content: -- This is a version of System.Console.GetOpt which has been hacked to
  -- support long options with a single dash. Since we don't want the annoying
  -- clash with short options that start with the same character as a long
  -- one, we don't allow short options to be given together (e.g. -zxf),
  -- nor do we allow options to be given as any unique prefix.
  
  -----------------------------------------------------------------------------
  -- |
  -- Module      :  System.Console.GetOpt
  -- Copyright   :  (c) Sven Panne 2002-2005
  -- License     :  BSD-style (see the file libraries/base/LICENSE)
  -- 
  -- Maintainer  :  libraries@haskell.org
  -- Stability   :  experimental
  -- Portability :  portable
  --
  -- This library provides facilities for parsing the command-line options
  -- in a standalone program.  It is essentially a Haskell port of the GNU 
  -- @getopt@ library.
  --
  -----------------------------------------------------------------------------
  
  {-
  Sven Panne <Sven.Panne@informatik.uni-muenchen.de> Oct. 1996 (small
  changes Dec. 1997)
  
  Two rather obscure features are missing: The Bash 2.0 non-option hack
  (if you don't already know it, you probably don't want to hear about
  it...) and the recognition of long options with a single dash
  (e.g. '-help' is recognised as '--help', as long as there is no short
  option 'h').
  
  Other differences between GNU's getopt and this implementation:
  
  * To enforce a coherent description of options and arguments, there
    are explanation fields in the option/argument descriptor.
  
  * Error messages are now more informative, but no longer POSIX
    compliant... :-(
  
  And a final Haskell advertisement: The GNU C implementation uses well
  over 1100 lines, we need only 195 here, including a 46 line example! 
  :-)
  -}
  
  --module System.Console.GetOpt (
  module GF.Infra.GetOpt (
     -- * GetOpt
     getOpt, getOpt',
     usageInfo,
     ArgOrder(..),
     OptDescr(..),
     ArgDescr(..),
  
     -- * Examples
  
     -- |To hopefully illuminate the role of the different data structures,
     -- here are the command-line options for a (very simple) compiler,
     -- done in two different ways.
     -- The difference arises because the type of 'getOpt' is
     -- parameterized by the type of values derived from flags.
  
     -- ** Interpreting flags as concrete values
     -- $example1
  
     -- ** Interpreting flags as transformations of an options record
     -- $example2
  ) where
  
  import Prelude -- necessary to get dependencies right
  
  --import Data.List ( isPrefixOf, find )
  
  -- |What to do with options following non-options
  data ArgOrder a
    = RequireOrder                -- ^ no option processing after first non-option
    | Permute                     -- ^ freely intersperse options and non-options
    | ReturnInOrder (String -> a) -- ^ wrap non-options into options
  
  {-|
  Each 'OptDescr' describes a single option.
  
  The arguments to 'Option' are:
  
  * list of short option characters
  
  * list of long option strings (without \"--\")
  
  * argument descriptor
  
  * explanation of option for user
  -}
  data OptDescr a =              -- description of a single options:
     Option [Char]                --    list of short option characters
            [String]              --    list of long option strings (without "--")
            (ArgDescr a)          --    argument descriptor
            String                --    explanation of option for user
  
  -- |Describes whether an option takes an argument or not, and if so
  -- how the argument is injected into a value of type @a@.
  data ArgDescr a
     = NoArg                   a         -- ^   no argument expected
     | ReqArg (String       -> a) String -- ^   option requires argument
     | OptArg (Maybe String -> a) String -- ^   optional argument
  
  data OptKind a                -- kind of cmd line arg (internal use only):
     = Opt       a                --    an option
     | UnreqOpt  String           --    an un-recognized option
     | NonOpt    String           --    a non-option
     | EndOfOpts                  --    end-of-options marker (i.e. "--")
     | OptErr    String           --    something went wrong...
  
