{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE TupleSections #-}

-- | Defunctionalization of typed, monomorphic Futhark programs without modules.
module Futhark.Internalise.Defunctionalise (transformProg) where

import qualified Control.Arrow as Arrow
import Control.Monad.Identity
import Control.Monad.RWS hiding (Sum)
import Control.Monad.State
import Data.Bifunctor
import Data.Bitraversable
import Data.Foldable
import Data.List (partition, sortOn, tails)
import qualified Data.List.NonEmpty as NE
import qualified Data.Map.Strict as M
import Data.Maybe
import qualified Data.Sequence as Seq
import qualified Data.Set as S
import Futhark.IR.Pretty ()
import qualified Futhark.Internalise.FreeVars as FV
import Futhark.MonadFreshNames
import Language.Futhark
import Language.Futhark.Traversals

-- | An expression or an extended 'Lambda' (with size parameters,
-- which AST lambdas do not support).
data ExtExp
  = ExtLambda [Pattern] Exp StructType SrcLoc
  | ExtExp Exp
  deriving (Show)

-- | A static value stores additional information about the result of
-- defunctionalization of an expression, aside from the residual expression.
data StaticVal
  = Dynamic PatternType
  | LambdaSV Pattern StructType ExtExp Env
  | RecordSV [(Name, StaticVal)]
  | -- | The constructor that is actually present, plus
    -- the others that are not.
    SumSV Name [StaticVal] [(Name, [PatternType])]
  | -- | The pair is the StaticVal and residual expression of this
    -- function as a whole, while the second StaticVal is its
    -- body. (Don't trust this too much, my understanding may have
    -- holes.)
    DynamicFun (Exp, StaticVal) StaticVal
  | IntrinsicSV
  deriving (Show)

-- | The type is Just if this is a polymorphic binding that must be
-- instantiated.
data Binding = Binding (Maybe ([VName], StructType)) StaticVal
  deriving (Show)

bindingSV :: Binding -> StaticVal
bindingSV (Binding _ sv) = sv

-- | Environment mapping variable names to their associated static
-- value.
type Env = M.Map VName Binding

localEnv :: Env -> DefM a -> DefM a
localEnv env = local $ Arrow.second (env <>)

-- Even when using a "new" environment (for evaluating closures) we
-- still ram the global environment of DynamicFuns in there.
localNewEnv :: Env -> DefM a -> DefM a
localNewEnv env = local $ \(globals, old_env) ->
  (globals, M.filterWithKey (\k _ -> k `S.member` globals) old_env <> env)

askEnv :: DefM Env
askEnv = asks snd

isGlobal :: VName -> DefM a -> DefM a
isGlobal v = local $ Arrow.first (S.insert v)

replaceTypeSizes ::
  M.Map VName SizeSubst ->
  TypeBase (DimDecl VName) als ->
  TypeBase (DimDecl VName) als
replaceTypeSizes substs = first onDim
  where
    onDim (NamedDim v) =
      case M.lookup (qualLeaf v) substs of
        Just (SubstNamed v') -> NamedDim v'
        Just (SubstConst d) -> ConstDim d
        Nothing -> NamedDim v
    onDim d = d

replaceStaticValSizes ::
  S.Set VName ->
  M.Map VName SizeSubst ->
  StaticVal ->
  StaticVal
replaceStaticValSizes globals orig_substs sv =
  case sv of
    _ | M.null orig_substs -> sv
    LambdaSV param t e closure_env ->
      let substs =
            foldl' (flip M.delete) orig_substs $
              S.fromList (M.keys closure_env)
       in LambdaSV
            (onAST substs param)
            (replaceTypeSizes substs t)
            (onExtExp substs e)
            (onEnv orig_substs closure_env) --intentional
    Dynamic t ->
      Dynamic $ replaceTypeSizes orig_substs t
    RecordSV fs ->
      RecordSV $ map (fmap (replaceStaticValSizes globals orig_substs)) fs
    SumSV c svs ts ->
      SumSV c (map (replaceStaticValSizes globals orig_substs) svs) $
        map (fmap $ map $ replaceTypeSizes orig_substs) ts
    DynamicFun (e, sv1) sv2 ->
      DynamicFun (onExp orig_substs e, replaceStaticValSizes globals orig_substs sv1) $
        replaceStaticValSizes globals orig_substs sv2
    IntrinsicSV ->
      IntrinsicSV
  where
    tv substs =
      identityMapper
        { mapOnPatternType = pure . replaceTypeSizes substs,
          mapOnStructType = pure . replaceTypeSizes substs,
          mapOnExp = pure . onExp substs,
          mapOnName = pure . onName substs
        }

    onName substs v =
      case M.lookup v substs of
        Just (SubstNamed v') -> qualLeaf v'
        _ -> v

    onExp substs (Var v t loc) =
      case M.lookup (qualLeaf v) substs of
        Just (SubstNamed v') ->
          Var v' t loc
        Just (SubstConst d) ->
          Literal (SignedValue (Int64Value (fromIntegral d))) loc
        Nothing ->
          Var v (replaceTypeSizes substs <$> t) loc
    onExp substs (Coerce e tdecl t loc) =
      Coerce (onExp substs e) tdecl' (first (fmap (replaceTypeSizes substs)) t) loc
      where
        tdecl' =
          TypeDecl
            { declaredType = onTypeExp substs $ declaredType tdecl,
              expandedType = replaceTypeSizes substs <$> expandedType tdecl
            }
    onExp substs e = onAST substs e

    onTypeExpDim substs d@(DimExpNamed v loc) =
      case M.lookup (qualLeaf v) substs of
        Just (SubstNamed v') ->
          DimExpNamed v' loc
        Just (SubstConst x) ->
          DimExpConst x loc
        Nothing ->
          d
    onTypeExpDim _ d = d

    onTypeArgExp substs (TypeArgExpDim d loc) =
      TypeArgExpDim (onTypeExpDim substs d) loc
    onTypeArgExp substs (TypeArgExpType te) =
      TypeArgExpType (onTypeExp substs te)

    onTypeExp substs (TEArray te d loc) =
      TEArray (onTypeExp substs te) (onTypeExpDim substs d) loc
    onTypeExp substs (TEUnique t loc) =
      TEUnique (onTypeExp substs t) loc
    onTypeExp substs (TEApply t1 t2 loc) =
      TEApply (onTypeExp substs t1) (onTypeArgExp substs t2) loc
    onTypeExp substs (TEArrow p t1 t2 loc) =
      TEArrow p (onTypeExp substs t1) (onTypeExp substs t2) loc
    onTypeExp substs (TETuple ts loc) =
      TETuple (map (onTypeExp substs) ts) loc
    onTypeExp substs (TERecord ts loc) =
      TERecord (map (fmap $ onTypeExp substs) ts) loc
    onTypeExp substs (TESum ts loc) =
      TESum (map (fmap $ map $ onTypeExp substs) ts) loc
    onTypeExp _ (TEVar v loc) =
      TEVar v loc

    onExtExp substs (ExtExp e) =
      ExtExp $ onExp substs e
    onExtExp substs (ExtLambda params e t loc) =
      ExtLambda (map (onAST substs) params) (onExp substs e) (replaceTypeSizes substs t) loc

    onEnv substs =
      M.fromList
        . map (second (onBinding substs))
        . M.toList

    onBinding substs (Binding t bsv) =
      Binding
        (second (replaceTypeSizes substs) <$> t)
        (replaceStaticValSizes globals substs bsv)

    onAST :: ASTMappable x => M.Map VName SizeSubst -> x -> x
    onAST substs = runIdentity . astMap (tv substs)

