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

    {- All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials provided
          with the distribution.

        * Neither the name of the University nor the names of other
          contributors may be used to endorse or promote products derived
          from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}

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

    -- #hide
    module Distribution.ParseUtils (
            LineNo, PError(..), PWarning, locatedErrorMsg, syntaxError, warning,
    	runP, ParseResult(..), catchParseError, parseFail,
    	Field(..), fName, lineNo,
    	FieldDescr(..), readFields,
    	parseFilePathQ, parseTokenQ,
    	parseModuleNameQ, parseDependency, parsePkgconfigDependency,
            parseOptVersion, parsePackageNameQ, parseVersionRangeQ,
    	parseTestedWithQ, parseLicenseQ, parseExtensionQ,
    	parseSepList, parseCommaList, parseOptCommaList,
    	showFilePath, showToken, showTestedWith, showDependency, showFreeText,
    	field, simpleField, listField, commaListField, optsField, liftField,
    	parseReadS, parseReadSQ, parseQuoted,
      ) where

    import Distribution.Compiler (CompilerFlavor)
    import Distribution.License
    import Distribution.Version
    import Distribution.Package	( parsePackageName )
    import Distribution.Compat.ReadP as ReadP hiding (get)
    import Language.Haskell.Extension (Extension)

    import Text.PrettyPrint.HughesPJ hiding (braces)
    import Data.Char        (isSpace, isUpper, toLower, isAlphaNum)
    import Data.Maybe	( fromMaybe)
    import Data.List        (intersperse)

    #ifdef DEBUG
    import Test.HUnit (Test(..), assertBool, Assertion, runTestTT, Counts, assertEqual)
    import IO
    import System.Environment ( getArgs )
    import Control.Monad ( zipWithM_ )
    #endif

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

    type LineNo = Int

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

    type PWarning = String

    data ParseResult a = ParseFailed PError | ParseOk [PWarning] a
            deriving Show

    instance Monad ParseResult where
    	return x = ParseOk [] x
    	ParseFailed err >>= _ = ParseFailed err
    	ParseOk ws x >>= f = case f x of
    	                       ParseFailed err -> ParseFailed err
    			       ParseOk ws' x' -> ParseOk (ws'++ws) x'
    	fail s = ParseFailed (FromString s Nothing)

    catchParseError :: ParseResult a -> (PError -> ParseResult a)
                    -> ParseResult a
    p@(ParseOk _ _) `catchParseError` _ = p
    ParseFailed e `catchParseError` k   = k e

    parseFail :: PError -> ParseResult a
    parseFail = ParseFailed

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

    locatedErrorMsg :: PError -> (Maybe LineNo, String)
    locatedErrorMsg (AmbigousParse f n) = (Just n, "Ambiguous parse in field '"++f++"'.")
    locatedErrorMsg (NoParse f n)       = (Just n, "Parse of field '"++f++"' failed.")
    locatedErrorMsg (TabsError n)       = (Just n, "Tab used as indentation.")
    locatedErrorMsg (FromString s n)    = (n, s)

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

    tabsError :: LineNo -> ParseResult a
    tabsError ln = ParseFailed $ TabsError ln

    warning :: String -> ParseResult ()
    warning s = ParseOk [s] ()

    -- | Field descriptor.  The parameter @a@ parameterizes over where the field's
    --   value is stored in.
    data FieldDescr a
      = FieldDescr
          { fieldName     :: String
          , fieldGet      :: a -> Doc
          , fieldSet      :: LineNo -> String -> a -> ParseResult a
            -- ^ @fieldSet n str x@ Parses the field value from the given input
            -- string @str@ and stores the result in @x@ if the parse was
            -- successful.  Otherwise, reports an error on line number @n@.
          }

    field :: String -> (a -> Doc) -> (ReadP a a) -> FieldDescr a
    field name showF readF =
      FieldDescr name showF (\line val _st -> runP line name readF val)