  -- | Return a string describing the usage of a command, derived from
  -- the header (first argument) and the options described by the 
  -- second argument.
  usageInfo :: String                    -- header
            -> [OptDescr a]              -- option descriptors
            -> String                    -- nicely formatted decription of options
  usageInfo header optDescr = unlines (header:table)
     where (ss,ls,ds)     = (unzip3 . concatMap fmtOpt) optDescr
           table          = zipWith3 paste (sameLen ss) (sameLen ls) ds
           paste x y z    = "  " ++ x ++ "  " ++ y ++ "  " ++ z
           sameLen xs     = flushLeft ((maximum . map length) xs) xs
           flushLeft n xs = [ take n (x ++ repeat ' ') | x <- xs ]
  
  fmtOpt :: OptDescr a -> [(String,String,String)]
  fmtOpt (Option sos los ad descr) =
     case lines descr of
       []     -> [(sosFmt,losFmt,"")]
       (d:ds) ->  (sosFmt,losFmt,d) : [ ("","",d') | d' <- ds ]
     where sepBy _  []     = ""
           sepBy _  [x]    = x
           sepBy ch (x:xs) = x ++ ch:' ':sepBy ch xs
           sosFmt = sepBy ',' (map (fmtShort ad) sos)
           losFmt = sepBy ',' (map (fmtLong  ad) los)
  
  fmtShort :: ArgDescr a -> Char -> String
  fmtShort (NoArg  _   ) so = "-" ++ [so]
  fmtShort (ReqArg _ ad) so = "-" ++ [so] ++ " " ++ ad
  fmtShort (OptArg _ ad) so = "-" ++ [so] ++ "[" ++ ad ++ "]"
  
  fmtLong :: ArgDescr a -> String -> String
  fmtLong (NoArg  _   ) lo = "--" ++ lo
  fmtLong (ReqArg _ ad) lo = "--" ++ lo ++ "=" ++ ad
  fmtLong (OptArg _ ad) lo = "--" ++ lo ++ "[=" ++ ad ++ "]"
  
  {-|
  Process the command-line, and return the list of values that matched
  (and those that didn\'t). The arguments are:
  
  * The order requirements (see 'ArgOrder')
  
  * The option descriptions (see 'OptDescr')
  
  * The actual command line arguments (presumably got from 
    'System.Environment.getArgs').
  
  'getOpt' returns a triple consisting of the option arguments, a list
  of non-options, and a list of error messages.
  -}
  getOpt :: ArgOrder a                   -- non-option handling
         -> [OptDescr a]                 -- option descriptors
         -> [String]                     -- the command-line arguments
         -> ([a],[String],[String])      -- (options,non-options,error messages)
  getOpt ordering optDescr args = (os,xs,es ++ map errUnrec us)
     where (os,xs,us,es) = getOpt' ordering optDescr args
  
  {-|
  This is almost the same as 'getOpt', but returns a quadruple
  consisting of the option arguments, a list of non-options, a list of
  unrecognized options, and a list of error messages.
  -}
  getOpt' :: ArgOrder a                         -- non-option handling
          -> [OptDescr a]                       -- option descriptors
          -> [String]                           -- the command-line arguments
          -> ([a],[String], [String] ,[String]) -- (options,non-options,unrecognized,error messages)
  getOpt' _        _        []         =  ([],[],[],[])
  getOpt' ordering optDescr (arg:args) = procNextOpt opt ordering
     where procNextOpt (Opt o)      _                 = (o:os,xs,us,es)
           procNextOpt (UnreqOpt u) _                 = (os,xs,u:us,es)
           procNextOpt (NonOpt x)   RequireOrder      = ([],x:rest,[],[])
           procNextOpt (NonOpt x)   Permute           = (os,x:xs,us,es)
           procNextOpt (NonOpt x)   (ReturnInOrder f) = (f x :os, xs,us,es)
           procNextOpt EndOfOpts    RequireOrder      = ([],rest,[],[])
           procNextOpt EndOfOpts    Permute           = ([],rest,[],[])
           procNextOpt EndOfOpts    (ReturnInOrder f) = (map f rest,[],[],[])
           procNextOpt (OptErr e)   _                 = (os,xs,us,e:es)
  
           (opt,rest) = getNext arg args optDescr
           (os,xs,us,es) = getOpt' ordering optDescr rest
  
  -- take a look at the next cmd line arg and decide what to do with it
  getNext :: String -> [String] -> [OptDescr a] -> (OptKind a,[String])
  getNext ('-':'-':[]) rest _        = (EndOfOpts,rest)
  getNext ('-':'-':xs) rest optDescr = longOpt xs rest optDescr
  getNext ('-'    :xs) rest optDescr = longOpt xs rest optDescr
  getNext a            rest _        = (NonOpt a,rest)
  
