ParseUtils.hs

-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.ParseUtils
-- Copyright   :  (c) The University of Glasgow 2004
-- 
-- Maintainer  :  libraries@haskell.org
-- Stability   :  alpha
-- Portability :  portable
--
-- Utilities for parsing PackageDescription and InstalledPackageInfo.


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-- This module is meant to be local-only to Distribution...

-- #hide
module Distribution.ParseUtils (
	LineNo, PError(..), showError, myError, runP,
	ParseResult(..),
	StanzaField(..), splitStanzas, Stanza, singleStanza,
	parseFilePathQ, parseTokenQ,
	parseModuleNameQ, parseDependency, parseOptVersion,
	parsePackageNameQ, parseVersionRangeQ,
	parseTestedWithQ, parseLicenseQ, parseExtensionQ, parseCommaList, parseOptCommaList,
	showFilePath, showToken, showTestedWith, showDependency, showFreeText,
	simpleField, listField, commaListField, optsField, 
	parseReadS, parseQuoted,
  ) where

import Text.PrettyPrint.HughesPJ
import Distribution.License
import Distribution.Version
import Distribution.Extension
import Distribution.Package	( parsePackageName )
import Distribution.Compat.ReadP as ReadP hiding (get)
import Distribution.Setup(CompilerFlavor(..))

import Data.Char

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

type LineNo = Int

data PError = AmbigousParse String LineNo
            | NoParse String LineNo
            | FromString String (Maybe LineNo)
        deriving Show

data ParseResult a = ParseFailed PError | ParseOk a
        deriving Show

instance Monad ParseResult where
	return x = ParseOk x
	ParseFailed err >>= _ = ParseFailed err
	ParseOk x >>= f = f x
	fail s = ParseFailed (FromString s Nothing)

runP :: LineNo -> String -> ReadP a a -> String -> ParseResult a
runP lineNo field p s =
  case [ x | (x,"") <- results ] of
    [a] -> ParseOk a
    []  -> case [ x | (x,ys) <- results, all isSpace ys ] of
             [a] -> ParseOk a
             []  -> ParseFailed (NoParse field lineNo)
             _   -> ParseFailed (AmbigousParse field lineNo)
    _   -> ParseFailed (AmbigousParse field lineNo)
  where results = readP_to_S p s

showError :: PError -> String
showError (AmbigousParse f n)     = "Line "++show n++": Ambigous parse in field '"++f++"'"
showError (NoParse f n)           = "Line "++show n++": Parse of field '"++f++"' failed"
showError (FromString s (Just n)) = "Line "++show n++": " ++ s
showError (FromString s Nothing)  = s

myError :: LineNo -> String -> ParseResult a
myError n s = ParseFailed $ FromString s (Just n)

data StanzaField a 
  = StanzaField 
      { fieldName     :: String
      , fieldGet      :: a -> Doc
      , fieldSet      :: LineNo -> String -> a -> ParseResult a
      }

simpleField :: String -> (a -> Doc) -> (ReadP a a) -> (b -> a) -> (a -> b -> b) -> StanzaField b
simpleField name showF readF get set = StanzaField name
   (\st -> showF (get st))
   (\lineNo val st -> do
       x <- runP lineNo name readF val
       return (set x st))

commaListField :: String -> (a -> Doc) -> (ReadP [a] a) -> (b -> [a]) -> ([a] -> b -> b) -> StanzaField b
commaListField name showF readF get set = StanzaField name
   (\st -> fsep (punctuate comma (map showF (get st))))
   (\lineNo val st -> do
       xs <- runP lineNo name (parseCommaList readF) val
       return (set xs st))

listField :: String -> (a -> Doc) -> (ReadP [a] a) -> (b -> [a]) -> ([a] -> b -> b) -> StanzaField b
listField name showF readF get set = StanzaField name
   (\st -> fsep (map showF (get st)))
   (\lineNo val st -> do
       xs <- runP lineNo name (parseOptCommaList readF) val
       return (set xs st))

optsField :: String -> CompilerFlavor -> (b -> [(CompilerFlavor,[String])]) -> ([(CompilerFlavor,[String])] -> b -> b) -> StanzaField b
optsField name flavor get set = StanzaField name
   (\st -> case lookup flavor (get st) of
        Just args -> hsep (map text args)
        Nothing   -> empty)
   (\_ val st -> 
       let
         old_val  = get st
         old_args = case lookup flavor old_val of
                       Just args -> args
                       Nothing   -> []
         val'     = filter (\(f,_) -> f/=flavor) old_val
       in return (set ((flavor,words val++old_args) : val') st))

type Stanza = [(LineNo,String,String)]

