FileIO.hs

{-----------------------------------------------------------------
 
  this module contains functions doing actual file IO

  (c) 2008-2009 Markus Dittrich 
 
  This program is free software; you can redistribute it 
  and/or modify it under the terms of the GNU General Public 
  License Version 3 as published by the Free Software Foundation. 
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License Version 3 for more details.
 
  You should have received a copy of the GNU General Public 
  License along with this program; if not, write to the Free 
  Software Foundation, Inc., 59 Temple Place - Suite 330, 
  Boston, MA 02111-1307, USA.

--------------------------------------------------------------------}
 
-- | this module contains file IO functionality
module Helpers.FileIO ( dataBaseDir
                      , filter_dot_dirs
                      , get_file_date
                      , read_file
                      , retrieve_directory_contents
                      , try_read_file
                      ) where


-- imports
import qualified Data.ByteString as B(ByteString, readFile)
import List(sort)
import Prelude
import System.Directory(getDirectoryContents, getModificationTime)
import System.FilePath.Posix((</>))
import System.IO.Error(isPermissionError, isDoesNotExistError, try)
import System.Locale(defaultTimeLocale)
import System.Time(formatCalendarTime, toCalendarTime)


-- local imports
import Helpers.PrettyPrint(Color(..), putColorStrLn)


-- location of database
dataBaseDir :: FilePath
--dataBaseDir = "/home/markus/programming/haskell/hark-data/db"
dataBaseDir = "/var/db/pkg"


-- | try to open the given file and return the content
-- as a Just ByteString if it exists and Nothing otherwise
try_read_file :: FilePath -> IO (Maybe B.ByteString)
try_read_file path = 
  
  try (B.readFile path)
  >>= \content ->
  
    case content of
      Right fileContent -> return (Just fileContent)
      Left _            -> return Nothing



-- | open the given file. If things fail try to detect
-- why and provide the user with some sort of useful error 
-- message (generic one otherwise); then quit 
read_file :: FilePath -> IO B.ByteString
read_file path = 
  
  try (B.readFile path)
  >>= \content ->
  
    case content of
      Right fileContent -> return fileContent
      Left e            -> 
        let 
          reason = analyze_error e
        in 
         (putColorStrLn Red  $ "\n\nERROR:  Cannot parse file\n") 
         >> (putColorStrLn Yellow $ dataBaseDir </> path ++ "\n")
         >> (putColorStrLn Red  $ "Reason: " ++ reason ++ "\n")
         >> (error "... aborting.")

      where
        analyze_error :: IOError -> String
        analyze_error err
          | isPermissionError err   = "Permission denied."
          | isDoesNotExistError err = "File does not exist."
          | otherwise               = "Unknown problem :("



-- | return the modification time of a file as a string of
-- the form mm-dd-yy-hh-mm
get_file_date :: FilePath -> IO String
get_file_date path = 
  
  getModificationTime path
  >>= toCalendarTime
  >>= \calTime ->
    return $ formatCalendarTime defaultTimeLocale "%m/%d/%y %H:%M" 
           calTime



-- | returns a list of the content of dir sans ".." and "."
retrieve_directory_contents :: FilePath -> IO [FilePath]
retrieve_directory_contents dir = 
  
   getDirectoryContents dir 
   >>= \rawPackages -> return (sort $ filter_dot_dirs rawPackages)



-- | filter the .. and . directories from a list of paths
filter_dot_dirs :: [FilePath] -> [FilePath]
filter_dot_dirs = filter (`notElem` [".",".."])