(;module:
  lux
  (lux (control monad
                pipe)
       [io #- run]
       (concurrency ["A" atom])
       (data [text "T/" Eq<Text>]
             text/format
             [ident]
             (coll [list "L/" Fold<List> Monoid<List> Monad<List>]
                   ["D" dict]
                   ["S" set])
             [number]
             [product])
       [macro #+ Monad<Lux>]
       (macro [code])
       [type]
       (type ["TC" check]))
  (luxc ["&" base]
        (lang ["la" analysis #+ Analysis])
        ["&;" module]
        ["&;" env]
        (analyser ["&;" common])))

## [Analysers]
(def: (analyse-typed-tuple analyse members)
  (-> &;Analyser (List Code) (Lux Analysis))
  (do Monad<Lux>
    [expected macro;expected-type]
    (let [member-types (type;flatten-tuple expected)
          num-types (list;size member-types)
          num-members (list;size members)]
      (cond (n.= num-types num-members)
            (do @
              [=tuple (: (Lux (List Analysis))
                         (mapM @
                               (function [[expected member]]
                                 (&;with-expected-type expected
                                   (analyse member)))
                               (list;zip2 member-types members)))]
              (wrap (#la;Tuple =tuple)))

            (n.< num-types num-members)
            (do @
              [#let [[head-ts tail-ts] (list;split (n.- +2 num-members)
                                                   member-types)]
               =prevs (mapM @
                            (function [[expected member]]
                              (&;with-expected-type expected
                                (analyse member)))
                            (list;zip2 head-ts members))
               =last (&;with-expected-type (type;tuple tail-ts)
                       (analyse (default (undefined)
                                  (list;last members))))]
              (wrap (#la;Tuple (L/append =prevs (list =last)))))

            ## (n.> num-types num-members)
            (do @
              [#let [[head-xs tail-xs] (list;split (n.- +2 num-types)
                                                   members)]
               =prevs (mapM @
                            (function [[expected member]]
                              (&;with-expected-type expected
                                (analyse member)))
                            (list;zip2 member-types head-xs))
               =last (&;with-expected-type (default (undefined)
                                             (list;last member-types))
                       (analyse-typed-tuple analyse tail-xs))]
              (wrap (#la;Tuple (L/append =prevs (list =last)))))
            ))))

(def: #export (analyse-tuple analyse members)
  (-> &;Analyser (List Code) (Lux Analysis))
  (do Monad<Lux>
    [expected macro;expected-type]
    (&;with-stacked-errors
      (function [_] (format "Invalid type for tuple: " (%type expected)))
      (case expected
        (#;Product _)
        (analyse-typed-tuple analyse members)

        (#;Named name unnamedT)
        (&;with-expected-type unnamedT
          (analyse-tuple analyse members))

        (#;Var id)
        (do @
          [bound? (&;within-type-env
                   (TC;bound? id))]
          (if bound?
            (do @
              [expected' (&;within-type-env
                          (TC;read-var id))]
              (&;with-expected-type expected'
                (analyse-tuple analyse members)))
            (do @
              [=members (mapM @ (|>. analyse &common;with-unknown-type)
                              members)
               #let [tuple-type (type;tuple (L/map product;left =members))]
               _ (&;within-type-env
                  (TC;check expected tuple-type))]
              (wrap (#la;Tuple (L/map product;right =members))))))

        (#;UnivQ _)
        (do @
          [[var-id var] (&;within-type-env
                         TC;existential)]
          (&;with-expected-type (assume (type;apply-type expected var))
            (analyse-tuple analyse members)))

        (#;ExQ _)
        (&common;with-var
          (function [[var-id var]]
            (&;with-expected-type (assume (type;apply-type expected var))
              (analyse-tuple analyse members))))
        
        _
        (&;fail "")
        ))))

