--  Copyright (C) 2004-2005 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.

{-# LANGUAGE CPP, ScopedTypeVariables, MultiParamTypeClasses, FlexibleInstances, Rank2Types #-}

#include "gadts.h"

-- | /First matcher, Second matcher and Nonrange matcher/
--
-- When we match for patches, we have a PatchSet, of which we want a
-- subset. This subset is formed by the patches in a given interval
-- which match a given criterion. If we represent time going left to
-- right, then we have (up to) three 'Matcher's:
--
-- * the 'firstMatcher' is the left bound of the interval,
--
-- * the 'secondMatcher' is the right bound, and
--
-- * the 'nonrangeMatcher' is the criterion we use to select among
--   patches in the interval.
---
-- Each of these matchers can be present or not according to the
-- options. The patches we want would then be the ones that all
-- present matchers have in common.
--
-- (Implementation note: keep in mind that the PatchSet is written
-- backwards with respect to the timeline, ie., from right to left)
module Darcs.Match ( matchFirstPatchset, matchSecondPatchset,
               matchPatch,
               matchAPatch, matchAPatchread,
               getFirstMatch, getNonrangeMatch, getNonrangeMatchS,
               getPartialFirstMatch, getPartialSecondMatch,
               getPartialNonrangeMatch,
               firstMatch, secondMatch, haveNonrangeMatch,
               havePatchsetMatch, getOnePatchset,
               checkMatchSyntax, applyInvToMatcher, nonrangeMatcher,
               InclusiveOrExclusive(..), matchExists, applyNInv, hasIndexRange
             ) where

import Text.Regex ( mkRegex, matchRegex )
import Control.Monad ( when )
import Data.Maybe ( isJust )
import Data.List ( isPrefixOf )

import Darcs.MonadProgress ( MonadProgress )
import Darcs.Patch.PatchInfoAnd ( PatchInfoAnd, info, piap,
                         conscientiously, hopefully )
import Darcs.Patch.Info ( justName )
import Darcs.Patch ( RepoPatch, Patchy, Named, invert, invertRL, patch2patchinfo, apply )
import Darcs.Patch.Dummy ( DummyPatch )
import Darcs.Repository ( Repository, readRepo, createPristineDirectoryTree )
import Darcs.Patch.Set ( PatchSet(..), Tagged(..), SealedPatchSet, newset2RL )
import Darcs.Patch.Apply( ApplyState )
#ifdef GADT_WITNESSES
import Darcs.Patch.Set ( Origin )
#endif
import Darcs.Repository.ApplyPatches ( applyPatches )
import Darcs.Patch.Depends ( getPatchesBeyondTag )
import Darcs.Witnesses.Ordered ( RL(..), consRLSealed )

import ByteStringUtils ( mmapFilePS )

import Darcs.Flags ( DarcsFlag( OnePatch, SeveralPatch, Context,
                               AfterPatch, UpToPatch, LastN, PatchIndexRange,
                               OneTag, AfterTag, UpToTag,
                               OnePattern, SeveralPattern,
                               AfterPattern, UpToPattern ) )
import Darcs.Patch.Bundle ( scanContext )
import Darcs.Patch.Match ( Matcher, MatchFun, matchPattern, applyMatcher, makeMatcher, parseMatch )
import Darcs.Patch.MatchData ( PatchMatch )
import Printer ( text, ($$) )

import Darcs.RepoPath ( toFilePath )
import Darcs.Patch.ApplyMonad ( ApplyMonad(..) )
import Darcs.Patch.FileName ( FileName )
import Darcs.Witnesses.Sealed ( FlippedSeal(..), Sealed2(..),
                      seal, flipSeal, seal2, unsealFlipped, unseal2, unseal )
import Storage.Hashed.Tree ( Tree )
#include "impossible.h"

data InclusiveOrExclusive = Inclusive | Exclusive deriving Eq

-- | @haveNonrangeMatch flags@ tells whether there is a flag in
-- @flags@ which corresponds to a match that is "non-range". Thus,
-- @--match@, @--patch@ and @--index@ make @haveNonrangeMatch@
-- true, but not @--from-patch@ or @--to-patch@.
haveNonrangeMatch :: [DarcsFlag] -> Bool
haveNonrangeMatch fs = isJust (hasIndexRange fs) || isJust (nonrangeMatcher fs::Maybe (Matcher DummyPatch))

