------------------------------------------------------------------------------
--- A compiler for Curry into JavaScript programs for WUIs.
---
--- @author Michael Hanus
--- @version January 16, 2007
------------------------------------------------------------------------------

import Distribution      (installDir)
import JavaScript
import List
import FlatCurry.Types
import FlatCurry.Files
import FlatCurry.Compact
import FlatCurry.Show
import Integer
import System            (system, getArgs)
import Directory
import Char              (isAlphaNum)
import Unsafe
import Maybe
import ReadNumeric       (readNat)

------------------------------------------------------------------------------
-- General definitions:

-- Should higher-order calls (i.e., "apply") be implemented as an explicit
-- apply function? Otherwise, they are implemented as anonymous functions.
explicitApply :: Bool
explicitApply = False


-- Optimization options:

-- Optimize single occurrences of variables in JavaScript code?
optimizeSingleVars :: Bool
optimizeSingleVars = True
-- Optimize cases on data types containing only a single constructor?
optimizeUniqueCase :: Bool
optimizeUniqueCase = True
-- Should strings be lazily converted into character lists?
lazyStringConversion :: Bool
lazyStringConversion = True

-- The name of the prelude module:
prelude :: String
prelude = "Prelude"
-- The name of the WUI module:
wuiModName :: String
wuiModName = "WUIjs"

------------------------------------------------------------------------------
-- Translator:

-- Translate a Curry program into a JavaScript program
flatprog2JS :: Prog -> [JSFDecl]
flatprog2JS (Prog _ _ tdecls allfdecls _) =
  map (flat2JS tdecls) fdecls ++
  (if explicitApply then [genApply (pafsOfFuncs fdecls)] else [])
 where
   fdecls = filter isRelevantFunction allfdecls

isRelevantFunction :: FuncDecl -> Bool
isRelevantFunction (Func fname _ _ _ (External _))
 | fname `elem` ignoredFunctions = False
 | otherwise = error $ "External function "++show fname++" not handled!"
isRelevantFunction (Func fname _ _ _ (Rule _ _)) =
  fname `notElem` ignoredFunctions


genApply :: [(QName,Int)] -> JSFDecl
genApply fs =
  JSFDecl "fullapply" [1,2]
    [JSSwitch (JSIArrayIdx 1 0)
              (concatMap branch4fun fs ++
               [JSDefault [JSReturn (JSFCall "fullconsapply"
                                             [JSIVar 1, JSIVar 2])]])]
 where
  branch4fun (fname,ar) = if ar==0 then [] else
    [JSCase (qname2JS fname)
      [JSReturn (curryFunc2JSFunc fname
                         (map (\i->JSIArrayIdx 1 i) [2..ar] ++ [JSIVar 2]))]]


flat2JS :: [TypeDecl] -> FuncDecl -> JSFDecl
flat2JS _ (Func _ _ _ _ (External _)) = error "flat2JS: external"
flat2JS tdecls (Func fname _ _ _ (Rule args rhs)) =
  JSFDecl (qname2JS fname) args
          (removeSingleVarsJSStatements
                   ([JSVarDecl retvar] ++
                     flatExp2JS tdecls retvar unknown [] retvar rhs ++
                     [JSReturn (JSIVar retvar)]))
 where
  retvar = maxlist (maxVarIndexInExp rhs : args) + 1


-- Translate a FlatCurry expression into JavaScript:
flatExp2JS :: [TypeDecl] -> Int -> Int -> [(Int,(Int,Int))]
           -> Int -> Expr -> [JSStat]
flatExp2JS _ maxo maxn patvars retvar (Var i) | maxn=:=maxo =
  maybe [JSAssign (JSIVar retvar) (JSIVar i)]
        (\ (cvar,pos) -> [JSAssign (JSIVar retvar) (JSIArrayIdx cvar pos)])
        (lookup i patvars)

flatExp2JS _ maxo maxn _ retvar (Lit (Intc i)) | maxn=:=maxo =
  [JSAssign (JSIVar retvar) (JSInt i)]

flatExp2JS _ _ _ _ _ (Lit (Floatc _)) =
  error "Float constants not yet supported!"

flatExp2JS _ maxo maxn _ retvar (Lit (Charc c)) | maxn=:=maxo =
  [JSAssign (JSIVar retvar) (JSString [c])]

flatExp2JS decls maxo maxn patvars retvar (Comb FuncCall fname args) =
 let maxa = maxo + length args
     argvars = [(maxo+1)..maxa]
  in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
     [JSAssign (JSIVar retvar)
               (curryFunc2JSFunc fname (map JSIVar argvars))]

flatExp2JS decls maxo maxn patvars retvar (Comb ConsCall cname args)
 | fst cname == prelude && snd cname `elem` ["True","False"]
   = maxn=:=maxo &> [JSAssign (JSIVar retvar) (JSBool (snd cname == "True"))]
 | otherwise =
 let maxa = maxo + length args
     argvars = [(maxo+1)..maxa]
  in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
     [JSAssign (JSIVar retvar)
               (jsConsTerm (consQName2JS cname) (map JSIVar argvars))]

