aboutsummaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/Class.hs
blob: ae538046a153952eb6fdc12fdbfa889e08e2a21a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
{-# LANGUAGE CPP #-}
{-# LANGUAGE PatternGuards #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE ScopedTypeVariables #-}
#if MIN_VERSION_base(4,8,0)
#else
{-# LANGUAGE OverlappingInstances #-}
#endif

{-
Copyright (C) 2016-17 Jesse Rosenthal <jrosenthal@jhu.edu>
and John MacFarlane.

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      : Text.Pandoc.Class
   Copyright   : Copyright (C) 2016-17 Jesse Rosenthal, John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : Jesse Rosenthal <jrosenthal@jhu.edu>
   Stability   : alpha
   Portability : portable

This module defines a type class, 'PandocMonad', for pandoc readers
and writers. A pure instance 'PandocPure' and an impure instance
'PandocIO' are provided.  This allows users of the library to choose
whether they want conversions to perform IO operations (such as
reading include files or images).
-}

module Text.Pandoc.Class ( PandocMonad(..)
                         , CommonState(..)
                         , PureState(..)
                         , getPureState
                         , getsPureState
                         , putPureState
                         , modifyPureState
                         , getPOSIXTime
                         , getZonedTime
                         , readFileFromDirs
                         , report
                         , setTrace
                         , setRequestHeader
                         , getLog
                         , setVerbosity
                         , getVerbosity
                         , getMediaBag
                         , setMediaBag
                         , insertMedia
                         , setUserDataDir
                         , getUserDataDir
                         , fetchItem
                         , getInputFiles
                         , setInputFiles
                         , getOutputFile
                         , setOutputFile
                         , setResourcePath
                         , getResourcePath
                         , PandocIO(..)
                         , PandocPure(..)
                         , FileTree
                         , FileInfo(..)
                         , addToFileTree
                         , insertInFileTree
                         , runIO
                         , runIOorExplode
                         , runPure
                         , readDefaultDataFile
                         , readDataFile
                         , fetchMediaResource
                         , fillMediaBag
                         , extractMedia
                         , toLang
                         , setTranslations
                         , translateTerm
                         , Translations
                         ) where

import Prelude hiding (readFile)
import System.Random (StdGen, next, mkStdGen)
import qualified System.Random as IO (newStdGen)
import Codec.Archive.Zip
import qualified Data.CaseInsensitive as CI
import Data.Unique (hashUnique)
import Data.List (stripPrefix)
import qualified Data.Unique as IO (newUnique)
import qualified Text.Pandoc.UTF8 as UTF8
import qualified System.Directory as Directory
import Text.Pandoc.Compat.Time (UTCTime)
import Text.Pandoc.Logging
import Text.Parsec (ParsecT, getPosition, sourceLine, sourceName)
import qualified Text.Pandoc.Compat.Time as IO (getCurrentTime)
import Text.Pandoc.MIME (MimeType, getMimeType, extensionFromMimeType)
import Text.Pandoc.Definition
import Data.Digest.Pure.SHA (sha1, showDigest)
import Data.Maybe (fromMaybe)
import Data.Time.Clock.POSIX ( utcTimeToPOSIXSeconds
                             , posixSecondsToUTCTime
                             , POSIXTime )
import Data.Time.LocalTime (TimeZone, ZonedTime, utcToZonedTime, utc)
import Data.ByteString.Base64 (decodeLenient)
import Network.URI ( escapeURIString, nonStrictRelativeTo,
                     unEscapeString, parseURIReference, isAllowedInURI,
                     parseURI, URI(..) )
import Network.HTTP.Client
       (httpLbs, responseBody, responseHeaders,
        Request(port, host, requestHeaders), parseRequest, newManager)
import Network.HTTP.Client.Internal (addProxy)
import Network.HTTP.Client.TLS (tlsManagerSettings)
import System.Environment (getEnv)
import Network.HTTP.Types.Header ( hContentType )
import Network (withSocketsDo)
import Data.ByteString.Lazy (toChunks)
import qualified Control.Exception as E
import qualified Data.Time.LocalTime as IO (getCurrentTimeZone)
import Text.Pandoc.MediaBag (MediaBag, lookupMedia, mediaDirectory)
import Text.Pandoc.Walk (walkM, walk)
import qualified Text.Pandoc.MediaBag as MB
import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as BL
import qualified System.Environment as IO (lookupEnv)
import System.FilePath.Glob (match, compile)
import System.Directory (createDirectoryIfMissing, getDirectoryContents,
                          doesDirectoryExist)
import System.FilePath
       ((</>), (<.>), takeDirectory, takeExtension, dropExtension,
        isRelative, normalise, splitDirectories)
import qualified System.FilePath.Glob as IO (glob)
import qualified System.FilePath.Posix as Posix
import qualified System.Directory as IO (getModificationTime)
import Control.Monad as M (fail)
import Control.Monad.State.Strict
import Control.Monad.Except
import Data.Word (Word8)
import Data.Default
import System.IO.Error
import System.IO (stderr)
import qualified Data.Map as M
import Text.Pandoc.Error
import Text.Pandoc.BCP47 (Lang(..), parseBCP47, renderLang)
import Text.Pandoc.Translations (Term(..), Translations, lookupTerm,
                                 readTranslations)
import qualified Debug.Trace
#ifdef EMBED_DATA_FILES
import Text.Pandoc.Data (dataFiles)
#else
import qualified Paths_pandoc as Paths
#endif

