(.module:
  lux
  (lux (control [monad #+ do]
                pipe)
       (data [product]
             [text]
             text/format
             (coll [list "list/" Functor<List> Fold<List>]))
       [macro])
  (luxc ["&" lang]
        (lang ["ls" synthesis]
              [".L" variable #+ Variable]
              (host [r #+ Expression Statement @@])))
  [//]
  (// [".T" reference]))

(def: #export (translate-apply translate functionS argsS+)
  (-> (-> ls.Synthesis (Meta Expression)) ls.Synthesis (List ls.Synthesis) (Meta Expression))
  (do macro.Monad<Meta>
    [functionO (translate functionS)
     argsO+ (monad.map @ translate argsS+)]
    (wrap (r.apply argsO+ functionO))))

(def: $curried (r.var "curried"))

(def: (input-declaration register)
  (r.set! (referenceT.variable (n/inc register))
          (|> (@@ $curried) (r.nth (|> register n/inc nat-to-int r.int)))))

(def: (with-closure function-name inits function-definition)
  (-> Text (List Expression) Statement (Meta Expression))
  (let [$closure (r.var (format function-name "___CLOSURE"))]
    (case inits
      #.Nil
      (do macro.Monad<Meta>
        [_ (//.save function-definition)]
        (wrap (r.global function-name)))

      _
      (do macro.Monad<Meta>
        [_ (//.save (r.set! $closure
                            (r.function (|> (list.enumerate inits)
                                            (list/map (|>> product.left referenceT.closure)))
                              ($_ r.then!
                                  function-definition
                                  (r.do! (r.global function-name))))))]
        (wrap (r.apply inits (@@ $closure)))))))

(def: #export (translate-function translate env arity bodyS)
  (-> (-> ls.Synthesis (Meta Expression))
      (List Variable) ls.Arity ls.Synthesis
      (Meta Expression))
  (do macro.Monad<Meta>
    [[function-name bodyO] (//.with-sub-context
                             (do @
                               [function-name //.context]
                               (//.with-anchor [function-name +1]
                                 (translate bodyS))))
     closureO+ (monad.map @ referenceT.translate-variable env)
     #let [args-inits! (|> (list.n/range +0 (n/dec arity))
                           (list/map input-declaration)
                           (case> #.Nil
                                  r.no-op!

                                  (#.Cons head tail)
                                  (list/fold r.then! head tail)))
           arityO (|> arity nat-to-int r.int)
           $num_args (r.var "num_args")
           $function (r.var function-name)
           apply-poly (function (_ args func)
                        (r.apply (list func args) (r.global "do.call")))]]
    (with-closure function-name closureO+
      (r.set! $function
              (r.function (list r.var-args)
                ($_ r.then!
                    ## (r.set! $curried (r.apply (list (@@ r.var-args)) (r.global "list")))
                    (r.set! $curried (@@ r.var-args))
                    (r.set! $num_args (r.length (@@ $curried)))
                    (r.do!
                     (r.cond (list [(|> (@@ $num_args) (r.= arityO))
                                    (r.block
                                     ($_ r.then!
                                         (r.set! (referenceT.variable +0) (@@ $function))
                                         args-inits!
                                         (r.do! bodyO)))]
                                   [(|> (@@ $num_args) (r.> arityO))
                                    (let [arity-args (r.slice (r.int 1) arityO (@@ $curried))
                                          output-func-args (r.slice arityO (@@ $num_args) (@@ $curried))]
                                      (|> (@@ $function)
                                          (apply-poly arity-args)
                                          (apply-poly output-func-args)))])
                             ## (|> (@@ $num_args) (r.< arityO))
                             (let [$missing (r.var "missing")]
                               (r.function (list r.var-args)
                                 ($_ r.then!
                                     ## (r.set! $missing (r.apply (list (@@ r.var-args)) (r.global "list")))
                                     (r.set! $missing (@@ r.var-args))
                                     (r.do! (|> (@@ $function)
                                                (apply-poly (r.apply (list (@@ $curried) (@@ $missing))
                                                                     (r.global "append"))))))))))))))
    ))