-- | @havePatchsetMatch flags@ tells whether there is a "patchset
-- match" in the flag list. A patchset match is @--match@ or
-- @--patch@, or @--context@, but not @--from-patch@ nor (!)
-- @--index@.
-- Question: Is it supposed not to be a subset of @haveNonrangeMatch@?
havePatchsetMatch :: [DarcsFlag] -> Bool
havePatchsetMatch fs = isJust (nonrangeMatcher fs::Maybe (Matcher DummyPatch)) || hasC fs
    where hasC [] = False
          hasC (Context _:_) = True
          hasC (_:xs) = hasC xs

getNonrangeMatch :: (ApplyMonad IO (ApplyState p), RepoPatch p, ApplyState p ~ Tree)
                 => Repository p C(r u t) -> [DarcsFlag] -> IO ()
getNonrangeMatch r fs = withRecordedMatch r (getNonrangeMatchS fs)

getPartialNonrangeMatch :: (RepoPatch p, ApplyMonad IO (ApplyState p), ApplyState p ~ Tree)
                        => Repository p C(r u t)
                           -> [DarcsFlag] -> [FileName] -> IO ()
getPartialNonrangeMatch r fs _ =
    withRecordedMatch r (getNonrangeMatchS fs)

getNonrangeMatchS :: (ApplyMonad m (ApplyState p), MonadProgress m, RepoPatch p, ApplyState p ~ Tree) =>
                        [DarcsFlag] -> PatchSet p C(Origin x) -> m ()
getNonrangeMatchS fs repo =
    case nonrangeMatcher fs of
        Just m -> if nonrangeMatcherIsTag fs
                        then getTagS m repo
                        else getMatcherS Exclusive m repo
        Nothing -> fail "Pattern not specified in getNonrangeMatch."

-- | @firstMatch fs@ tells whether @fs@ implies a "first match", that
-- is if we match against patches from a point in the past on, rather
-- than against all patches since the creation of the repository.
firstMatch :: [DarcsFlag] -> Bool
firstMatch fs = isJust (hasLastn fs)
                 || isJust (firstMatcher fs::Maybe (Matcher DummyPatch))
                 || isJust (hasIndexRange fs)

getFirstMatch :: (ApplyMonad IO (ApplyState p), RepoPatch p, ApplyState p ~ Tree)
              => Repository p C(r u t) -> [DarcsFlag] -> IO ()
getFirstMatch r fs = withRecordedMatch r (getFirstMatchS fs)

getPartialFirstMatch :: (RepoPatch p, ApplyMonad IO (ApplyState p), ApplyState p ~ Tree)
                     => Repository p C(r u t)
                        -> [DarcsFlag] -> Maybe [FileName] -> IO ()
getPartialFirstMatch r fs _ =
    withRecordedMatch r (getFirstMatchS fs)

getFirstMatchS :: (ApplyMonad m (ApplyState p), MonadProgress m, RepoPatch p) =>
                     [DarcsFlag] -> PatchSet p C(Origin x) -> m ()
getFirstMatchS fs repo =
    case hasLastn fs of
    Just n -> unpullLastN repo n
    Nothing ->
     case hasIndexRange fs of
     Just (_,b) -> unpullLastN repo b -- b is chronologically earlier than a
     Nothing    ->
      case firstMatcher fs of
               Nothing -> fail "Pattern not specified in getFirstMatch."
               Just m -> if firstMatcherIsTag fs
                         then getTagS m repo
                         else getMatcherS Inclusive m repo

