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|
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-
Copyright (C) 2010 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 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
, space
, text
, char
, prefixed
, flush
, nest
, hang
, beforeNonBlank
, nowrap
, offset
, height
, lblock
, cblock
, rblock
, (<>)
, (<+>)
, ($$)
, ($+$)
, isEmpty
, empty
, cat
, hcat
, hsep
, vcat
, vsep
, chomp
, inside
, braces
, brackets
, parens
, quotes
, doubleQuotes
, charWidth
, realLength
)
where
import Data.DList (DList, fromList, toList, cons, singleton)
import Data.List (intercalate)
import Data.Monoid
import Data.String
import Control.Monad.State
import Data.Char (isSpace)
data Monoid a =>
RenderState a = RenderState{
output :: [a] -- ^ In reverse order
, prefix :: String
, usePrefix :: Bool
, lineLength :: Maybe Int -- ^ 'Nothing' means no wrapping
, column :: Int
, newlines :: Int -- ^ Number of preceding newlines
}
type DocState a = State (RenderState a) ()
data D = Text Int String
| Block Int [String]
| Prefixed String Doc
| BeforeNonBlank Doc
| Flush Doc
| BreakingSpace
| CarriageReturn
| NewLine
| BlankLine
deriving (Show)
newtype Doc = Doc { unDoc :: DList D }
deriving (Monoid)
instance Show Doc where
show = render Nothing
instance IsString Doc where
fromString = text
isBlank :: D -> Bool
isBlank BreakingSpace = True
isBlank CarriageReturn = True
isBlank NewLine = True
isBlank BlankLine = True
isBlank (Text _ (c:_)) = isSpace c
isBlank _ = False
-- | True if the document is empty.
isEmpty :: Doc -> Bool
isEmpty = null . toList . unDoc
-- | The empty document.
empty :: Doc
empty = mempty
-- | @a <> b@ is the result of concatenating @a@ with @b@.
(<>) :: Doc -> Doc -> Doc
(<>) = mappend
-- | Concatenate a list of 'Doc's.
cat :: [Doc] -> Doc
cat = mconcat
-- | Same as 'cat'.
hcat :: [Doc] -> Doc
hcat = mconcat
-- | Concatenate a list of 'Doc's, putting breakable spaces
-- between them.
(<+>) :: Doc -> Doc -> Doc
(<+>) x y = if isEmpty x
then y
else if isEmpty y
then x
else x <> space <> y
-- | Same as 'cat', but putting breakable spaces between the
-- 'Doc's.
hsep :: [Doc] -> Doc
hsep = foldr (<+>) empty
-- | @a $$ 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
-- | @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
-- | Chomps trailing blank space off of a 'Doc'.
chomp :: Doc -> Doc
chomp d = Doc (fromList dl')
where dl = toList (unDoc d)
dl' = reverse $ dropWhile removeable $ reverse dl
removeable BreakingSpace = True
removeable CarriageReturn = True
removeable NewLine = True
removeable BlankLine = True
removeable _ = False
outp :: (IsString a, Monoid a)
=> Int -> String -> DocState a
outp off s | off <= 0 = do
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 }
when (off < 0) $ do
modify $ \st -> st { output = fromString s : output st
, column = 0
, newlines = newlines st + 1 }
outp off s = do
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 :: (Monoid a, 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
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 (BlankLine : xs) = do
st <- get
case output st of
_ | newlines st > 1 || null xs -> return ()
_ | column st == 0 -> do
outp (-1) "\n"
_ -> do
outp (-1) "\n"
outp (-1) "\n"
renderList 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 : BlankLine : xs) = renderList (BlankLine: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 (b1@Block{} : b2@Block{} : xs) =
renderList (mergeBlocks False b1 b2 : xs)
renderList (b1@Block{} : BreakingSpace : b2@Block{} : xs) =
renderList (mergeBlocks True b1 b2 : 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 ()
renderDoc $ blockToDoc width lns
modify $ \s -> s{ prefix = oldPref }
renderList xs
mergeBlocks :: Bool -> D -> D -> D
mergeBlocks addSpace (Block w1 lns1) (Block w2 lns2) =
Block (w1 + w2 + if addSpace then 1 else 0) $
zipWith (\l1 l2 -> pad w1 l1 ++ l2) (lns1 ++ empties) (map sp lns2 ++ empties)
where empties = replicate (abs $ length lns1 - length lns2) ""
pad n s = s ++ replicate (n - realLength s) ' '
sp "" = ""
sp xs = if addSpace then (' ' : xs) else xs
mergeBlocks _ _ _ = error "mergeBlocks tried on non-Block!"
blockToDoc :: Int -> [String] -> Doc
blockToDoc _ lns = text $ intercalate "\n" lns
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 -> DList D
toChunks [] = mempty
toChunks s = case break (=='\n') s of
([], _:ys) -> NewLine `cons` toChunks ys
(xs, _:ys) -> Text (realLength xs) xs `cons`
NewLine `cons` 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@.
-- If you want multiple blank lines, use @text "\\n\\n"@.
blankline :: Doc
blankline = Doc $ singleton BlankLine
-- | 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 $ fromList $ map replaceSpace $ toList $ 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
block :: (String -> String) -> Int -> Doc -> Doc
block filler width = Doc . singleton . Block width .
map filler . chop width . render (Just width)
-- | @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
chop :: Int -> String -> [String]
chop _ [] = []
chop n cs = case break (=='\n') cs of
(xs, ys) -> if len <= n
then case ys of
[] -> [xs]
(_:[]) -> [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 >= '\x300' && c <= '\x36e' -> 0 -- combining
| c == '\x3000' -> 2 -- full
| c >= '\xFF01' && c <= '\xFF60' -> 2
| c >= '\xFFE0' && c <= '\xFFE6' -> 2
| c >= '\x1100' && c <= '\x1159' -> 2 -- wide
| c >= '\x115F' && c <= '\x115F' -> 2
| c >= '\x2329' && c <= '\x232A' -> 2
| c >= '\x2E80' && c <= '\x2E99' -> 2
| c >= '\x2E9B' && c <= '\x2EF3' -> 2
| c >= '\x2F00' && c <= '\x2FD5' -> 2
| c >= '\x2FF0' && c <= '\x2FFB' -> 2
| c >= '\x3001' && c <= '\x303E' -> 2
| c >= '\x3041' && c <= '\x3096' -> 2
| c >= '\x3099' && c <= '\x30FF' -> 2
| c >= '\x3105' && c <= '\x312C' -> 2
| c >= '\x3131' && c <= '\x318E' -> 2
| c >= '\x3190' && c <= '\x31B7' -> 2
| c >= '\x31F0' && c <= '\x321E' -> 2
| c >= '\x3220' && c <= '\x3243' -> 2
| c >= '\x3250' && c <= '\x327D' -> 2
| c >= '\x327F' && c <= '\x32FE' -> 2
| c >= '\x3300' && c <= '\x33FF' -> 2
| c >= '\xA000' && c <= '\xA48C' -> 2
| c >= '\xA490' && c <= '\xA4C6' -> 2
| c >= '\xF900' && c <= '\xFA2D' -> 2
| c >= '\xFA30' && c <= '\xFA6A' -> 2
| c >= '\xFE30' && c <= '\xFE52' -> 2
| c >= '\xFE54' && c <= '\xFE66' -> 2
| c >= '\xFE68' && c <= '\xFE6B' -> 2
| c >= '\x2F800' && c <= '\x2FA1D' -> 2
| otherwise -> 1
-- | Get real length of string, taking into account combining and double-wide
-- characters.
realLength :: String -> Int
realLength = sum . map charWidth
|