flatExp2JS decls maxo maxn patvars retvar (Comb (FuncPartCall m) fname args) =
 if explicitApply
 then
  let maxa = maxo + length args
      argvars = [(maxo+1)..maxa]
   in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
      [JSAssign (JSIVar retvar)
                (JSFCall "new Array"
                         (JSString (qname2JS fname) : JSInt m :
                          map JSIVar argvars))]
 else
  let maxa = maxo + length args + m
      argvars = [(maxo+1)..(maxo+length args)]
      missvars = [(maxo+length args+1)..maxa]
      genLambda ai =
        if ai==maxa
        then JSLambda [ai] [JSReturn (curryFunc2JSFunc fname
                                            (map JSIVar (argvars++missvars)))]
        else JSLambda [ai] [JSReturn (genLambda (ai+1))]
   in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
     [JSAssign (JSIVar retvar) (genLambda (head missvars))]


flatExp2JS decls maxo maxn patvars retvar (Comb (ConsPartCall m) cname args) =
 if explicitApply
 then
  let maxa = maxo + length args
      argvars = [(maxo+1)..maxa]
   in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
      [JSAssign (JSIVar retvar)
                (JSFCall "new Array"
                         (JSString (consQName2JS cname) : JSInt m :
                          map JSIVar argvars))]
 else
  let maxa = maxo + length args + m
      argvars = [(maxo+1)..(maxo+length args)]
      missvars = [(maxo+length args+1)..maxa]
      genLambda ai =
        if ai==maxa
        then JSLambda [ai] [JSReturn (jsConsTerm (consQName2JS cname)
                                            (map JSIVar (argvars++missvars)))]
        else JSLambda [ai] [JSReturn (genLambda (ai+1))]
   in flatExps2JS decls maxa maxn patvars (zip argvars args) ++
     [JSAssign (JSIVar retvar) (genLambda (head missvars))]

flatExp2JS decls maxo maxn patvars retvar (Let bindings exp) =
  maybe (error "Translation of recursive Let bindings not supported!")
        (\seqbs -> let maxi free in
                   flatExps2JS decls maxo maxi patvars seqbs ++
                   flatExp2JS decls maxi maxn patvars retvar exp)
        (trySequentializeLetBindings bindings)

flatExp2JS decls maxo maxn patvars retvar (Case _ cexp branches) =
  if length branches == 2 && hasConstPattern "True"  (branches!!0)
                          && hasConstPattern "False" (branches!!1)
  then ite2JS decls maxo maxn patvars retvar cexp
              (expOfBranch (branches!!0)) (expOfBranch (branches!!1))
  else case2JS decls maxo maxn patvars retvar cexp branches
 where
  hasConstPattern c b = case b of
   Branch (Pattern ("Prelude",pc) []) _ -> pc == c
   _ -> False

  expOfBranch (Branch _ exp) = exp

flatExp2JS decls maxo maxn patvars retvar (Typed exp _) =
  flatExp2JS decls maxo maxn patvars retvar exp

flatExp2JS _ _ _ _ _ (Free _ _) =
  error "Translation of Free not yet supported!"

flatExp2JS _ _ _ _ _ (Or _ _) =
  error "Translation of Or not yet supported!"


-- Translate list of FlatCurry expressions:
flatExps2JS :: [TypeDecl] -> Int -> Int -> [(Int,(Int,Int))] -> [(Int,Expr)] -> [JSStat]
flatExps2JS _ maxo maxn _ [] | maxn=:=maxo = []
flatExps2JS decls maxo maxn patvars ((retvar,exp):retvarexps) =
  JSVarDecl retvar : flatExp2JS decls maxo maxe patvars retvar exp ++
  flatExps2JS decls maxe maxn patvars retvarexps
 where
   maxe free


-- Translate case expressions:
case2JS :: [TypeDecl] -> Int -> Int -> [(Int,(Int,Int))] -> Int -> Expr -> [BranchExpr] -> [JSStat]
case2JS decls maxo maxn patvars retvar cexp branches =
 let casevar = maxo+1
     max1 free
  in [JSVarDecl casevar] ++
     flatExp2JS decls casevar max1 patvars casevar cexp ++
     caseStringProlog casevar ++
     if optimizeUniqueCase && length branches == 1
                           && branchWithUniqueCase (head branches)
     then let [JSCase _ cstats] =

                    branch2JS decls max1 maxn patvars casevar retvar branches
           in cstats
     else [JSSwitch (JSIArrayIdx casevar 0)
                 (branch2JS decls max1 maxn patvars casevar retvar branches)]
 where
  caseStringProlog var =
    if lazyStringConversion && listBranches branches
    then [JSIf (JSOp "==" (JSFCall "typeof" [JSIVar var]) (JSString "string"))
               [JSAssign (JSIVar var) (JSFCall "string2charlist" [JSIVar var])]
               []]
    else []

  listBranches bs = case bs of
    (Branch (Pattern cname _) _ : _) -> snd cname `elem` ["[]",":"]
    _ -> False