-- | @secondMatch fs@ tells whether @fs@ implies a "second match", that
-- is if we match against patches up to a point in the past on, rather
-- than against all patches until now.
secondMatch :: [DarcsFlag] -> Bool
secondMatch fs = isJust (secondMatcher fs::Maybe (Matcher DummyPatch)) || isJust (hasIndexRange fs)

getPartialSecondMatch :: (RepoPatch p, ApplyMonad IO (ApplyState p), ApplyState p ~ Tree)
                      => Repository p C(r u t)
                        -> [DarcsFlag] -> Maybe [FileName] -> IO ()
getPartialSecondMatch r fs _ =
    withRecordedMatch r $ \repo ->
    case secondMatcher fs of
    Nothing -> case hasIndexRange fs of
                Just (a,_) -> unpullLastN repo (a-1)
                Nothing    -> fail "Two patterns not specified in get_second_match."
    Just m -> if secondMatcherIsTag fs
              then getTagS m repo
              else getMatcherS Exclusive m repo

unpullLastN :: (ApplyMonad m (ApplyState p), MonadProgress m, Patchy p) => PatchSet p C(x y) -> Int -> m ()
unpullLastN repo n = applyInvRL `unsealFlipped` (safetake n $ newset2RL repo)

checkMatchSyntax :: [DarcsFlag] -> IO ()
checkMatchSyntax opts =
 case getMatchPattern opts of
  Nothing -> return ()
  Just p  -> either fail (const $ return ()) $ (parseMatch p::Either String (MatchFun DummyPatch))

getMatchPattern :: [DarcsFlag] -> Maybe PatchMatch
getMatchPattern [] = Nothing
getMatchPattern (OnePattern m:_) = Just m
getMatchPattern (SeveralPattern m:_) = Just m
getMatchPattern (_:fs) = getMatchPattern fs

tagmatch :: String -> Matcher p
tagmatch r = makeMatcher ("tag-name "++r) tm
    where tm (Sealed2 p) =
              let n = justName (info p) in
              "TAG " `isPrefixOf` n && isJust (matchRegex (mkRegex r) $ drop 4 n)

mymatch :: String -> Matcher p
mymatch r = makeMatcher ("patch-name "++r) mm
    where mm (Sealed2 p) = isJust . matchRegex (mkRegex r) . justName . info $ p


-- | strictJust is a strict version of the Just constructor, used to ensure
-- that if we claim we've got a pattern match, that the pattern will
-- actually match (rathern than fail to compile properly).
strictJust :: a -> Maybe a
strictJust x = Just $! x

-- | @nonrangeMatcher@ is the criterion that is used to match against
-- patches in the interval. It is 'Just m' when the @--patch@, @--match@,
-- @--tag@ options are passed (or their plural variants).
nonrangeMatcher :: Patchy p => [DarcsFlag] -> Maybe (Matcher p)
nonrangeMatcher [] = Nothing
nonrangeMatcher (OnePattern m:_) = strictJust $ matchPattern m
nonrangeMatcher (OneTag t:_) = strictJust $ tagmatch t
nonrangeMatcher (OnePatch p:_) = strictJust $ mymatch p
nonrangeMatcher (SeveralPattern m:_) = strictJust $ matchPattern m
nonrangeMatcher (SeveralPatch p:_) = strictJust $ mymatch p
nonrangeMatcher (_:fs) = nonrangeMatcher fs

-- | @nonrangeMatcherIsTag@ returns true if the matching option was
-- '--tag'
nonrangeMatcherIsTag :: [DarcsFlag] -> Bool
nonrangeMatcherIsTag [] = False
nonrangeMatcherIsTag (OneTag _:_) = True
nonrangeMatcherIsTag (_:fs) = nonrangeMatcherIsTag fs

-- | @firstMatcher@ returns the left bound of the matched interval.
-- This left bound is also specified when we use the singular versions
-- of @--patch@, @--match@ and @--tag@. Otherwise, @firstMatcher@
-- returns @Nothing@.
firstMatcher :: Patchy p => [DarcsFlag] -> Maybe (Matcher p)
firstMatcher [] = Nothing
firstMatcher (OnePattern m:_) = strictJust $ matchPattern m
firstMatcher (AfterPattern m:_) = strictJust $ matchPattern m
firstMatcher (AfterTag t:_) = strictJust $ tagmatch t
firstMatcher (OnePatch p:_) = strictJust $ mymatch p
firstMatcher (AfterPatch p:_) = strictJust $ mymatch p
firstMatcher (_:fs) = firstMatcher fs

firstMatcherIsTag :: [DarcsFlag] -> Bool
firstMatcherIsTag [] = False
firstMatcherIsTag (AfterTag _:_) = True
firstMatcherIsTag (_:fs) = firstMatcherIsTag fs

