-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.ParseUtils
-- Copyright   :  (c) The University of Glasgow 2004
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- Utilities for parsing 'PackageDescription' and 'InstalledPackageInfo'.
--
-- The @.cabal@ file format is not trivial, especially with the introduction
-- of configurations and the section syntax that goes with that. This module
-- has a bunch of parsing functions that is used by the @.cabal@ parser and a
-- couple others. It has the parsing framework code and also little parsers for
-- many of the formats we get in various @.cabal@ file fields, like module
-- names, comma separated lists etc.

{- 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...

{-# OPTIONS_HADDOCK hide #-}
module Distribution.ParseUtils (
        LineNo, PError(..), PWarning(..), locatedErrorMsg, syntaxError, warning,
        runP, runE, ParseResult(..), catchParseError, parseFail, showPWarning,
        Field(..), fName, lineNo,
        FieldDescr(..), ppField, ppFields, readFields, readFieldsFlat,
        showFields, showSingleNamedField, showSimpleSingleNamedField,
        parseFields, parseFieldsFlat,
        parseFilePathQ, parseTokenQ, parseTokenQ',
        parseModuleNameQ, parseBuildTool, parsePkgconfigDependency,
        parseOptVersion, parsePackageNameQ, parseVersionRangeQ,
        parseTestedWithQ, parseLicenseQ, parseLanguageQ, parseExtensionQ,
        parseSepList, parseCommaList, parseOptCommaList,
        showFilePath, showToken, showTestedWith, showFreeText, parseFreeText,
        field, simpleField, listField, spaceListField, commaListField,
        optsField, liftField, boolField, parseQuoted,

        UnrecFieldParser, warnUnrec, ignoreUnrec,
  ) where

import Distribution.Compiler (CompilerFlavor, parseCompilerFlavorCompat)
import Distribution.License
import Distribution.Version
         ( Version(..), VersionRange, anyVersion )
import Distribution.Package     ( PackageName(..), Dependency(..) )
import Distribution.ModuleName (ModuleName)
import Distribution.Compat.ReadP as ReadP hiding (get)
import Distribution.ReadE
import Distribution.Text
         ( Text(..) )
import Distribution.Simple.Utils
         ( comparing, intercalate, lowercase, normaliseLineEndings )
import Language.Haskell.Extension
         ( Language, Extension )

import Text.PrettyPrint hiding (braces)
import Data.Char (isSpace, toLower, isAlphaNum, isDigit)
import Data.Maybe       (fromMaybe)
import Data.Tree as Tree (Tree(..), flatten)
import qualified Data.Map as Map
import Control.Monad (foldM, ap) 
import Control.Applicative (Applicative(..))
import System.FilePath (normalise)
import Data.List (sortBy)

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

type LineNo = Int

data PError = AmbiguousParse String LineNo
            | NoParse String LineNo
            | TabsError LineNo
            | FromString String (Maybe LineNo)
        deriving (Eq, Show)

data PWarning = PWarning String
              | UTFWarning LineNo String
        deriving (Eq, Show)

showPWarning :: FilePath -> PWarning -> String
showPWarning fpath (PWarning msg) =
  normalise fpath ++ ": " ++ msg
showPWarning fpath (UTFWarning line fname) =
  normalise fpath ++ ":" ++ show line
        ++ ": Invalid UTF-8 text in the '" ++ fname ++ "' field."

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

instance Functor ParseResult where
        fmap _ (ParseFailed err) = ParseFailed err
        fmap f (ParseOk ws x) = ParseOk ws $ f x
        
instance Applicative ParseResult where
        pure = return
        (<*>) = ap
        

instance Monad ParseResult where
        return = ParseOk []
        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 (utf8Warnings line fieldname s) a
    --TODO: what is this double parse thing all about?
    --      Can't we just do the all isSpace test the first time?
    []  -> case [ x | (x,ys) <- results, all isSpace ys ] of
             [a] -> ParseOk (utf8Warnings line fieldname s) a
             []  -> ParseFailed (NoParse fieldname line)
             _   -> ParseFailed (AmbiguousParse fieldname line)
    _   -> ParseFailed (AmbiguousParse fieldname line)
  where results = readP_to_S p s

runE :: LineNo -> String -> ReadE a -> String -> ParseResult a
runE line fieldname p s =
    case runReadE p s of
      Right a -> ParseOk (utf8Warnings line fieldname s) a
      Left  e -> syntaxError line $
        "Parse of field '" ++ fieldname ++ "' failed (" ++ e ++ "): " ++ s