  branchWithUniqueCase (Branch (LPattern _) _) = False
  branchWithUniqueCase (Branch (Pattern cname _) _) =
    isUniqueConstructor decls cname

branch2JS :: [TypeDecl] -> Int -> Int -> [(Int,(Int,Int))] -> Int -> Int
          -> [BranchExpr] -> [JSBranch]
branch2JS _ maxo maxn _ _ _ [] | maxn=:=maxo = []
branch2JS decls maxo maxn patvars casevar retvar
          (Branch (Pattern cname cargs) bexp : branches) =
 let maxa = maxo + length cargs
     maxi free
     newpatvars = map (\(pos,pi) -> (pi,(casevar,pos))) (zip [1..] cargs)
  in JSCase (consQName2JS cname)
            (flatExp2JS decls maxa maxi (newpatvars++patvars) retvar bexp) :
     branch2JS decls maxi maxn patvars casevar retvar branches
branch2JS _ _ _ _ _ _ (Branch (LPattern _) _ : _) =
  error "branch2JS: LPattern"

-- Check whether some constructor is the only constructor of a type:
isUniqueConstructor :: [TypeDecl] -> QName -> Bool
isUniqueConstructor [] c =
  error ("Internal error in isUniqueConstructor: definition of " ++ show c ++
         " not found!")
isUniqueConstructor (TypeSyn _ _ _ _ : tdecls) c = isUniqueConstructor tdecls c
isUniqueConstructor (Type _ _ _ cdecls : tdecls) c =
  if c `elem` (map (\ (Cons cname _ _ _) -> cname) cdecls)
  then length cdecls == 1
  else isUniqueConstructor tdecls c

-- Translate if-then-else
ite2JS :: [TypeDecl] -> Int -> Int -> [(Int,(Int,Int))] -> Int -> Expr -> Expr -> Expr -> [JSStat]
ite2JS decls maxo maxn patvars retvar bexp exp1 exp2 =
 let ifretvar = maxo+1
     max1,max2 free
  in [JSVarDecl ifretvar] ++
     flatExp2JS decls ifretvar max1 patvars ifretvar bexp ++
     [JSIf (JSIVar ifretvar)
           (flatExp2JS decls max1 max2 patvars retvar exp1)
           (flatExp2JS decls max2 maxn patvars retvar exp2)]

-- translates a function call into the corresponding JavaScript operator
-- or function call:
curryFunc2JSFunc :: QName -> [JSExp] -> JSExp
curryFunc2JSFunc fname args = case args of
  [a1,a2] -> maybe (let jsfname = qname2JS fname in
                    if jsfname/="apply" || explicitApply
                    then JSFCall (qname2JS fname) [a1,a2]
                    else JSApply a1 a2)
                   (\jsop -> JSOp jsop a1 a2)
                   (lookup fname jsOperators)
  _       -> JSFCall (qname2JS fname) args

consQName2JS :: QName -> String
consQName2JS qname@(md,f)
  | take 2 f == "(," = f
  | otherwise = maybe (md ++ "_" ++ encodeCurryId f)
                      id
                      (lookup qname jsConstructors)


qname2JS :: QName -> String
qname2JS qname@(md,f) =
  maybe (md ++ "_" ++ encodeCurryId f)
        id
        (lookup qname (jsFunctions++jsOperators))

-- encode a Curry identifier into a form allowed in JavaScript:
encodeCurryId :: String -> String
encodeCurryId [] = []
encodeCurryId (c:cs)
  | isAlphaNum c = c : encodeCurryId cs
  | otherwise =  let oc = ord c
    in '_' : int2hex(oc `div` 16) : int2hex(oc `mod` 16) : encodeCurryId cs
 where
   int2hex i = if i<10 then chr (ord '0' + i)
                       else chr (ord 'A' + i - 10)

jsFunctions :: [(QName,String)]
jsFunctions =
  [((prelude,"apply"),"apply"),
   ((prelude,"$#"),"apply"),
   ((prelude,"$##"),"apply"),
   ((prelude,"$!"),"apply"),
   ((prelude,"$!!"),"apply"),
   ((prelude,"div"),"preludeDiv"),
   ((prelude,"ord"),"preludeOrd"),
   ((prelude,"chr"),"preludeChr"),
   ((prelude,"failed"),"alertFailed"),
   ((prelude,"=="),"boolEq")]

jsConstructors :: [(QName,String)]
jsConstructors =
  [((prelude,":"),":"),
   ((prelude,"[]"),"[]")
  ]

jsOperators :: [(QName,String)]
jsOperators =
  [((prelude,"+"),"+"),
   ((prelude,"-"),"-"),
   ((prelude,"*"),"*"),
   ((prelude,"mod"),"%"),
   ((prelude,"&&"),"&&"),
   ((prelude,"||"),"||"),
   ((prelude,"not"),"!"),
   ((prelude,">="),">="),
   ((prelude,"<="),"<="),
   ((prelude,">"),">"),
   ((prelude,"<"),"<")
  ]

ignoredFunctions :: [QName]
ignoredFunctions =
  map fst (jsFunctions ++ jsOperators) ++
  [(prelude,"prim_Int_plus"),(prelude,"prim_Int_minus"),
   (prelude,"prim_Int_times"),(prelude,"prim_Int_div"),
   (prelude,"prim_Int_mod"),
   (prelude,"prim_ord"),(prelude,"prim_chr"),
   (prelude,"compare")]