-- |Split a string into blank line-separated stanzas of
-- "Field: value" groups
splitStanzas :: String -> ParseResult [Stanza]
splitStanzas = mapM mkStanza . map merge . groupStanzas . filter validLine . zip [1..] . lines
  where validLine (_,s) = case dropWhile isSpace s of
                            '-':'-':_ -> False      -- Comment
                            _         -> True
        groupStanzas :: [(Int,String)] -> [[(Int,String)]]
        groupStanzas [] = []
        groupStanzas xs = let (ys,zs) = break allSpaces xs
                           in ys : groupStanzas (dropWhile allSpaces zs)

allSpaces :: (a, String) -> Bool
allSpaces (_,xs) = all isSpace xs

-- |Split a file into "Field: value" groups, but blank lines have no
-- significance, unlike 'splitStanzas'.  A field value may span over blank
-- lines.
singleStanza :: String -> ParseResult Stanza
singleStanza = mkStanza . merge . filter validLine . zip [1..] . lines
  where validLine (_,s) = case dropWhile isSpace s of
                            '-':'-':_ -> False      -- Comment
                            []        -> False      -- blank line
                            _         -> True

merge :: [(a, [Char])] -> [(a, [Char])]
merge ((n,x):(_,c:s):ys) 
  | c == ' ' || c == '\t' = case dropWhile isSpace s of
                               ('.':s') -> merge ((n,x++"\n"++s'):ys)
                               s'       -> merge ((n,x++"\n"++s'):ys)
merge ((n,x):ys) = (n,x) : merge ys
merge []         = []

mkStanza :: [(Int,String)] -> ParseResult Stanza
mkStanza []          = return []
mkStanza ((n,xs):ys) =
  case break (==':') xs of
    (fld', ':':val) -> do
       let fld = map toLower fld'
       ss <- mkStanza ys
       checkDuplField fld ss
       return ((n, fld, dropWhile isSpace val):ss)
    (_, _)       -> fail $ "Line "++show n++": Invalid syntax (no colon after field name)"
  where
    checkDuplField _ [] = return ()
    checkDuplField fld ((n',fld',_):xs')
      | fld' == fld = fail ("The field "++fld++" is defined on both line "++show n++" and "++show n')
      | otherwise   = checkDuplField fld xs'

-- |parse a module name
parseModuleNameQ :: ReadP r String
parseModuleNameQ = parseQuoted modu <++ modu
 where modu = do 
	  c <- satisfy isUpper
	  cs <- munch (\x -> isAlphaNum x || x `elem` "_'.")
	  return (c:cs)

parseFilePathQ :: ReadP r FilePath
parseFilePathQ = parseTokenQ

parseReadS :: Read a => ReadP r a
parseReadS = readS_to_P reads

parseDependency :: ReadP r Dependency
parseDependency = do name <- parsePackageNameQ
                     skipSpaces
                     ver <- parseVersionRangeQ <++ return AnyVersion
                     skipSpaces
                     return $ Dependency name ver

parsePackageNameQ :: ReadP r String
parsePackageNameQ = parseQuoted parsePackageName <++ parsePackageName 

parseVersionRangeQ :: ReadP r VersionRange
parseVersionRangeQ = parseQuoted parseVersionRange <++ parseVersionRange

parseOptVersion :: ReadP r Version
parseOptVersion = parseQuoted ver <++ ver
  where ver = parseVersion <++ return noVersion
	noVersion = Version{ versionBranch=[], versionTags=[] }

parseTestedWithQ :: ReadP r (CompilerFlavor,VersionRange)
parseTestedWithQ = parseQuoted tw <++ tw
  where tw = do compiler <- parseReadS
		skipSpaces
		version <- parseVersionRange <++ return AnyVersion
		skipSpaces
		return (compiler,version)

parseLicenseQ :: ReadP r License
parseLicenseQ = parseQuoted parseReadS <++ parseReadS

-- urgh, we can't define optQuotes :: ReadP r a -> ReadP r a
-- because the "compat" version of ReadP isn't quite powerful enough.  In
-- particular, the type of <++ is ReadP r r -> ReadP r a -> ReadP r a
-- Hence the trick above to make 'lic' polymorphic.

parseExtensionQ :: ReadP r Extension
parseExtensionQ = parseQuoted parseReadS <++ parseReadS

parseTokenQ :: ReadP r String
parseTokenQ = parseReadS <++ munch1 (\x -> not (isSpace x) && x /= ',')

parseCommaList :: ReadP r a -- ^The parser for the stuff between commas
               -> ReadP r [a]
parseCommaList p = sepBy p separator
    where separator = skipSpaces >> ReadP.char ',' >> skipSpaces

parseOptCommaList :: ReadP r a -- ^The parser for the stuff between commas
               -> ReadP r [a]
parseOptCommaList p = sepBy p separator
    where separator = skipSpaces >> optional (ReadP.char ',') >> skipSpaces

parseQuoted :: ReadP r a -> ReadP r a
parseQuoted p = between (ReadP.char '"') (ReadP.char '"') p

-- --------------------------------------------
-- ** Pretty printing

showFilePath :: FilePath -> Doc
showFilePath = showToken

showToken :: String -> Doc
showToken str
 | not (any dodgy str) &&
   not (null str)       = text str
 | otherwise            = text (show str)
  where dodgy c = isSpace c || c == ','

showTestedWith :: (CompilerFlavor,VersionRange) -> Doc
showTestedWith (compiler,version) = text (show compiler ++ " " ++ showVersionRange version)

showDependency :: Dependency -> Doc
showDependency (Dependency name ver) = text name <+> text (showVersionRange ver)

-- | Pretty-print free-format text, ensuring that it is vertically aligned,
-- and with blank lines replaced by dots for correct re-parsing.
showFreeText :: String -> Doc
showFreeText s = vcat [text (if null l then "." else l) | l <- lines s]