||| take freshly-parsed input, scope check, type check, add to env
module Quox.Parser.FromParser

import Quox.Parser.Syntax
import Quox.Parser.Parser
import Quox.Typechecker

import Data.List
import Data.Maybe
import Data.SnocVect
import Quox.EffExtra

import System.File
import System.Path
import Data.IORef

import public Quox.Parser.FromParser.Error as Quox.Parser.FromParser

%default total

%hide Typing.Error
%hide Lexer.Error
%hide Parser.Error


public export
NDefinition : Type
NDefinition = (Name, Definition)

public export
IncludePath : Type
IncludePath = List String

public export
SeenFiles : Type
SeenFiles = SortedSet String


public export
data StateTag = NS | SEEN

public export
FromParserPure : List (Type -> Type)
FromParserPure =
  [Except Error, DefsState, StateL NS Mods, NameGen]

public export
LoadFile' : List (Type -> Type)
LoadFile' = [IO, StateL SEEN SeenFiles, Reader IncludePath]

public export
LoadFile : List (Type -> Type)
LoadFile = LoadFile' ++ [Except Error]

public export
FromParserIO : List (Type -> Type)
FromParserIO = FromParserPure ++ LoadFile'


parameters {auto _ : Functor m} (b : Var n -> m a) (f : PName -> m a)
           (xs : Context' PatVar n)
  private
  fromBaseName : PBaseName -> m a
  fromBaseName x = maybe (f $ MakePName [<] x) b $
                   Context.find (\y => y.name == Just x) xs

  private
  fromName : PName -> m a
  fromName x = if null x.mods then fromBaseName x.base else f x

export
fromPDimWith : Has (Except Error) fs =>
               Context' PatVar d -> PDim -> Eff fs (Dim d)
fromPDimWith ds (K e loc) = pure $ K e loc
fromPDimWith ds (V i loc) =
  fromBaseName (\i => pure $ B i loc)
               (const $ throw $ DimNotInScope loc i) ds i

private
avoidDim : Has (Except Error) fs =>
           Context' PatVar d -> Loc -> PName -> Eff fs Name
avoidDim ds loc x =
  fromName (const $ throw $ DimNameInTerm loc x.base) (pure . fromPName) ds x

private
resolveName : Mods -> Loc -> Name -> Eff FromParserPure (Term d n)
resolveName ns loc x =
  let here = addMods ns x in
  if isJust $ lookup here !(getAt DEFS) then
    pure $ FT here loc
  else do
    let ns :< _ = ns
      | _ => throw $ TermNotInScope loc x
    resolveName ns loc x

export
fromPatVar : PatVar -> BindName
fromPatVar (Unused loc) = BN Unused loc
fromPatVar (PV x   loc) = BN (UN x) loc

export
fromPQty : PQty -> Qty
fromPQty (PQ q _) = q

export
fromPTagVal : PTagVal -> TagVal
fromPTagVal (PT t _) = t


mutual
  export
  fromPTermWith : Context' PatVar d -> Context' PatVar n ->
                  PTerm -> Eff FromParserPure (Term d n)
  fromPTermWith ds ns t0 = case t0 of
    TYPE k loc =>
      pure $ TYPE k loc

    Pi pi x s t loc =>
      Pi (fromPQty pi)
        <$> fromPTermWith ds ns s
        <*> fromPTermTScope ds ns [< x] t
        <*> pure loc

    Lam x s loc =>
      Lam <$> fromPTermTScope ds ns [< x] s <*> pure loc

    App s t loc =>
      map E $ App
        <$> fromPTermElim ds ns s
        <*> fromPTermWith ds ns t
        <*> pure loc

    Sig x s t loc =>
      Sig <$> fromPTermWith ds ns s
          <*> fromPTermTScope ds ns [< x] t
          <*> pure loc

    Pair s t loc =>
      Pair <$> fromPTermWith ds ns s <*> fromPTermWith ds ns t <*> pure loc

    Case pi pair (r, ret) (CasePair (x, y) body _) loc =>
      map E $ CasePair (fromPQty pi)
        <$> fromPTermElim ds ns pair
        <*> fromPTermTScope ds ns [< r] ret
        <*> fromPTermTScope ds ns [< x, y] body
        <*> pure loc