------------------------------------------------------------------------------
--- Try to sequentialize a list of let bindings.
--- Returns Nothing if this is not possible due to a recursive let.
trySequentializeLetBindings :: [(Int,Expr)] -> Maybe [(Int,Expr)]
trySequentializeLetBindings = trySequentializeLetBinding 0

trySequentializeLetBinding :: Int -> [(Int,Expr)] -> Maybe [(Int,Expr)]
trySequentializeLetBinding try bindings
  | bindings==[] = Just []
  | try >= length bindings = Nothing -- no non-recursive binding found
  | any (`elem` (freeVarsInExp (snd (bindings!!try)))) (map fst bindings)
    = trySequentializeLetBinding (try+1) bindings -- try next binding
  | otherwise
    = maybe Nothing
            (\newbs -> Just ((bindings!!try) : newbs))
            (trySequentializeLetBinding 0
                                 (take try bindings ++ drop (try+1) bindings))

-- get all unbound variables of an expression:
freeVarsInExp :: Expr -> [Int]
freeVarsInExp (Var v) = [v]
freeVarsInExp (Lit _) = []
freeVarsInExp (Comb _ _ exps) = concatMap freeVarsInExp exps
freeVarsInExp (Or e1 e2) = freeVarsInExp e1 ++ freeVarsInExp e2
freeVarsInExp (Let bs e) = let (bvs,bes) = unzip bs in
  filter (`notElem` bvs) (concatMap freeVarsInExp (e : bes))
freeVarsInExp (Free vs exp) = filter (`notElem` vs) (freeVarsInExp exp)
freeVarsInExp (Case _ e bs) = freeVarsInExp e ++ concatMap freeVarsInBranch bs
freeVarsInExp (Typed exp _) = freeVarsInExp exp

freeVarsInBranch :: BranchExpr -> [Int]
freeVarsInBranch (Branch (Pattern _ vs) e) =
                                        filter (`notElem` vs) (freeVarsInExp e)
freeVarsInBranch (Branch (LPattern _) e) = freeVarsInExp e


-- get maximum variable index occurring in an expression:
maxVarIndexInExp :: Expr -> Int
maxVarIndexInExp exp = let allvars = allVarsInExp exp in
  if null allvars then 0 else maxlist allvars
 where
  allVarsInExp (Var v) = [v]
  allVarsInExp (Lit _) = []
  allVarsInExp (Comb _ _ exps) = concatMap allVarsInExp exps
  allVarsInExp (Or e1 e2) = allVarsInExp e1 ++ allVarsInExp e2
  allVarsInExp (Let bs e) = let (bvs,bes) = unzip bs
                             in bvs ++ concatMap allVarsInExp (e : bes)
  allVarsInExp (Free vs e) = vs ++ allVarsInExp e
  allVarsInExp (Case _ e bs) = allVarsInExp e ++ concatMap allVarsInBranch bs
  allVarsInExp (Typed e _) = allVarsInExp e
  
  allVarsInBranch (Branch (Pattern _ vs) e) = vs ++ allVarsInExp e
  allVarsInBranch (Branch (LPattern _) e) = allVarsInExp e

------------------------------------------------------------------------------
-- compute all partially applied functions in a program:
pafsOfProg :: Prog -> [(QName,Int)]
pafsOfProg (Prog _ _ _ fdecls _) =
  pafsOfFuncs (filter isRelevantFunction fdecls)

pafsOfFuncs :: [FuncDecl] -> [(QName,Int)]
pafsOfFuncs fdecls = mapUnion (map pafsOfFunc fdecls)

pafsOfFunc :: FuncDecl -> [(QName,Int)]
pafsOfFunc (Func _ _ _ _ (External _)) = []
pafsOfFunc (Func _ _ _ _ (Rule _ exp)) = pafsOfExpr exp

pafsOfExpr :: Expr -> [(QName,Int)]
pafsOfExpr (Var _) = []
pafsOfExpr (Lit _) = []
pafsOfExpr (Comb FuncCall _ args) = mapUnion (map pafsOfExpr args)
pafsOfExpr (Comb ConsCall _ args) = mapUnion (map pafsOfExpr args)
pafsOfExpr (Comb (ConsPartCall _) _ args) = mapUnion (map pafsOfExpr args)
pafsOfExpr (Comb (FuncPartCall m) f args) =
  union [(f,m+length args)] (mapUnion (map pafsOfExpr args))
pafsOfExpr (Case _ cexp branches) =
  mapUnion (map pafsOfExpr (cexp : map (\ (Branch _ exp) -> exp) branches))
pafsOfExpr (Let defs exp) =
  mapUnion (map pafsOfExpr (exp : map snd defs))
pafsOfExpr (Free _ exp) = pafsOfExpr exp
pafsOfExpr (Or exp1 exp2) = union (pafsOfExpr exp1) (pafsOfExpr exp2)
pafsOfExpr (Typed exp _) = pafsOfExpr exp

mapUnion :: [[a]] -> [a]
mapUnion = foldr union []