-- | The PandocMonad typeclass contains all the potentially
-- IO-related functions used in pandoc's readers and writers.
-- Instances of this typeclass may implement these functions
-- in IO (as in 'PandocIO') or using an internal state that
-- represents a file system, time, and so on (as in 'PandocPure').
class (Functor m, Applicative m, Monad m, MonadError PandocError m)
      => PandocMonad m where
  -- | Lookup an environment variable.
  lookupEnv :: String -> m (Maybe String)
  -- | Get the current (UTC) time.
  getCurrentTime :: m UTCTime
  -- | Get the locale's time zone.
  getCurrentTimeZone :: m TimeZone
  -- | Return a new generator for random numbers.
  newStdGen :: m StdGen
  -- | Return a new unique integer.
  newUniqueHash :: m Int
  -- | Retrieve contents and mime type from a URL, raising
  -- an error on failure.
  openURL :: String -> m (B.ByteString, Maybe MimeType)
  -- | Read the lazy ByteString contents from a file path,
  -- raising an error on failure.
  readFileLazy :: FilePath -> m BL.ByteString
  -- | Read the strict ByteString contents from a file path,
  -- raising an error on failure.
  readFileStrict :: FilePath -> m B.ByteString
  -- | Return a list of paths that match a glob, relative to
  -- the working directory.  See 'System.FilePath.Glob' for
  -- the glob syntax.
  glob :: String -> m [FilePath]
  -- | Returns True if file exists.
  fileExists :: FilePath -> m Bool
  -- | Returns the path of data file.
  getDataFileName :: FilePath -> m FilePath
  -- | Return the modification time of a file.
  getModificationTime :: FilePath -> m UTCTime
  -- | Get the value of the 'CommonState' used by all instances
  -- of 'PandocMonad'.
  getCommonState :: m CommonState
  -- | Set the value of the 'CommonState' used by all instances
  -- of 'PandocMonad'.
  -- | Get the value of a specific field of 'CommonState'.
  putCommonState :: CommonState -> m ()
  -- | Get the value of a specific field of 'CommonState'.
  getsCommonState :: (CommonState -> a) -> m a
  getsCommonState f = f <$> getCommonState
  -- | Modify the 'CommonState'.
  modifyCommonState :: (CommonState -> CommonState) -> m ()
  modifyCommonState f = getCommonState >>= putCommonState . f
  -- Output a log message.
  logOutput :: LogMessage -> m ()
  -- Output a debug message to sterr, using 'Debug.Trace.trace',
  -- if tracing is enabled.  Note: this writes to stderr even in
  -- pure instances.
  trace :: String -> m ()
  trace msg = do
    tracing <- getsCommonState stTrace
    when tracing $ Debug.Trace.trace ("[trace] " ++ msg) (return ())

-- * Functions defined for all PandocMonad instances

-- | Set the verbosity level.
setVerbosity :: PandocMonad m => Verbosity -> m ()
setVerbosity verbosity =
  modifyCommonState $ \st -> st{ stVerbosity = verbosity }

-- | Get the verbosity level.
getVerbosity :: PandocMonad m => m Verbosity
getVerbosity = getsCommonState stVerbosity

-- Get the accomulated log messages (in temporal order).
getLog :: PandocMonad m => m [LogMessage]
getLog = reverse <$> getsCommonState stLog

-- | Log a message using 'logOutput'.  Note that 'logOutput' is
-- called only if the verbosity level exceeds the level of the
-- message, but the message is added to the list of log messages
-- that will be retrieved by 'getLog' regardless of its verbosity level.
report :: PandocMonad m => LogMessage -> m ()
report msg = do
  verbosity <- getsCommonState stVerbosity
  let level = messageVerbosity msg
  when (level <= verbosity) $ logOutput msg
  modifyCommonState $ \st -> st{ stLog = msg : stLog st }

-- | Determine whether tracing is enabled.  This affects
-- the behavior of 'trace'.  If tracing is not enabled,
-- 'trace' does nothing.
setTrace :: PandocMonad m => Bool -> m ()
setTrace useTracing = modifyCommonState $ \st -> st{stTrace = useTracing}

-- | Set request header to use in HTTP requests.
setRequestHeader :: PandocMonad m
                 => String  -- ^ Header name
                 -> String  -- ^ Value
                 -> m ()
setRequestHeader name val = modifyCommonState $ \st ->
  st{ stRequestHeaders =
       (name, val) : filter (\(n,_) -> n /= name) (stRequestHeaders st)  }

-- | Initialize the media bag.
setMediaBag :: PandocMonad m => MediaBag -> m ()
setMediaBag mb = modifyCommonState $ \st -> st{stMediaBag = mb}

-- Retrieve the media bag.
getMediaBag :: PandocMonad m => m MediaBag
getMediaBag = getsCommonState stMediaBag

-- Insert an item into the media bag.
insertMedia :: PandocMonad m => FilePath -> Maybe MimeType -> BL.ByteString -> m ()
insertMedia fp mime bs = do
  mb <- getMediaBag
  let mb' = MB.insertMedia fp mime bs mb
  setMediaBag mb'