-- | Returns the defunctionalization environment restricted
-- to the given set of variable names and types.
restrictEnvTo :: FV.NameSet -> DefM Env
restrictEnvTo (FV.NameSet m) = restrict <$> ask
  where
    restrict (globals, env) = M.mapMaybeWithKey keep env
      where
        keep k (Binding t sv) = do
          guard $ not $ k `S.member` globals
          u <- uniqueness <$> M.lookup k m
          Just $ Binding t $ restrict' u sv
    restrict' Nonunique (Dynamic t) =
      Dynamic $ t `setUniqueness` Nonunique
    restrict' _ (Dynamic t) =
      Dynamic t
    restrict' u (LambdaSV pat t e env) =
      LambdaSV pat t e $ M.map (restrict'' u) env
    restrict' u (RecordSV fields) =
      RecordSV $ map (fmap $ restrict' u) fields
    restrict' u (SumSV c svs fields) =
      SumSV c (map (restrict' u) svs) fields
    restrict' u (DynamicFun (e, sv1) sv2) =
      DynamicFun (e, restrict' u sv1) $ restrict' u sv2
    restrict' _ IntrinsicSV = IntrinsicSV
    restrict'' u (Binding t sv) = Binding t $ restrict' u sv

-- | Defunctionalization monad.  The Reader environment tracks both
-- the current Env as well as the set of globally defined dynamic
-- functions.  This is used to avoid unnecessarily large closure
-- environments.
newtype DefM a = DefM (RWS (S.Set VName, Env) (Seq.Seq ValBind) VNameSource a)
  deriving
    ( Functor,
      Applicative,
      Monad,
      MonadReader (S.Set VName, Env),
      MonadWriter (Seq.Seq ValBind),
      MonadFreshNames
    )

-- | Run a computation in the defunctionalization monad. Returns the result of
-- the computation, a new name source, and a list of lifted function declations.
runDefM :: VNameSource -> DefM a -> (a, VNameSource, Seq.Seq ValBind)
runDefM src (DefM m) = runRWS m mempty src

collectFuns :: DefM a -> DefM (a, Seq.Seq ValBind)
collectFuns m = pass $ do
  (x, decs) <- listen m
  return ((x, decs), const mempty)

-- | Looks up the associated static value for a given name in the environment.
lookupVar :: StructType -> SrcLoc -> VName -> DefM StaticVal
lookupVar t loc x = do
  env <- askEnv
  case M.lookup x env of
    Just (Binding (Just (dims, sv_t)) sv) -> do
      globals <- asks fst
      instStaticVal globals dims t sv_t sv
    Just (Binding Nothing sv) ->
      pure sv
    Nothing -- If the variable is unknown, it may refer to the 'intrinsics'
    -- module, which we will have to treat specially.
      | baseTag x <= maxIntrinsicTag -> return IntrinsicSV
      | otherwise -> -- Anything not in scope is going to be an
      -- existential size.
        return $ Dynamic $ Scalar $ Prim $ Signed Int64
      | otherwise ->
        error $
          "Variable " ++ pretty x ++ " at "
            ++ locStr loc
            ++ " is out of scope."

-- Like patternDimNames, but ignores sizes that are only found in
-- funtion types.
arraySizes :: StructType -> S.Set VName
arraySizes (Scalar Arrow {}) = mempty
arraySizes (Scalar (Record fields)) = foldMap arraySizes fields
arraySizes (Scalar (Sum cs)) = foldMap (foldMap arraySizes) cs
arraySizes (Scalar (TypeVar _ _ _ targs)) =
  mconcat $ map f targs
  where
    f (TypeArgDim (NamedDim d) _) = S.singleton $ qualLeaf d
    f TypeArgDim {} = mempty
    f (TypeArgType t _) = arraySizes t
arraySizes (Scalar Prim {}) = mempty
arraySizes (Array _ _ t shape) =
  arraySizes (Scalar t) <> foldMap dimName (shapeDims shape)
  where
    dimName :: DimDecl VName -> S.Set VName
    dimName (NamedDim qn) = S.singleton $ qualLeaf qn
    dimName _ = mempty

patternArraySizes :: Pattern -> S.Set VName
patternArraySizes = arraySizes . patternStructType

data SizeSubst
  = SubstNamed (QualName VName)
  | SubstConst Int
  deriving (Eq, Ord, Show)

dimMapping ::
  Monoid a =>
  TypeBase (DimDecl VName) a ->
  TypeBase (DimDecl VName) a ->
  M.Map VName SizeSubst
dimMapping t1 t2 = execState (matchDims f t1 t2) mempty
  where
    f (NamedDim d1) (NamedDim d2) = do
      modify $ M.insert (qualLeaf d1) $ SubstNamed d2
      return $ NamedDim d1
    f (NamedDim d1) (ConstDim d2) = do
      modify $ M.insert (qualLeaf d1) $ SubstConst d2
      return $ NamedDim d1
    f d _ = return d

dimMapping' ::
  Monoid a =>
  TypeBase (DimDecl VName) a ->
  TypeBase (DimDecl VName) a ->
  M.Map VName VName
dimMapping' t1 t2 = M.mapMaybe f $ dimMapping t1 t2
  where
    f (SubstNamed d) = Just $ qualLeaf d
    f _ = Nothing

sizesToRename :: StaticVal -> S.Set VName
sizesToRename (DynamicFun (_, sv1) sv2) =
  sizesToRename sv1 <> sizesToRename sv2
sizesToRename IntrinsicSV =
  mempty
sizesToRename Dynamic {} =
  mempty
sizesToRename (RecordSV fs) =
  foldMap (sizesToRename . snd) fs
sizesToRename (SumSV _ svs _) =
  foldMap sizesToRename svs
sizesToRename (LambdaSV param _ _ _) =
  patternDimNames param
    <> S.map identName (S.filter couldBeSize $ patternIdents param)
  where
    couldBeSize ident =
      unInfo (identType ident) == Scalar (Prim (Signed Int64))

