Operations.hs

module GF.Data.Operations (
     -- ** The Error monad
     Err(..), err, maybeErr, testErr, fromErr, errIn,
     lookupErr,

     -- ** Error monad class
     ErrorMonad(..), checks, --doUntil, allChecks, checkAgain,
                 liftErr,

     -- ** Checking
     checkUnique, unifyMaybeBy, unifyMaybe,

         -- ** Monadic operations on lists and pairs
     mapPairsM, pairM,

     -- ** Printing
     indent, (+++), (++-), (++++), (+++-), (+++++),
     prUpper, prReplicate, prTList, prQuotedString, prParenth, prCurly,
     prBracket, prArgList, prSemicList, prCurlyList, restoreEscapes,
     numberedParagraphs, prConjList, prIfEmpty, wrapLines,

     -- ** Topological sorting
     topoTest, topoTest2,

     -- ** Misc
     readIntArg,
     iterFix,  chunks,

    ) where

import Data.Char (isSpace, toUpper, isSpace, isDigit)
import Data.List (nub, partition, (\\))
import qualified Data.Map as Map
import Data.Map (Map)
--import Control.Applicative(Applicative(..))
import Control.Monad (liftM,liftM2) --,ap

import GF.Data.ErrM
import GF.Data.Relation
import qualified Control.Monad.Fail as Fail

infixr 5 +++
infixr 5 ++-
infixr 5 ++++
infixr 5 +++++

-- the Error monad

-- | Add msg s to 'Maybe' failures
maybeErr :: ErrorMonad m => String -> Maybe a -> m a
maybeErr s = maybe (raise s) return

testErr :: ErrorMonad m => Bool -> String -> m ()
testErr cond msg = if cond then return () else raise msg

errIn :: ErrorMonad m => String -> m a -> m a
errIn msg m = handle m (\s -> raise (s ++++ "OCCURRED IN" ++++ msg))

lookupErr :: (ErrorMonad m,Eq a,Show a) => a -> [(a,b)] -> m b
lookupErr a abs = maybeErr ("Unknown" +++ show a) (lookup a abs)

mapPairsM :: Monad m => (b -> m c) -> [(a,b)] -> m [(a,c)]
mapPairsM f xys = mapM (\ (x,y) -> liftM ((,) x) (f y)) xys

pairM :: Monad m => (b -> m c) -> (b,b) -> m (c,c)
pairM op (t1,t2) = liftM2 (,) (op t1) (op t2)

-- checking

checkUnique :: (Show a, Eq a) => [a] -> [String]
checkUnique ss = ["overloaded" +++ show s | s <- nub overloads] where
  overloads = filter overloaded ss
  overloaded s = length (filter (==s) ss) > 1

-- | this is what happens when matching two values in the same module
unifyMaybe :: (Eq a, Fail.MonadFail m) => Maybe a -> Maybe a -> m (Maybe a)
unifyMaybe = unifyMaybeBy id

unifyMaybeBy :: (Eq b, Fail.MonadFail m) => (a->b) -> Maybe a -> Maybe a -> m (Maybe a)
unifyMaybeBy f (Just p1) (Just p2)
  | f p1==f p2                     = return (Just p1)
  | otherwise                      = fail ""
unifyMaybeBy _ Nothing   mp2       = return mp2
unifyMaybeBy _ mp1       _         = return mp1

-- printing

indent :: Int -> String -> String
indent i s = replicate i ' ' ++ s

(+++), (++-), (++++), (+++-), (+++++) :: String -> String -> String
a +++ b   = a ++ " "    ++ b

a ++- ""  = a
a ++- b   = a +++ b

a ++++ b  = a ++ "\n"   ++ b

a +++- "" = a
a +++- b  = a ++++ b

a +++++ b = a ++ "\n\n" ++ b


prUpper :: String -> String
prUpper s = s1 ++ s2' where
 (s1,s2) = span isSpace s
 s2' = case s2 of
   c:t -> toUpper c : t
   _ -> s2

prReplicate :: Int -> String -> String
prReplicate n s = concat (replicate n s)

prTList :: String -> [String] -> String
prTList t ss = case ss of
  []   -> ""
  [s]  -> s
  s:ss -> s ++ t ++ prTList t ss

prQuotedString :: String -> String
prQuotedString x = "\"" ++ restoreEscapes x ++ "\""

prParenth :: String -> String
prParenth s = if s == "" then "" else "(" ++ s ++ ")"

prCurly, prBracket :: String -> String
prCurly   s = "{" ++ s ++ "}"
prBracket s = "[" ++ s ++ "]"