-- Retrieve the input filenames.
getInputFiles :: PandocMonad m => m [FilePath]
getInputFiles = getsCommonState stInputFiles

-- Set the input filenames.
setInputFiles :: PandocMonad m => [FilePath] -> m ()
setInputFiles fs = do
  let sourceURL = case fs of
                    []    -> Nothing
                    (x:_) -> case parseURI x of
                                Just u
                                  | uriScheme u `elem` ["http:","https:"] ->
                                      Just $ show u{ uriQuery = "",
                                                     uriFragment = "" }
                                _ -> Nothing

  modifyCommonState $ \st -> st{ stInputFiles = fs
                               , stSourceURL = sourceURL }

-- Retrieve the output filename.
getOutputFile :: PandocMonad m => m (Maybe FilePath)
getOutputFile = getsCommonState stOutputFile

-- Set the output filename.
setOutputFile :: PandocMonad m => Maybe FilePath -> m ()
setOutputFile mbf = modifyCommonState $ \st -> st{ stOutputFile = mbf }

-- Retrieve the resource path searched by 'fetchItem'.
getResourcePath :: PandocMonad m => m [FilePath]
getResourcePath = getsCommonState stResourcePath

-- Set the resource path searched by 'fetchItem'.
setResourcePath :: PandocMonad m => [FilePath] -> m ()
setResourcePath ps = modifyCommonState $ \st -> st{stResourcePath = ps}

-- Get the POSIX time.
getPOSIXTime :: PandocMonad m => m POSIXTime
getPOSIXTime = utcTimeToPOSIXSeconds <$> getCurrentTime

-- Get the zoned time.
getZonedTime :: PandocMonad m => m ZonedTime
getZonedTime = do
  t <- getCurrentTime
  tz <- getCurrentTimeZone
  return $ utcToZonedTime tz t

-- | Read file, checking in any number of directories.
readFileFromDirs :: PandocMonad m => [FilePath] -> FilePath -> m (Maybe String)
readFileFromDirs [] _ = return Nothing
readFileFromDirs (d:ds) f = catchError
    ((Just . UTF8.toStringLazy) <$> readFileLazy (d </> f))
    (\_ -> readFileFromDirs ds f)

--

-- | 'CommonState' represents state that is used by all
-- instances of 'PandocMonad'.  Normally users should not
-- need to interact with it directly; instead, auxiliary
-- functions like 'setVerbosity' and 'withMediaBag' should be used.
data CommonState = CommonState { stLog          :: [LogMessage]
                                 -- ^ A list of log messages in reverse order
                               , stUserDataDir  :: Maybe FilePath
                                 -- ^ Directory to search for data files
                               , stSourceURL    :: Maybe String
                                 -- ^ Absolute URL + dir of 1st source file
                               , stRequestHeaders :: [(String, String)]
                                 -- ^ Headers to add for HTTP requests
                               , stMediaBag     :: MediaBag
                                 -- ^ Media parsed from binary containers
                               , stTranslations :: Maybe
                                                  (Lang, Maybe Translations)
                                 -- ^ Translations for localization
                               , stInputFiles   :: [FilePath]
                                 -- ^ List of input files from command line
                               , stOutputFile   :: Maybe FilePath
                                 -- ^ Output file from command line
                               , stResourcePath :: [FilePath]
                                 -- ^ Path to search for resources like
                                 -- included images
                               , stVerbosity    :: Verbosity
                                 -- ^ Verbosity level
                               , stTrace        :: Bool
                                 -- ^ Controls whether tracing messages are
                                 -- issued.
                               }

instance Default CommonState where
  def = CommonState { stLog = []
                    , stUserDataDir = Nothing
                    , stSourceURL = Nothing
                    , stRequestHeaders = []
                    , stMediaBag = mempty
                    , stTranslations = Nothing
                    , stInputFiles = []
                    , stOutputFile = Nothing
                    , stResourcePath = ["."]
                    , stVerbosity = WARNING
                    , stTrace = False
                    }

-- | Convert BCP47 string to a Lang, issuing warning
-- if there are problems.
toLang :: PandocMonad m => Maybe String -> m (Maybe Lang)
toLang Nothing = return Nothing
toLang (Just s) =
  case parseBCP47 s of
       Left _ -> do
         report $ InvalidLang s
         return Nothing
       Right l -> return (Just l)

-- | Select the language to use with 'translateTerm'.
-- Note that this does not read a translation file;
-- that is only done the first time 'translateTerm' is
-- used.
setTranslations :: PandocMonad m => Lang -> m ()
setTranslations lang =
  modifyCommonState $ \st -> st{ stTranslations = Just (lang, Nothing) }

