aboutsummaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/Pretty.hs
blob: b9f646282e2c408d832eb744e1ef28bebadd570f (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
{-# LANGUAGE GeneralizedNewtypeDeriving, CPP #-}
{-
Copyright (C) 2010-2016 John MacFarlane <jgm@berkeley.edu>

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(-1)307  USA
-}

{- |
   Module      : Text.Pandoc.Pretty
   Copyright   : Copyright (C) 2010-2016 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

A prettyprinting library for the production of text documents,
including wrapped text, indentated blocks, and tables.
-}

module Text.Pandoc.Pretty (
       Doc
     , render
     , cr
     , blankline
     , blanklines
     , space
     , text
     , char
     , prefixed
     , flush
     , nest
     , hang
     , beforeNonBlank
     , nowrap
     , offset
     , minOffset
     , height
     , lblock
     , cblock
     , rblock
     , (<>)
     , (<+>)
     , ($$)
     , ($+$)
     , isEmpty
     , empty
     , cat
     , hcat
     , hsep
     , vcat
     , vsep
     , nestle
     , chomp
     , inside
     , braces
     , brackets
     , parens
     , quotes
     , doubleQuotes
     , charWidth
     , realLength
     )

where
import Data.Sequence (Seq, fromList, (<|), singleton, mapWithIndex, viewl, ViewL(..))
import qualified Data.Sequence as Seq
import Data.Foldable (toList)
import Data.List (intersperse)
import Data.String
import Control.Monad.State
import Data.Char (isSpace)
import Data.Monoid ((<>))

data RenderState a = RenderState{
         output       :: [a]        -- ^ In reverse order
       , prefix       :: String
       , usePrefix    :: Bool
       , lineLength   :: Maybe Int  -- ^ 'Nothing' means no wrapping
       , column       :: Int
       , newlines     :: Int        -- ^ Number of preceding newlines
       }

type DocState a = State (RenderState a) ()

data D = Text Int String
       | Block Int [String]
       | Prefixed String Doc
       | BeforeNonBlank Doc
       | Flush Doc
       | BreakingSpace
       | CarriageReturn
       | NewLine
       | BlankLines Int  -- number of blank lines
       deriving (Show)

newtype Doc = Doc { unDoc :: Seq D }
              deriving (Monoid, Show)

instance IsString Doc where
  fromString = text

isBlank :: D -> Bool
isBlank BreakingSpace  = True
isBlank CarriageReturn = True
isBlank NewLine        = True
isBlank (BlankLines _) = True
isBlank (Text _ (c:_)) = isSpace c
isBlank _              = False

-- | True if the document is empty.
isEmpty :: Doc -> Bool
isEmpty = Seq.null . unDoc

-- | The empty document.
empty :: Doc
empty = mempty

-- | Concatenate a list of 'Doc's.
cat :: [Doc] -> Doc
cat = mconcat

-- | Same as 'cat'.
hcat :: [Doc] -> Doc
hcat = mconcat

-- | Concatenate a list of 'Doc's, putting breakable spaces
-- between them.
infixr 6 <+>
(<+>) :: Doc -> Doc -> Doc
(<+>) x y = if isEmpty x
               then y
               else if isEmpty y
                    then x
                    else x <> space <> y

-- | Same as 'cat', but putting breakable spaces between the
-- 'Doc's.
hsep :: [Doc] -> Doc
hsep = foldr (<+>) empty

infixr 5 $$
-- | @a $$ b@ puts @a@ above @b@.
($$) :: Doc -> Doc -> Doc
($$) x y = if isEmpty x
              then y
              else if isEmpty y
                   then x
                   else x <> cr <> y

infixr 5 $+$
-- | @a $+$ b@ puts @a@ above @b@, with a blank line between.
($+$) :: Doc -> Doc -> Doc
($+$) x y = if isEmpty x
               then y
               else if isEmpty y
                    then x
                    else x <> blankline <> y

-- | List version of '$$'.
vcat :: [Doc] -> Doc
vcat = foldr ($$) empty

-- | List version of '$+$'.
vsep :: [Doc] -> Doc
vsep = foldr ($+$) empty

-- | Removes leading blank lines from a 'Doc'.
nestle :: Doc -> Doc
nestle (Doc d) = Doc $ go d
  where go x = case viewl x of
               (BlankLines _ :< rest) -> go rest
               (NewLine :< rest)   -> go rest
               _                   -> x