    -- Lift a field descriptor storing into an 'a' to a field descriptor storing
    -- into a 'b'.
    liftField :: (b -> a) -> (a -> b -> b) -> FieldDescr a -> FieldDescr b
    liftField get set (FieldDescr name showF parseF)
     = FieldDescr name (\b -> showF (get b))
    	(\line str b -> do
    	    a <- parseF line str (get b)
    	    return (set a b))

    -- Parser combinator for simple fields.  Takes a field name, a pretty printer,
    -- a parser function, an accessor, and a setter, returns a FieldDescr over the
    -- compoid structure.
    simpleField :: String -> (a -> Doc) -> (ReadP a a)
                -> (b -> a) -> (a -> b -> b) -> FieldDescr b
    simpleField name showF readF get set
      = liftField get set $ field name showF readF

    commaListField :: String -> (a -> Doc) -> (ReadP [a] a)
    		 -> (b -> [a]) -> ([a] -> b -> b) -> FieldDescr b
    commaListField name showF readF get set =
      liftField get set' $
        field name (fsep . punctuate comma . map showF) (parseCommaList readF)
      where
        set' xs b = set (get b ++ xs) b

    listField :: String -> (a -> Doc) -> (ReadP [a] a)
    		 -> (b -> [a]) -> ([a] -> b -> b) -> FieldDescr b
    listField name showF readF get set =
      liftField get set' $
        field name (fsep . map showF) (parseOptCommaList readF)
      where
        set' xs b = set (get b ++ xs) b

    optsField :: String -> CompilerFlavor -> (b -> [(CompilerFlavor,[String])]) -> ([(CompilerFlavor,[String])] -> b -> b) -> FieldDescr b
    optsField name flavor get set =
       liftField (fromMaybe [] . lookup flavor . get)
    	     (\opts b -> set (update flavor opts (get b)) b) $
    	field name (hsep . map text)
    		   (sepBy parseTokenQ' (munch1 isSpace))
      where
            update f opts [] = [(f,opts)]
    	update f opts ((f',opts'):rest)
               | f == f'   = (f, opts' ++ opts) : rest
               | otherwise = (f',opts') : update f opts rest

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

    -- The data type for our three syntactic categories
    data Field
        = F LineNo String String
          -- ^ A regular @<property>: <value>@ field
        | Section LineNo String String [Field]
          -- ^ A section with a name and possible parameter.  The syntactic
          -- structure is:
          --
          -- @
          --   <sectionname> <arg> {
          --     <field>*
          --   }
          -- @
        | IfBlock LineNo String [Field] [Field]
          -- ^ A conditional block with an optional else branch:
          --
          -- @
          --  if <condition> {
          --    <field>*
          --  } else {
          --    <field>*
          --  }
          -- @
          deriving (Show
                   ,Eq)   -- for testing

    lineNo :: Field -> LineNo
    lineNo (F n _ _) = n
    lineNo (Section n _ _ _) = n
    lineNo (IfBlock n _ _ _) = n

    fName :: Field -> String
    fName (F _ n _) = n
    fName (Section _ n _ _) = n
    fName _ = error "fname: not a field or section"

    readFields :: String -> ParseResult [Field]
    readFields input =
          ifelse
      =<< mapM (mkField 0)
      =<< mkTree (tokenise input)

      where tokenise = concatMap tokeniseLine
                     . trimLines
                     . lines
                     . normaliseLineEndings
                     -- TODO: should decode UTF8

    -- attach line number and determine indentation
    trimLines :: [String] -> [(LineNo, Indent, HasTabs, String)]
    trimLines ls = [ (lineno, indent, hastabs, (trimTrailing l'))
                   | (lineno, l) <- zip [1..] ls
                   , let (sps, l') = span isSpace l
                         indent    = length sps
                         hastabs   = '\t' `elem` sps
                   , validLine l' ]
      where validLine ('-':'-':_) = False      -- Comment
            validLine []          = False      -- blank line
            validLine _           = True