-- | Load term map.
getTranslations :: PandocMonad m => m Translations
getTranslations = do
  mbtrans <- getsCommonState stTranslations
  case mbtrans of
       Nothing -> return mempty  -- no language defined
       Just (_, Just t) -> return t
       Just (lang, Nothing) -> do  -- read from file
         let translationFile = "translations/" ++ renderLang lang ++ ".yaml"
         let fallbackFile = "translations/" ++ langLanguage lang ++ ".yaml"
         let getTrans fp = do
               bs <- readDataFile fp
               case readTranslations (UTF8.toString bs) of
                    Left e   -> do
                      report $ CouldNotLoadTranslations (renderLang lang)
                        (fp ++ ": " ++ e)
                      -- make sure we don't try again...
                      modifyCommonState $ \st ->
                        st{ stTranslations = Nothing }
                      return mempty
                    Right t -> do
                      modifyCommonState $ \st ->
                                  st{ stTranslations = Just (lang, Just t) }
                      return t
         catchError (getTrans translationFile)
           (\_ ->
             catchError (getTrans fallbackFile)
               (\e -> do
                 report $ CouldNotLoadTranslations (renderLang lang)
                          $ case e of
                               PandocCouldNotFindDataFileError _ ->
                                 "data file " ++ fallbackFile ++ " not found"
                               _ -> ""
                 -- make sure we don't try again...
                 modifyCommonState $ \st -> st{ stTranslations = Nothing }
                 return mempty))

-- | Get a translation from the current term map.
-- Issue a warning if the term is not defined.
translateTerm :: PandocMonad m => Term -> m String
translateTerm term = do
  translations <- getTranslations
  case lookupTerm term translations of
       Just s -> return s
       Nothing -> do
         report $ NoTranslation (show term)
         return ""

-- | Evaluate a 'PandocIO' operation.
runIO :: PandocIO a -> IO (Either PandocError a)
runIO ma = flip evalStateT def $ runExceptT $ unPandocIO ma

-- | Evaluate a 'PandocIO' operation, handling any errors
-- by exiting with an appropriate message and error status.
runIOorExplode :: PandocIO a -> IO a
runIOorExplode ma = runIO ma >>= handleError

newtype PandocIO a = PandocIO {
  unPandocIO :: ExceptT PandocError (StateT CommonState IO) a
  } deriving ( MonadIO
             , Functor
             , Applicative
             , Monad
             , MonadError PandocError
             )

-- | Utility function to lift IO errors into 'PandocError's.
liftIOError :: (String -> IO a) -> String -> PandocIO a
liftIOError f u = do
  res <- liftIO $ tryIOError $ f u
  case res of
         Left e  -> throwError $ PandocIOError u e
         Right r -> return r

instance PandocMonad PandocIO where
  lookupEnv = liftIO . IO.lookupEnv
  getCurrentTime = liftIO IO.getCurrentTime
  getCurrentTimeZone = liftIO IO.getCurrentTimeZone
  newStdGen = liftIO IO.newStdGen
  newUniqueHash = hashUnique <$> liftIO IO.newUnique

  openURL u
   | Just u'' <- stripPrefix "data:" u = do
       let mime     = takeWhile (/=',') u''
       let contents = UTF8.fromString $
                       unEscapeString $ drop 1 $ dropWhile (/=',') u''
       return (decodeLenient contents, Just mime)
   | otherwise = do
       let toReqHeader (n, v) = (CI.mk (UTF8.fromString n), UTF8.fromString v)
       customHeaders <- map toReqHeader <$> getsCommonState stRequestHeaders
       report $ Fetching u
       res <- liftIO $ E.try $ withSocketsDo $ do
         let parseReq = parseRequest
         proxy <- tryIOError (getEnv "http_proxy")
         let addProxy' x = case proxy of
                              Left _ -> return x
                              Right pr -> parseReq pr >>= \r ->
                                  return (addProxy (host r) (port r) x)
         req <- parseReq u >>= addProxy'
         let req' = req{requestHeaders = customHeaders ++ requestHeaders req}
         resp <- newManager tlsManagerSettings >>= httpLbs req'
         return (B.concat $ toChunks $ responseBody resp,
                 UTF8.toString `fmap` lookup hContentType (responseHeaders resp))

       case res of
            Right r -> return r
            Left e  -> throwError $ PandocHttpError u e

  readFileLazy s = liftIOError BL.readFile s
  readFileStrict s = liftIOError B.readFile s

  glob = liftIOError IO.glob
  fileExists = liftIOError Directory.doesFileExist
#ifdef EMBED_DATA_FILES
  getDataFileName = return
#else
  getDataFileName = liftIOError Paths.getDataFileName
#endif
  getModificationTime = liftIOError IO.getModificationTime
  getCommonState = PandocIO $ lift get
  putCommonState x = PandocIO $ lift $ put x
  logOutput msg = liftIO $ do
    UTF8.hPutStr stderr $
        "[" ++ show (messageVerbosity msg) ++ "] "
    alertIndent $ lines $ showLogMessage msg

alertIndent :: [String] -> IO ()
alertIndent [] = return ()
alertIndent (l:ls) = do
  UTF8.hPutStrLn stderr l
  mapM_ go ls
  where go l' = do UTF8.hPutStr stderr "  "
                   UTF8.hPutStrLn stderr l'

-- | Specialized version of parseURIReference that disallows
-- single-letter schemes.  Reason:  these are usually windows absolute
-- paths.
parseURIReference' :: String -> Maybe URI
parseURIReference' s =
  case parseURIReference s of
       Just u
         | length (uriScheme u) > 2  -> Just u
         | null (uriScheme u)        -> Just u  -- protocol-relative
       _                             -> Nothing

