{-|

Module : $Header$

Copyright : (c) Klaus L�ttich, Till Mossakowski, Christian Maeder, Uni Bremen 2002-2004

Licence : similar to LGPL, see HetCATS/LICENCE.txt or LIZENZ.txt

Maintainer : hets@tzi.de

Stability : provisional

Portability : portable

This module provides a 'Result' type and some monadic functions

for accumulating 'Diagnosis' messages during analysis phases.

-}

module Common.Result where

import Common.Id

import Common.PrettyPrint

import Common.Lib.Pretty

import Data.List

import Text.ParserCombinators.Parsec.Error

import Common.Lexer (fromSourcePos)

-- | severness of diagnostic messages

data DiagKind = Error | Warning | Hint | Debug

| MessageW -- ^ used for messages in the web interface

deriving (Eq, Ord, Show)

-- | a diagnostic message with 'Pos'

data Diagnosis = Diag { diagKind :: DiagKind

, diagString :: String

, diagPos :: [Pos]

} deriving Eq

-- | construct a message for a printable item that carries a position

mkDiag :: (PosItem a, PrettyPrint a) => DiagKind -> String -> a -> Diagnosis

mkDiag k s a = let q = char '\'' in

Diag k (s ++ show (space <> q <> nest 2 (printText a) <> q)) $ get_pos a

-- | check whether a diagnosis is an error

isErrorDiag :: Diagnosis -> Bool

isErrorDiag d = case diagKind d of

Error -> True

_ -> False

-- | Check whether a diagnosis list contains errors

hasErrors :: [Diagnosis] -> Bool

hasErrors = any isErrorDiag

-- | adjust a null position of a diagnosis

adjustDiagPos :: [Pos] -> Diagnosis -> Diagnosis

adjustDiagPos p d = let o = diagPos d in

d {diagPos = if null o then p else p++o}

-- | A uniqueness check yields errors for duplicates in a given list.

checkUniqueness :: (PrettyPrint a, PosItem a, Ord a) => [a] -> [Diagnosis]

checkUniqueness l =

let vd = filter ( not . null . tail) $ group $ sort l

in map ( \ vs -> mkDiag Error ("duplicates at '" ++

showSepList (showString " ") shortPosShow

(concatMap get_pos (tail vs)) "'"

++ " for") (head vs)) vd

where shortPosShow :: Pos -> ShowS

shortPosShow p = showParen True

(shows (sourceLine p) .

showString "," .

shows (sourceColumn p))

-- | The result monad. A failing result should include an error message.

data Result a = Result { diags :: [Diagnosis]

, maybeResult :: (Maybe a)

} deriving (Show)

instance Eq a => Eq (Result a) where

Result _ res1 == Result _ res2 = res1==res2

instance Functor Result where

fmap f (Result errs m) = Result errs $ fmap f m

instance Monad Result where

return x = Result [] $ Just x

Result errs Nothing >>= _ = Result errs Nothing

Result errs1 (Just x) >>= f = Result (errs1++errs2) y

where Result errs2 y = f x

fail s = fatal_error s []

-- | join two results

joinResultWith :: (a -> b -> c) -> Result a -> Result b -> Result c

joinResultWith f (Result d1 m1) (Result d2 m2) = Result (d1 ++ d2) $

case m1 of

Nothing -> Nothing

Just r1 -> case m2 of

Nothing -> Nothing

Just r2 -> Just $ f r1 r2

-- | join a list of results that are independently computed

mapR :: (a -> Result a) -> [a] -> Result [a]

mapR ana = foldr (joinResultWith (:)) (Result [] $ Just []) . map ana

-- | bind results within the 'IO' monad

ioBind :: IO(Result a) -> (a -> IO(Result b)) -> IO(Result b)

x `ioBind` f = do

res <- x

case res of

Result errs Nothing -> return (Result errs Nothing)

Result errs1 (Just v) -> do

Result errs2 y <- f v

return (Result (errs1++errs2) y)

newtype IOResult a = IOResult (IO(Result a))

instance Monad IOResult where

return x = IOResult (return (return x))

IOResult x >>= f = IOResult (x `ioBind` (\y -> let IOResult z = f y in z))