-- | Chomps trailing blank space off of a 'Doc'.
chomp :: Doc -> Doc
chomp d = Doc (fromList dl')
  where dl = toList (unDoc d)
        dl' = reverse $ go $ reverse dl
        go [] = []
        go (BreakingSpace : xs) = go xs
        go (CarriageReturn : xs) = go xs
        go (NewLine : xs) = go xs
        go (BlankLines _ : xs) = go xs
        go (Prefixed s d' : xs) = Prefixed s (chomp d') : xs
        go xs = xs

outp :: (IsString a) => Int -> String -> DocState a
outp off s | off < 0 = do  -- offset < 0 means newline characters
  st' <- get
  let rawpref = prefix st'
  when (column st' == 0 && usePrefix st' && not (null rawpref)) $ do
    let pref = reverse $ dropWhile isSpace $ reverse rawpref
    modify $ \st -> st{ output = fromString pref : output st
                      , column = column st + realLength pref }
  let numnewlines = length $ takeWhile (=='\n') $ reverse s
  modify $ \st -> st { output = fromString s : output st
                     , column = 0
                     , newlines = newlines st + numnewlines }
outp off s = do           -- offset >= 0 (0 might be combining char)
  st' <- get
  let pref = prefix st'
  when (column st' == 0 && usePrefix st' && not (null pref)) $ do
    modify $ \st -> st{ output = fromString pref : output st
                      , column = column st + realLength pref }
  modify $ \st -> st{ output = fromString s : output st
                    , column = column st + off
                    , newlines = 0 }

-- | Renders a 'Doc'.  @render (Just n)@ will use
-- a line length of @n@ to reflow text on breakable spaces.
-- @render Nothing@ will not reflow text.
render :: (IsString a) => Maybe Int -> Doc -> a
render linelen doc = fromString . mconcat . reverse . output $
  execState (renderDoc doc) startingState
   where startingState = RenderState{
                            output = mempty
                          , prefix = ""
                          , usePrefix = True
                          , lineLength = linelen
                          , column = 0
                          , newlines = 2 }

renderDoc :: (IsString a, Monoid a)
          => Doc -> DocState a
renderDoc = renderList . toList . unDoc

data IsBlock = IsBlock Int [String]

-- This would be nicer with a pattern synonym
-- pattern VBlock i s <- mkIsBlock -> Just (IsBlock ..)

renderList :: (IsString a, Monoid a)
           => [D] -> DocState a
renderList [] = return ()
renderList (Text off s : xs) = do
  outp off s
  renderList xs

renderList (Prefixed pref d : xs) = do
  st <- get
  let oldPref = prefix st
  put st{ prefix = prefix st ++ pref }
  renderDoc d
  modify $ \s -> s{ prefix = oldPref }
  renderList xs

renderList (Flush d : xs) = do
  st <- get
  let oldUsePrefix = usePrefix st
  put st{ usePrefix = False }
  renderDoc d
  modify $ \s -> s{ usePrefix = oldUsePrefix }
  renderList xs

renderList (BeforeNonBlank d : xs) =
  case xs of
    (x:_) | isBlank x -> renderList xs
          | otherwise -> renderDoc d >> renderList xs
    []                -> renderList xs

renderList [BlankLines _] = return ()

renderList (BlankLines m : BlankLines n : xs) =
  renderList (BlankLines (max m n) : xs)

renderList (BlankLines num : xs) = do
  st <- get
  case output st of
     _ | newlines st > num -> return ()
       | otherwise -> replicateM_ (1 + num - newlines st) (outp (-1) "\n")
  renderList xs

renderList (CarriageReturn : BlankLines m : xs) =
  renderList (BlankLines m : xs)

renderList (CarriageReturn : xs) = do
  st <- get
  if newlines st > 0 || null xs
     then renderList xs
     else do
       outp (-1) "\n"
       renderList xs

renderList (NewLine : xs) = do
  outp (-1) "\n"
  renderList xs

renderList (BreakingSpace : CarriageReturn : xs) = renderList (CarriageReturn:xs)
renderList (BreakingSpace : NewLine : xs) = renderList (NewLine:xs)
renderList (BreakingSpace : BlankLines n : xs) = renderList (BlankLines n:xs)
renderList (BreakingSpace : BreakingSpace : xs) = renderList (BreakingSpace:xs)
renderList (BreakingSpace : xs) = do
  let isText (Text _ _)       = True
      isText (Block _ _)      = True
      isText _                = False
  let isBreakingSpace BreakingSpace = True
      isBreakingSpace _             = False
  let xs' = dropWhile isBreakingSpace xs
  let next = takeWhile isText xs'
  st <- get
  let off = sum $ map offsetOf next
  case lineLength st of
        Just l | column st + 1 + off > l -> do
          outp (-1) "\n"
          renderList xs'
        _  -> do
          outp 1 " "
          renderList xs'

renderList (Block i1 s1 : Block i2 s2  : xs) =
  renderList (mergeBlocks False (IsBlock i1 s1) (IsBlock i2 s2) : xs)

renderList (Block i1 s1 : BreakingSpace : Block i2 s2 : xs) =
  renderList (mergeBlocks True (IsBlock i1 s1) (IsBlock i2 s2) : xs)

