src/CommandLine.hs

   1 {-# LANGUAGE DeriveDataTypeable #-}
   2
   3 module CommandLine (
   4   Args(..),
   5   apply_args,
   6   program_name,
   7   show_help)
   8 where
   9
  10 -- Get the version from Cabal.
  11 import Paths_lwn_epub (version)
  12 import Data.Version (showVersion)
  13
  14 import Data.String.Utils (startswith)
  15 import System.Console.CmdArgs (
  16   CmdArgs,
  17   Data,
  18   Mode,
  19   Typeable,
  20   (&=),
  21   argPos,
  22   cmdArgsApply,
  23   cmdArgsMode,
  24   def,
  25   details,
  26   help,
  27   program,
  28   typ,
  29   typFile,
  30   summary
  31   )
  32
  33 import System.Console.CmdArgs.Explicit (process)
  34 import System.Environment (getArgs, withArgs)
  35 import System.Exit (ExitCode(..), exitWith)
  36 import System.IO (hPutStrLn, stderr)
  37
  38 import ExitCodes
  39
  40
  41
  42 data Args =
  43   Args { output :: FilePath,
  44          article :: String }
  45   deriving   (Show, Data, Typeable)
  46
  47
  48 description :: String
  49 description = "Convert LWN articles to EPUB format."
  50
  51 program_name :: String
  52 program_name = "lwn_epub"
  53
  54 lwn_epub_summary :: String
  55 lwn_epub_summary =
  56   program_name ++ "-" ++ (showVersion version)
  57
  58 output_help :: String
  59 output_help = "Output file, defaults to stdout"
  60
  61 arg_spec :: Mode (CmdArgs Args)
  62 arg_spec = cmdArgsMode $
  63              Args {
  64                output = def  &= typFile &= help output_help,
  65                article = def &= argPos 0 &= typ "ARTICLE"
  66              }
  67              &= program program_name
  68              &= summary lwn_epub_summary
  69              &= details [description]
  70
  71
  72 -- Infix notation won't work, the arguments are backwards!
  73 is_missing_arg_error :: String -> Bool
  74 is_missing_arg_error s =
  75   startswith "Requires at least" s
  76
  77
  78 show_help :: IO (CmdArgs Args)
  79 show_help = withArgs ["--help"] parse_args
  80
  81 parse_args :: IO (CmdArgs Args)
  82 parse_args = do
  83   x <- getArgs
  84   let y = process arg_spec x
  85   case y of
  86       Right result -> return result
  87       Left err ->
  88         if (is_missing_arg_error err) then
  89           -- Disregard the error message, show help instead.
  90           show_help
  91         else do
  92           hPutStrLn stderr err
  93           exitWith (ExitFailure exit_args_parse_failed)
  94
  95
  96 -- | Really get the command-line arguments. This calls 'parse_args'
  97 --   first to replace the default "wrong number of arguments" error,
  98 --   and then runs 'cmdArgsApply' on the result to do what the
  99 --   'cmdArgs' function usually does.
 100 apply_args :: IO Args
 101 apply_args =
 102   parse_args >>= cmdArgsApply