    Case pi tag (r, ret) (CaseEnum arms _) loc =>
      map E $ CaseEnum (fromPQty pi)
        <$> fromPTermElim ds ns tag
        <*> fromPTermTScope ds ns [< r] ret
        <*> assert_total fromPTermEnumArms ds ns arms
        <*> pure loc

    Nat loc => pure $ Nat loc
    Zero loc => pure $ Zero loc
    Succ n loc => [|Succ (fromPTermWith ds ns n) (pure loc)|]

    Case pi nat (r, ret) (CaseNat zer (s, pi', ih, suc) _) loc =>
      map E $ CaseNat (fromPQty pi) (fromPQty pi')
        <$> fromPTermElim ds ns nat
        <*> fromPTermTScope ds ns [< r] ret
        <*> fromPTermWith ds ns zer
        <*> fromPTermTScope ds ns [< s, ih] suc
        <*> pure loc

    Enum strs loc =>
      let set = SortedSet.fromList strs in
      if length strs == length (SortedSet.toList set) then
        pure $ Enum set loc
      else
        throw $ DuplicatesInEnum loc strs

    Tag str loc => pure $ Tag str loc

    Eq (i, ty) s t loc =>
      Eq <$> fromPTermDScope ds ns [< i] ty
         <*> fromPTermWith ds ns s
         <*> fromPTermWith ds ns t
         <*> pure loc

    DLam i s loc =>
      DLam <$> fromPTermDScope ds ns [< i] s <*> pure loc

    DApp s p loc =>
      map E $ DApp
        <$> fromPTermElim ds ns s
        <*> fromPDimWith ds p
        <*> pure loc

    BOX q ty loc => BOX (fromPQty q) <$> fromPTermWith ds ns ty <*> pure loc

    Box val loc => Box <$> fromPTermWith ds ns val <*> pure loc

    Case pi box (r, ret) (CaseBox b body _) loc =>
      map E $ CaseBox (fromPQty pi)
        <$> fromPTermElim ds ns box
        <*> fromPTermTScope ds ns [< r] ret
        <*> fromPTermTScope ds ns [< b] body
        <*> pure loc

    V x loc =>
      fromName (\i => pure $ E $ B i loc)
               (resolveName !(getAt NS) loc <=< avoidDim ds loc) ns x

    Ann s a loc =>
      map E $ Ann
        <$> fromPTermWith ds ns s
        <*> fromPTermWith ds ns a
        <*> pure loc

    Coe (i, ty) p q val loc =>
      map E $ Coe
        <$> fromPTermDScope ds ns [< i] ty
        <*> fromPDimWith ds p
        <*> fromPDimWith ds q
        <*> fromPTermWith ds ns val
        <*> pure loc

    Comp (i, ty) p q val r (j0, val0) (j1, val1) loc =>
      map E $ CompH'
        <$> fromPTermDScope ds ns [< i] ty
        <*> fromPDimWith ds p
        <*> fromPDimWith ds q
        <*> fromPTermWith ds ns val
        <*> fromPDimWith ds r
        <*> fromPTermDScope ds ns [< j0] val0
        <*> fromPTermDScope ds ns [< j1] val1
        <*> pure loc

  private
  fromPTermEnumArms : Context' PatVar d -> Context' PatVar n ->
                      List (PTagVal, PTerm) ->
                      Eff FromParserPure (CaseEnumArms d n)
  fromPTermEnumArms ds ns =
    map SortedMap.fromList .
    traverse (bitraverse (pure . fromPTagVal) (fromPTermWith ds ns))

  private
  fromPTermElim : Context' PatVar d -> Context' PatVar n ->
                  PTerm -> Eff FromParserPure (Elim d n)
  fromPTermElim ds ns e =
    case !(fromPTermWith ds ns e) of
      E e => pure e
      t   => let ctx = MkNameContexts (map fromPatVar ds) (map fromPatVar ns) in
             throw $ AnnotationNeeded t.loc ctx t