-- When we instantiate a polymorphic StaticVal, we rename all the
-- sizes to avoid name conflicts later on.  This is a bit of a hack...
instStaticVal ::
  MonadFreshNames m =>
  S.Set VName ->
  [VName] ->
  StructType ->
  StructType ->
  StaticVal ->
  m StaticVal
instStaticVal globals dims t sv_t sv = do
  fresh_substs <- mkSubsts $ S.toList $ S.fromList dims <> sizesToRename sv

  let dims' = map (onName fresh_substs) dims
      isDim k _ = k `elem` dims'
      dim_substs =
        M.filterWithKey isDim $ dimMapping (replaceTypeSizes fresh_substs sv_t) t
      replace (SubstNamed k) = fromMaybe (SubstNamed k) $ M.lookup (qualLeaf k) dim_substs
      replace k = k
      substs = M.map replace fresh_substs <> dim_substs

  pure $ replaceStaticValSizes globals substs sv
  where
    mkSubsts names =
      M.fromList . zip names . map (SubstNamed . qualName)
        <$> mapM newName names

    onName substs v =
      case M.lookup v substs of
        Just (SubstNamed v') -> qualLeaf v'
        _ -> v

defuncFun ::
  [VName] ->
  [Pattern] ->
  Exp ->
  StructType ->
  SrcLoc ->
  DefM (Exp, StaticVal)
defuncFun tparams pats e0 ret loc = do
  -- Extract the first parameter of the lambda and "push" the
  -- remaining ones (if there are any) into the body of the lambda.
  let (pat, ret', e0') = case pats of
        [] -> error "Received a lambda with no parameters."
        [pat'] -> (pat', ret, ExtExp e0)
        (pat' : pats') ->
          ( pat',
            foldFunType (map (toStruct . patternType) pats') ret,
            ExtLambda pats' e0 ret loc
          )

  -- Construct a record literal that closes over the environment of
  -- the lambda.  Closed-over 'DynamicFun's are converted to their
  -- closure representation.
  let used =
        FV.freeVars (Lambda pats e0 Nothing (Info (mempty, ret)) loc)
          `FV.without` S.fromList tparams
  used_env <- restrictEnvTo used

  -- The closure parts that are sizes are proactively turned into size
  -- parameters.
  let sizes_of_arrays =
        foldMap (arraySizes . toStruct . typeFromSV . bindingSV) used_env
          <> patternArraySizes pat
      notSize = not . (`S.member` sizes_of_arrays)
      (fields, env) =
        second M.fromList . unzip . map closureFromDynamicFun
          . filter (notSize . fst)
          $ M.toList used_env

  return
    ( RecordLit fields loc,
      LambdaSV pat ret' e0' env
    )
  where
    closureFromDynamicFun (vn, Binding _ (DynamicFun (clsr_env, sv) _)) =
      let name = nameFromString $ pretty vn
       in ( RecordFieldExplicit name clsr_env mempty,
            (vn, Binding Nothing sv)
          )
    closureFromDynamicFun (vn, Binding _ sv) =
      let name = nameFromString $ pretty vn
          tp' = typeFromSV sv
       in ( RecordFieldExplicit
              name
              (Var (qualName vn) (Info tp') mempty)
              mempty,
            (vn, Binding Nothing sv)
          )

