content: ----------------------------------------------------------------------
  -- |
  -- Module      : PGFtoHaskell
  -- Maintainer  : Aarne Ranta
  -- Stability   : (stable)
  -- Portability : (portable)
  --
  -- > CVS $Date: 2005/06/17 12:39:07 $ 
  -- > CVS $Author: bringert $
  -- > CVS $Revision: 1.8 $
  --
  -- to write a GF abstract grammar into a Haskell module with translations from
  -- data objects into GF trees. Example: GSyntax for Agda.
  -- AR 11/11/1999 -- 7/12/2000 -- 18/5/2004
  -----------------------------------------------------------------------------
  
  module GF.Compile.PGFtoHaskell (grammar2haskell) where
  
  import PGF(showCId)
  import PGF.Internal
  
  import GF.Data.Operations
  import GF.Infra.Option
  
  import Data.List --(isPrefixOf, find, intersperse)
  import qualified Data.Map as Map
  
  type Prefix = String -> String
  
  -- | the main function
  grammar2haskell :: Options
                  -> String  -- ^ Module name.
                  -> PGF
                  -> String
  grammar2haskell opts name gr = foldr (++++) [] $  
    pragmas ++ haskPreamble gadt name ++ [types, gfinstances gId lexical gr'] ++ compos
      where gr' = hSkeleton gr
            gadt = haskellOption opts HaskellGADT
            lexical cat = haskellOption opts HaskellLexical && isLexicalCat opts cat
            gId | haskellOption opts HaskellNoPrefix = id
                | otherwise = ("G"++)
            pragmas | gadt = ["{-# OPTIONS_GHC -fglasgow-exts #-}"]
                    | otherwise = []
            types | gadt = datatypesGADT gId lexical gr'
                  | otherwise = datatypes gId lexical gr'
            compos | gadt = prCompos gId lexical gr' ++ composClass
                   | otherwise = []
  
  haskPreamble gadt name =
   [
    "module " ++ name ++ " where",
    ""
   ] ++
   (if gadt then [
    "import Control.Monad.Identity",
    "import Data.Monoid"
    ] else []) ++
   [
    "import PGF hiding (Tree)",
    "----------------------------------------------------",
    "-- automatic translation from GF to Haskell",
    "----------------------------------------------------",
    "", 
    "class Gf a where",
    "  gf :: a -> Expr",
    "  fg :: Expr -> a",
    "",
    predefInst gadt "GString" "String"  "unStr"    "mkStr",
    "",
    predefInst gadt "GInt"    "Int"     "unInt"    "mkInt",
    "",
    predefInst gadt "GFloat"  "Double"  "unFloat"  "mkFloat",
    "",
    "----------------------------------------------------",
    "-- below this line machine-generated",
    "----------------------------------------------------",
    ""
   ]
  
  predefInst gadt gtyp typ destr consr = 
    (if gadt
      then [] 
      else ("newtype" +++ gtyp +++ "=" +++ gtyp +++ typ +++ " deriving Show\n\n") 
      ) 
    ++
    "instance Gf" +++ gtyp +++ "where" ++++
    "  gf (" ++ gtyp +++ "x) =" +++ consr +++ "x" ++++
    "  fg t =" ++++
    "    case "++destr++" t of" ++++
    "      Just x  -> " +++ gtyp +++ "x" ++++
    "      Nothing -> error (\"no" +++ gtyp +++ "\" ++ show t)"
  
  type OIdent = String
  
  type HSkeleton = [(OIdent, [(OIdent, [OIdent])])]
  
  datatypes :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> String
  datatypes gId lexical = (foldr (+++++) "") . (filter (/="")) . (map (hDatatype gId lexical)) . snd
  
  gfinstances :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> String
  gfinstances gId lexical (m,g) = (foldr (+++++) "") $ (filter (/="")) $ (map (gfInstance gId lexical m)) g
  
