--
-- Copyright (c) 2005 Don Stewart - http://www.cse.unsw.edu.au/~dons
--
-- 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 of
-- the License, 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; if not, write to the Free Software
-- Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
-- 02111-1307, USA.
--

-- | String manipulation utilities
--

module Yi.String (chomp,split) where

import Data.List    (isSuffixOf,isPrefixOf)

-- | Remove any trailing strings matching /irs/ (input record separator)
-- from input string. Like perl's chomp(1).
--
chomp :: String -> String -> String
chomp irs st
    | irs `isSuffixOf` st
    = let st' = reverse $ drop (length irs) (reverse st) in chomp irs st'
    | otherwise = st
{-# INLINE chomp #-}

--
-- | Split a list into pieces that were held together by glue.  Example:
--
-- > split ", " "one, two, three" ===> ["one","two","three"]
--
split :: Eq a => [a] -- ^ Glue that holds pieces together
      -> [a]         -- ^ List to break into pieces
      -> [[a]]       -- ^ Result: list of pieces

split glue xs = split' xs
    where
    split' [] = []
    split' xs' = piece : split' (dropGlue rest)
        where (piece, rest) = breakOnGlue glue xs'
    dropGlue = drop (length glue)
{-# INLINE split #-}

--
-- | Break off the first piece of a list held together by glue,
--   leaving the glue attached to the remainder of the list.  Example:
--   Like break, but works with a [a] match.
--
-- > breakOnGlue ", " "one, two, three" ===> ("one", ", two, three")
--
breakOnGlue :: (Eq a) => [a] -- ^ Glue that holds pieces together
            -> [a]           -- ^ List from which to break off a piece
            -> ([a],[a])     -- ^ Result: (first piece, glue ++ rest of list)
breakOnGlue _ [] = ([],[])
breakOnGlue glue rest@(x:xs)
    | glue `isPrefixOf` rest = ([], rest)
    | otherwise = (x:piece, rest')
        where (piece, rest') = breakOnGlue glue xs
{-# INLINE breakOnGlue #-}