(.module:
  lux
  (lux (control ["ex" exception #+ exception:])
       (data [bit]
             [maybe]
             ["e" error #+ Error]
             text/format
             (coll [array]))
       [host])
  (luxc [lang]
        (lang (host [lua #+ Lua Expression Statement])))
  [//])

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

  [Unknown-Kind-Of-Host-Object]
  [Null-Has-No-Lux-Representation]
  [Cannot-Evaluate]
  )

(host.import: java/lang/Object
  (toString [] String)
  (getClass [] (Class Object)))

(host.import: java/lang/Long
  (intValue [] Integer))

(host.import: net/sandius/rembulan/ByteString
  (decode [] String))

(host.import: net/sandius/rembulan/Table
  (rawget #as get-idx [long] #? Object)
  (rawget #as get-key [Object] #? Object)
  (rawlen [] long))

(host.import: net/sandius/rembulan/impl/DefaultTable)

(def: (variant lux-object host-object)
  (-> (-> Object (Error Any)) DefaultTable (Maybe Any))
  (case [(Table::get-key [//.variant-tag-field] host-object)
         (Table::get-key [//.variant-flag-field] host-object)
         (Table::get-key [//.variant-value-field] host-object)]
    (^multi [(#.Some tag) ?flag (#.Some value)]
            [(lux-object value)
             (#.Some value)])
    (#.Some [(Long::intValue [] (:coerce Long tag))
             (: Any (case ?flag (#.Some _) "" #.None (host.null)))
             value])

    _
    #.None))

(def: (array lux-object host-object)
  (-> (-> Object (Error Any)) DefaultTable (Maybe (Array Object)))
  (let [init-num-keys (:coerce Nat (Table::rawlen [] host-object))]
    (loop [num-keys init-num-keys
           idx +0
           output (: (Array Object)
                     (array.new init-num-keys))]
      (if (n/< num-keys idx)
        (case (Table::get-idx (:coerce Long (inc idx)) host-object)
          (#.Some member)
          (case (lux-object member)
            (#e.Success parsed-member)
            (recur num-keys (inc idx) (array.write idx (:coerce Object parsed-member) output))

            (#e.Error error)
            #.None)

          #.None
          (recur num-keys (inc idx) output))
        (#.Some output)))))

(def: (lux-object host-object)
  (-> Object (Error Any))
  (cond (host.null? host-object)
        (ex.throw Null-Has-No-Lux-Representation "")

        (or (host.instance? java/lang/Boolean host-object)
            (host.instance? java/lang/Long host-object)
            (host.instance? java/lang/Double host-object)
            (host.instance? java/lang/String host-object))
        (ex.return host-object)

        (host.instance? ByteString host-object)
        (ex.return (ByteString::decode [] (:coerce ByteString host-object)))

        (host.instance? DefaultTable host-object)
        (let [host-object (:coerce DefaultTable host-object)]
          (case (variant lux-object host-object)
            (#.Some value)
            (ex.return value)

            #.None
            (case (array lux-object host-object)
              (#.Some value)
              (ex.return value)

              #.None
              (ex.throw Unknown-Kind-Of-Host-Object (format "SECOND " (Object::toString [] (:coerce Object host-object)))))))

        ## else
        (ex.throw Unknown-Kind-Of-Host-Object (format "FIRST " (Object::toString [] (:coerce Object host-object))))
        ))

(def: #export (eval code)
  (-> Expression (Meta Any))
  (function (_ compiler)
    (let [interpreter (|> compiler (get@ #.host) (:coerce //.Host) (get@ #//.interpreter))]
      (case (interpreter (format "return " code ";"))
        (#e.Error error)
        ((lang.throw Cannot-Evaluate error) compiler)

        (#e.Success output)
        (case (lux-object (|> output
                              (:coerce (Array Object))
                              (array.read +0)
                              maybe.assume))
          (#e.Success parsed-output)
          (#e.Success [compiler parsed-output])

          (#e.Error error)
          ((lang.throw Cannot-Evaluate error) compiler))))))