utf8Warnings :: LineNo -> String -> String -> [PWarning]
utf8Warnings line fieldname s =
  take 1 [ UTFWarning n fieldname
         | (n,l) <- zip [line..] (lines s)
         , '\xfffd' `elem` l ]

locatedErrorMsg :: PError -> (Maybe LineNo, String)
locatedErrorMsg (AmbiguousParse 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 [PWarning 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 (showF . get)
        (\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

spaceListField :: String -> (a -> Doc) -> ReadP [a] a
                 -> (b -> [a]) -> ([a] -> b -> b) -> FieldDescr b
spaceListField name showF readF get set =
  liftField get set' $
    field name (fsep . map showF) (parseSpaceList 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 (reorder (update flavor opts (get b))) b) $
        field name (hsep . map text)
                   (sepBy parseTokenQ' (munch1 isSpace))
  where
        update _ opts l | all null opts = l  --empty opts as if no opts
        update f opts [] = [(f,opts)]
        update f opts ((f',opts'):rest)
           | f == f'   = (f, opts' ++ opts) : rest
           | otherwise = (f',opts') : update f opts rest
        reorder = sortBy (comparing fst)

-- TODO: this is a bit smelly hack. It's because we want to parse bool fields
--       liberally but not accept new parses. We cannot do that with ReadP
--       because it does not support warnings. We need a new parser framework!
boolField :: String -> (b -> Bool) -> (Bool -> b -> b) -> FieldDescr b
boolField name get set = liftField get set (FieldDescr name showF readF)
  where
    showF = text . show
    readF line str _
      |  str == "True"  = ParseOk [] True
      |  str == "False" = ParseOk [] False
      | lstr == "true"  = ParseOk [caseWarning] True
      | lstr == "false" = ParseOk [caseWarning] False
      | otherwise       = ParseFailed (NoParse name line)
      where
        lstr = lowercase str
        caseWarning = PWarning $
          "The '" ++ name ++ "' field is case sensitive, use 'True' or 'False'."

ppFields :: [FieldDescr a] -> a -> Doc
ppFields fields x = vcat [ ppField name (getter x)
                         | FieldDescr name getter _ <- fields]

ppField :: String -> Doc -> Doc
ppField name fielddoc = text name <> colon <+> fielddoc

showFields :: [FieldDescr a] -> a -> String
showFields fields = render . ($+$ text "") . ppFields fields

showSingleNamedField :: [FieldDescr a] -> String -> Maybe (a -> String)
showSingleNamedField fields f =
  case [ get | (FieldDescr f' get _) <- fields, f' == f ] of
    []      -> Nothing
    (get:_) -> Just (render . ppField f . get)

showSimpleSingleNamedField :: [FieldDescr a] -> String -> Maybe (a -> String)
showSimpleSingleNamedField fields f =
  case [ get | (FieldDescr f' get _) <- fields, f' == f ] of
    []      -> Nothing
    (get:_) -> Just (renderStyle myStyle . get)
 where myStyle = style { mode = LeftMode }

parseFields :: [FieldDescr a] -> a -> String -> ParseResult a
parseFields fields initial str =
  readFields str >>= accumFields fields initial

parseFieldsFlat :: [FieldDescr a] -> a -> String -> ParseResult a
parseFieldsFlat fields initial str =
  readFieldsFlat str >>= accumFields fields initial

accumFields :: [FieldDescr a] -> a -> [Field] -> ParseResult a
accumFields fields = foldM setField
  where
    fieldMap = Map.fromList
      [ (name, f) | f@(FieldDescr name _ _) <- fields ]
    setField accum (F line name value) = case Map.lookup name fieldMap of
      Just (FieldDescr _ _ set) -> set line value accum
      Nothing -> do
        warning ("Unrecognized field " ++ name ++ " on line " ++ show line)
        return accum
    setField accum f = do
      warning ("Unrecognized stanza on line " ++ show (lineNo f))
      return accum

-- | The type of a function which, given a name-value pair of an
--   unrecognized field, and the current structure being built,
--   decides whether to incorporate the unrecognized field
--   (by returning  Just x, where x is a possibly modified version
--   of the structure being built), or not (by returning Nothing).
type UnrecFieldParser a = (String,String) -> a -> Maybe a