-- | Set the user data directory in common state.
setUserDataDir :: PandocMonad m
               => Maybe FilePath
               -> m ()
setUserDataDir mbfp = modifyCommonState $ \st -> st{ stUserDataDir = mbfp }

-- | Get the user data directory from common state.
getUserDataDir :: PandocMonad m
               => m (Maybe FilePath)
getUserDataDir = getsCommonState stUserDataDir

-- | Fetch an image or other item from the local filesystem or the net.
-- Returns raw content and maybe mime type.
fetchItem :: PandocMonad m
          => String
          -> m (B.ByteString, Maybe MimeType)
fetchItem s = do
  mediabag <- getMediaBag
  case lookupMedia s mediabag of
    Just (mime, bs) -> return (BL.toStrict bs, Just mime)
    Nothing -> downloadOrRead s

downloadOrRead :: PandocMonad m
               => String
               -> m (B.ByteString, Maybe MimeType)
downloadOrRead s = do
  sourceURL <- getsCommonState stSourceURL
  case (sourceURL >>= parseURIReference' .
                       ensureEscaped, ensureEscaped s) of
    (Just u, s') -> -- try fetching from relative path at source
       case parseURIReference' s' of
            Just u' -> openURL $ show $ u' `nonStrictRelativeTo` u
            Nothing -> openURL s' -- will throw error
    (Nothing, s'@('/':'/':_)) ->  -- protocol-relative URI
       case parseURIReference' s' of
            Just u' -> openURL $ show $ u' `nonStrictRelativeTo` httpcolon
            Nothing -> openURL s' -- will throw error
    (Nothing, s') ->
       case parseURI s' of  -- requires absolute URI
            -- We don't want to treat C:/ as a scheme:
            Just u' | length (uriScheme u') > 2 -> openURL (show u')
            Just u' | uriScheme u' == "file:" ->
                 readLocalFile $ dropWhile (=='/') (uriPath u')
            _ -> readLocalFile fp -- get from local file system
   where readLocalFile f = do
             resourcePath <- getResourcePath
             cont <- if isRelative f
                        then withPaths resourcePath readFileStrict f
                        else readFileStrict f
             return (cont, mime)
         httpcolon = URI{ uriScheme = "http:",
                          uriAuthority = Nothing,
                          uriPath = "",
                          uriQuery = "",
                          uriFragment = "" }
         dropFragmentAndQuery = takeWhile (\c -> c /= '?' && c /= '#')
         fp = unEscapeString $ dropFragmentAndQuery s
         mime = case takeExtension fp of
                     ".gz" -> getMimeType $ dropExtension fp
                     ".svgz" -> getMimeType $ dropExtension fp ++ ".svg"
                     x     -> getMimeType x
         ensureEscaped = escapeURIString isAllowedInURI . map convertSlash
         convertSlash '\\' = '/'
         convertSlash x    = x

-- Retrieve default reference.docx.
getDefaultReferenceDocx :: PandocMonad m => m Archive
getDefaultReferenceDocx = do
  let paths = ["[Content_Types].xml",
               "_rels/.rels",
               "docProps/app.xml",
               "docProps/core.xml",
               "word/document.xml",
               "word/fontTable.xml",
               "word/footnotes.xml",
               "word/comments.xml",
               "word/numbering.xml",
               "word/settings.xml",
               "word/webSettings.xml",
               "word/styles.xml",
               "word/_rels/document.xml.rels",
               "word/_rels/footnotes.xml.rels",
               "word/theme/theme1.xml"]
  let toLazy = BL.fromChunks . (:[])
  let pathToEntry path = do
        epochtime <- (floor . utcTimeToPOSIXSeconds) <$> getCurrentTime
        contents <- toLazy <$> readDataFile ("docx/" ++ path)
        return $ toEntry path epochtime contents
  datadir <- getUserDataDir
  mbArchive <- case datadir of
                    Nothing   -> return Nothing
                    Just d    -> do
                       exists <- fileExists (d </> "reference.docx")
                       if exists
                          then return (Just (d </> "reference.docx"))
                          else return Nothing
  case mbArchive of
     Just arch -> toArchive <$> readFileLazy arch
     Nothing   -> foldr addEntryToArchive emptyArchive <$>
                     mapM pathToEntry paths

-- Retrieve default reference.odt.
getDefaultReferenceODT :: PandocMonad m => m Archive
getDefaultReferenceODT = do
  let paths = ["mimetype",
               "manifest.rdf",
               "styles.xml",
               "content.xml",
               "meta.xml",
               "settings.xml",
               "Configurations2/accelerator/current.xml",
               "Thumbnails/thumbnail.png",
               "META-INF/manifest.xml"]
  let pathToEntry path = do epochtime <- floor `fmap` getPOSIXTime
                            contents <- (BL.fromChunks . (:[])) `fmap`
                                          readDataFile ("odt/" ++ path)
                            return $ toEntry path epochtime contents
  datadir <- getUserDataDir
  mbArchive <- case datadir of
                    Nothing   -> return Nothing
                    Just d    -> do
                       exists <- fileExists (d </> "reference.odt")
                       if exists
                          then return (Just (d </> "reference.odt"))
                          else return Nothing
  case mbArchive of
     Just arch -> toArchive <$> readFileLazy arch
     Nothing   -> foldr addEntryToArchive emptyArchive <$>
                     mapM pathToEntry paths