    -- | We parse generically based on indent level and braces '{' '}'. To do that
    -- we split into lines and then '{' '}' tokens and other spans within a line.
    data Token =
           -- | The 'Line' token is for bits that /start/ a line, eg:
           --
           -- > "\n  blah blah { blah"
           --
           -- tokenises to:
           --
           -- > [Line n 2 False "blah blah", OpenBracket, Span n "blah"]
           --
           -- so lines are the only ones that can have nested layout, since they
           -- have a known indentation level.
           --
           -- eg: we can't have this:
           --
           -- > if ... {
           -- > } else
           -- >     other
           --
           -- because other cannot nest under else, since else doesn't start a line
           -- so cannot have nested layout. It'd have to be:
           --
           -- > if ... {
           -- > }
           -- >   else
           -- >     other
           --
           -- but that's not so common, people would normally use layout or
           -- brackets not both in a single @if else@ construct.
           --
           -- > if ... { foo : bar }
           -- > else
           -- >    other
           --
           -- this is ok
           Line LineNo Indent HasTabs String
         | Span LineNo                String  -- ^ span in a line, following brackets
         | OpenBracket LineNo | CloseBracket LineNo

    type Indent = Int
    type HasTabs = Bool

    -- | Tokenise a single line, splitting on '{' '}' and the spans inbetween.
    -- Also trims leading & trailing space on those spans within the line.
    tokeniseLine :: (LineNo, Indent, HasTabs, String) -> [Token]
    tokeniseLine (n0, i, t, l) = case split n0 l of
                                (Span _ l':ss) -> Line n0 i t l' :ss
                                cs              -> cs
      where split _ "" = []
            split n s  = case span (\c -> c /='}' && c /= '{') s of
              ("", '{' : s') ->             OpenBracket  n : split n s'
              (w , '{' : s') -> mkspan n w (OpenBracket  n : split n s')
              ("", '}' : s') ->             CloseBracket n : split n s'
              (w , '}' : s') -> mkspan n w (CloseBracket n : split n s')
              (w ,        _) -> mkspan n w []

            mkspan n s ss | null s'   =             ss
                          | otherwise = Span n s' : ss
              where s' = trimTrailing (trimLeading s)

    trimLeading, trimTrailing :: String -> String
    trimLeading  = dropWhile isSpace
    trimTrailing = reverse . dropWhile isSpace . reverse

    -- | Fix different systems silly line ending conventions
    normaliseLineEndings :: String -> String
    normaliseLineEndings [] = []
    normaliseLineEndings ('\r':'\n':s) = '\n' : normaliseLineEndings s -- windows
    normaliseLineEndings ('\r':s)      = '\n' : normaliseLineEndings s -- old osx
    normaliseLineEndings (  c :s)      =   c  : normaliseLineEndings s

    type SyntaxTree = Tree (LineNo, HasTabs, String)

    -- | Parse the stream of tokens into a tree of them, based on indent \/ layout
    mkTree :: [Token] -> ParseResult [SyntaxTree]
    mkTree toks =
      layout 0 [] toks >>= \(trees, trailing) -> case trailing of
        []               -> return trees
        OpenBracket  n:_ -> syntaxError n "mismatched backets, unexpected {"
        CloseBracket n:_ -> syntaxError n "mismatched backets, unexpected }"
        -- the following two should never happen:
        Span n     l  :_ -> syntaxError n $ "unexpected span: " ++ show l
        Line n _ _ l  :_ -> syntaxError n $ "unexpected line: " ++ show l

    -- | Parse the stream of tokens into a tree of them, based on indent
    -- This parse state expect to be in a layout context, though possibly
    -- nested within a braces context so we may still encounter closing braces.
    layout :: Indent       -- ^ indent level of the parent\/previous line
           -> [SyntaxTree] -- ^ accumulating param, trees in this level
           -> [Token]      -- ^ remaining tokens
           -> ParseResult ([SyntaxTree], [Token])
                           -- ^ collected trees on this level and trailing tokens
    layout _ a []                               = return (reverse a, [])
    layout i a (s@(Line _ i' _ _):ss) | i' < i  = return (reverse a, s:ss)
    layout i a (Line n _ t l:OpenBracket n':ss) = do
        (sub, ss') <- braces n' [] ss
        layout i (Node (n,t,l) sub:a) ss'

    layout i a (Span n     l:OpenBracket n':ss) = do
        (sub, ss') <- braces n' [] ss
        layout i (Node (n,False,l) sub:a) ss'