secondMatcher :: Patchy p => [DarcsFlag] -> Maybe (Matcher p)
secondMatcher [] = Nothing
secondMatcher (OnePattern m:_) = strictJust $ matchPattern m
secondMatcher (UpToPattern m:_) = strictJust $ matchPattern m
secondMatcher (OnePatch p:_) = strictJust $ mymatch p
secondMatcher (UpToPatch p:_) = strictJust $ mymatch p
secondMatcher (UpToTag t:_) = strictJust $ tagmatch t
secondMatcher (_:fs) = secondMatcher fs

secondMatcherIsTag :: [DarcsFlag] -> Bool
secondMatcherIsTag [] = False
secondMatcherIsTag (UpToTag _:_) = True
secondMatcherIsTag (_:fs) = secondMatcherIsTag fs

-- | @matchAPatchread fs p@ tells whether @p@ matches the matchers in
-- the flags listed in @fs@.
matchAPatchread :: Patchy p => [DarcsFlag] -> PatchInfoAnd p C(x y) -> Bool
matchAPatchread fs = case nonrangeMatcher fs of
                       Nothing -> const True
                       Just m -> applyMatcher m

-- | @matchAPatch fs p@ tells whether @p@ matches the matchers in
-- the flags @fs@
matchAPatch :: Patchy p => [DarcsFlag] -> Named p C(x y) -> Bool
matchAPatch fs p =
    case nonrangeMatcher fs of
    Nothing -> True
    Just m -> applyMatcher m (patch2patchinfo p `piap` p)

matchPatch :: RepoPatch p => [DarcsFlag] -> PatchSet p C(start x) -> Sealed2 (Named p)
matchPatch fs ps =
    case hasIndexRange fs of
    Just (a,a') | a == a' -> case (unseal myhead) $ dropn (a-1) ps of
                             Just (Sealed2 p) -> seal2 $ hopefully p
                             Nothing -> error "Patch out of range!"
                | otherwise -> bug ("Invalid index range match given to matchPatch: "++
                                    show (PatchIndexRange a a'))
                where myhead :: PatchSet p C(start x) -> Maybe (Sealed2 (PatchInfoAnd p))
                      myhead (PatchSet NilRL (Tagged t _ _ :<: _)) = Just $ seal2 t
                      myhead (PatchSet (x:<:_) _) = Just $ seal2 x
                      myhead _ = Nothing
    Nothing -> case nonrangeMatcher fs of
                    Nothing -> bug "Couldn't matchPatch"
                    Just m -> findAPatch m ps

getOnePatchset :: (RepoPatch p, ApplyState p ~ Tree) => Repository p C(r u t) -> [DarcsFlag] ->
                 IO (SealedPatchSet p C(Origin))
getOnePatchset repository fs =
    case nonrangeMatcher fs of
        Just m -> do ps <- readRepo repository
                     if nonrangeMatcherIsTag fs
                        then return $ getMatchingTag m ps
                        else return $ matchAPatchset m ps
        Nothing -> (seal . scanContext) `fmap` mmapFilePS (toFilePath $ context_f fs)
    where context_f [] = bug "Couldn't match_nonrange_patchset"
          context_f (Context f:_) = f
          context_f (_:xs) = context_f xs

-- | @hasLastn fs@ return the @--last@ argument in @fs@, if any.
hasLastn :: [DarcsFlag] -> Maybe Int
hasLastn [] = Nothing
hasLastn (LastN (-1):_) = error "--last requires a positive integer argument."
hasLastn (LastN n:_) = Just n
hasLastn (_:fs) = hasLastn fs

hasIndexRange :: [DarcsFlag] -> Maybe (Int,Int)
hasIndexRange [] = Nothing
hasIndexRange (PatchIndexRange x y:_) = Just (x,y)
hasIndexRange (_:fs) = hasIndexRange fs

