CharSequence (r.expression code))]
                                 module-buffer)]]
    (load! code)))

(def: #export run interpret)

(def: #export (save-module! target)
  (-> File (Meta (Process Any)))
  (do macro.Monad<Meta>
    [module macro.current-module-name
     module-buffer module-buffer
     program-buffer program-buffer
     #let [module-code (StringBuilder::toString [] module-buffer)
           _ (Appendable::append [(:coerce CharSequence (format module-code "\n"))]
                                 program-buffer)]]
    (wrap (ioC.write target
                     (format (lang.normalize-name module) "/" r-module-name)
                     (|> module-code
                         (String::getBytes ["UTF-8"])
                         e.assume)))))