src/Main.hs

   1 {-# LANGUAGE ScopedTypeVariables, RecordWildCards #-}
   2 module Main
   3 where
   4
   5 import Prelude hiding (readFile)
   6 import System.Directory(doesFileExist)
   7 import System.IO (
   8   Handle,
   9   IOMode (WriteMode),
  10   openBinaryFile,
  11   stdout
  12   )
  13 import System.IO.UTF8 (readFile)
  14 import Text.XML.HXT.Core
  15
  16 import CommandLine (Args(..), apply_args, show_help)
  17 import LWN.Page
  18
  19
  20 my_read_opts :: SysConfigList
  21 my_read_opts = [ withValidate  no,
  22                  withParseHTML yes,
  23                  withWarnings no ]
  24
  25 -- | My version of HandsomeSoup's parseHTML.
  26 my_read :: String -> IOStateArrow s b XmlTree
  27 my_read = readString my_read_opts
  28
  29 -- | Try to parse the given article using HXT. We try a few different
  30 --   methods; if none of them work, we return 'Nothing'.
  31 get_xml_from_article :: String -> IO (Maybe (IOStateArrow s b XmlTree))
  32 get_xml_from_article s = do
  33   article <- real_article_path s
  34   is_file <- doesFileExist article
  35   case is_file of
  36     True -> do
  37       contents <- readFile article
  38       return $ Just $ my_read contents
  39     False -> do
  40       -- Download the URL and try to parse it.
  41       return Nothing
  42
  43 -- | If we're given an empty path, return a handle to
  44 --   'stdout'. Otherwise, open the given file and return a read/write
  45 --   handle to that.
  46 get_output_handle :: FilePath -> IO Handle
  47 get_output_handle path =
  48   if (null path) then
  49     return stdout
  50   else
  51     openBinaryFile path WriteMode
  52
  53
  54 -- | Convert the given article to either a URL or a filesystem
  55 --   path. If the given article exists on the filesystem, we assume
  56 --   it's a file. Otherwise, we check to see if it's a URL. Failing
  57 --   that, we try to construct a URL from what we're given and do our
  58 --   best.
  59 real_article_path :: String -> IO String
  60 real_article_path = return . id
  61
  62 main :: IO ()
  63 main = do
  64   Args{..} <- apply_args
  65   output_handle <- get_output_handle output
  66   maybe_html <- get_xml_from_article article
  67
  68   case maybe_html of
  69
  70     Just html -> do
  71       result <- parse html
  72       case result of
  73         Just stuff  -> epublish stuff output_handle
  74         Nothing     -> return ()
  75
  76     Nothing -> do
  77       _ <- show_help
  78       return ()
  79
  80   putStrLn "Done."