(def: #export (analyse-variant analyse tag value)
  (-> &;Analyser Nat Code (Lux Analysis))
  (do Monad<Lux>
    [expected macro;expected-type]
    (&;with-stacked-errors
      (function [_] (format "Invalid type for variant: " (%type expected)))
      (case expected
        (#;Sum _)
        (let [flat (type;flatten-variant expected)
              type-size (list;size flat)]
          (if (n.< type-size tag)
            (do @
              [#let [last? (n.= tag (n.dec type-size))
                     variant-type (default (undefined)
                                    (list;nth tag flat))]
               =value (&;with-expected-type variant-type
                        (analyse value))]
              (wrap (#la;Variant tag last? =value)))
            (&;fail (format "Trying to create variant with tag beyond type's limitations." "\n"
                            "      Tag: " (%n tag) "\n"
                            "Type size: " (%n type-size) "\n"
                            "     Type: " (%type expected) "\n"))))

        (#;Named name unnamedT)
        (&;with-expected-type unnamedT
          (analyse-variant analyse tag value))

        (#;Var id)
        (do @
          [bound? (&;within-type-env
                   (TC;bound? id))]
          (if bound?
            (do @
              [expected' (&;within-type-env
                          (TC;read-var id))]
              (&;with-expected-type expected'
                (analyse-variant analyse tag value)))
            (&;fail (format "Invalid type for variant: " (%type expected)))))

        (#;UnivQ _)
        (do @
          [[var-id var] (&;within-type-env
                         TC;existential)]
          (&;with-expected-type (assume (type;apply-type expected var))
            (analyse-variant analyse tag value)))

        (#;ExQ _)
        (&common;with-var
          (function [[var-id var]]
            (&;with-expected-type (assume (type;apply-type expected var))
              (analyse-variant analyse tag value))))
        
        _
        (&;fail "")))))

(def: (resolve-pair [key val])
  (-> [Ident Code] (Lux [Type Nat Code]))
  (do Monad<Lux>
    [key (macro;normalize key)
     [idx tag-set recordT] (macro;resolve-tag key)]
    (wrap [recordT idx val])))

(def: #export (normalize-record pairs)
  (-> (List [Code Code]) (Lux (List [Ident Code])))
  (mapM Monad<Lux>
        (function [[key val]]
          (case key
            [_ (#;Tag key)]
            (do Monad<Lux>
              [key (macro;normalize key)]
              (wrap [key val]))

            _
            (&;fail (format "Cannot use non-tag tokens in key positions in records: " (%code key)))))
        pairs))

(def: #export (order-record pairs)
  (-> (List [Ident Code]) (Lux [(List Code) Type]))
  (case pairs
    (#;Cons [head-k head-v] _)
    (do Monad<Lux>
      [head-k (macro;normalize head-k)
       [_ tag-set recordT] (macro;resolve-tag head-k)
       #let [size-record (list;size pairs)
             size-ts (list;size tag-set)]
       _ (if (n.= size-ts size-record)
           (wrap [])
           (&;fail (format "Record size does not match tag-set size." "\n"
                           "Expected: " (|> size-ts nat-to-int %i) "\n"
                           "  Actual: " (|> size-record nat-to-int %i) "\n"
                           "For type: " (%type recordT))))
       #let [tuple-range (list;n.range +0 size-ts)
             tag->idx (D;from-list ident;Hash<Ident> (list;zip2 tag-set tuple-range))]
       idx->val (foldM @
                       (function [[key val] idx->val]
                         (do @
                           [key (macro;normalize key)]
                           (case (D;get key tag->idx)
                             #;None
                             (&;fail (format "Tag " (%code (code;tag key))
                                             " does not belong to tag-set for type " (%type recordT)))

                             (#;Some idx)
                             (if (D;contains? idx idx->val)
                               (&;fail (format "Cannot repeat tag inside record: " (%code (code;tag key))))
                               (wrap (D;put idx val idx->val))))))
                       (: (D;Dict Nat Code)
                          (D;new number;Hash<Nat>))
                       pairs)
       #let [ordered-tuple (L/map (function [idx]
                                    (assume (D;get idx idx->val)))
                                  tuple-range)]]
      (wrap [ordered-tuple recordT]))

    _
    (:: Monad<Lux> wrap [(list) Unit])))