renderList (Block _width lns : xs) = do
  st <- get
  let oldPref = prefix st
  case column st - realLength oldPref of
        n | n > 0 -> modify $ \s -> s{ prefix = oldPref ++ replicate n ' ' }
        _         -> return ()
  renderList $ intersperse CarriageReturn (map (Text 0) lns)
  modify $ \s -> s{ prefix = oldPref }
  renderList xs

mergeBlocks :: Bool -> IsBlock -> IsBlock -> D
mergeBlocks addSpace (IsBlock w1 lns1) (IsBlock w2 lns2) =
  Block (w1 + w2 + if addSpace then 1 else 0) $
     zipWith (\l1 l2 -> pad w1 l1 ++ l2) lns1' (map sp lns2')
    where (lns1', lns2') = case (length lns1, length lns2) of
                                (x, y) | x > y -> (lns1,
                                                   lns2 ++ replicate (x - y) "")
                                       | x < y -> (lns1 ++ replicate (y - x) "",
                                                   lns2)
                                       | otherwise -> (lns1, lns2)
          pad n s = s ++ replicate (n - realLength s) ' '
          sp "" = ""
          sp xs = if addSpace then (' ' : xs) else xs

offsetOf :: D -> Int
offsetOf (Text o _)       = o
offsetOf (Block w _)      = w
offsetOf BreakingSpace    = 1
offsetOf _                = 0

-- | A literal string.
text :: String -> Doc
text = Doc . toChunks
  where toChunks :: String -> Seq D
        toChunks [] = mempty
        toChunks s = case break (=='\n') s of
                          ([], _:ys) -> NewLine <| toChunks ys
                          (xs, _:ys) -> Text (realLength xs) xs <|
                                            (NewLine <| toChunks ys)
                          (xs, [])      -> singleton $ Text (realLength xs) xs

-- | A character.
char :: Char -> Doc
char c = text [c]

-- | A breaking (reflowable) space.
space :: Doc
space = Doc $ singleton BreakingSpace

-- | A carriage return.  Does nothing if we're at the beginning of
-- a line; otherwise inserts a newline.
cr :: Doc
cr = Doc $ singleton CarriageReturn

-- | Inserts a blank line unless one exists already.
-- (@blankline <> blankline@ has the same effect as @blankline@.
blankline :: Doc
blankline = Doc $ singleton (BlankLines 1)

-- | Inserts a blank lines unless they exists already.
-- (@blanklines m <> blanklines n@ has the same effect as @blankline (max m n)@.
blanklines :: Int -> Doc
blanklines n = Doc $ singleton (BlankLines n)

-- | Uses the specified string as a prefix for every line of
-- the inside document (except the first, if not at the beginning
-- of the line).
prefixed :: String -> Doc -> Doc
prefixed pref doc = Doc $ singleton $ Prefixed pref doc

-- | Makes a 'Doc' flush against the left margin.
flush :: Doc -> Doc
flush doc = Doc $ singleton $ Flush doc

-- | Indents a 'Doc' by the specified number of spaces.
nest :: Int -> Doc -> Doc
nest ind = prefixed (replicate ind ' ')

-- | A hanging indent. @hang ind start doc@ prints @start@,
-- then @doc@, leaving an indent of @ind@ spaces on every
-- line but the first.
hang :: Int -> Doc -> Doc -> Doc
hang ind start doc = start <> nest ind doc

-- | @beforeNonBlank d@ conditionally includes @d@ unless it is
-- followed by blank space.
beforeNonBlank :: Doc -> Doc
beforeNonBlank d = Doc $ singleton (BeforeNonBlank d)

-- | Makes a 'Doc' non-reflowable.
nowrap :: Doc -> Doc
nowrap doc = Doc $ mapWithIndex replaceSpace $ unDoc doc
  where replaceSpace _ BreakingSpace = Text 1 " "
        replaceSpace _ x = x

-- | Returns the width of a 'Doc'.
offset :: Doc -> Int
offset d = case map realLength . lines . render Nothing $ d of
                []    -> 0
                os    -> maximum os

-- | Returns the minimal width of a 'Doc' when reflowed at breakable spaces.
minOffset :: Doc -> Int
minOffset d = maximum (0: map realLength (lines $ render (Just 0) d))

-- | @lblock n d@ is a block of width @n@ characters, with
-- text derived from @d@ and aligned to the left.
lblock :: Int -> Doc -> Doc
lblock = block id

-- | Like 'lblock' but aligned to the right.
rblock :: Int -> Doc -> Doc
rblock w = block (\s -> replicate (w - realLength s) ' ' ++ s) w

-- | Like 'lblock' but aligned centered.
cblock :: Int -> Doc -> Doc
cblock w = block (\s -> replicate ((w - realLength s) `div` 2) ' ' ++ s) w

