BoyerMoore.hs

--
-- Copyright (c) 2013 Bonelli Nicola <bonelli@antifork.org>
--
-- 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.
--


module CGrep.Strategy.BoyerMoore (search) where

import qualified Data.ByteString.Char8  as C
import qualified Data.ByteString.Search as SC

import Data.List

import CGrep.Common
import CGrep.Output
import CGrep.Filter
import CGrep.Lang
import CGrep.Types

import qualified CGrep.Token as T

import Options
import Debug

import Control.Arrow as A

search :: CgrepFunction
search opt ps f = do

    let filename = getFileName f

    text <- getText f

    -- transform text

    let text' = expandMultiline opt . ignoreCase opt $ text

    -- quick search...

    let found = quickSearch opt ps text'

    -- put banners...

    putStrLevel1 (debug opt) $ "strategy  : running string search on " ++ filename ++ "..."

    if maybe False not found
        then return $ mkOutput opt filename text []
        else do

            let text'' = contextFilter (getLang opt filename) (mkContextFilter opt) text

            -- search for matching tokens

            let tokens  = map (A.second C.unpack) $ ps >>= (\p -> map (\i -> (i,p)) (p `SC.nonOverlappingIndices` text''))

            -- filter exact matching tokens

            let tokens' = if word_match opt || prefix_match opt || suffix_match opt
                            then filter (checkToken opt text'') tokens
                            else tokens

            putStrLevel2 (debug opt) $ "tokens    : " ++ show tokens
            putStrLevel2 (debug opt) $ "tokens'   : " ++ show tokens'
            putStrLevel3 (debug opt) $ "---\n" ++ C.unpack text'' ++ "\n---"

            return $ mkOutput opt filename text tokens'


checkToken :: Options -> Text8 -> (Offset, String) -> Bool
checkToken opt text (off, str)
     | word_match    opt = (off - off', str) `elem` ts
     | prefix_match  opt = any (\(o,s) -> str `isPrefixOf` s && o + off' == off) ts
     | suffix_match  opt = any (\(o,s) -> str `isSuffixOf` s && o + off' + (length s - length str) == off) ts
     where (text',off') = getLineByOffset off text
           ts           = T.tokenizer text'

checkToken _ _ (_,_)     = undefined


splitLines :: Text8 -> [(Text8,Offset)]
splitLines xs = zip ls off
    where ls  = C.lines xs
          off = scanl (\o l -> 1 + o + C.length l) 0 ls


getLineByOffset :: Offset -> Text8 -> (Text8, Offset)
getLineByOffset off xs = last $ takeWhile (\(_,o) -> o <= off) sl
        where sl = splitLines xs