  
  hDatatype  :: Prefix -> (OIdent -> Bool) -> (OIdent, [(OIdent, [OIdent])]) -> String
  hDatatype _ _ ("Cn",_) = "" ---
  hDatatype gId _ (cat,[]) = "data" +++ gId cat
  hDatatype gId _ (cat,rules) | isListCat (cat,rules) = 
   "newtype" +++ gId cat +++ "=" +++ gId cat +++ "[" ++ gId (elemCat cat) ++ "]" 
    +++ "deriving Show"
  hDatatype gId lexical (cat,rules) =
   "data" +++ gId cat +++ "=" ++
   (if length rules == 1 then "" else "\n  ") +++
   foldr1 (\x y -> x ++ "\n |" +++ y) constructors ++++
   "  deriving Show"
    where
      constructors = [gId f +++ foldr (+++) "" (map (gId) xx) | (f,xx) <- nonLexicalRules (lexical cat) rules]
                     ++ if lexical cat then [lexicalConstructor cat +++ "String"] else []
  
  nonLexicalRules :: Bool -> [(OIdent, [OIdent])] -> [(OIdent, [OIdent])]
  nonLexicalRules False rules = rules
  nonLexicalRules True rules = [r | r@(f,t) <- rules, not (null t)]
  
  lexicalConstructor :: OIdent -> String
  lexicalConstructor cat = "Lex" ++ cat
  
  predefTypeSkel = [(c,[]) | c <- ["String", "Int", "Float"]]
  
  -- GADT version of data types
  datatypesGADT :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> String
  datatypesGADT gId lexical (_,skel) = unlines $ 
      concatMap (hCatTypeGADT gId) (skel ++ predefTypeSkel) ++
      [ 
        "", 
        "data Tree :: * -> * where"
      ] ++ 
      concatMap (map ("  "++) . hDatatypeGADT gId lexical) skel ++
      [
        "  GString :: String -> Tree GString_",
        "  GInt :: Int -> Tree GInt_",
        "  GFloat :: Double -> Tree GFloat_",
        "",
        "instance Eq (Tree a) where",
        "  i == j = case (i,j) of"
      ] ++
      concatMap (map ("    "++) . hEqGADT gId lexical) skel ++
      [
        "    (GString x, GString y) -> x == y",
        "    (GInt x, GInt y) -> x == y",
        "    (GFloat x, GFloat y) -> x == y",
        "    _ -> False"
      ]
  
  hCatTypeGADT :: Prefix -> (OIdent, [(OIdent, [OIdent])]) -> [String]
  hCatTypeGADT gId (cat,rules)
      = ["type"+++gId cat+++"="+++"Tree"+++gId cat++"_",
         "data"+++gId cat++"_"]
  
  hDatatypeGADT :: Prefix -> (OIdent -> Bool) -> (OIdent, [(OIdent, [OIdent])]) -> [String]
  hDatatypeGADT gId lexical (cat, rules) 
      | isListCat (cat,rules) = [gId cat+++"::"+++"["++gId (elemCat cat)++"]" +++ "->" +++ t]
      | otherwise =
          [ gId f +++ "::" +++ concatMap (\a -> gId a +++ "-> ") args ++ t 
            | (f,args) <- nonLexicalRules (lexical cat) rules ]
          ++ if lexical cat then [lexicalConstructor cat +++ ":: String ->"+++ t] else []
    where t = "Tree" +++ gId cat ++ "_"
  
  hEqGADT :: Prefix -> (OIdent -> Bool) -> (OIdent, [(OIdent, [OIdent])]) -> [String]
  hEqGADT gId lexical (cat, rules)
    | isListCat (cat,rules) = let r = listr cat in ["(" ++ patt "x" r ++ "," ++ patt "y" r ++ ") -> " ++ listeqs] 
    | otherwise = ["(" ++ patt "x" r ++ "," ++ patt "y" r ++ ") -> " ++ eqs r | r <- nonLexicalRules (lexical cat) rules]
            ++ if lexical cat then ["(" ++ lexicalConstructor cat +++ "x" ++ "," ++ lexicalConstructor cat +++ "y" ++ ") -> x == y"] else []
  
   where
     patt s (f,xs) = unwords (gId f : mkSVars s (length xs))
     eqs (_,xs) = unwords ("and" : "[" : intersperse "," [x ++ " == " ++ y | 
       (x,y) <- zip (mkSVars "x" (length xs)) (mkSVars "y" (length xs)) ] ++ ["]"])
     listr c = (c,["foo"]) -- foo just for length = 1
     listeqs = "and [x == y | (x,y) <- zip x1 y1]"
  