-- | A default unrecognized field parser which simply returns Nothing,
--   i.e. ignores all unrecognized fields, so warnings will be generated.
warnUnrec :: UnrecFieldParser a
warnUnrec _ _ = Nothing

-- | A default unrecognized field parser which silently (i.e. no
--   warnings will be generated) ignores unrecognized fields, by
--   returning the structure being built unmodified.
ignoreUnrec :: UnrecFieldParser a
ignoreUnrec _ = Just

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

-- 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 tokens

  where ls = (lines . normaliseLineEndings) input
        tokens = (concatMap tokeniseLine . trimLines) ls

readFieldsFlat :: String -> ParseResult [Field]
readFieldsFlat input = mapM (mkField 0)
                   =<< mkTree tokens
  where ls = (lines . normaliseLineEndings) input
        tokens = (concatMap tokeniseLineFlat . trimLines) ls

-- 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)

tokeniseLineFlat :: (LineNo, Indent, HasTabs, String) -> [Token]
tokeniseLineFlat (n0, i, t, l)
  | null l'   = []
  | otherwise = [Line n0 i t l']
  where
    l' = trimTrailing (trimLeading l)

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


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 Tree.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 intercalate "\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 ModuleName
parseModuleNameQ = parseQuoted parse <++ parse

parseFilePathQ :: ReadP r FilePath
parseFilePathQ = parseTokenQ
  -- removed until normalise is no longer broken, was:
  --   liftM normalise parseTokenQ

betweenSpaces :: ReadP r a -> ReadP r a
betweenSpaces act = do skipSpaces
                       res <- act
                       skipSpaces
                       return res

parseBuildTool :: ReadP r Dependency
parseBuildTool = do name <- parseBuildToolNameQ
                    ver <- betweenSpaces $
                           parseVersionRangeQ <++ return anyVersion
                    return $ Dependency name ver

parseBuildToolNameQ :: ReadP r PackageName
parseBuildToolNameQ = parseQuoted parseBuildToolName <++ parseBuildToolName

-- like parsePackageName but accepts symbols in components
parseBuildToolName :: ReadP r PackageName
parseBuildToolName = do ns <- sepBy1 component (ReadP.char '-')
                        return (PackageName (intercalate "-" ns))
  where component = do
          cs <- munch1 (\c -> isAlphaNum c || c == '+' || c == '_')
          if all isDigit cs then pfail else return cs

-- 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` "+-._")
                              ver <- betweenSpaces $
                                     parseVersionRangeQ <++ return anyVersion
                              return $ Dependency (PackageName name) ver

parsePackageNameQ :: ReadP r PackageName
parsePackageNameQ = parseQuoted parse <++ parse

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

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

parseTestedWithQ :: ReadP r (CompilerFlavor,VersionRange)
parseTestedWithQ = parseQuoted tw <++ tw
  where
    tw :: ReadP r (CompilerFlavor,VersionRange)
    tw = do compiler <- parseCompilerFlavorCompat
            version <- betweenSpaces $ parse <++ return anyVersion
            return (compiler,version)

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

-- 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.

parseLanguageQ :: ReadP r Language
parseLanguageQ = parseQuoted parse <++ parse

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

parseHaskellString :: ReadP r String
parseHaskellString = readS_to_P reads

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

parseTokenQ' :: ReadP r String
parseTokenQ' = parseHaskellString <++ munch1 (not . isSpace)

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 = betweenSpaces sepr

parseSpaceList :: ReadP r a -- ^The parser for the stuff between commas
               -> ReadP r [a]
parseSpaceList p = sepBy p 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 = between (ReadP.char '"') (ReadP.char '"')

parseFreeText :: ReadP.ReadP s String
parseFreeText = ReadP.munch (const True)

-- --------------------------------------------
-- ** 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) <+> disp version

-- | 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 "" = empty
showFreeText ('\n' :r)  = text " " $+$ text "." $+$ showFreeText r
showFreeText s  = vcat [text (if null l then "." else l) | l <- lines_ s]

-- | 'lines_' breaks a string up into a list of strings at newline
-- characters.  The resulting strings do not contain newlines.
lines_                   :: String -> [String]
lines_ []                =  [""]
lines_ s                 =  let (l, s') = break (== '\n') s
                            in  l : case s' of
                                        []    -> []
                                        (_:s'') -> lines_ s''