    -- look ahead to see if following lines are more indented, giving a sub-tree
    layout i a (Line n i' t l:ss) = do
        lookahead <- layout (i'+1) [] ss
        case lookahead of
            ([], _)   -> layout i (Node (n,t,l) [] :a) ss
            (ts, ss') -> layout i (Node (n,t,l) ts :a) ss'

    layout _ _ (   OpenBracket  n :_)  = syntaxError n $ "unexpected '{'"
    layout _ a (s@(CloseBracket _):ss) = return (reverse a, s:ss)
    layout _ _ (   Span n l       : _) = syntaxError n $ "unexpected span: "
                                                      ++ show l

    -- | Parse the stream of tokens into a tree of them, based on explicit braces
    -- This parse state expects to find a closing bracket.
    braces :: LineNo       -- ^ line of the '{', used for error messages
           -> [SyntaxTree] -- ^ accumulating param, trees in this level
           -> [Token]      -- ^ remaining tokens
           -> ParseResult ([SyntaxTree],[Token])
                           -- ^ collected trees on this level and trailing tokens
    braces m a (Line n _ t l:OpenBracket n':ss) = do
        (sub, ss') <- braces n' [] ss
        braces m (Node (n,t,l) sub:a) ss'

    braces m a (Span n     l:OpenBracket n':ss) = do
        (sub, ss') <- braces n' [] ss
        braces m (Node (n,False,l) sub:a) ss'

    braces m a (Line n i t l:ss) = do
        lookahead <- layout (i+1) [] ss
        case lookahead of
            ([], _)   -> braces m (Node (n,t,l) [] :a) ss
            (ts, ss') -> braces m (Node (n,t,l) ts :a) ss'

    braces m a (Span n       l:ss) = braces m (Node (n,False,l) []:a) ss
    braces _ a (CloseBracket _:ss) = return (reverse a, ss)
    braces n _ []                  = syntaxError n $ "opening brace '{'"
                                  ++ "has no matching closing brace '}'"
    braces _ _ (OpenBracket  n:_)  = syntaxError n "unexpected '{'"

    -- | Convert the parse tree into the Field AST
    -- Also check for dodgy uses of tabs in indentation.
    mkField :: Int -> SyntaxTree -> ParseResult Field
    mkField d (Node (n,t,_) _) | d >= 1 && t = tabsError n
    mkField d (Node (n,_,l) ts) = case span (\c -> isAlphaNum c || c == '-') l of
      ([], _)       -> syntaxError n $ "unrecognised field or section: " ++ show l
      (name, rest)  -> case trimLeading rest of
        (':':rest') -> do let followingLines = concatMap flatten ts
                              tabs = not (null [()| (_,True,_) <- followingLines ])
                          if tabs && d >= 1
                            then tabsError n
                            else return $ F n (map toLower name)
                                              (fieldValue rest' followingLines)
        rest'       -> do ts' <- mapM (mkField (d+1)) ts
                          return (Section n (map toLower name) rest' ts')
        where fieldValue firstLine followingLines =
                let firstLine' = trimLeading firstLine
                    followingLines' = map (\(_,_,s) -> stripDot s) followingLines
                    allLines | null firstLine' =              followingLines'
                             | otherwise       = firstLine' : followingLines'
                 in (concat . intersperse "\n") allLines
              stripDot "." = ""
              stripDot s   = s