-- | unpack an IOResult

ioresToIO :: IOResult a -> IO(Result a)

ioresToIO (IOResult x) = x

-- | pack an IO value as IOResult

ioToIORes :: IO a -> IOResult a

ioToIORes = IOResult . (fmap return)

-- | pack a pure result as IOResult

resToIORes :: Result a -> IOResult a

resToIORes = IOResult . return

-- | a failing result with a proper position

fatal_error :: String -> [Pos] -> Result a

fatal_error s p = Result [Diag Error s p] Nothing

-- | a failing result using pretty printed 'Doc'

pfatal_error :: Doc -> [Pos] -> Result a

pfatal_error s p = fatal_error (show s) p

-- | a failing result constructing a message from a type

mkError :: (PosItem a, PrettyPrint a) => String -> a -> Result b

mkError s c = Result [mkDiag Error s c] Nothing

-- | add an error message but don't fail

plain_error :: a -> String -> [Pos] -> Result a

plain_error x s p = Result [Diag Error s p] $ Just x

-- | add an error message using a pretty printed 'Doc' but don't fail

pplain_error :: a -> Doc -> [Pos] -> Result a

pplain_error x s p = plain_error x (show s) p

-- | add a warning

warning :: a -> String -> [Pos] -> Result a

warning x s p = Result [Diag Warning s p] $ Just x

-- | add a warning using a pretty printed 'Doc'

pwarning :: a -> Doc -> [Pos] -> Result a

pwarning x s p = warning x (show s) p

-- | add a hint

hint :: a -> String -> [Pos] -> Result a

hint x s p = Result [Diag Hint s p] $ Just x

-- | add a hint using a pretty printed 'Doc'

phint :: a -> Doc -> [Pos] -> Result a

phint x s p = hint x (show s) p

-- | add a (web interface) message

message :: a -> String -> Result a

message x m = Result [Diag MessageW m []] $ Just x

-- | add a failure message to 'Nothing'

maybeToResult :: [Pos] -> String -> Maybe a -> Result a

maybeToResult p s m = Result (case m of

Nothing -> [Diag Error s p]

Just _ -> []) m

-- | add a failure message to 'Nothing'

-- (alternative for 'maybeToResult' with 'nullPos')

maybeToMonad :: Monad m => String -> Maybe a -> m a

maybeToMonad s m = case m of

Nothing -> fail s

Just v -> return v

-- | check whether no errors are present, coerce into 'Maybe'

resultToMaybe :: Result a -> Maybe a

resultToMaybe (Result ds val) = if hasErrors ds then Nothing else val

-- | adjust positions of diagnoses

adjustPos :: [Pos] -> Result a -> Result a

adjustPos p r =

r {diags = map (adjustDiagPos p) $ diags r}

-- | Propagate errors using the error function

propagateErrors :: Result a -> a

propagateErrors r =

case (hasErrors $ diags r, maybeResult r) of

(False,Just x) -> x

_ -> error $ unlines $ map show $ diags r

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

-- instances for Result

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

-- | showing (Parsec) parse errors using our own 'showPos' function

showErr :: ParseError -> String

showErr err

= showPos (fromSourcePos $ errorPos err) ":" ++

showErrorMessages "or" "unknown parse error"

"expecting" "unexpected" "end of input"

(errorMessages err)

instance Show Diagnosis where

showsPrec _ = showPretty

instance PrettyPrint Diagnosis where

printText0 _ (Diag k s sp) =

text "***"

<+> text (show k)

<> (case sp of

[] -> comma

_ -> space <> let

mi = minimumBy comparePos sp

ma = maximumBy comparePos sp

in case comparePos mi ma of

EQ -> text (showPos ma ",")

_ -> text $ showPos mi "-"

++ showPos ma {sourceName = ""} "," )

<+> text s

instance PosItem Diagnosis where

get_pos d = diagPos d

instance PrettyPrint a => PrettyPrint (Result a) where

printText0 g (Result ds m) = vcat ((case m of

Nothing -> empty

Just x -> printText0 g x) :

map (printText0 g) ds)

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

-- debugging

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

-- | add a debug point

debug :: (PosItem a, PrettyPrint a) => Int -> (String, a) -> Result ()

debug n (s, a) = Result [mkDiag Debug

(" point " ++ show n ++ "\nVariable "++s++":\n") a ]

$ Just ()