-- | Defunctionalization of an expression. Returns the residual expression and
-- the associated static value in the defunctionalization monad.
defuncExp :: Exp -> DefM (Exp, StaticVal)
defuncExp e@Literal {} =
  return (e, Dynamic $ typeOf e)
defuncExp e@IntLit {} =
  return (e, Dynamic $ typeOf e)
defuncExp e@FloatLit {} =
  return (e, Dynamic $ typeOf e)
defuncExp e@StringLit {} =
  return (e, Dynamic $ typeOf e)
defuncExp (Parens e loc) = do
  (e', sv) <- defuncExp e
  return (Parens e' loc, sv)
defuncExp (QualParens qn e loc) = do
  (e', sv) <- defuncExp e
  return (QualParens qn e' loc, sv)
defuncExp (TupLit es loc) = do
  (es', svs) <- unzip <$> mapM defuncExp es
  return (TupLit es' loc, RecordSV $ zip tupleFieldNames svs)
defuncExp (RecordLit fs loc) = do
  (fs', names_svs) <- unzip <$> mapM defuncField fs
  return (RecordLit fs' loc, RecordSV names_svs)
  where
    defuncField (RecordFieldExplicit vn e loc') = do
      (e', sv) <- defuncExp e
      return (RecordFieldExplicit vn e' loc', (vn, sv))
    defuncField (RecordFieldImplicit vn (Info t) loc') = do
      sv <- lookupVar (toStruct t) loc' vn
      case sv of
        -- If the implicit field refers to a dynamic function, we
        -- convert it to an explicit field with a record closing over
        -- the environment and bind the corresponding static value.
        DynamicFun (e, sv') _ ->
          let vn' = baseName vn
           in return
                ( RecordFieldExplicit vn' e loc',
                  (vn', sv')
                )
        -- The field may refer to a functional expression, so we get the
        -- type from the static value and not the one from the AST.
        _ ->
          let tp = Info $ typeFromSV sv
           in return (RecordFieldImplicit vn tp loc', (baseName vn, sv))
defuncExp (ArrayLit es t@(Info t') loc) = do
  es' <- mapM defuncExp' es
  return (ArrayLit es' t loc, Dynamic t')
defuncExp (Range e1 me incl t@(Info t', _) loc) = do
  e1' <- defuncExp' e1
  me' <- mapM defuncExp' me
  incl' <- mapM defuncExp' incl
  return (Range e1' me' incl' t loc, Dynamic t')
defuncExp e@(Var qn (Info t) loc) = do
  sv <- lookupVar (toStruct t) loc (qualLeaf qn)
  case sv of
    -- If the variable refers to a dynamic function, we return its closure
    -- representation (i.e., a record expression capturing the free variables
    -- and a 'LambdaSV' static value) instead of the variable itself.
    DynamicFun closure _ -> return closure
    -- Intrinsic functions used as variables are eta-expanded, so we
    -- can get rid of them.
    IntrinsicSV -> do
      (pats, body, tp) <- etaExpand (typeOf e) e
      defuncExp $ Lambda pats body Nothing (Info (mempty, tp)) mempty
    _ ->
      let tp = typeFromSV sv
       in return (Var qn (Info tp) loc, sv)
defuncExp (Ascript e0 tydecl loc)
  | orderZero (typeOf e0) = do
    (e0', sv) <- defuncExp e0
    return (Ascript e0' tydecl loc, sv)
  | otherwise = defuncExp e0
defuncExp (Coerce e0 tydecl t loc)
  | orderZero (typeOf e0) = do
    (e0', sv) <- defuncExp e0
    return (Coerce e0' tydecl t loc, sv)
  | otherwise = defuncExp e0
defuncExp (LetPat pat e1 e2 (Info t, retext) loc) = do
  (e1', sv1) <- defuncExp e1
  let env = matchPatternSV pat sv1
      pat' = updatePattern pat sv1
  (e2', sv2) <- localEnv env $ defuncExp e2
  -- To maintain any sizes going out of scope, we need to compute the
  -- old size substitution induced by retext and also apply it to the
  -- newly computed body type.
  let mapping = dimMapping' (typeOf e2) t
      subst v = fromMaybe v $ M.lookup v mapping
      t' = first (fmap subst) $ typeOf e2'
  return (LetPat pat' e1' e2' (Info t', retext) loc, sv2)
defuncExp (LetFun vn _ _ _ _) =
  error $ "defuncExp: Unexpected LetFun: " ++ prettyName vn
defuncExp (If e1 e2 e3 tp loc) = do
  (e1', _) <- defuncExp e1
  (e2', sv) <- defuncExp e2
  (e3', _) <- defuncExp e3
  return (If e1' e2' e3' tp loc, sv)
defuncExp e@(Apply f@(Var f' _ _) arg d (t, ext) loc)
  | baseTag (qualLeaf f') <= maxIntrinsicTag,
    TupLit es tuploc <- arg = do
    -- defuncSoacExp also works fine for non-SOACs.
    es' <- mapM defuncSoacExp es
    return
      ( Apply f (TupLit es' tuploc) d (t, ext) loc,
        Dynamic $ typeOf e
      )
defuncExp e@Apply {} = defuncApply 0 e
defuncExp (Negate e0 loc) = do
  (e0', sv) <- defuncExp e0
  return (Negate e0' loc, sv)
defuncExp (Lambda pats e0 _ (Info (_, ret)) loc) =
  defuncFun [] pats e0 ret loc
-- Operator sections are expected to be converted to lambda-expressions
-- by the monomorphizer, so they should no longer occur at this point.
defuncExp OpSection {} = error "defuncExp: unexpected operator section."
defuncExp OpSectionLeft {} = error "defuncExp: unexpected operator section."
defuncExp OpSectionRight {} = error "defuncExp: unexpected operator section."
defuncExp ProjectSection {} = error "defuncExp: unexpected projection section."
defuncExp IndexSection {} = error "defuncExp: unexpected projection section."
defuncExp (DoLoop sparams pat e1 form e3 ret loc) = do
  (e1', sv1) <- defuncExp e1
  let env1 = matchPatternSV pat sv1
  (form', env2) <- case form of
    For v e2 -> do
      e2' <- defuncExp' e2
      return (For v e2', envFromIdent v)
    ForIn pat2 e2 -> do
      e2' <- defuncExp' e2
      return (ForIn pat2 e2', envFromPattern pat2)
    While e2 -> do
      e2' <- localEnv env1 $ defuncExp' e2
      return (While e2', mempty)
  (e3', sv) <- localEnv (env1 <> env2) $ defuncExp e3
  return (DoLoop sparams pat e1' form' e3' ret loc, sv)
  where
    envFromIdent (Ident vn (Info tp) _) =
      M.singleton vn $ Binding Nothing $ Dynamic tp
defuncExp e@BinOp {} =
  error $ "defuncExp: unexpected binary operator: " ++ pretty e
defuncExp (Project vn e0 tp@(Info tp') loc) = do
  (e0', sv0) <- defuncExp e0
  case sv0 of
    RecordSV svs -> case lookup vn svs of
      Just sv -> return (Project vn e0' (Info $ typeFromSV sv) loc, sv)
      Nothing -> error "Invalid record projection."
    Dynamic _ -> return (Project vn e0' tp loc, Dynamic tp')
    _ -> error $ "Projection of an expression with static value " ++ show sv0
defuncExp (LetWith id1 id2 idxs e1 body t loc) = do
  e1' <- defuncExp' e1
  idxs' <- mapM defuncDimIndex idxs
  let id1_binding = Binding Nothing $ Dynamic $ unInfo $ identType id1
  (body', sv) <-
    localEnv (M.singleton (identName id1) id1_binding) $
      defuncExp body
  return (LetWith id1 id2 idxs' e1' body' t loc, sv)
defuncExp expr@(Index e0 idxs info loc) = do
  e0' <- defuncExp' e0
  idxs' <- mapM defuncDimIndex idxs
  return (Index e0' idxs' info loc, Dynamic $ typeOf expr)
defuncExp (Update e1 idxs e2 loc) = do
  (e1', sv) <- defuncExp e1
  idxs' <- mapM defuncDimIndex idxs
  e2' <- defuncExp' e2
  return (Update e1' idxs' e2' loc, sv)

-- Note that we might change the type of the record field here.  This
-- is not permitted in the type checker due to problems with type
-- inference, but it actually works fine.
defuncExp (RecordUpdate e1 fs e2 _ loc) = do
  (e1', sv1) <- defuncExp e1
  (e2', sv2) <- defuncExp e2
  let sv = staticField sv1 sv2 fs
  return
    ( RecordUpdate e1' fs e2' (Info $ typeFromSV sv1) loc,
      sv
    )
  where
    staticField (RecordSV svs) sv2 (f : fs') =
      case lookup f svs of
        Just sv ->
          RecordSV $
            (f, staticField sv sv2 fs') : filter ((/= f) . fst) svs
        Nothing -> error "Invalid record projection."
    staticField (Dynamic t@(Scalar Record {})) sv2 fs'@(_ : _) =
      staticField (svFromType t) sv2 fs'
    staticField _ sv2 _ = sv2
defuncExp (Assert e1 e2 desc loc) = do
  (e1', _) <- defuncExp e1
  (e2', sv) <- defuncExp e2
  return (Assert e1' e2' desc loc, sv)
defuncExp (Constr name es (Info (Scalar (Sum all_fs))) loc) = do
  (es', svs) <- unzip <$> mapM defuncExp es
  let sv =
        SumSV name svs $
          M.toList $
            name `M.delete` M.map (map defuncType) all_fs
  return (Constr name es' (Info (typeFromSV sv)) loc, sv)
  where
    defuncType ::
      Monoid als =>
      TypeBase (DimDecl VName) als ->
      TypeBase (DimDecl VName) als
    defuncType (Array as u t shape) = Array as u (defuncScalar t) shape
    defuncType (Scalar t) = Scalar $ defuncScalar t

    defuncScalar ::
      Monoid als =>
      ScalarTypeBase (DimDecl VName) als ->
      ScalarTypeBase (DimDecl VName) als
    defuncScalar (Record fs) = Record $ M.map defuncType fs
    defuncScalar Arrow {} = Record mempty
    defuncScalar (Sum fs) = Sum $ M.map (map defuncType) fs
    defuncScalar (Prim t) = Prim t
    defuncScalar (TypeVar as u tn targs) = TypeVar as u tn targs
defuncExp (Constr name _ (Info t) loc) =
  error $
    "Constructor " ++ pretty name ++ " given type "
      ++ pretty t
      ++ " at "
      ++ locStr loc
defuncExp (Match e cs t loc) = do
  (e', sv) <- defuncExp e
  csPairs <- mapM (defuncCase sv) cs
  let cs' = fmap fst csPairs
      sv' = snd $ NE.head csPairs
  return (Match e' cs' t loc, sv')
defuncExp (Attr info e loc) = do
  (e', sv) <- defuncExp e
  return (Attr info e' loc, sv)