  -- [todo] use SN if the var is named but still unused
  private
  fromPTermTScope : {s : Nat} -> Context' PatVar d -> Context' PatVar n ->
                    SnocVect s PatVar -> PTerm ->
                    Eff FromParserPure (ScopeTermN s d n)
  fromPTermTScope ds ns xs t =
    if all isUnused xs then
      SN <$> fromPTermWith ds ns t
    else
      ST (fromSnocVect $ map fromPatVar xs) <$> fromPTermWith ds (ns ++ xs) t

  private
  fromPTermDScope : {s : Nat} -> Context' PatVar d -> Context' PatVar n ->
                    SnocVect s PatVar -> PTerm ->
                    Eff FromParserPure (DScopeTermN s d n)
  fromPTermDScope ds ns xs t =
    if all isUnused xs then
      SN <$> fromPTermWith ds ns t
    else
      DST (fromSnocVect $ map fromPatVar xs) <$> fromPTermWith (ds ++ xs) ns t


export %inline
fromPTerm : PTerm -> Eff FromParserPure (Term 0 0)
fromPTerm = fromPTermWith [<] [<]


export
globalPQty : Loc -> (q : Qty) -> Eff [Except Error] (So $ isGlobal q)
globalPQty loc pi = case choose $ isGlobal pi of
  Left  y => pure y
  Right _ => throw $ QtyNotGlobal loc pi


export
fromPBaseNameNS : PBaseName -> Eff [StateL NS Mods] Name
fromPBaseNameNS name = pure $ addMods !(getAt NS) $ fromPBaseName name

private
liftTC : TC a -> Eff FromParserPure a
liftTC act = do
  res <- lift $ runExcept $ runReaderAt DEFS !(getAt DEFS) act
  rethrow $ mapFst WrapTypeError res

export covering
fromPDef : PDefinition -> Eff FromParserPure NDefinition
fromPDef (MkPDef qty pname ptype pterm defLoc) = do
  name <- lift $ fromPBaseNameNS pname
  qtyGlobal <- lift $ globalPQty qty.loc qty.val
  let gqty = Element qty.val qtyGlobal
      sqty = globalToSubj gqty
  type <- lift $ traverse fromPTerm ptype
  term <- lift $ fromPTerm pterm
  case type of
    Just type => do
      liftTC $ checkTypeC empty type Nothing
      liftTC $ ignore $ checkC empty sqty term type
      let def = mkDef gqty type term defLoc
      modifyAt DEFS $ insert name def
      pure (name, def)
    Nothing => do
      let E elim = term | _ => throw $ AnnotationNeeded term.loc empty term
      res <- liftTC $ inferC empty sqty elim
      let def = mkDef gqty res.type term defLoc
      modifyAt DEFS $ insert name def
      pure (name, def)

export covering
fromPDecl : PDecl -> Eff FromParserPure (List NDefinition)
fromPDecl (PDef def) = singleton <$> fromPDef def
fromPDecl (PNs  ns)  =
  localAt NS (<+> ns.name) $ concat <$> traverse fromPDecl ns.decls


export covering
loadFile : Loc -> String -> Eff LoadFile (Maybe String)
loadFile loc file =
  if contains file !(getAt SEEN) then
    pure Nothing
  else do
    Just ifile <- firstExists (map (</> file) !ask)
      | Nothing => throw $ LoadError loc file FileNotFound
    case !(readFile ifile) of
      Right res => modifyAt SEEN (insert file) $> Just res
      Left  err => throw $ LoadError loc ifile err

mutual
  export covering
  loadProcessFile : Loc -> String -> Eff FromParserIO (List NDefinition)
  loadProcessFile loc file =
    case !(lift $ loadFile loc file) of
      Just inp => do
        tl <- either (throw . WrapParseError file) pure $ lexParseInput file inp
        concat <$> traverse fromPTopLevel tl
      Nothing => pure []

  ||| populates the `defs` field of the state
  export covering
  fromPTopLevel : PTopLevel -> Eff FromParserIO (List NDefinition)
  fromPTopLevel (PD    decl)     = lift $ fromPDecl decl
  fromPTopLevel (PLoad file loc) = loadProcessFile loc file

export
fromParserPure : NameSuf -> Definitions ->
                 Eff FromParserPure a ->
                 (Either Error (a, Definitions), NameSuf)
fromParserPure suf defs act =
  extract $
  runStateAt GEN suf $
  runExcept $
  evalStateAt NS [<] $
  runStateAt DEFS defs act

export
fromParserIO : (MonadRec io, HasIO io) =>
               IncludePath ->
               IORef SeenFiles -> IORef NameSuf -> IORef Definitions ->
               Eff FromParserIO a -> io (Either Error a)
fromParserIO inc seen suf defs act =
  runIO $
  runStateIORefAt GEN suf $
  runExcept $
  evalStateAt NS [<] $
  runStateIORefAt SEEN seen $
  runStateIORefAt DEFS defs $
  runReader inc act