prArgList, prSemicList, prCurlyList :: [String] -> String
prArgList   = prParenth . prTList ","
prSemicList = prTList " ; "
prCurlyList = prCurly . prSemicList

restoreEscapes :: String -> String
restoreEscapes s =
  case s of
    []       -> []
    '"' : t  -> '\\' : '"'  : restoreEscapes t
    '\\': t  -> '\\' : '\\' : restoreEscapes t
    c   : t  -> c : restoreEscapes t

numberedParagraphs :: [[String]] -> [String]
numberedParagraphs t = case t of
  []   -> []
  p:[] -> p
  _    -> concat [(show n ++ ".") : s | (n,s) <- zip [1..] t]

prConjList :: String -> [String] -> String
prConjList c []     = ""
prConjList c [s]    = s
prConjList c [s,t]  = s +++ c +++ t
prConjList c (s:tt) = s ++ "," +++ prConjList c tt

prIfEmpty :: String -> String -> String -> String -> String
prIfEmpty em _    _    [] = em
prIfEmpty em nem1 nem2 s  = nem1 ++ s ++ nem2

-- | Thomas Hallgren's wrap lines
wrapLines :: Int -> String -> String
wrapLines n "" = ""
wrapLines n s@(c:cs) =
      if isSpace c
      then c:wrapLines (n+1) cs
      else case lex s of
            [(w,rest)] -> if n'>=76
                          then '\n':w++wrapLines l rest
                          else w++wrapLines n' rest
               where n' = n+l
                     l = length w
            _ -> s -- give up!!

-- | Topological sorting with test of cyclicity
topoTest :: Ord a => [(a,[a])] -> Either [a] [[a]]
topoTest = topologicalSort . mkRel'

-- | Topological sorting with test of cyclicity, new version /TH 2012-06-26
topoTest2 :: Ord a => [(a,[a])] -> Either [[a]] [[a]]
topoTest2 g0 = maybe (Right cycles) Left (tsort g)
  where
    g = g0++[(n,[])|n<-nub (concatMap snd g0)\\map fst g0]

    cycles = findCycles (mkRel' g)

    tsort nes =
      case partition (null.snd) nes of
        ([],[]) -> Just []
        ([],_) -> Nothing
        (ns,rest) -> (leaves:) `fmap` tsort [(n,es \\ leaves) | (n,es)<-rest]
            where leaves = map fst ns


-- | Fix point iterator (for computing e.g. transitive closures or reachability)
iterFix :: Eq a => ([a] -> [a]) -> [a] -> [a]
iterFix more start = iter start start
  where
    iter old new = if (null new')
                      then old
                      else iter (new' ++ old) new'
      where
        new' = filter (`notElem` old) (more new)

-- | chop into separator-separated parts
chunks :: Eq a => a -> [a] -> [[a]]
chunks sep ws = case span (/= sep) ws of
  (a,_:b) -> a : bs where bs = chunks sep b
  (a, []) -> if null a then [] else [a]

readIntArg :: String -> Int
readIntArg n = if (not (null n) && all isDigit n) then read n else 0

class (Functor m,Monad m) => ErrorMonad m where
  raise   :: String -> m a
  handle  :: m a -> (String -> m a) -> m a
  handle_ :: m a -> m a -> m a
  handle_ a b =  a `handle` (\_ -> b)

instance ErrorMonad Err where
  raise  = Bad
  handle a@(Ok _) _ = a
  handle (Bad i) f  = f i

liftErr e = err raise return e
{-
instance ErrorMonad (STM s) where
  raise msg = STM (\s -> raise msg)
  handle (STM f) g = STM (\s -> (f s)
                                `handle` (\e -> let STM g' = (g e) in
                                                    g' s))

-}

-- | if the first check fails try another one
checkAgain :: ErrorMonad m => m a -> m a -> m a
checkAgain c1 c2 = handle_ c1 c2

checks :: ErrorMonad m => [m a] -> m a
checks [] = raise "no chance to pass"
checks cs = foldr1 checkAgain cs
{-
allChecks :: ErrorMonad m => [m a] -> m [a]
allChecks ms = case ms of
  (m: ms) -> let rs = allChecks ms in handle_ (liftM2 (:) m rs) rs
  _ -> return []

doUntil :: ErrorMonad m => (a -> Bool) -> [m a] -> m a
doUntil cond ms = case ms of
  a:as -> do
    v <- a
    if cond v then return v else doUntil cond as
  _ -> raise "no result"
-}