-- | Same as 'defuncExp', except it ignores the static value.
defuncExp' :: Exp -> DefM Exp
defuncExp' = fmap fst . defuncExp

defuncExtExp :: ExtExp -> DefM (Exp, StaticVal)
defuncExtExp (ExtExp e) = defuncExp e
defuncExtExp (ExtLambda pats e0 ret loc) =
  defuncFun [] pats e0 ret loc

defuncCase :: StaticVal -> Case -> DefM (Case, StaticVal)
defuncCase sv (CasePat p e loc) = do
  let p' = updatePattern p sv
      env = matchPatternSV p sv
  (e', sv') <- localEnv env $ defuncExp e
  return (CasePat p' e' loc, sv')

-- | Defunctionalize the function argument to a SOAC by eta-expanding if
-- necessary and then defunctionalizing the body of the introduced lambda.
defuncSoacExp :: Exp -> DefM Exp
defuncSoacExp e@OpSection {} = return e
defuncSoacExp e@OpSectionLeft {} = return e
defuncSoacExp e@OpSectionRight {} = return e
defuncSoacExp e@ProjectSection {} = return e
defuncSoacExp (Parens e loc) =
  Parens <$> defuncSoacExp e <*> pure loc
defuncSoacExp (Lambda params e0 decl tp loc) = do
  let env = foldMap envFromPattern params
  e0' <- localEnv env $ defuncSoacExp e0
  return $ Lambda params e0' decl tp loc
defuncSoacExp e
  | Scalar Arrow {} <- typeOf e = do
    (pats, body, tp) <- etaExpand (typeOf e) e
    let env = foldMap envFromPattern pats
    body' <- localEnv env $ defuncExp' body
    return $ Lambda pats body' Nothing (Info (mempty, tp)) mempty
  | otherwise = defuncExp' e

etaExpand :: PatternType -> Exp -> DefM ([Pattern], Exp, StructType)
etaExpand e_t e = do
  let (ps, ret) = getType e_t
  (pats, vars) <- fmap unzip . forM ps $ \(p, t) -> do
    x <- case p of
      Named x -> pure x
      Unnamed -> newNameFromString "x"
    return
      ( Id x (Info t) mempty,
        Var (qualName x) (Info t) mempty
      )
  let e' =
        foldl'
          ( \e1 (e2, t2, argtypes) ->
              Apply
                e1
                e2
                (Info (diet t2, Nothing))
                (Info (foldFunType argtypes ret), Info [])
                mempty
          )
          e
          $ zip3 vars (map snd ps) (drop 1 $ tails $ map snd ps)
  return (pats, e', toStruct ret)
  where
    getType (Scalar (Arrow _ p t1 t2)) =
      let (ps, r) = getType t2 in ((p, t1) : ps, r)
    getType t = ([], t)

-- | Defunctionalize an indexing of a single array dimension.
defuncDimIndex :: DimIndexBase Info VName -> DefM (DimIndexBase Info VName)
defuncDimIndex (DimFix e1) = DimFix . fst <$> defuncExp e1
defuncDimIndex (DimSlice me1 me2 me3) =
  DimSlice <$> defunc' me1 <*> defunc' me2 <*> defunc' me3
  where
    defunc' = mapM defuncExp'

-- | Defunctionalize a let-bound function, while preserving parameters
-- that have order 0 types (i.e., non-functional).
defuncLet ::
  [VName] ->
  [Pattern] ->
  Exp ->
  StructType ->
  DefM ([VName], [Pattern], Exp, StaticVal)
defuncLet dims ps@(pat : pats) body rettype
  | patternOrderZero pat = do
    let bound_by_pat = (`S.member` patternDimNames pat)
        -- Take care to not include more size parameters than necessary.
        (pat_dims, rest_dims) = partition bound_by_pat dims
        env = envFromPattern pat <> envFromDimNames pat_dims
    (rest_dims', pats', body', sv) <- localEnv env $ defuncLet rest_dims pats body rettype
    closure <- defuncFun dims ps body rettype mempty
    return
      ( pat_dims ++ rest_dims',
        pat : pats',
        body',
        DynamicFun closure sv
      )
  | otherwise = do
    (e, sv) <- defuncFun dims ps body rettype mempty
    return ([], [], e, sv)
defuncLet _ [] body rettype = do
  (body', sv) <- defuncExp body
  return ([], [], body', imposeType sv rettype)
  where
    imposeType Dynamic {} t =
      Dynamic $ fromStruct t
    imposeType (RecordSV fs1) (Scalar (Record fs2)) =
      RecordSV $ M.toList $ M.intersectionWith imposeType (M.fromList fs1) fs2
    imposeType sv _ = sv

sizesForAll :: MonadFreshNames m => S.Set VName -> [Pattern] -> m ([VName], [Pattern])
sizesForAll bound_sizes params = do
  (params', sizes) <- runStateT (mapM (astMap tv) params) mempty
  return (S.toList sizes, params')
  where
    bound = bound_sizes <> foldMap patternNames params
    tv = identityMapper {mapOnPatternType = bitraverse onDim pure}
    onDim AnyDim = do
      v <- lift $ newVName "size"
      modify $ S.insert v
      pure $ NamedDim $ qualName v
    onDim (NamedDim d) = do
      unless (qualLeaf d `S.member` bound) $
        modify $ S.insert $ qualLeaf d
      pure $ NamedDim d
    onDim d = pure d

-- | Defunctionalize an application expression at a given depth of application.
-- Calls to dynamic (first-order) functions are preserved at much as possible,
-- but a new lifted function is created if a dynamic function is only partially
-- applied.
defuncApply :: Int -> Exp -> DefM (Exp, StaticVal)
defuncApply depth e@(Apply e1 e2 d t@(Info ret, Info ext) loc) = do
  let (argtypes, _) = unfoldFunType ret
  (e1', sv1) <- defuncApply (depth + 1) e1
  (e2', sv2) <- defuncExp e2
  let e' = Apply e1' e2' d t loc
  case sv1 of
    LambdaSV pat e0_t e0 closure_env -> do
      let env' = matchPatternSV pat sv2
          dims = mempty
      (e0', sv) <-
        localNewEnv (env' <> closure_env) $
          defuncExtExp e0

      let closure_pat = buildEnvPattern dims closure_env
          pat' = updatePattern pat sv2

      globals <- asks fst

      -- Lift lambda to top-level function definition.  We put in
      -- a lot of effort to try to infer the uniqueness attributes
      -- of the lifted function, but this is ultimately all a sham
      -- and a hack.  There is some piece we're missing.
      let params = [closure_pat, pat']
          params_for_rettype = params ++ svParams sv1 ++ svParams sv2
          svParams (LambdaSV sv_pat _ _ _) = [sv_pat]
          svParams _ = []
          rettype = buildRetType closure_env params_for_rettype e0_t $ typeOf e0'

          already_bound =
            globals <> S.fromList dims
              <> S.map identName (foldMap patternIdents params)

          more_dims =
            S.toList $
              S.filter (`S.notMember` already_bound) $
                foldMap patternArraySizes params