------------------------------------------------------------------------------
-- compute the name of all functions in a FlatCurry program
-- occurring in a "withConditionJS" or "withConditionJSName"
-- together with a flag which is true if the
-- occurrence was in a "withConditionJS":
jscOfProg :: Prog -> [(QName,Bool)]
jscOfProg (Prog _ _ _ fdecls _) = jscOfFuncs fdecls

jscOfFuncs :: [FuncDecl] -> [(QName,Bool)]
jscOfFuncs fdecls = mapUnion (map jscOfFunc fdecls)

jscOfFunc :: FuncDecl -> [(QName,Bool)]
jscOfFunc (Func _ _ _ _ (External _)) = []
jscOfFunc (Func _ _ _ _ (Rule _ exp)) = jscOfExpr exp

jscOfExpr :: Expr -> [(QName,Bool)]
jscOfExpr (Var _) = []
jscOfExpr (Lit _) = []
jscOfExpr (Comb ct (m,f) args)
 | ct==FuncCall && m==wuiModName && f=="withConditionJS"
  = union (maybe [] (\i->[(i,True)]) (getCurryFunc (args!!1))) jscOfArgs
 | ct==FuncCall && m==wuiModName && f=="withConditionJSName"
  = union (maybe [] (\i->[(i,False)]) (getCurryFunc (fstFlatCurry (args!!1))))
          jscOfArgs
 | otherwise = jscOfArgs
 where
  getCurryFunc cpred = case cpred of
    Comb (FuncPartCall 1) fname [] -> Just fname
    _ -> Nothing

  fstFlatCurry e = case e of Comb _ _ [arg,_] -> arg
                             _ -> error "jscOfExpr.fstFlatCurry"

  jscOfArgs = mapUnion (map jscOfExpr args)

jscOfExpr (Case _ cexp branches) =
  mapUnion (map jscOfExpr (cexp : map (\ (Branch _ exp) -> exp) branches))
jscOfExpr (Let defs exp) =
  mapUnion (map jscOfExpr (exp : map snd defs))
jscOfExpr (Free _ exp) = jscOfExpr exp
jscOfExpr (Or exp1 exp2) = union (jscOfExpr exp1) (jscOfExpr exp2)
jscOfExpr (Typed exp _) = jscOfExpr exp


------------------------------------------------------------------------------
-- Transform a WUI application program:
-- * replace all functions occurring in a "withConditionJS" by
--   "withConditionJSName" including the JavaScript function name
-- * replace (wCons<j> cons) by ((wCons<j>JS "cons") cons)
--   if cons is an j-ary data constructor, .e.g., replace
--   Comb FuncCall ("Prelude","apply")
--     [Comb FuncCall ("WUI","wCons3") [],
--      Comb (ConsPartCall 3) ("mod","Date") []]
--   
--   by
--   
--   Comb FuncCall ("Prelude","apply")
--     [Comb (FuncPartCall 4) ("WUI","wCons3JS")
--           [(Comb ConsCall ("Prelude","Just") 
--                  [Comb (FuncPartCall 1) ("JavaScript","jsConsTerm")
--                        [<"mod_Date" FlatCurry string]])],
--      Comb (ConsPartCall 3) ("mod","Date") []]

replaceJscOfProg :: Prog -> Prog
replaceJscOfProg (Prog mname imps ddecls fdecls ops) =
  Prog mname imps ddecls (map replaceJscOfFunc fdecls) ops

replaceJscOfFunc :: FuncDecl -> FuncDecl
replaceJscOfFunc fdecl@(Func _ _ _ _ (External _)) = fdecl
replaceJscOfFunc (Func f ar vis typ (Rule lhs exp)) =
  Func f ar vis typ (Rule lhs (replaceJscOfExpr exp))

replaceJscOfExpr :: Expr -> Expr
replaceJscOfExpr (Var i) = Var i
replaceJscOfExpr (Lit l) = Lit l
replaceJscOfExpr (Comb ct (m,f) args)
  | ct==FuncCall && m==wuiModName && f=="withConditionJS" &&
    isJSTranslatable (args!!1)
   = Comb ct (m,"withConditionJSName")
             [replaceJscOfExpr (head args),
              Comb ConsCall (prelude,"(,)") (replaceCurryFunc (args!!1))]
  | ct==FuncCall && m==prelude && f=="apply" && 
    isWCons (args!!0) && isDataCons (args!!1)
   = let arity = wConsArity (args!!0)
      in Comb ct (m,f)
              [Comb (FuncPartCall (arity+1))
                    (wuiModName,"wCons"++show arity++"JS")
                    [Comb ConsCall (prelude,"Just")
                      [Comb (FuncPartCall 1) ("JavaScript","jsConsTerm")
                        [flatString (consQName2JS (dataConsName (args!!1)))]]],
                     (args!!1)]
  | otherwise
   = Comb ct (m,f) (map replaceJscOfExpr args)
 where
  isWCons exp = case exp of
    Comb FuncCall (mod,fname) [] -> mod==wuiModName && take 5 fname == "wCons"
    _ -> False