-- | @matchFirstPatchset fs ps@ returns the part of @ps@ before its
-- first matcher, ie the one that comes first dependencywise. Hence,
-- patches in @matchFirstPatchset fs ps@ are the context for the ones
-- we don't want.
matchFirstPatchset :: RepoPatch p => [DarcsFlag] -> PatchSet p C(start x)
                   -> SealedPatchSet p C(start)
matchFirstPatchset fs patchset =
    case hasLastn fs of
    Just n -> dropn n patchset
    Nothing ->
        case hasIndexRange fs of
        Just (_,b) -> dropn b patchset
        Nothing ->
               case firstMatcher fs of
               Nothing -> bug "Couldn't matchFirstPatchset"
               Just m -> unseal (dropn 1) $ if firstMatcherIsTag fs
                                            then getMatchingTag m patchset
                                            else matchAPatchset m patchset

-- | @dropn n ps@ drops the @n@ last patches from @ps@.
dropn :: Int -> PatchSet p C(start x) -> SealedPatchSet p C(start)
dropn n ps | n <= 0 = seal ps
dropn n (PatchSet NilRL (Tagged t _ ps :<: ts)) = dropn n $ PatchSet (t:<:ps) ts
dropn _ (PatchSet NilRL NilRL) = seal $ PatchSet NilRL NilRL
dropn n (PatchSet (_:<:ps) ts) = dropn (n-1) $ PatchSet ps ts

-- | @matchSecondPatchset fs ps@ returns the part of @ps@ before its
-- second matcher, ie the one that comes last dependencywise.
matchSecondPatchset :: RepoPatch p => [DarcsFlag] -> PatchSet p C(start x)
                    -> SealedPatchSet p C(start)
matchSecondPatchset fs ps =
  case hasIndexRange fs of
  Just (a,_) -> dropn (a-1) ps
  Nothing ->
    case secondMatcher fs of
    Nothing -> bug "Couldn't matchSecondPatchset"
    Just m -> if secondMatcherIsTag fs
              then getMatchingTag m ps
              else matchAPatchset m ps

-- | @findAPatch m ps@ returns the last patch in @ps@ matching @m@, and
-- calls 'error' if there is none.
findAPatch :: RepoPatch p => Matcher p -> PatchSet p C(start x) -> Sealed2 (Named p)
findAPatch m (PatchSet NilRL NilRL) = error $ "Couldn't find patch matching " ++ show m
findAPatch m (PatchSet NilRL (Tagged t _ ps :<: ts)) = findAPatch m (PatchSet (t:<:ps) ts)
findAPatch m (PatchSet (p:<:ps) ts) | applyMatcher m p = seal2 $ hopefully p
                                    | otherwise = findAPatch m (PatchSet ps ts)

-- | @matchAPatchset m ps@ returns a (the largest?) subset of @ps@
-- ending in patch which matches @m@. Calls 'error' if there is none.
matchAPatchset :: RepoPatch p => Matcher p -> PatchSet p C(start x)
               -> SealedPatchSet p C(start)
matchAPatchset m (PatchSet NilRL NilRL) = error $ "Couldn't find patch matching " ++ show m
matchAPatchset m (PatchSet NilRL (Tagged t _ ps :<: ts)) = matchAPatchset m (PatchSet (t:<:ps) ts)
matchAPatchset m (PatchSet (p:<:ps) ts) | applyMatcher m p = seal (PatchSet (p:<:ps) ts)
                                        | otherwise = matchAPatchset m (PatchSet ps ts)

-- | @getMatchingTag m ps@, where @m@ is a 'Matcher' which matches tags
-- returns a 'SealedPatchSet' containing all patches in the last tag which
-- matches @m@. Last tag means the most recent tag in repository order,
-- i.e. the last one you'd see if you ran darcs changes -t @m@. Calls
-- 'error' if there is no matching tag.
getMatchingTag :: RepoPatch p => Matcher p -> PatchSet p C(start x) -> SealedPatchSet p C(start)
getMatchingTag m (PatchSet NilRL NilRL) = error $ "Couldn't find a tag matching " ++ show m
getMatchingTag m (PatchSet NilRL (Tagged t _ ps :<: ts)) = getMatchingTag m (PatchSet (t:<:ps) ts)
getMatchingTag m (PatchSet (p:<:ps) ts)
    | applyMatcher m p = seal $ PatchSet (p:<:ps) ts
    | otherwise = getMatchingTag m (PatchSet ps ts)