          -- Embed some information about the original function
          -- into the name of the lifted function, to make the
          -- result slightly more human-readable.
          liftedName i (Var f _ _) =
            "defunc_" ++ show i ++ "_" ++ baseString (qualLeaf f)
          liftedName i (Apply f _ _ _ _) =
            liftedName (i + 1) f
          liftedName _ _ = "defunc"

      -- Ensure that no parameter sizes are AnyDim.  The internaliser
      -- expects this.  This is easy, because they are all
      -- first-order.
      let bound_sizes = S.fromList (dims <> more_dims) <> globals
      (missing_dims, params') <- sizesForAll bound_sizes params

      fname <- newNameFromString $ liftedName (0 :: Int) e1
      liftValDec
        fname
        rettype
        (dims ++ more_dims ++ missing_dims)
        params'
        e0'

      let t1 = toStruct $ typeOf e1'
          t2 = toStruct $ typeOf e2'
          fname' = qualName fname
          fname'' =
            Var
              fname'
              ( Info
                  ( Scalar $
                      Arrow mempty Unnamed (fromStruct t1) $
                        Scalar $ Arrow mempty Unnamed (fromStruct t2) rettype
                  )
              )
              loc

          -- FIXME: what if this application returns both a function
          -- and a value?
          callret
            | orderZero ret = (Info ret, Info ext)
            | otherwise = (Info rettype, Info ext)

      return
        ( Parens
            ( Apply
                ( Apply
                    fname''
                    e1'
                    (Info (Observe, Nothing))
                    ( Info $ Scalar $ Arrow mempty Unnamed (fromStruct t2) rettype,
                      Info []
                    )
                    loc
                )
                e2'
                d
                callret
                loc
            )
            mempty,
          sv
        )

    -- If e1 is a dynamic function, we just leave the application in place,
    -- but we update the types since it may be partially applied or return
    -- a higher-order term.
    DynamicFun _ sv -> do
      let (argtypes', rettype) = dynamicFunType sv argtypes
          restype = foldFunType argtypes' rettype `setAliases` aliases ret
          -- FIXME: what if this application returns both a function
          -- and a value?
          callret
            | orderZero ret = (Info ret, Info ext)
            | otherwise = (Info restype, Info ext)
          apply_e = Apply e1' e2' d callret loc
      return (apply_e, sv)
    -- Propagate the 'IntrinsicsSV' until we reach the outermost application,
    -- where we construct a dynamic static value with the appropriate type.
    IntrinsicSV
      | depth == 0 ->
        -- If the intrinsic is fully applied, then we are done.
        -- Otherwise we need to eta-expand it and recursively
        -- defunctionalise. XXX: might it be better to simply
        -- eta-expand immediately any time we encounter a
        -- non-fully-applied intrinsic?
        if null argtypes
          then return (e', Dynamic $ typeOf e)
          else do
            (pats, body, tp) <- etaExpand (typeOf e') e'
            defuncExp $ Lambda pats body Nothing (Info (mempty, tp)) mempty
      | otherwise -> return (e', IntrinsicSV)
    _ ->
      error $
        "Application of an expression\n"
          ++ pretty e1
          ++ "\nthat is neither a static lambda "
          ++ "nor a dynamic function, but has static value:\n"
          ++ show sv1
defuncApply depth e@(Var qn (Info t) loc) = do
  let (argtypes, _) = unfoldFunType t
  sv <- lookupVar (toStruct t) loc (qualLeaf qn)

  case sv of
    DynamicFun _ _
      | fullyApplied sv depth -> do
        -- We still need to update the types in case the dynamic
        -- function returns a higher-order term.
        let (argtypes', rettype) = dynamicFunType sv argtypes
        return (Var qn (Info (foldFunType argtypes' rettype)) loc, sv)
      | otherwise -> do
        fname <- newName $ qualLeaf qn
        let (pats, e0, sv') = liftDynFun (pretty qn) sv depth
            (argtypes', rettype) = dynamicFunType sv' argtypes
            dims' = mempty

        -- Ensure that no parameter sizes are AnyDim.  The internaliser
        -- expects this.  This is easy, because they are all
        -- first-order.
        globals <- asks fst
        let bound_sizes = S.fromList dims' <> globals
        (missing_dims, pats') <- sizesForAll bound_sizes pats

        liftValDec fname (fromStruct rettype) (dims' ++ missing_dims) pats' e0
        return
          ( Var
              (qualName fname)
              (Info (foldFunType argtypes' $ fromStruct rettype))
              loc,
            sv'
          )
    IntrinsicSV -> return (e, IntrinsicSV)
    _ -> return (Var qn (Info (typeFromSV sv)) loc, sv)
defuncApply depth (Parens e _) = defuncApply depth e
defuncApply _ expr = defuncExp expr

-- | Check if a 'StaticVal' and a given application depth corresponds
-- to a fully applied dynamic function.
fullyApplied :: StaticVal -> Int -> Bool
fullyApplied (DynamicFun _ sv) depth
  | depth == 0 = False
  | depth > 0 = fullyApplied sv (depth -1)
fullyApplied _ _ = True

-- | Converts a dynamic function 'StaticVal' into a list of
-- dimensions, a list of parameters, a function body, and the
-- appropriate static value for applying the function at the given
-- depth of partial application.
liftDynFun :: String -> StaticVal -> Int -> ([Pattern], Exp, StaticVal)
liftDynFun _ (DynamicFun (e, sv) _) 0 = ([], e, sv)
liftDynFun s (DynamicFun clsr@(_, LambdaSV pat _ _ _) sv) d
  | d > 0 =
    let (pats, e', sv') = liftDynFun s sv (d -1)
     in (pat : pats, e', DynamicFun clsr sv')
liftDynFun s sv d =
  error $
    s
      ++ " Tried to lift a StaticVal "
      ++ take 100 (show sv)
      ++ ", but expected a dynamic function.\n"
      ++ pretty d