  prCompos :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> [String]
  prCompos gId lexical (_,catrules) =
      ["instance Compos Tree where",
       "  compos r a f t = case t of"]
      ++ 
      ["    " ++ prComposCons (gId f) xs | (c,rs) <- catrules, not (isListCat (c,rs)),
                                           (f,xs) <- rs, not (null xs)] 
      ++ 
      ["    " ++ prComposCons (gId c) ["x1"] | (c,rs) <- catrules, isListCat (c,rs)]
      ++ 
      ["    _ -> r t"]
    where
      prComposCons f xs = let vs = mkVars (length xs) in 
                          f +++ unwords vs +++ "->" +++ rhs f (zip vs xs)
      rhs f vcs = "r" +++ f +++ unwords (map (prRec f) vcs)
      prRec f (v,c) 
        | isList f  = "`a` foldr (a . a (r (:)) . f) (r [])" +++ v
        | otherwise = "`a`" +++ "f" +++ v
      isList f = (gId "List") `isPrefixOf` f
  
  gfInstance :: Prefix -> (OIdent -> Bool) -> String -> (OIdent, [(OIdent, [OIdent])]) -> String
  gfInstance gId lexical m crs = hInstance gId lexical m crs ++++ fInstance gId lexical m crs
  
  ----hInstance m ("Cn",_) = "" --- seems to belong to an old applic. AR 18/5/2004
  hInstance gId _ m (cat,[]) = unlines [
    "instance Show" +++ gId cat,
    "",
    "instance Gf" +++ gId cat +++ "where",
    "  gf _ = undefined",
    "  fg _ = undefined"
    ]
  hInstance gId lexical m (cat,rules) 
   | isListCat (cat,rules) =
    "instance Gf" +++ gId cat +++ "where" ++++
       "  gf (" ++ gId cat +++ "[" ++ concat (intersperse "," baseVars) ++ "])" 
             +++ "=" +++ mkRHS ("Base"++ec) baseVars ++++
       "  gf (" ++ gId cat +++ "(x:xs)) = " 
             ++ mkRHS ("Cons"++ec) ["x",prParenth (gId cat+++"xs")] 
  -- no show for GADTs
  --     ++++ " gf (" ++ gId cat +++ "xs) = error (\"Bad " ++ cat ++ " value: \" ++ show xs)" 
   | otherwise =
    "instance Gf" +++ gId cat +++ "where\n" ++
    unlines ([mkInst f xx | (f,xx) <- nonLexicalRules (lexical cat) rules]
              ++ if lexical cat then ["  gf (" ++ lexicalConstructor cat +++ "x) = mkApp (mkCId x) []"] else [])
   where
     ec = elemCat cat
     baseVars = mkVars (baseSize (cat,rules))
     mkInst f xx = let xx' = mkVars (length xx) in "  gf " ++
       (if length xx == 0 then gId f else prParenth (gId f +++ foldr1 (+++) xx')) +++
       "=" +++ mkRHS f xx'
     mkRHS f vars = "mkApp (mkCId \"" ++ f ++ "\")" +++ 
  		   "[" ++ prTList ", " ["gf" +++ x | x <- vars] ++ "]"
  
  mkVars = mkSVars "x"
  mkSVars s n = [s ++ show i | i <- [1..n]]
  
  ----fInstance m ("Cn",_) = "" ---
  fInstance _ _ m (cat,[]) = ""
  fInstance gId lexical m (cat,rules) =
    "  fg t =" ++++
    (if isList 
      then "    " ++ gId cat ++ " (fgs t) where\n     fgs t = case unApp t of"
      else "    case unApp t of") ++++
    unlines [mkInst f xx | (f,xx) <- nonLexicalRules (lexical cat) rules] ++++
    (if lexical cat then "      Just (i,[]) -> " ++ lexicalConstructor cat +++ "(showCId i)" else "") ++++
    "      _ -> error (\"no" +++ cat ++ " \" ++ show t)"
     where
      isList = isListCat (cat,rules)
      mkInst f xx =
       "      Just (i," ++
       "[" ++ prTList "," xx' ++ "])" +++
       "| i == mkCId \"" ++ f ++ "\" ->" +++ mkRHS f xx'
         where xx' = ["x" ++ show i | (_,i) <- zip xx [1..]]
  	     mkRHS f vars 
  		 | isList =
  		     if "Base" `isPrefixOf` f 
                         then "[" ++ prTList ", " [ "fg" +++ x | x <- vars ] ++ "]"
  		       else "fg" +++ (vars !! 0) +++ ":" +++ "fgs" +++ (vars !! 1)
  		 | otherwise = 
  		     gId f +++  
  		     prTList " " [prParenth ("fg" +++ x) | x <- vars]
  
