    {- arch-tag: Parser for Debian control file
    Copyright (c) 2004-2011 John Goerzen <jgoerzen@complete.org>

    All rights reserved.

    For license and copyright information, see the file LICENSE
    -}

    {- |
       Module     : System.Debian.ControlParser
       Copyright  : Copyright (C) 2004-2011 John Goerzen
       License    : BSD3

       Maintainer : John Goerzen <jgoerzen@complete.org>
       Stability  : provisional
       Portability: portable

    This module provides various helpful utilities for dealing with Debian
    files and programs.

    Written by John Goerzen, jgoerzen\@complete.org
    -}

    module System.Debian.ControlParser(control, depPart)
        where

    import Text.ParserCombinators.Parsec
    import Data.String.Utils (split)

    eol, extline :: GenParser Char st String
    eol = (try (string "\r\n"))
          <|> string "\n" <?> "EOL"

    extline = try (do char ' '
                      content <- many (noneOf "\r\n")
                      eol
                      return content )

    entry :: GenParser Char st (String, String)
    entry = do key <- many1 (noneOf ":\r\n")
               char ':'
               val <- many (noneOf "\r\n")
               eol
               exts <- many extline
               return (key, unlines ([val] ++ exts))

    {- | Main parser for the control file -}
    control :: CharParser a [(String, String)]
    control = do many header
                 retval <- many entry
                 return retval

    headerPGP, blankLine, header, headerHash :: GenParser Char st ()
    headerPGP = do string "-----BEGIN PGP"
                   manyTill (noneOf "\r\n") eol
                   return ()
    blankLine = do many (oneOf " \t")
                   eol
                   return ()
    headerHash = do string "Hash: "
                    manyTill (noneOf "\r\n") eol
                    return ()
    header = (try headerPGP) <|> (try blankLine) <|> (try headerHash)

    {- | Dependency parser.

    Returns (package name, Maybe version, arch list)

    version is (operator, operand) -}
    depPart :: CharParser a (String, (Maybe (String, String)), [String])
    depPart = do packagename <- many1 (noneOf " (")
                 many (char ' ')
                 version <- (do char '('
                                op <- many1 (oneOf "<>=")
                                many (char ' ')
                                vers <- many1 (noneOf ") ")
                                many (char ' ')
                                char ')'
                                return $ Just (op, vers)
                            ) <|> return Nothing
                 many (char ' ')
                 archs <- (do char '['
                              t <- many1 (noneOf "]")
                              many (char ' ')
                              char ']'
                              return (split " " t)
                          ) <|> return []
                 return (packagename, version, archs)