-- | Converts a pattern to an environment that binds the individual names of the
-- pattern to their corresponding types wrapped in a 'Dynamic' static value.
envFromPattern :: Pattern -> Env
envFromPattern pat = case pat of
  TuplePattern ps _ -> foldMap envFromPattern ps
  RecordPattern fs _ -> foldMap (envFromPattern . snd) fs
  PatternParens p _ -> envFromPattern p
  Id vn (Info t) _ -> M.singleton vn $ Binding Nothing $ Dynamic t
  Wildcard _ _ -> mempty
  PatternAscription p _ _ -> envFromPattern p
  PatternLit {} -> mempty
  PatternConstr _ _ ps _ -> foldMap envFromPattern ps

envFromDimNames :: [VName] -> Env
envFromDimNames = M.fromList . flip zip (repeat d)
  where
    d = Binding Nothing $ Dynamic $ Scalar $ Prim $ Signed Int64

-- | Create a new top-level value declaration with the given function name,
-- return type, list of parameters, and body expression.
liftValDec :: VName -> PatternType -> [VName] -> [Pattern] -> Exp -> DefM ()
liftValDec fname rettype dims pats body = tell $ Seq.singleton dec
  where
    dims' = map (`TypeParamDim` mempty) dims
    -- FIXME: this pass is still not correctly size-preserving, so
    -- forget those return sizes that we forgot to propagate along
    -- the way.  Hopefully the internaliser is conservative and
    -- will insert reshapes...
    bound_here = S.fromList dims <> S.map identName (foldMap patternIdents pats)
    anyDimIfNotBound (NamedDim v)
      | qualLeaf v `S.member` bound_here = NamedDim v
      | otherwise = AnyDim
    anyDimIfNotBound d = d
    rettype_st = first anyDimIfNotBound $ toStruct rettype

    dec =
      ValBind
        { valBindEntryPoint = Nothing,
          valBindName = fname,
          valBindRetDecl = Nothing,
          valBindRetType = Info (rettype_st, []),
          valBindTypeParams = dims',
          valBindParams = pats,
          valBindBody = body,
          valBindDoc = Nothing,
          valBindAttrs = mempty,
          valBindLocation = mempty
        }

-- | Given a closure environment, construct a record pattern that
-- binds the closed over variables.  Insert wildcard for any patterns
-- that would otherwise clash with size parameters.
buildEnvPattern :: [VName] -> Env -> Pattern
buildEnvPattern sizes env = RecordPattern (map buildField $ M.toList env) mempty
  where
    buildField (vn, Binding _ sv) =
      ( nameFromString (pretty vn),
        if vn `elem` sizes
          then Wildcard (Info $ typeFromSV sv) mempty
          else Id vn (Info $ typeFromSV sv) mempty
      )

-- | Given a closure environment pattern and the type of a term,
-- construct the type of that term, where uniqueness is set to
-- `Nonunique` for those arrays that are bound in the environment or
-- pattern (except if they are unique there).  This ensures that a
-- lifted function can create unique arrays as long as they do not
-- alias any of its parameters.  XXX: it is not clear that this is a
-- sufficient property, unfortunately.
buildRetType :: Env -> [Pattern] -> StructType -> PatternType -> PatternType
buildRetType env pats = comb
  where
    bound =
      S.fromList (M.keys env) <> S.map identName (foldMap patternIdents pats)
    boundAsUnique v =
      maybe False (unique . unInfo . identType) $
        find ((== v) . identName) $ S.toList $ foldMap patternIdents pats
    problematic v = (v `S.member` bound) && not (boundAsUnique v)
    comb (Scalar (Record fs_annot)) (Scalar (Record fs_got)) =
      Scalar $ Record $ M.intersectionWith comb fs_annot fs_got
    comb (Scalar (Sum cs_annot)) (Scalar (Sum cs_got)) =
      Scalar $ Sum $ M.intersectionWith (zipWith comb) cs_annot cs_got
    comb (Scalar Arrow {}) t =
      descend t
    comb got et =
      descend $ fromStruct got `setAliases` aliases et

    descend t@Array {}
      | any (problematic . aliasVar) (aliases t) = t `setUniqueness` Nonunique
    descend (Scalar (Record t)) = Scalar $ Record $ fmap descend t
    descend t = t

-- | Compute the corresponding type for the *representation* of a
-- given static value (not the original possibly higher-order value).
typeFromSV :: StaticVal -> PatternType
typeFromSV (Dynamic tp) =
  tp
typeFromSV (LambdaSV _ _ _ env) =
  Scalar $
    Record $
      M.fromList $
        map (bimap (nameFromString . pretty) (typeFromSV . bindingSV)) $
          M.toList env
typeFromSV (RecordSV ls) =
  let ts = map (fmap typeFromSV) ls
   in Scalar $ Record $ M.fromList ts
typeFromSV (DynamicFun (_, sv) _) =
  typeFromSV sv
typeFromSV (SumSV name svs fields) =
  let svs' = map typeFromSV svs
   in Scalar $ Sum $ M.insert name svs' $ M.fromList fields
typeFromSV IntrinsicSV =
  error "Tried to get the type from the static value of an intrinsic."

-- | Construct the type for a fully-applied dynamic function from its
-- static value and the original types of its arguments.
dynamicFunType :: StaticVal -> [PatternType] -> ([PatternType], PatternType)
dynamicFunType (DynamicFun _ sv) (p : ps) =
  let (ps', ret) = dynamicFunType sv ps in (p : ps', ret)
dynamicFunType sv _ = ([], typeFromSV sv)

-- | Match a pattern with its static value. Returns an environment with
-- the identifier components of the pattern mapped to the corresponding
-- subcomponents of the static value.
matchPatternSV :: PatternBase Info VName -> StaticVal -> Env
matchPatternSV (TuplePattern ps _) (RecordSV ls) =
  mconcat $ zipWith (\p (_, sv) -> matchPatternSV p sv) ps ls
matchPatternSV (RecordPattern ps _) (RecordSV ls)
  | ps' <- sortOn fst ps,
    ls' <- sortOn fst ls,
    map fst ps' == map fst ls' =
    mconcat $ zipWith (\(_, p) (_, sv) -> matchPatternSV p sv) ps' ls'
matchPatternSV (PatternParens pat _) sv = matchPatternSV pat sv
matchPatternSV (Id vn (Info t) _) sv =
  -- When matching a pattern with a zero-order STaticVal, the type of
  -- the pattern wins out.  This is important when matching a
  -- nonunique pattern with a unique value.
  if orderZeroSV sv
    then dim_env <> M.singleton vn (Binding Nothing $ Dynamic t)
    else dim_env <> M.singleton vn (Binding Nothing sv)
  where
    dim_env =
      M.fromList $ map (,i64) $ S.toList $ typeDimNames t
    i64 = Binding Nothing $ Dynamic $ Scalar $ Prim $ Signed Int64
matchPatternSV (Wildcard _ _) _ = mempty
matchPatternSV (PatternAscription pat _ _) sv = matchPatternSV pat sv
matchPatternSV PatternLit {} _ = mempty
matchPatternSV (PatternConstr c1 _ ps _) (SumSV c2 ls fs)
  | c1 == c2 =
    mconcat $ zipWith matchPatternSV ps ls
  | Just ts <- lookup c1 fs =
    mconcat $ zipWith matchPatternSV ps $ map svFromType ts
  | otherwise =
    error $ "matchPatternSV: missing constructor in type: " ++ pretty c1
matchPatternSV (PatternConstr c1 _ ps _) (Dynamic (Scalar (Sum fs)))
  | Just ts <- M.lookup c1 fs =
    mconcat $ zipWith matchPatternSV ps $ map svFromType ts
  | otherwise =
    error $ "matchPatternSV: missing constructor in type: " ++ pretty c1
matchPatternSV pat (Dynamic t) = matchPatternSV pat $ svFromType t
matchPatternSV pat sv =
  error $
    "Tried to match pattern " ++ pretty pat
      ++ " with static value "
      ++ show sv
      ++ "."

