{-# LANGUAGE CPP, NoOverloadedLists, NoOverloadedStrings #-}
{-# OPTIONS_GHC -Wno-missing-signatures #-}

module Exon.Haskell.Translate (toExp) where

import qualified Data.ByteString as B
import qualified Data.List.NonEmpty as NonEmpty
import GHC.Data.FastString
import GHC.Driver.Ppr (showSDoc)
import GHC.Driver.Session (DynFlags)
import GHC.Hs.Expr as Expr
import GHC.Hs.Extension as Ext
import GHC.Hs.Lit
import GHC.Hs.Pat as Pat
import GHC.Hs.Type (HsSigType (HsSig), HsType (..), HsWildCardBndrs (..), sig_body)
import GHC.Types.Basic (Boxity (..))
import GHC.Types.Name
import GHC.Types.Name.Reader
import GHC.Types.SourceText (il_value, rationalFromFractionalLit)
import GHC.Types.SrcLoc
import qualified GHC.Unit.Module as Module
import GHC.Utils.Outputable (ppr)
import qualified Language.Haskell.TH.Syntax as TH
#if MIN_VERSION_ghc(9,6,0)
import Language.Haskell.Syntax.Basic (FieldLabelString (..))
#endif

import qualified Exon.Haskell.Settings as Settings

-- TODO: why this disapears in GHC >= 9.2?
fl_value = rationalFromFractionalLit



-----------------------------

toLit :: HsLit GhcPs -> TH.Lit
toLit (HsChar _ c) = TH.CharL c
toLit (HsCharPrim _ c) = TH.CharPrimL c
toLit (HsString _ s) = TH.StringL (unpackFS s)
toLit (HsStringPrim _ s) = TH.StringPrimL (B.unpack s)
toLit (HsInt _ i) = TH.IntegerL (il_value i)
toLit (HsIntPrim _ i) = TH.IntPrimL i
toLit (HsWordPrim _ i) = TH.WordPrimL i
toLit (HsInt64Prim _ i) = TH.IntegerL i
toLit (HsWord64Prim _ i) = TH.WordPrimL i
toLit (HsInteger _ i _) = TH.IntegerL i
toLit (HsRat _ f _) = TH.FloatPrimL (fl_value f)
toLit (HsFloatPrim _ f) = TH.FloatPrimL (fl_value f)
toLit (HsDoublePrim _ f) = TH.DoublePrimL (fl_value f)

toLit' :: OverLitVal -> TH.Lit
toLit' (HsIntegral i) = TH.IntegerL (il_value i)
toLit' (HsFractional f) = TH.RationalL (fl_value f)
toLit' (HsIsString _ fs) = TH.StringL (unpackFS fs)

toType :: HsType GhcPs -> TH.Type
toType (HsWildCardTy _) = TH.WildCardT
toType (HsTyVar _ _ n) =
  let n' = unLoc n
   in if isRdrTyVar n'
        then TH.VarT (toName n')
        else TH.ConT (toName n')
toType t = todo "toType" (showSDoc(Settings.baseDynFlags []) . ppr $ t)

toName :: RdrName -> TH.Name
toName n = case n of
  (Unqual o) -> TH.mkName (occNameString o)
  (Qual m o) -> TH.mkName (Module.moduleNameString m <> "." <> occNameString o)
  (Orig _ _) -> error "orig"
  (Exact _) -> error "exact"

toFieldExp :: a
toFieldExp = undefined

toPat :: DynFlags -> Pat.Pat GhcPs -> TH.Pat
toPat _dynFlags (Pat.VarPat _ (unLoc -> name)) = TH.VarP (toName name)
toPat dynFlags p = todo "toPat" (showSDoc dynFlags . ppr $ p)

toExp :: DynFlags -> Expr.HsExpr GhcPs -> TH.Exp
toExp _ (Expr.HsVar _ n) =
  let n' = unLoc n
   in if isRdrDataCon n'
        then TH.ConE (toName n')
        else TH.VarE (toName n')

toExp _ (Expr.HsUnboundVar _ n)              = TH.UnboundVarE (TH.mkName . occNameString . occName $ n)

toExp _ Expr.HsIPVar {}
  = noTH "toExp" "HsIPVar"

toExp _ (Expr.HsLit _ l)
  = TH.LitE (toLit l)

toExp _ (Expr.HsOverLit _ OverLit {ol_val})
  = TH.LitE (toLit' ol_val)

toExp d (Expr.HsApp _ e1 e2)
  = TH.AppE (toExp d . unLoc $ e1) (toExp d . unLoc $ e2)

