FileName.hs

-- Copyright (C) 2002-2003 David Roundy
--
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2, or (at your option)
-- any later version.
--
-- 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 for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program; see the file COPYING.  If not, write to
-- the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
-- Boston, MA 02110-1301, USA.

-- | FileName is an abstract type intended to facilitate the input and output of
-- unicode filenames.
module Darcs.Patch.FileName ( FileName( ),
                              fp2fn, fn2fp,
                              fn2ps, ps2fn,
                              niceps2fn, fn2niceps,
                              break_on_dir, norm_path, own_name, superName,
                              movedirfilename,
                              encode_white, decode_white,
                              (///),
                              breakup
                            ) where

import System.IO
import Data.Char ( isSpace, chr, ord )
import qualified Codec.Binary.UTF8.String as UTF8 ( encode )
import Codec.Binary.UTF8.Generic ( toString )
import Data.Word ( Word8( ) )
import qualified Data.ByteString.Char8 as BC (unpack, pack)
import qualified Data.ByteString       as B  (ByteString, pack)

newtype FileName = FN FilePath deriving ( Eq, Ord )
encode :: [Char] -> [Word8]
encode = UTF8.encode

instance Show FileName where
   showsPrec d (FN fp) = showParen (d > app_prec) $ showString "fp2fn " . showsPrec (app_prec + 1) fp
      where app_prec = 10

{-# INLINE fp2fn #-}
fp2fn :: FilePath -> FileName
fp2fn fp = FN fp

{-# INLINE fn2fp #-}
fn2fp :: FileName -> FilePath
fn2fp (FN fp) = fp

{-# INLINE niceps2fn #-}
niceps2fn :: B.ByteString -> FileName
niceps2fn = FN . decode_white . BC.unpack

{-# INLINE fn2niceps #-}
fn2niceps :: FileName -> B.ByteString
fn2niceps (FN fp) = BC.pack $ encode_white fp

{-# INLINE fn2ps #-}
fn2ps :: FileName -> B.ByteString
fn2ps (FN fp) = B.pack $ encode $ encode_white fp

{-# INLINE ps2fn #-}
ps2fn :: B.ByteString -> FileName
ps2fn ps = FN $ decode_white $ toString ps

-- | 'encode_white' translates whitespace in filenames to a darcs-specific
--   format (backslash followed by numerical representation according to 'ord').
--   Note that backslashes are also escaped since they are used in the encoding.
--
--   > encode_white "hello there" == "hello\32there"
--   > encode_white "hello\there" == "hello\\there"
encode_white :: FilePath -> String
encode_white (c:cs) | isSpace c || c == '\\' =
    '\\' : (show $ ord c) ++ "\\" ++ encode_white cs
encode_white (c:cs) = c : encode_white cs
encode_white [] = []

-- | 'decode_white' interprets the Darcs-specific \"encoded\" filenames
--   produced by 'encode_white'
--
--   > decode_white "hello\32there" == "hello there"
--   > decode_white "hello\\there"  == "hello\there"
--   > decode_white "hello\there"   == error "malformed filename"
decode_white :: String -> FilePath
decode_white ('\\':cs) =
    case break (=='\\') cs of
    (theord, '\\':rest) ->
        chr (read theord) : decode_white rest
    _ -> error "malformed filename"
decode_white (c:cs) = c: decode_white cs
decode_white "" = ""

own_name :: FileName -> FileName
own_name (FN f) = case breakLast '/' f of Nothing -> FN f
                                          Just (_,f') -> FN f'
superName :: FileName -> FileName
superName fn = case norm_path fn of
                FN f -> case breakLast '/' f of
                        Nothing -> FN "."
                        Just (d,_) -> FN d
break_on_dir :: FileName -> Maybe (FileName,FileName)
break_on_dir (FN p) = case breakFirst '/' p of
                      Nothing -> Nothing
                      Just (d,f) | d == "." -> break_on_dir $ FN f
                                 | otherwise -> Just (FN d, FN f)
norm_path :: FileName -> FileName -- remove "./"
norm_path (FN p) = FN $ repath $ drop_dotdot $ breakup p

repath :: [String] -> String
repath [] = ""
repath [f] = f
repath (d:p) = d ++ "/" ++ repath p

drop_dotdot :: [String] -> [String]
drop_dotdot ("":p) = drop_dotdot p
drop_dotdot (".":p) = drop_dotdot p
drop_dotdot ("..":p) = ".." : (drop_dotdot p)
drop_dotdot (_:"..":p) = drop_dotdot p
drop_dotdot (d:p) = case drop_dotdot p of
                    ("..":p') -> p'
                    p' -> d : p'
drop_dotdot [] = []

-- | Split a file path at the slashes
breakup :: String -> [String]
breakup p = case break (=='/') p of
            (d,"") -> [d]
            (d,p') -> d : breakup (tail p')

breakFirst :: Char -> String -> Maybe (String,String)
breakFirst c l = bf [] l
    where bf a (r:rs) | r == c = Just (reverse a,rs)
                      | otherwise = bf (r:a) rs
          bf _ [] = Nothing
breakLast :: Char -> String -> Maybe (String,String)
breakLast c l = case breakFirst c (reverse l) of
                Nothing -> Nothing
                Just (a,b) -> Just (reverse b, reverse a)

(///) :: FileName -> FileName -> FileName
(FN "")///b = norm_path b
a///b = norm_path $ fp2fn $ fn2fp a ++ "/" ++ fn2fp b

movedirfilename :: FileName -> FileName -> FileName -> FileName
movedirfilename old new name =
    if name' == old' then new
                     else if length name' > length old' &&
                             take (length old'+1) name' == old'++"/"
                          then fp2fn ("./"++new'++drop (length old') name')
                          else name
    where old' = fn2fp $ norm_path old
          new' = fn2fp $ norm_path new
          name' = fn2fp $ norm_path name