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 { full_stories :: Bool,
  44          output :: FilePath,
  45          article :: String }
  46   deriving   (Show, Data, Typeable)
  47
  48
  49 description :: String
  50 description = "Convert LWN articles to EPUB format."
  51
  52 program_name :: String
  53 program_name = "lwn-epub"
  54
  55 lwn_epub_summary :: String
  56 lwn_epub_summary =
  57   program_name ++ "-" ++ (showVersion version)
  58
  59 output_help :: String
  60 output_help = "Output file, defaults to stdout"
  61
  62 full_stories_help :: String
  63 full_stories_help = "Replace \"Full Story\" links with their content"
  64
  65 arg_spec :: Mode (CmdArgs Args)
  66 arg_spec = cmdArgsMode $
  67              Args {
  68                full_stories = def &= help full_stories_help,
  69                output       = def &= typFile  &= help output_help,
  70                article      = def &= argPos 0 &= typ "ARTICLE"
  71              }
  72              &= program program_name
  73              &= summary lwn_epub_summary
  74              &= details [description]
  75
  76
  77 -- Infix notation won't work, the arguments are backwards!
  78 is_missing_arg_error :: String -> Bool
  79 is_missing_arg_error s =
  80   startswith "Requires at least" s
  81
  82
  83 show_help :: IO (CmdArgs Args)
  84 show_help = withArgs ["--help"] parse_args
  85
  86 parse_args :: IO (CmdArgs Args)
  87 parse_args = do
  88   x <- getArgs
  89   let y = process arg_spec x
  90   case y of
  91       Right result -> return result
  92       Left err ->
  93         if (is_missing_arg_error err) then
  94           -- Disregard the error message, show help instead.
  95           show_help
  96         else do
  97           hPutStrLn stderr err
  98           exitWith (ExitFailure exit_args_parse_failed)
  99
 100
 101 -- | Really get the command-line arguments. This calls 'parse_args'
 102 --   first to replace the default "wrong number of arguments" error,
 103 --   and then runs 'cmdArgsApply' on the result to do what the
 104 --   'cmdArgs' function usually does.
 105 apply_args :: IO Args
 106 apply_args =
 107   parse_args >>= cmdArgsApply