  wConsArity e = case e of
    Comb _ (_,fname) [] -> fst (fromJust (readNat (drop 5 fname)))
    _ -> error "replaceJscOfExpr.wConsArity"

  isDataCons exp = case exp of
    Comb (ConsPartCall 3) _ [] -> True
    _ -> False

  dataConsName (Comb _ cname _) = cname

  isJSTranslatable cpred = case cpred of
    Comb (FuncPartCall 1) _ [] -> True
    _ -> False

  replaceCurryFunc pred@(Comb _ fname _) = [pred, flatString (qname2JS fname)]

replaceJscOfExpr (Case ct cexp branches) =
  Case ct (replaceJscOfExpr cexp)
         (map (\ (Branch cl exp) -> Branch cl (replaceJscOfExpr exp)) branches)
replaceJscOfExpr (Let defs exp) =
  Let (map (\ (i,d) -> (i,replaceJscOfExpr d)) defs) (replaceJscOfExpr exp)
replaceJscOfExpr (Free fvs exp) = Free fvs (replaceJscOfExpr exp)
replaceJscOfExpr (Or exp1 exp2) =
  Or (replaceJscOfExpr exp1) (replaceJscOfExpr exp2)
replaceJscOfExpr (Typed exp te) =
  Typed (replaceJscOfExpr exp) te

-- is a FlatCurry expression the representation of an empty list:
flatEmptyList :: Expr -> Bool
flatEmptyList e = case e of
  Comb ConsCall ("Prelude","[]") [] -> True
  _ -> False

-- generate FlatCurry representation of a string:
flatString :: String -> Expr
flatString []     = Comb ConsCall (prelude,"[]") []
flatString (c:cs) = Comb ConsCall (prelude,":") [Lit (Charc c), flatString cs]


------------------------------------------------------------------------------
-- JavaScript code optimization:

-- Type of variable definitions used in code optimization.
-- (SimpleVar i) represents definition of ... = xi
-- (ComplexDef exp n) represents definition of ... = exp where n contains
-- the number of occurrences of the defined variable in the subsequent code
data VarDef = SimpleVar Int
            | ComplexDef JSExp Int -- value / number of applications

-- compute the number of uses of variables with a unique assignment
-- in a sequence of statements:
uniqueDefsOfStats :: [(Int,Maybe VarDef)] -> [JSStat] -> [(Int,Maybe VarDef)]
uniqueDefsOfStats defs [] = defs
uniqueDefsOfStats defs (stat:stats) =
  uniqueDefsOfStats (uniqueDefsOfStat defs stat) stats


uniqueDefsOfStat :: [(Int,Maybe VarDef)] -> JSStat -> [(Int,Maybe VarDef)]
uniqueDefsOfStat defs (JSAssign lhs rhs) =
  case lhs of
    JSIVar i -> maybe ((i,Just (rhs2vardef rhs)):rdefs)
                      (\_ -> updateAssoc i Nothing rdefs)
                      (lookup i rdefs)
    _ -> uniqueDefsOfExp rdefs lhs
 where
  rdefs = uniqueDefsOfExp defs rhs

  rhs2vardef exp = case exp of
    JSIVar i -> SimpleVar i
    _ -> ComplexDef exp 0

uniqueDefsOfStat defs (JSIf bexp s1 s2) =
  uniqueDefsOfStats (uniqueDefsOfStats (uniqueDefsOfExp defs bexp) s1) s2

uniqueDefsOfStat defs (JSSwitch exp branches) =
  uniqueDefsOfStats (uniqueDefsOfExp defs exp) (concatMap statsOf branches)
 where
  statsOf (JSCase _ stats) = stats
  statsOf (JSDefault stats) = stats

uniqueDefsOfStat defs (JSPCall _ exps) = uniqueDefsOfExps defs exps

uniqueDefsOfStat defs (JSReturn exp) = uniqueDefsOfExp defs exp

uniqueDefsOfStat defs (JSVarDecl _) = defs


uniqueDefsOfExp :: [(Int,Maybe VarDef)] -> JSExp -> [(Int,Maybe VarDef)]
uniqueDefsOfExp defs (JSString _) = defs
uniqueDefsOfExp defs (JSInt _) = defs
uniqueDefsOfExp defs (JSBool _) = defs
uniqueDefsOfExp defs (JSIVar i) =
  maybe defs
        (maybe defs
               (\vd -> updateAssoc i (Just (incVarDef vd)) defs))
        (lookup i defs)
 where
  incVarDef (ComplexDef val occ) = ComplexDef val (occ+1)
  incVarDef (SimpleVar vi) = SimpleVar vi

