src/CommandLine.hs

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