  -- handle long option
  longOpt :: String -> [String] -> [OptDescr a] -> (OptKind a,[String])
  longOpt ls rs optDescr = long ads arg rs
     where (opt,arg) = break (=='=') ls
           options   = [ o | o@(Option ss xs _ _) <- optDescr
                           , opt `elem` map (:[]) ss || opt `elem` xs ]
           ads       = [ ad | Option _ _ ad _ <- options ]
           optStr    = ("--"++opt)
  
           long (_:_:_)      _        rest     = (errAmbig options optStr,rest)
           long [NoArg  a  ] []       rest     = (Opt a,rest)
           long [NoArg  _  ] ('=':_)  rest     = (errNoArg optStr,rest)
           long [ReqArg _ d] []       []       = (errReq d optStr,[])
           long [ReqArg f _] []       (r:rest) = (Opt (f r),rest)
           long [ReqArg f _] ('=':xs) rest     = (Opt (f xs),rest)
           long [OptArg f _] []       rest     = (Opt (f Nothing),rest)
           long [OptArg f _] ('=':xs) rest     = (Opt (f (Just xs)),rest)
           long _            _        rest     = (UnreqOpt ("--"++ls),rest)
  
  
  -- miscellaneous error formatting
  
  errAmbig :: [OptDescr a] -> String -> OptKind a
  errAmbig ods optStr = OptErr (usageInfo header ods)
     where header = "option `" ++ optStr ++ "' is ambiguous; could be one of:"
  
  errReq :: String -> String -> OptKind a
  errReq d optStr = OptErr ("option `" ++ optStr ++ "' requires an argument " ++ d ++ "\n")
  
  errUnrec :: String -> String
  errUnrec optStr = "unrecognized option `" ++ optStr ++ "'\n"
  
  errNoArg :: String -> OptKind a
  errNoArg optStr = OptErr ("option `" ++ optStr ++ "' doesn't allow an argument\n")
  
  {-
  -----------------------------------------------------------------------------------------
  -- and here a small and hopefully enlightening example:
  
  data Flag = Verbose | Version | Name String | Output String | Arg String   deriving Show
  
  options :: [OptDescr Flag]
  options =
     [Option ['v']     ["verbose"]           (NoArg Verbose)      "verbosely list files",
      Option ['V','?'] ["version","release"] (NoArg Version)      "show version info",
      Option ['o']     ["output"]            (OptArg out "FILE")  "use FILE for dump",
      Option ['n']     ["name"]              (ReqArg Name "USER") "only dump USER's files"]
  
  out :: Maybe String -> Flag
  out Nothing  = Output "stdout"
  out (Just o) = Output o
  
  test :: ArgOrder Flag -> [String] -> String
  test order cmdline = case getOpt order options cmdline of
                          (o,n,[]  ) -> "options=" ++ show o ++ "  args=" ++ show n ++ "\n"
                          (_,_,errs) -> concat errs ++ usageInfo header options
     where header = "Usage: foobar [OPTION...] files..."
  
  -- example runs:
  -- putStr (test RequireOrder ["foo","-v"])
  --    ==> options=[]  args=["foo", "-v"]
  -- putStr (test Permute ["foo","-v"])
  --    ==> options=[Verbose]  args=["foo"]
  -- putStr (test (ReturnInOrder Arg) ["foo","-v"])
  --    ==> options=[Arg "foo", Verbose]  args=[]
  -- putStr (test Permute ["foo","--","-v"])
  --    ==> options=[]  args=["foo", "-v"]
  -- putStr (test Permute ["-?o","--name","bar","--na=baz"])
  --    ==> options=[Version, Output "stdout", Name "bar", Name "baz"]  args=[]
  -- putStr (test Permute ["--ver","foo"])
  --    ==> option `--ver' is ambiguous; could be one of:
  --          -v      --verbose             verbosely list files
  --          -V, -?  --version, --release  show version info   
  --        Usage: foobar [OPTION...] files...
  --          -v        --verbose             verbosely list files  
  --          -V, -?    --version, --release  show version info     
  --          -o[FILE]  --output[=FILE]       use FILE for dump     
  --          -n USER   --name=USER           only dump USER's files
  -----------------------------------------------------------------------------------------
  -}
  