uniqueDefsOfExp defs (JSIArrayIdx i _) =
  maybe defs
        (maybe defs
               (\vd -> updateAssoc i (newVarDef vd) defs))
        (lookup i defs)
 where
  newVarDef (SimpleVar vi) = Just (SimpleVar vi)
  newVarDef (ComplexDef _ _) = Nothing -- don't optimize complex array vars

uniqueDefsOfExp defs (JSOp _ exp1 exp2) =
  uniqueDefsOfExp (uniqueDefsOfExp defs exp1) exp2
uniqueDefsOfExp defs (JSFCall _ exps) = uniqueDefsOfExps defs exps
uniqueDefsOfExp defs (JSApply exp1 exp2) =
  uniqueDefsOfExp (uniqueDefsOfExp defs exp1) exp2
uniqueDefsOfExp defs (JSLambda _ body) = uniqueDefsOfStats defs body

uniqueDefsOfExps :: [(Int,Maybe VarDef)] -> [JSExp] -> [(Int,Maybe VarDef)]
uniqueDefsOfExps defs [] = defs
uniqueDefsOfExps defs (exp:exps) =
  uniqueDefsOfExps (uniqueDefsOfExp defs exp) exps

updateAssoc :: a -> b -> [(a,b)] -> [(a,b)]
updateAssoc _ _ [] = error "updateAssoc on []"
updateAssoc r newval ((i,val):assocs) =
  if r==i then (i,newval) : assocs
          else (i,val) : updateAssoc r newval assocs


-- Optimize a sequence of statements by removing single-assigned variables:
removeSingleVarsJSStatements :: [JSStat] -> [JSStat]
removeSingleVarsJSStatements stats =
  if optimizeSingleVars
  then removeSingleVarsInStats (uniqueDefsOfStats [] stats) $## stats
  else --trace (show (uniqueDefsOfStats [] $## stats) ++ "\n")
       stats

removeSingleVarsInStats :: [(Int,Maybe VarDef)] -> [JSStat] -> [JSStat]
removeSingleVarsInStats defs stats =
  concatMap (removeSingleVarsInStat defs) stats


maybeReplaceVar :: a -> a -> VarDef -> a
maybeReplaceVar rep _ (SimpleVar _) = rep
maybeReplaceVar rep notrep (ComplexDef _ occ) =
  if occ<=1 then rep else notrep

removeSingleVarsInStat :: [(Int,Maybe VarDef)] -> JSStat -> [JSStat]
removeSingleVarsInStat defs (JSAssign lhs rhs) =
  case lhs of
    JSIVar i -> maybe [JSAssign lhs newrhs]
                      (maybe [JSAssign lhs newrhs]
                             (maybeReplaceVar [] [JSAssign lhs newrhs]))
                      (lookup i defs)
    _ -> [JSAssign (removeSingleVarsInExp defs lhs) newrhs]
 where
  newrhs = removeSingleVarsInExp defs rhs

removeSingleVarsInStat defs (JSIf bexp s1 s2) =
  [JSIf  (removeSingleVarsInExp defs bexp)
         (removeSingleVarsInStats defs s1)
         (removeSingleVarsInStats defs s2)]

removeSingleVarsInStat defs (JSSwitch exp branches) =
  [JSSwitch (removeSingleVarsInExp defs exp)
            (map removeInBranch branches)]
 where
  removeInBranch (JSCase s sts) = JSCase s (removeSingleVarsInStats defs sts)
  removeInBranch (JSDefault sts) = JSDefault (removeSingleVarsInStats defs sts)

removeSingleVarsInStat defs (JSPCall s exps) =
  [JSPCall s (map (removeSingleVarsInExp defs) exps)]

removeSingleVarsInStat defs (JSReturn exp) =
  [JSReturn (removeSingleVarsInExp defs exp)]

removeSingleVarsInStat defs stat@(JSVarDecl i) =
  maybe [stat]
        (maybe [stat] (maybeReplaceVar [] [stat]))
        (lookup i defs)


removeSingleVarsInExp :: [(Int,Maybe VarDef)] -> JSExp -> JSExp
removeSingleVarsInExp _ (JSString s) = JSString s
removeSingleVarsInExp _ (JSInt i) = JSInt i
removeSingleVarsInExp _ (JSBool b) = JSBool b
removeSingleVarsInExp defs (JSIVar i) =
  maybe (JSIVar i)
        (maybe (JSIVar i) replaceVar)
        (lookup i defs)
 where
  replaceVar (SimpleVar v) = removeSingleVarsInExp defs (JSIVar v) --dereference
  replaceVar (ComplexDef exp occ) =
    if occ<=1 then removeSingleVarsInExp defs exp
              else JSIVar i

removeSingleVarsInExp defs (JSIArrayIdx i j) =
  maybe (JSIArrayIdx i j)
        (maybe (JSIArrayIdx i j) replaceVar)
        (lookup i defs)
 where
  replaceVar (SimpleVar v) = JSIArrayIdx v j
  replaceVar (ComplexDef _ _) =
    error "Internal error in removeSingleVars in JSIArrayIdx"

removeSingleVarsInExp defs (JSOp op exp1 exp2) =
  JSOp op (removeSingleVarsInExp defs exp1) (removeSingleVarsInExp defs exp2)
removeSingleVarsInExp defs (JSFCall f exps) =
  JSFCall f (map (removeSingleVarsInExp defs) exps)
removeSingleVarsInExp defs (JSApply exp1 exp2) =
  JSApply (removeSingleVarsInExp defs exp1) (removeSingleVarsInExp defs exp2)
removeSingleVarsInExp defs (JSLambda params body) =
  JSLambda params (removeSingleVarsInStats defs body)