#if MIN_VERSION_ghc(9,6,0)
toExp d (Expr.HsAppType _ e _ HsWC {hswc_body}) = TH.AppTypeE (toExp d . unLoc $ e) (toType . unLoc $ hswc_body)
#else
toExp d (Expr.HsAppType _ e HsWC {hswc_body}) = TH.AppTypeE (toExp d . unLoc $ e) (toType . unLoc $ hswc_body)
#endif

toExp d (Expr.ExprWithTySig _ e HsWC{hswc_body=unLoc -> HsSig{sig_body}}) = TH.SigE (toExp d . unLoc $ e) (toType . unLoc $ sig_body)

toExp d (Expr.OpApp _ e1 o e2)
  = TH.UInfixE (toExp d . unLoc $ e1) (toExp d . unLoc $ o) (toExp d . unLoc $ e2)

toExp d (Expr.NegApp _ e _)
  = TH.AppE (TH.VarE 'negate) (toExp d . unLoc $ e)

-- NOTE: for lambda, there is only one match
#if MIN_VERSION_ghc(9,6,0)
toExp d (Expr.HsLam _ (Expr.MG _ (unLoc -> (map unLoc -> [Expr.Match _ _ (map unLoc -> ps) (Expr.GRHSs _ [unLoc -> Expr.GRHS _ _ (unLoc -> e)] _)]))))
#else
toExp d (Expr.HsLam _ (Expr.MG _ (unLoc -> (map unLoc -> [Expr.Match _ _ (map unLoc -> ps) (Expr.GRHSs _ [unLoc -> Expr.GRHS _ _ (unLoc -> e)] _)])) _))
#endif
  = TH.LamE (fmap (toPat d) ps) (toExp d e)

-- toExp (Expr.Let _ bs e)                       = TH.LetE (toDecs bs) (toExp e)
--
toExp d (Expr.HsIf _ a b c)                   = TH.CondE (toExp d (unLoc a)) (toExp d (unLoc b)) (toExp d (unLoc c))

-- toExp (Expr.MultiIf _ ifs)                    = TH.MultiIfE (map toGuard ifs)
-- toExp (Expr.Case _ e alts)                    = TH.CaseE (toExp e) (map toMatch alts)
-- toExp (Expr.Do _ ss)                          = TH.DoE (map toStmt ss)
-- toExp e@Expr.MDo{}                            = noTH "toExp" e
--
toExp d (Expr.ExplicitTuple _ args boxity) = ctor tupArgs
  where
    toTupArg (Expr.Present _ e) = Just $ unLoc e
    toTupArg (Expr.Missing _) = Nothing
    toTupArg _ = error "impossible case"

    ctor = case boxity of
      Boxed -> TH.TupE
      Unboxed -> TH.UnboxedTupE

    tupArgs = fmap ((fmap (toExp d)) . toTupArg) args

-- toExp (Expr.List _ xs)                        = TH.ListE (fmap toExp xs)
#if MIN_VERSION_ghc(9, 4, 0)
toExp d (Expr.HsPar _ _ e _)
#else
toExp d (Expr.HsPar _ e)
#endif
  = TH.ParensE (toExp d . unLoc $ e)

toExp d (Expr.SectionL _ (unLoc -> a) (unLoc -> b))
  = TH.InfixE (Just . toExp d $ a) (toExp d b) Nothing

toExp d (Expr.SectionR _ (unLoc -> a) (unLoc -> b))
  = TH.InfixE Nothing (toExp d a) (Just . toExp d $ b)

toExp _ (Expr.RecordCon _ name HsRecFields {rec_flds})
  = TH.RecConE (toName . unLoc $ name) (fmap toFieldExp rec_flds)