getDefaultReferencePptx :: PandocMonad m => m Archive
getDefaultReferencePptx = do
  -- We're going to narrow this down substantially once we get it
  -- working.
  let paths = [ "[Content_Types].xml"
              , "_rels/.rels"
              , "docProps/app.xml"
              , "docProps/core.xml"
              , "ppt/_rels/presentation.xml.rels"
              , "ppt/presProps.xml"
              , "ppt/presentation.xml"
              , "ppt/slideLayouts/_rels/slideLayout1.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout2.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout3.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout4.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout5.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout6.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout7.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout8.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout9.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout10.xml.rels"
              , "ppt/slideLayouts/_rels/slideLayout11.xml.rels"
              , "ppt/slideLayouts/slideLayout1.xml"
              , "ppt/slideLayouts/slideLayout10.xml"
              , "ppt/slideLayouts/slideLayout11.xml"
              , "ppt/slideLayouts/slideLayout2.xml"
              , "ppt/slideLayouts/slideLayout3.xml"
              , "ppt/slideLayouts/slideLayout4.xml"
              , "ppt/slideLayouts/slideLayout5.xml"
              , "ppt/slideLayouts/slideLayout6.xml"
              , "ppt/slideLayouts/slideLayout7.xml"
              , "ppt/slideLayouts/slideLayout8.xml"
              , "ppt/slideLayouts/slideLayout9.xml"
              , "ppt/slideMasters/_rels/slideMaster1.xml.rels"
              , "ppt/slideMasters/slideMaster1.xml"
              , "ppt/slides/_rels/slide1.xml.rels"
              , "ppt/slides/slide1.xml"
              , "ppt/slides/_rels/slide2.xml.rels"
              , "ppt/slides/slide2.xml"
              , "ppt/tableStyles.xml"
              , "ppt/theme/theme1.xml"
              , "ppt/viewProps.xml"
              ]
  let toLazy = BL.fromChunks . (:[])
  let pathToEntry path = do
        epochtime <- (floor . utcTimeToPOSIXSeconds) <$> getCurrentTime
        contents <- toLazy <$> readDataFile ("pptx/" ++ path)
        return $ toEntry path epochtime contents
  datadir <- getUserDataDir
  mbArchive <- case datadir of
                    Nothing   -> return Nothing
                    Just d    -> do
                       exists <- fileExists (d </> "reference.pptx")
                       if exists
                          then return (Just (d </> "reference.pptx"))
                          else return Nothing
  case mbArchive of
     Just arch -> toArchive <$> readFileLazy arch
     Nothing   -> foldr addEntryToArchive emptyArchive <$>
                     mapM pathToEntry paths


-- | Read file from user data directory or,
-- if not found there, from Cabal data directory.
readDataFile :: PandocMonad m => FilePath -> m B.ByteString
readDataFile fname = do
  datadir <- getUserDataDir
  case datadir of
       Nothing -> readDefaultDataFile fname
       Just userDir -> do
         exists <- fileExists (userDir </> fname)
         if exists
            then readFileStrict (userDir </> fname)
            else readDefaultDataFile fname

-- | Read file from from Cabal data directory.
readDefaultDataFile :: PandocMonad m => FilePath -> m B.ByteString
readDefaultDataFile "reference.docx" =
  (B.concat . BL.toChunks . fromArchive) <$> getDefaultReferenceDocx
readDefaultDataFile "reference.pptx" =
  (B.concat . BL.toChunks . fromArchive) <$> getDefaultReferencePptx
readDefaultDataFile "reference.odt" =
  (B.concat . BL.toChunks . fromArchive) <$> getDefaultReferenceODT
readDefaultDataFile fname =
#ifdef EMBED_DATA_FILES
  case lookup (makeCanonical fname) dataFiles of
    Nothing       -> throwError $ PandocCouldNotFindDataFileError fname
    Just contents -> return contents
#else
  getDataFileName fname' >>= checkExistence >>= readFileStrict
    where fname' = if fname == "MANUAL.txt" then fname else "data" </> fname

checkExistence :: PandocMonad m => FilePath -> m FilePath
checkExistence fn = do
  exists <- fileExists fn
  if exists
     then return fn
     else throwError $ PandocCouldNotFindDataFileError fn
#endif

makeCanonical :: FilePath -> FilePath
makeCanonical = Posix.joinPath . transformPathParts . splitDirectories
 where  transformPathParts = reverse . foldl go []
        go as     "."  = as
        go (_:as) ".." = as
        go as     x    = x : as

withPaths :: PandocMonad m => [FilePath] -> (FilePath -> m a) -> FilePath -> m a
withPaths [] _ fp = throwError $ PandocResourceNotFound fp
withPaths (p:ps) action fp =
  catchError (action (p </> fp))
             (\_ -> withPaths ps action fp)

-- | Fetch local or remote resource (like an image) and provide data suitable
-- for adding it to the MediaBag.
fetchMediaResource :: PandocMonad m
              => String -> m (FilePath, Maybe MimeType, BL.ByteString)
fetchMediaResource src = do
  (bs, mt) <- downloadOrRead src
  let ext = fromMaybe (takeExtension src)
                      (mt >>= extensionFromMimeType)
  let bs' = BL.fromChunks [bs]
  let basename = showDigest $ sha1 bs'
  let fname = basename <.> ext
  return (fname, mt, bs')