orderZeroSV :: StaticVal -> Bool
orderZeroSV Dynamic {} = True
orderZeroSV (RecordSV fields) = all (orderZeroSV . snd) fields
orderZeroSV _ = False

-- | Given a pattern and the static value for the defunctionalized argument,
-- update the pattern to reflect the changes in the types.
updatePattern :: Pattern -> StaticVal -> Pattern
updatePattern (TuplePattern ps loc) (RecordSV svs) =
  TuplePattern (zipWith updatePattern ps $ map snd svs) loc
updatePattern (RecordPattern ps loc) (RecordSV svs)
  | ps' <- sortOn fst ps,
    svs' <- sortOn fst svs =
    RecordPattern
      ( zipWith
          ( \(n, p) (_, sv) ->
              (n, updatePattern p sv)
          )
          ps'
          svs'
      )
      loc
updatePattern (PatternParens pat loc) sv =
  PatternParens (updatePattern pat sv) loc
updatePattern (Id vn (Info tp) loc) sv =
  Id vn (Info $ comb tp (typeFromSV sv `setUniqueness` Nonunique)) loc
  where
    -- Preserve any original zeroth-order types.
    comb (Scalar Arrow {}) t2 = t2
    comb (Scalar (Record m1)) (Scalar (Record m2)) =
      Scalar $ Record $ M.intersectionWith comb m1 m2
    comb (Scalar (Sum m1)) (Scalar (Sum m2)) =
      Scalar $ Sum $ M.intersectionWith (zipWith comb) m1 m2
    comb t1 _ = t1 -- t1 must be array or prim.
updatePattern pat@(Wildcard (Info tp) loc) sv
  | orderZero tp = pat
  | otherwise = Wildcard (Info $ typeFromSV sv) loc
updatePattern (PatternAscription pat tydecl loc) sv
  | orderZero . unInfo $ expandedType tydecl =
    PatternAscription (updatePattern pat sv) tydecl loc
  | otherwise = updatePattern pat sv
updatePattern p@PatternLit {} _ = p
updatePattern pat@(PatternConstr c1 (Info t) ps loc) sv@(SumSV _ svs _)
  | orderZero t = pat
  | otherwise = PatternConstr c1 (Info t') ps' loc
  where
    t' = typeFromSV sv `setUniqueness` Nonunique
    ps' = zipWith updatePattern ps svs
updatePattern (PatternConstr c1 _ ps loc) (Dynamic t) =
  PatternConstr c1 (Info t) ps loc
updatePattern pat (Dynamic t) = updatePattern pat (svFromType t)
updatePattern pat sv =
  error $
    "Tried to update pattern " ++ pretty pat
      ++ "to reflect the static value "
      ++ show sv

-- | Convert a record (or tuple) type to a record static value. This is used for
-- "unwrapping" tuples and records that are nested in 'Dynamic' static values.
svFromType :: PatternType -> StaticVal
svFromType (Scalar (Record fs)) = RecordSV . M.toList $ M.map svFromType fs
svFromType t = Dynamic t

-- | Defunctionalize a top-level value binding. Returns the
-- transformed result as well as an environment that binds the name of
-- the value binding to the static value of the transformed body.  The
-- boolean is true if the function is a 'DynamicFun'.
defuncValBind :: ValBind -> DefM (ValBind, Env, Bool)
-- Eta-expand entry points with a functional return type.
defuncValBind (ValBind entry name _ (Info (rettype, retext)) tparams params body _ attrs loc)
  | Scalar Arrow {} <- rettype = do
    (body_pats, body', rettype') <- etaExpand (fromStruct rettype) body
    defuncValBind $
      ValBind
        entry
        name
        Nothing
        (Info (rettype', retext))
        tparams
        (params <> body_pats)
        body'
        Nothing
        attrs
        loc
defuncValBind valbind@(ValBind _ name retdecl (Info (rettype, retext)) tparams params body _ _ _) = do
  when (any isTypeParam tparams) $
    error $
      prettyName name ++ " has type parameters, "
        ++ "but the defunctionaliser expects a monomorphic input program."
  (tparams', params', body', sv) <-
    defuncLet (map typeParamName tparams) params body rettype
  let rettype' = combineTypeShapes rettype $ anySizes $ toStruct $ typeOf body'
  globals <- asks fst
  let bound_sizes = S.fromList tparams' <> globals
  (missing_dims, params'') <- sizesForAll bound_sizes params'
  return
    ( valbind
        { valBindRetDecl = retdecl,
          valBindRetType =
            Info
              ( if null params'
                  then rettype' `setUniqueness` Nonunique
                  else rettype',
                retext
              ),
          valBindTypeParams =
            map (`TypeParamDim` mempty) $ tparams' ++ missing_dims,
          valBindParams = params'',
          valBindBody = body'
        },
      M.singleton name $
        Binding
          ( Just
              ( first
                  (map typeParamName)
                  (valBindTypeScheme valbind)
              )
          )
          sv,
      case sv of
        DynamicFun {} -> True
        Dynamic {} -> True
        _ -> False
    )

-- | Defunctionalize a list of top-level declarations.
defuncVals :: [ValBind] -> DefM (Seq.Seq ValBind)
defuncVals [] = return mempty
defuncVals (valbind : ds) = do
  ((valbind', env, dyn), defs) <- collectFuns $ defuncValBind valbind
  ds' <-
    localEnv env $
      if dyn
        then isGlobal (valBindName valbind') $ defuncVals ds
        else defuncVals ds
  return $ defs <> Seq.singleton valbind' <> ds'

{-# NOINLINE transformProg #-}

-- | Transform a list of top-level value bindings. May produce new
-- lifted function definitions, which are placed in front of the
-- resulting list of declarations.
transformProg :: MonadFreshNames m => [ValBind] -> m [ValBind]
transformProg decs = modifyNameSource $ \namesrc ->
  let (decs', namesrc', liftedDecs) = runDefM namesrc $ defuncVals decs
   in (toList $ liftedDecs <> decs', namesrc')