    -- | Convert if/then/else 'Section's to 'IfBlock's
    ifelse :: [Field] -> ParseResult [Field]
    ifelse [] = return []
    ifelse (Section n "if"   cond thenpart
           :Section _ "else" as   elsepart:fs)
           | null cond     = syntaxError n "'if' with missing condition"
           | null thenpart = syntaxError n "'then' branch of 'if' is empty"
           | not (null as) = syntaxError n "'else' takes no arguments"
           | null elsepart = syntaxError n "'else' branch of 'if' is empty"
           | otherwise     = do tp  <- ifelse thenpart
                                ep  <- ifelse elsepart
                                fs' <- ifelse fs
                                return (IfBlock n cond tp ep:fs')
    ifelse (Section n "if"   cond thenpart:fs)
           | null cond     = syntaxError n "'if' with missing condition"
           | null thenpart = syntaxError n "'then' branch of 'if' is empty"
           | otherwise     = do tp  <- ifelse thenpart
                                fs' <- ifelse fs
                                return (IfBlock n cond tp []:fs')
    ifelse (Section n "else" _ _:_) = syntaxError n "stray 'else' with no preceding 'if'"
    ifelse (Section n s a fs':fs) = do fs''  <- ifelse fs'
                                       fs''' <- ifelse fs
                                       return (Section n s a fs'' : fs''')
    ifelse (f:fs) = do fs' <- ifelse fs
                       return (f : fs')

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

    -- |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
      -- removed until normalise is no longer broken, was:
      --   liftM normalise 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

    -- pkg-config allows versions and other letters in package names,
    -- eg "gtk+-2.0" is a valid pkg-config package _name_.
    -- It then has a package version number like 2.10.13
    parsePkgconfigDependency :: ReadP r Dependency
    parsePkgconfigDependency = do name <- munch1 (\c -> isAlphaNum c || c `elem` "+-._")
                                  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

    -- | Parse something optionally wrapped in quotes.
    parseReadSQ :: Read a => ReadP r a
    parseReadSQ = parseQuoted parseReadS <++ parseReadS

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

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

    parseSepList :: ReadP r b
    	     -> ReadP r a -- ^The parser for the stuff between commas
                 -> ReadP r [a]
    parseSepList sepr p = sepBy p separator
        where separator = skipSpaces >> sepr >> skipSpaces

    parseCommaList :: ReadP r a -- ^The parser for the stuff between commas
                   -> ReadP r [a]
    parseCommaList = parseSepList (ReadP.char ',')

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

    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]

    -- --------------------------------------------
    -- ** Tree bits

    -- Data.Tree was not present in ghc-6.2, and we only need these bits:

    data Tree a = Node a (Forest a)
    type Forest a = [Tree a]

    flatten :: Tree a -> [a]
    flatten t = squish t []
      where squish (Node x ts) xs = x:foldr squish xs ts

    ------------------------------------------------------------------------------
    -- TESTING

    #ifdef DEBUG
    test_readFields = case
                        readFields testFile
                      of
                        ParseOk _ x -> x == expectedResult
                        _ -> False
      where
        testFile = unlines $
              [ "Cabal-version: 3"
              , ""
              , "Description: This is a test file   "
              , "  with a description longer than two lines.  "
              , "if os(windows) {"
              , "  License:  You may not use this software"
              , "    ."
              , "    If you do use this software you will be seeked and destroyed."
              , "}"
              , "if os(linux) {"
              , "  Main-is:  foo1  "
              , "}"
              , ""
              , "if os(vista) {"
              , "  executable RootKit {"
              , "    Main-is: DRMManager.hs"
              , "  }"
              , "} else {"
              , "  executable VistaRemoteAccess {"
              , "    Main-is: VCtrl"
              , "}}"
              , ""
              , "executable Foo-bar {"
              , "  Main-is: Foo.hs"
              , "}"
              ]
        expectedResult =
              [ F 1 "cabal-version" "3"
              , F 3 "description"
                      "This is a test file\nwith a description longer than two lines."
              , IfBlock 5 "os(windows) "
                  [ F 6 "license"
                          "You may not use this software\n\nIf you do use this software you will be seeked and destroyed."
                  ]
                  []
              , IfBlock 10 "os(linux) "
                  [ F 11 "main-is" "foo1" ]
                  [ ]
              , IfBlock 14 "os(vista) "
                  [ Section 15 "executable" "RootKit "
                    [ F 16 "main-is" "DRMManager.hs"]
                  ]
                  [ Section 19 "executable" "VistaRemoteAccess "
                     [F 20 "main-is" "VCtrl"]
                  ]
              , Section 23 "executable" "Foo-bar "
                  [F 24 "main-is" "Foo.hs"]
              ]