------------------------------------------------------------------------------
-- Top-level functions:

--- Reads a (Flat)Curry program and compiles it to JavaScript code that
--- is returned.
curry2js :: String -> IO String
curry2js modname = do
  prog <- readFlatCurry modname
  return (concatMap showJSFDecl (flatprog2JS prog))


-- Transforms a WUI program and some imported modules by inserting
-- JavaScript code for WUI conditions with ...`withConditionJS(Name)`
transformWUI :: String -> [String] -> String -> IO ()
transformWUI mainmodname imports target = do
  jscmodfuns <- mapIO getAndTransformWUIConditions (mainmodname:imports)
  let jscfuntags = concat jscmodfuns
      jscfuns = nub (map fst jscfuntags)
  putStrLn "WUI conditions (Curry predicates) to be translated into JavaScript:"
  putStr (concatMap ((++"\n") . showQName) jscfuns)
  targetnewer <- fileExistsAndNewerThan target (flatCurryFileName mainmodname)
  if targetnewer && not (or (map snd jscfuntags))
   then putStrLn "Nothing to be done!"
   else generateJavaScript mainmodname imports jscfuns target

-- Transforms a module containing WUI specifications by replacing
-- `withConditionsJS` by `withConditionsJSName` and return all functions
-- contained in such conditions.
getAndTransformWUIConditions :: String -> IO [(QName,Bool)]
getAndTransformWUIConditions modname = do
  prog <- readFlatCurry modname
  fcyname <- getFlatCurryFileInLoadPath modname
  let jscfuns = jscOfProg prog
      newflatprogname = fcyname++"_withjs"
  if or (map snd jscfuns) -- is there some withConditionJS to be transformed?
   then do
    putStr $ "Changing WUI conditions in FlatCurry module '"++modname++"'..."
    writeFCY newflatprogname (replaceJscOfProg prog)
    system $ "mv "++newflatprogname++" "++fcyname
    putStrLn "done"
   else done
  return jscfuns

-- Generate a JavaScript program for Curry functions w.r.t. a main module:
generateJavaScript :: String -> [String] -> [QName] -> String -> IO ()
generateJavaScript mainmodname imports mainfuns target = do
  putStrLn "Computing Curry functions to be translated..."
  prog <- computeCompactFlatCurry (InitFuncs mainfuns : map Import imports)
                                  mainmodname
  putStrLn "Translating Curry functions to JavaScript..."
  writeFile target
            (concatMap showJSFDecl (flatprog2JS prog) ++
             "var LazyStringConversion = " ++
                 (if lazyStringConversion then "true" else "false") ++ ";\n\n")
  readFile (installDir++"/include/curry2js_prims.js") >>= appendFile target
  readFile (installDir++"/include/wui_prims.js") >>= appendFile target
  putStrLn $ "JavaScript program written into \""++target++"\""
  system $ "chmod 644 "++target
  done

-- Does newfile exists and is it newer than oldfile?
fileExistsAndNewerThan :: String -> String -> IO Bool
fileExistsAndNewerThan newfile oldfile = do
  nfexists <- doesFileExist newfile
  ofexists <- doesFileExist oldfile
  if nfexists && ofexists
   then do oftime <- getModificationTime oldfile
           nftime <- getModificationTime newfile
           return (nftime > oftime)
   else return False

showQName :: QName -> String
showQName (m,f) = m++'.':f


-- Check arguments and call main function:
main :: IO ()
main = do
  args <- getArgs
  case args of
    [prog]                     -> curry2js prog >>= putStrLn
    ["-o",target,prog]         -> curry2js prog >>= writeFile target
    ("-wui":"-o":target:prog:imps) -> transformWUI prog imps target
    ("-wui":prog:imps)         -> transformWUI prog imps (prog++".js")
    _ -> putStrLn $ "ERROR: Illegal arguments: " ++
                    concat (intersperse " " args) ++ "\n" ++
                    "Usage: curry2js [-wui] [-o <targetfile>] <main_module_name> <imports_with_wuis>"


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

-- Testing:

mp :: IO ()
mp = curry2js "test" >>= putStrLn

mo :: IO ()
mo = do
  jscode <- curry2js "test"
  writeFile "test.js" (jscode ++ "\nalert(test_main());\n")
  system "chmod 644 test.js"
  done

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