  --type HSkeleton = [(OIdent, [(OIdent, [OIdent])])]
  hSkeleton :: PGF -> (String,HSkeleton)
  hSkeleton gr = 
    (showCId (absname gr), 
     let fs = 
           [(showCId c, [(showCId f, map showCId cs) | (f, (cs,_)) <- fs]) | 
                                          fs@((_, (_,c)):_) <- fns]
     in fs ++ [(sc, []) | c <- cts, let sc = showCId c, notElem sc (["Int", "Float", "String"] ++ map fst fs)]
    )
   where
     cts = Map.keys (cats (abstract gr)) 
     fns = groupBy valtypg (sortBy valtyps (map jty (Map.assocs (funs (abstract gr)))))
     valtyps (_, (_,x)) (_, (_,y)) = compare x y
     valtypg (_, (_,x)) (_, (_,y)) = x == y
     jty (f,(ty,_,_,_)) = (f,catSkeleton ty)
  {-
  updateSkeleton :: OIdent -> HSkeleton -> (OIdent, [OIdent]) -> HSkeleton
  updateSkeleton cat skel rule =
   case skel of
     (cat0,rules):rr | cat0 == cat -> (cat0, rule:rules) : rr
     (cat0,rules):rr               -> (cat0, rules) : updateSkeleton cat rr rule
  -}
  isListCat :: (OIdent, [(OIdent, [OIdent])]) -> Bool
  isListCat (cat,rules) = "List" `isPrefixOf` cat && length rules == 2
  		    && ("Base"++c) `elem` fs && ("Cons"++c) `elem` fs
      where c = elemCat cat
  	  fs = map fst rules
  
  -- | Gets the element category of a list category.
  elemCat :: OIdent -> OIdent
  elemCat = drop 4
  {-
  isBaseFun :: OIdent -> Bool
  isBaseFun f = "Base" `isPrefixOf` f
  
  isConsFun :: OIdent -> Bool
  isConsFun f = "Cons" `isPrefixOf` f
  -}
  baseSize :: (OIdent, [(OIdent, [OIdent])]) -> Int
  baseSize (_,rules) = length bs
      where Just (_,bs) = find (("Base" `isPrefixOf`) . fst) rules
  
  composClass :: [String]
  composClass = 
      [
       "",
       "class Compos t where",
       "  compos :: (forall a. a -> m a) -> (forall a b. m (a -> b) -> m a -> m b)",
       "         -> (forall a. t a -> m (t a)) -> t c -> m (t c)",
       "",
       "composOp :: Compos t => (forall a. t a -> t a) -> t c -> t c",
       "composOp f = runIdentity . composOpM (Identity . f)",
       "",
       "composOpM :: (Compos t, Monad m) => (forall a. t a -> m (t a)) -> t c -> m (t c)",
       "composOpM = compos return ap",
       "",
       "composOpM_ :: (Compos t, Monad m) => (forall a. t a -> m ()) -> t c -> m ()",
       "composOpM_ = composOpFold (return ()) (>>)",
       "",
       "composOpMonoid :: (Compos t, Monoid m) => (forall a. t a -> m) -> t c -> m",
       "composOpMonoid = composOpFold mempty mappend",
       "",
       "composOpMPlus :: (Compos t, MonadPlus m) => (forall a. t a -> m b) -> t c -> m b",
       "composOpMPlus = composOpFold mzero mplus",
       "",
       "composOpFold :: Compos t => b -> (b -> b -> b) -> (forall a. t a -> b) -> t c -> b",
       "composOpFold z c f = unC . compos (\\_ -> C z) (\\(C x) (C y) -> C (c x y)) (C . f)",
       "",
       "newtype C b a = C { unC :: b }"
      ]
  
  