-- | @matchExists m ps@ tells whether there is a patch matching
-- @m@ in @ps@
matchExists :: Matcher p -> PatchSet p C(start x) -> Bool
matchExists _ (PatchSet NilRL NilRL) = False
matchExists m (PatchSet NilRL (Tagged t _ ps :<: ts)) = matchExists m (PatchSet (t:<:ps) ts)
matchExists m (PatchSet (p:<:ps) ts) | applyMatcher m $ p = True
                                     | otherwise = matchExists m (PatchSet ps ts)

applyInvToMatcher :: (RepoPatch p, ApplyMonad m (ApplyState p))
                  => InclusiveOrExclusive -> Matcher p -> PatchSet p C(Origin x) -> m ()
applyInvToMatcher _ _ (PatchSet NilRL NilRL) = impossible
applyInvToMatcher ioe m (PatchSet NilRL (Tagged t _ ps :<: ts)) = applyInvToMatcher ioe m
                                                                  (PatchSet (t:<:ps) ts)
applyInvToMatcher ioe m (PatchSet (p:<:ps) xs)
    | applyMatcher m p = when (ioe == Inclusive) (applyInvp p)
    | otherwise = applyInvp p >> applyInvToMatcher ioe m (PatchSet ps xs)

-- | @applyNInv@ n ps applies the inverse of the last @n@ patches of @ps@.
applyNInv :: (RepoPatch p, ApplyMonad m (ApplyState p)) => Int -> PatchSet p C(Origin x) -> m ()
applyNInv n _ | n <= 0 = return ()
applyNInv _ (PatchSet NilRL NilRL) = error "Index out of range."
applyNInv n (PatchSet NilRL (Tagged t _ ps :<: ts)) =
  applyNInv n (PatchSet (t :<: ps) ts)
applyNInv n (PatchSet (p :<: ps) xs) =
  applyInvp p >> applyNInv (n - 1) (PatchSet ps xs)


getMatcherS :: (ApplyMonad m (ApplyState p), RepoPatch p) =>
                 InclusiveOrExclusive -> Matcher p -> PatchSet p C(Origin x) -> m ()
getMatcherS ioe m repo =
    if matchExists m repo
    then applyInvToMatcher ioe m repo
    else fail $ "Couldn't match pattern "++ show m

getTagS :: (ApplyMonad m (ApplyState p), MonadProgress m, RepoPatch p) =>
             Matcher p -> PatchSet p C(Origin x) -> m ()
getTagS match repo = do
    let pinfo = patch2patchinfo `unseal2` (findAPatch match repo)
    case getPatchesBeyondTag pinfo repo of
        FlippedSeal extras -> applyInvRL extras

-- | @applyInvp@ tries to get the patch that's in a 'PatchInfoAnd
-- patch', and to apply its inverse. If we fail to fetch the patch
-- (presumably in a partial repositiory), then we share our sorrow
-- with the user.
applyInvp :: (Patchy p, ApplyMonad m (ApplyState p)) => PatchInfoAnd p C(x y) -> m ()
applyInvp hp = apply (invert $ fromHopefully hp)
    where fromHopefully = conscientiously $ \e ->
                     text "Sorry, partial repository problem.  Patch not available:"
                     $$ e
                     $$ text ""
                     $$ text "If you think what you're trying to do is ok then"
                     $$ text "report this as a bug on the darcs-user list."

-- | a version of 'take' for 'RL' lists that cater for contexts.
safetake :: Int -> RL a C(x y) -> FlippedSeal (RL a) C(y)
safetake 0 _ = flipSeal NilRL
safetake _ NilRL = error "There aren't that many patches..."
safetake i (a:<:as) = a `consRLSealed` safetake (i-1) as

withRecordedMatch :: (RepoPatch p, ApplyState p ~ Tree) => Repository p C(r u t)
                  -> (PatchSet p C(Origin r) -> IO ()) -> IO ()
withRecordedMatch r job = do createPristineDirectoryTree r "."
                             readRepo r >>= job

applyInvRL :: (ApplyMonad m (ApplyState p), MonadProgress m, Patchy p) => RL (PatchInfoAnd p) C(x r) -> m ()
applyInvRL = applyPatches . invertRL -- this gives nicer feedback