-- toExp (Expr.RecUpdate _ e xs)                 = TH.RecUpdE (toExp e) (fmap toFieldExp xs)
-- toExp (Expr.ListComp _ e ss)                  = TH.CompE $ map convert ss ++ [TH.NoBindS (toExp e)]
--  where
--   convert (Expr.QualStmt _ st)                = toStmt st
--   convert s                                   = noTH "toExp ListComp" s
-- toExp (Expr.ExpTypeSig _ e t)                 = TH.SigE (toExp e) (toType t)
--
toExp d (Expr.ExplicitList _ (map unLoc -> args)) = TH.ListE (map (toExp d) args)

toExp d (Expr.ArithSeq _ _ e)
  = TH.ArithSeqE $ case e of
    (From a) -> TH.FromR (toExp d $ unLoc a)
    (FromThen a b) -> TH.FromThenR (toExp d $ unLoc a) (toExp d $ unLoc b)
    (FromTo a b) -> TH.FromToR (toExp d $ unLoc a) (toExp d $ unLoc b)
    (FromThenTo a b c) -> TH.FromThenToR (toExp d $ unLoc a) (toExp d $ unLoc b) (toExp d $ unLoc c)

#if MIN_VERSION_ghc(9, 6, 0)
toExp _ (Expr.HsProjection _ locatedFields) =
  let
    extractFieldLabel (DotFieldOcc _ locatedStr) = field_label <$> locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.ProjectionE (NonEmpty.map (unpackFS . unLoc . extractFieldLabel . unLoc) locatedFields)

toExp d (Expr.HsGetField _ expr locatedField) =
  let
    extractFieldLabel (DotFieldOcc _ locatedStr) = field_label <$> locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.GetFieldE (toExp d (unLoc expr)) (unpackFS . unLoc . extractFieldLabel . unLoc $ locatedField)
#elif MIN_VERSION_ghc(9, 4, 0)
toExp _ (Expr.HsProjection _ locatedFields) =
  let
    extractFieldLabel (DotFieldOcc _ locatedStr) = locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.ProjectionE (NonEmpty.map (unpackFS . unLoc . extractFieldLabel . unLoc) locatedFields)

toExp d (Expr.HsGetField _ expr locatedField) =
  let
    extractFieldLabel (DotFieldOcc _ locatedStr) = locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.GetFieldE (toExp d (unLoc expr)) (unpackFS . unLoc . extractFieldLabel . unLoc $ locatedField)
#else
toExp _ (Expr.HsProjection _ locatedFields) =
  let
    extractFieldLabel (HsFieldLabel _ locatedStr) = locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.ProjectionE (NonEmpty.map (unpackFS . unLoc . extractFieldLabel . unLoc) locatedFields)

toExp d (Expr.HsGetField _ expr locatedField) =
  let
    extractFieldLabel (HsFieldLabel _ locatedStr) = locatedStr
    extractFieldLabel _ = error "Don't know how to handle XHsFieldLabel constructor..."
  in
    TH.GetFieldE (toExp d (unLoc expr)) (unpackFS . unLoc . extractFieldLabel . unLoc $ locatedField)
#endif

#if MIN_VERSION_ghc(9, 6, 0)
toExp _ (Expr.HsOverLabel _ _ fastString) = TH.LabelE (unpackFS fastString)
#else
toExp _ (Expr.HsOverLabel _ fastString) = TH.LabelE (unpackFS fastString)
#endif

toExp dynFlags e = todo "toExp" (showSDoc dynFlags . ppr $ e)

todo :: (HasCallStack, Show e) => String -> e -> a
todo fun thing = error . concat $ [moduleName, ".", fun, ": not implemented: ", show thing]

noTH :: (HasCallStack, Show e) => String -> e -> a
noTH fun thing = error . concat $ [moduleName, ".", fun, ": no TemplateHaskell for: ", show thing]

moduleName :: String
moduleName = "Language.Haskell.Meta.Translate"