-- | Traverse tree, filling media bag for any images that
-- aren't already in the media bag.
fillMediaBag :: PandocMonad m => Pandoc -> m Pandoc
fillMediaBag d = walkM handleImage d
  where handleImage :: PandocMonad m => Inline -> m Inline
        handleImage (Image attr lab (src, tit)) = catchError
          (do mediabag <- getMediaBag
              case lookupMedia src mediabag of
                Just (_, _) -> return $ Image attr lab (src, tit)
                Nothing -> do
                  (fname, mt, bs) <- fetchMediaResource src
                  insertMedia fname mt bs
                  return $ Image attr lab (fname, tit))
          (\e ->
              case e of
                PandocResourceNotFound _ -> do
                  report $ CouldNotFetchResource src
                            "replacing image with description"
                  -- emit alt text
                  return $ Span ("",["image"],[]) lab
                PandocHttpError u er -> do
                  report $ CouldNotFetchResource u
                            (show er ++ "\rReplacing image with description.")
                  -- emit alt text
                  return $ Span ("",["image"],[]) lab
                _ -> throwError e)
        handleImage x = return x

-- | Extract media from the mediabag into a directory.
extractMedia :: FilePath -> Pandoc -> PandocIO Pandoc
extractMedia dir d = do
  media <- getMediaBag
  case [fp | (fp, _, _) <- mediaDirectory media] of
        []  -> return d
        fps -> do
          mapM_ (writeMedia dir media) fps
          return $ walk (adjustImagePath dir fps) d

-- Write the contents of a media bag to a path.
writeMedia :: FilePath -> MediaBag -> FilePath -> PandocIO ()
writeMedia dir mediabag subpath = do
  -- we join and split to convert a/b/c to a\b\c on Windows;
  -- in zip containers all paths use /
  let fullpath = dir </> normalise subpath
  let mbcontents = lookupMedia subpath mediabag
  case mbcontents of
       Nothing -> throwError $ PandocResourceNotFound subpath
       Just (_, bs) -> do
         report $ Extracting fullpath
         liftIOError (createDirectoryIfMissing True) (takeDirectory fullpath)
         liftIOError (\p -> BL.writeFile p bs) fullpath

adjustImagePath :: FilePath -> [FilePath] -> Inline -> Inline
adjustImagePath dir paths (Image attr lab (src, tit))
   | src `elem` paths = Image attr lab (dir ++ "/" ++ src, tit)
adjustImagePath _ _ x = x

-- | The 'PureState' contains ersatz representations
-- of things that would normally be obtained through IO.
data PureState = PureState { stStdGen     :: StdGen
                           , stWord8Store :: [Word8] -- should be
                                                     -- inifinite,
                                                     -- i.e. [1..]
                           , stUniqStore  :: [Int] -- should be
                                                   -- inifinite and
                                                   -- contain every
                                                   -- element at most
                                                   -- once, e.g. [1..]
                           , stEnv :: [(String, String)]
                           , stTime :: UTCTime
                           , stTimeZone :: TimeZone
                           , stReferenceDocx :: Archive
                           , stReferencePptx :: Archive
                           , stReferenceODT :: Archive
                           , stFiles :: FileTree
                           , stUserDataFiles :: FileTree
                           , stCabalDataFiles :: FileTree
                           }

instance Default PureState where
  def = PureState { stStdGen = mkStdGen 1848
                  , stWord8Store = [1..]
                  , stUniqStore = [1..]
                  , stEnv = [("USER", "pandoc-user")]
                  , stTime = posixSecondsToUTCTime 0
                  , stTimeZone = utc
                  , stReferenceDocx = emptyArchive
                  , stReferencePptx = emptyArchive
                  , stReferenceODT = emptyArchive
                  , stFiles = mempty
                  , stUserDataFiles = mempty
                  , stCabalDataFiles = mempty
                  }


getPureState :: PandocPure PureState
getPureState = PandocPure $ lift $ lift get

getsPureState :: (PureState -> a) -> PandocPure a
getsPureState f = f <$> getPureState

putPureState :: PureState -> PandocPure ()
putPureState ps= PandocPure $ lift $ lift $ put ps

modifyPureState :: (PureState -> PureState) -> PandocPure ()
modifyPureState f = PandocPure $ lift $ lift $ modify f


data FileInfo = FileInfo { infoFileMTime :: UTCTime
                         , infoFileContents :: B.ByteString
                         }

newtype FileTree = FileTree {unFileTree :: M.Map FilePath FileInfo}
  deriving (Monoid)

getFileInfo :: FilePath -> FileTree -> Maybe FileInfo
getFileInfo fp tree =
  M.lookup (makeCanonical fp) (unFileTree tree)