  {- $example1
  
  A simple choice for the type associated with flags is to define a type
  @Flag@ as an algebraic type representing the possible flags and their
  arguments:
  
  >    module Opts1 where
  >    
  >    import System.Console.GetOpt
  >    import Data.Maybe ( fromMaybe )
  >    
  >    data Flag 
  >     = Verbose  | Version 
  >     | Input String | Output String | LibDir String
  >       deriving Show
  >    
  >    options :: [OptDescr Flag]
  >    options =
  >     [ Option ['v']     ["verbose"] (NoArg Verbose)       "chatty output on stderr"
  >     , Option ['V','?'] ["version"] (NoArg Version)       "show version number"
  >     , Option ['o']     ["output"]  (OptArg outp "FILE")  "output FILE"
  >     , Option ['c']     []          (OptArg inp  "FILE")  "input FILE"
  >     , Option ['L']     ["libdir"]  (ReqArg LibDir "DIR") "library directory"
  >     ]
  >    
  >    inp,outp :: Maybe String -> Flag
  >    outp = Output . fromMaybe "stdout"
  >    inp  = Input  . fromMaybe "stdin"
  >    
  >    compilerOpts :: [String] -> IO ([Flag], [String])
  >    compilerOpts argv = 
  >       case getOpt Permute options argv of
  >          (o,n,[]  ) -> return (o,n)
  >          (_,_,errs) -> ioError (userError (concat errs ++ usageInfo header options))
  >      where header = "Usage: ic [OPTION...] files..."
  
  Then the rest of the program will use the constructed list of flags
  to determine it\'s behaviour.
  
  -}
  
  {- $example2
  
  A different approach is to group the option values in a record of type
  @Options@, and have each flag yield a function of type
  @Options -> Options@ transforming this record.
  
  >    module Opts2 where
  >
  >    import System.Console.GetOpt
  >    import Data.Maybe ( fromMaybe )
  >
  >    data Options = Options
  >     { optVerbose     :: Bool
  >     , optShowVersion :: Bool
  >     , optOutput      :: Maybe FilePath
  >     , optInput       :: Maybe FilePath
  >     , optLibDirs     :: [FilePath]
  >     } deriving Show
  >
  >    defaultOptions    = Options
  >     { optVerbose     = False
  >     , optShowVersion = False
  >     , optOutput      = Nothing
  >     , optInput       = Nothing
  >     , optLibDirs     = []
  >     }
  >
  >    options :: [OptDescr (Options -> Options)]
  >    options =
  >     [ Option ['v']     ["verbose"]
  >         (NoArg (\ opts -> opts { optVerbose = True }))
  >         "chatty output on stderr"
  >     , Option ['V','?'] ["version"]
  >         (NoArg (\ opts -> opts { optShowVersion = True }))
  >         "show version number"
  >     , Option ['o']     ["output"]
  >         (OptArg ((\ f opts -> opts { optOutput = Just f }) . fromMaybe "output")
  >                 "FILE")
  >         "output FILE"
  >     , Option ['c']     []
  >         (OptArg ((\ f opts -> opts { optInput = Just f }) . fromMaybe "input")
  >                 "FILE")
  >         "input FILE"
  >     , Option ['L']     ["libdir"]
  >         (ReqArg (\ d opts -> opts { optLibDirs = optLibDirs opts ++ [d] }) "DIR")
  >         "library directory"
  >     ]
  >
  >    compilerOpts :: [String] -> IO (Options, [String])
  >    compilerOpts argv =
  >       case getOpt Permute options argv of
  >          (o,n,[]  ) -> return (foldl (flip id) defaultOptions o, n)
  >          (_,_,errs) -> ioError (userError (concat errs ++ usageInfo header options))
  >      where header = "Usage: ic [OPTION...] files..."
  
  Similarly, each flag could yield a monadic function transforming a record,
  of type @Options -> IO Options@ (or any other monad), allowing option
  processing to perform actions of the chosen monad, e.g. printing help or
  version messages, checking that file arguments exist, etc.
  
  -}
  