    test_readFieldsCompat' = case test_readFieldsCompat of
                               ParseOk _ fs -> mapM_ (putStrLn . show) fs
                               x -> putStrLn $ "Failed: " ++ show x
    test_readFieldsCompat = readFields testPkgDesc
      where
        testPkgDesc = unlines [
            "-- Required",
            "Name: Cabal",
            "Version: 0.1.1.1.1-rain",
            "License: LGPL",
            "License-File: foo",
            "Copyright: Free Text String",
            "Cabal-version: >1.1.1",
            "-- Optional - may be in source?",
            "Author: Happy Haskell Hacker",
            "Homepage: http://www.haskell.org/foo",
            "Package-url: http://www.haskell.org/foo",
            "Synopsis: a nice package!",
            "Description: a really nice package!",
            "Category: tools",
            "buildable: True",
            "CC-OPTIONS: -g -o",
            "LD-OPTIONS: -BStatic -dn",
            "Frameworks: foo",
            "Tested-with: GHC",
            "Stability: Free Text String",
            "Build-Depends: haskell-src, HUnit>=1.0.0-rain",
            "Other-Modules: Distribution.Package, Distribution.Version,",
            "                Distribution.Simple.GHCPackageConfig",
            "Other-files: file1, file2",
            "Extra-Tmp-Files:    file1, file2",
            "C-Sources: not/even/rain.c, such/small/hands",
            "HS-Source-Dirs: src, src2",
            "Exposed-Modules: Distribution.Void, Foo.Bar",
            "Extensions: OverlappingInstances, TypeSynonymInstances",
            "Extra-Libraries: libfoo, bar, bang",
            "Extra-Lib-Dirs: \"/usr/local/libs\"",
            "Include-Dirs: your/slightest, look/will",
            "Includes: /easily/unclose, /me, \"funky, path\\\\name\"",
            "Install-Includes: /easily/unclose, /me, \"funky, path\\\\name\"",
            "GHC-Options: -fTH -fglasgow-exts",
            "Hugs-Options: +TH",
            "Nhc-Options: ",
            "Jhc-Options: ",
            "",
            "-- Next is an executable",
            "Executable: somescript",
            "Main-is: SomeFile.hs",
            "Other-Modules: Foo1, Util, Main",
            "HS-Source-Dir: scripts",
            "Extensions: OverlappingInstances",
            "GHC-Options: ",
            "Hugs-Options: ",
            "Nhc-Options: ",
            "Jhc-Options: "
            ]
    {-
    test' = do h <- openFile "../Cabal.cabal" ReadMode
               s <- hGetContents h
               let r = readFields s
               case r of
                 ParseOk _ fs -> mapM_ (putStrLn . show) fs
                 x -> putStrLn $ "Failed: " ++ show x
               putStrLn "==================="
               mapM_ (putStrLn . show) $
                     merge . zip [1..] . lines $ s
               hClose h
    -}

    -- ghc -DDEBUG --make Distribution/ParseUtils.hs -o test

    main :: IO ()
    main = do
      inputFiles <- getArgs
      ok <- mapM checkResult inputFiles

      zipWithM_ summary inputFiles ok
      putStrLn $ show (length (filter not ok)) ++ " out of " ++ show (length ok) ++ " failed"

      where summary f True  = return ()
            summary f False = putStrLn $ f  ++ " failed :-("

    checkResult :: FilePath -> IO Bool
    checkResult inputFile = do
      file <- readFile inputFile
      case readFields file of
        ParseOk _ result -> do
           hPutStrLn stderr $ inputFile ++ " parses ok :-)"
           return True
        ParseFailed err -> do
           hPutStrLn stderr $ inputFile ++ " parse failed:"
           hPutStrLn stderr $ show err
           return False

    --
    #endif