-- | Add the specified file to the FileTree. If file
-- is a directory, add its contents recursively.
addToFileTree :: FileTree -> FilePath -> IO FileTree
addToFileTree tree fp = do
  isdir <- doesDirectoryExist fp
  if isdir
     then do -- recursively add contents of directories
       let isSpecial ".." = True
           isSpecial "."  = True
           isSpecial _    = False
       fs <- (map (fp </>) . filter (not . isSpecial)) <$> getDirectoryContents fp
       foldM addToFileTree tree fs
     else do
       contents <- B.readFile fp
       mtime <- IO.getModificationTime fp
       return $ insertInFileTree fp FileInfo{ infoFileMTime = mtime
                                            , infoFileContents = contents } tree

-- | Insert an ersatz file into the 'FileTree'.
insertInFileTree :: FilePath -> FileInfo -> FileTree -> FileTree
insertInFileTree fp info (FileTree treemap) =
  FileTree $ M.insert (makeCanonical fp) info treemap

newtype PandocPure a = PandocPure {
  unPandocPure :: ExceptT PandocError
                  (StateT CommonState (State PureState)) a
  } deriving ( Functor
             , Applicative
             , Monad
             , MonadError PandocError
             )

-- Run a 'PandocPure' operation.
runPure :: PandocPure a -> Either PandocError a
runPure x = flip evalState def $
            flip evalStateT def $
            runExceptT $
            unPandocPure x

instance PandocMonad PandocPure where
  lookupEnv s = do
    env <- getsPureState stEnv
    return (lookup s env)

  getCurrentTime = getsPureState stTime

  getCurrentTimeZone = getsPureState stTimeZone

  newStdGen = do
    g <- getsPureState stStdGen
    let (_, nxtGen) = next g
    modifyPureState $ \st -> st { stStdGen = nxtGen }
    return g

  newUniqueHash = do
    uniqs <- getsPureState stUniqStore
    case uniqs of
      u : us -> do
        modifyPureState $ \st -> st { stUniqStore = us }
        return u
      _ -> M.fail "uniq store ran out of elements"
  openURL u = throwError $ PandocResourceNotFound u
  readFileLazy fp = do
    fps <- getsPureState stFiles
    case infoFileContents <$> getFileInfo fp fps of
      Just bs -> return (BL.fromStrict bs)
      Nothing -> throwError $ PandocResourceNotFound fp
  readFileStrict fp = do
    fps <- getsPureState stFiles
    case infoFileContents <$> getFileInfo fp fps of
      Just bs -> return bs
      Nothing -> throwError $ PandocResourceNotFound fp

  glob s = do
    FileTree ftmap <- getsPureState stFiles
    return $ filter (match (compile s)) $ M.keys ftmap

  fileExists fp = do
    fps <- getsPureState stFiles
    case getFileInfo fp fps of
         Nothing -> return False
         Just _  -> return True

  getDataFileName fp = return $ "data/" ++ fp

  getModificationTime fp = do
    fps <- getsPureState stFiles
    case infoFileMTime <$> getFileInfo fp fps of
      Just tm -> return tm
      Nothing -> throwError $ PandocIOError fp
                    (userError "Can't get modification time")

  getCommonState = PandocPure $ lift get
  putCommonState x = PandocPure $ lift $ put x

  logOutput _msg = return ()

-- This requires UndecidableInstances.  We could avoid that
-- by repeating the definitions below for every monad transformer
-- we use: ReaderT, WriterT, StateT, RWST.  But this seems to
-- be harmless.
instance (MonadTrans t, PandocMonad m, Functor (t m),
          MonadError PandocError (t m), Monad (t m),
          Applicative (t m)) => PandocMonad (t m) where
  lookupEnv = lift . lookupEnv
  getCurrentTime = lift getCurrentTime
  getCurrentTimeZone = lift getCurrentTimeZone
  newStdGen = lift newStdGen
  newUniqueHash = lift newUniqueHash
  openURL = lift . openURL
  readFileLazy = lift . readFileLazy
  readFileStrict = lift . readFileStrict
  glob = lift . glob
  fileExists = lift . fileExists
  getDataFileName = lift . getDataFileName
  getModificationTime = lift . getModificationTime
  getCommonState = lift getCommonState
  putCommonState = lift . putCommonState
  logOutput = lift . logOutput

#if MIN_VERSION_base(4,8,0)
instance {-# OVERLAPS #-} PandocMonad m => PandocMonad (ParsecT s st m) where
#else
instance PandocMonad m => PandocMonad (ParsecT s st m) where
#endif
  lookupEnv = lift . lookupEnv
  getCurrentTime = lift getCurrentTime
  getCurrentTimeZone = lift getCurrentTimeZone
  newStdGen = lift newStdGen
  newUniqueHash = lift newUniqueHash
  openURL = lift . openURL
  readFileLazy = lift . readFileLazy
  readFileStrict = lift . readFileStrict
  glob = lift . glob
  fileExists = lift . fileExists
  getDataFileName = lift . getDataFileName
  getModificationTime = lift . getModificationTime
  getCommonState = lift getCommonState
  putCommonState = lift . putCommonState
  trace msg = do
    tracing <- getsCommonState stTrace
    when tracing $ do
      pos <- getPosition
      Debug.Trace.trace
        ("[trace] Parsed " ++ msg ++ " at line " ++
            show (sourceLine pos) ++
            if sourceName pos == "chunk"
               then " of chunk"
               else "")
        (return ())
  logOutput = lift . logOutput