-- | Returns the height of a block or other 'Doc'.
height :: Doc -> Int
height = length . lines . render Nothing

block :: (String -> String) -> Int -> Doc -> Doc
block filler width d
  | width < 1 && not (isEmpty d) = error "Text.Pandoc.Pretty.block: width < 1"
  | otherwise                    = Doc $ singleton $ Block width $ map filler
                                 $ chop width $ render (Just width) d

chop :: Int -> String -> [String]
chop _ [] = []
chop n cs = case break (=='\n') cs of
                  (xs, ys)     -> if len <= n
                                     then case ys of
                                             []     -> [xs]
                                             ['\n'] -> [xs]
                                             (_:zs) -> xs : chop n zs
                                     else take n xs : chop n (drop n xs ++ ys)
                                   where len = realLength xs

-- | Encloses a 'Doc' inside a start and end 'Doc'.
inside :: Doc -> Doc -> Doc -> Doc
inside start end contents =
  start <> contents <> end

-- | Puts a 'Doc' in curly braces.
braces :: Doc -> Doc
braces = inside (char '{') (char '}')

-- | Puts a 'Doc' in square brackets.
brackets :: Doc -> Doc
brackets = inside (char '[') (char ']')

-- | Puts a 'Doc' in parentheses.
parens :: Doc -> Doc
parens = inside (char '(') (char ')')

-- | Wraps a 'Doc' in single quotes.
quotes :: Doc -> Doc
quotes = inside (char '\'') (char '\'')

-- | Wraps a 'Doc' in double quotes.
doubleQuotes :: Doc -> Doc
doubleQuotes = inside (char '"') (char '"')

-- | Returns width of a character in a monospace font:  0 for a combining
-- character, 1 for a regular character, 2 for an East Asian wide character.
charWidth :: Char -> Int
charWidth c =
  case c of
      _ | c <  '\x0300'                    -> 1
        | c >= '\x0300' && c <= '\x036F'   -> 0  -- combining
        | c >= '\x0370' && c <= '\x10FC'   -> 1
        | c >= '\x1100' && c <= '\x115F'   -> 2
        | c >= '\x1160' && c <= '\x11A2'   -> 1
        | c >= '\x11A3' && c <= '\x11A7'   -> 2
        | c >= '\x11A8' && c <= '\x11F9'   -> 1
        | c >= '\x11FA' && c <= '\x11FF'   -> 2
        | c >= '\x1200' && c <= '\x2328'   -> 1
        | c >= '\x2329' && c <= '\x232A'   -> 2
        | c >= '\x232B' && c <= '\x2E31'   -> 1
        | c >= '\x2E80' && c <= '\x303E'   -> 2
        | c == '\x303F'                    -> 1
        | c >= '\x3041' && c <= '\x3247'   -> 2
        | c >= '\x3248' && c <= '\x324F'   -> 1 -- ambiguous
        | c >= '\x3250' && c <= '\x4DBF'   -> 2
        | c >= '\x4DC0' && c <= '\x4DFF'   -> 1
        | c >= '\x4E00' && c <= '\xA4C6'   -> 2
        | c >= '\xA4D0' && c <= '\xA95F'   -> 1
        | c >= '\xA960' && c <= '\xA97C'   -> 2
        | c >= '\xA980' && c <= '\xABF9'   -> 1
        | c >= '\xAC00' && c <= '\xD7FB'   -> 2
        | c >= '\xD800' && c <= '\xDFFF'   -> 1
        | c >= '\xE000' && c <= '\xF8FF'   -> 1 -- ambiguous
        | c >= '\xF900' && c <= '\xFAFF'   -> 2
        | c >= '\xFB00' && c <= '\xFDFD'   -> 1
        | c >= '\xFE00' && c <= '\xFE0F'   -> 1 -- ambiguous
        | c >= '\xFE10' && c <= '\xFE19'   -> 2
        | c >= '\xFE20' && c <= '\xFE26'   -> 1
        | c >= '\xFE30' && c <= '\xFE6B'   -> 2
        | c >= '\xFE70' && c <= '\xFEFF'   -> 1
        | c >= '\xFF01' && c <= '\xFF60'   -> 2
        | c >= '\xFF61' && c <= '\x16A38'  -> 1
        | c >= '\x1B000' && c <= '\x1B001' -> 2
        | c >= '\x1D000' && c <= '\x1F1FF' -> 1
        | c >= '\x1F200' && c <= '\x1F251' -> 2
        | c >= '\x1F300' && c <= '\x1F773' -> 1
        | c >= '\x20000' && c <= '\x3FFFD' -> 2
        | otherwise                        -> 1

-- | Get real length of string, taking into account combining and double-wide
-- characters.
realLength :: String -> Int
realLength = foldr (\a b -> charWidth a + b) 0