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path: root/src/Text/Pandoc/Entities.hs
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{-
Copyright (C) 2006 John MacFarlane <jgm at berkeley dot 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  02111-1307  USA
-}

{- |
   Module      : Text.Pandoc.Entities
   Copyright   : Copyright (C) 2006 John MacFarlane
   License     : GNU GPL, version 2 or above 

   Maintainer  : John MacFarlane <jgm at berkeley dot edu>
   Stability   : alpha
   Portability : portable

Functions for encoding unicode characters as entity references,
and vice versa.
-}
module Text.Pandoc.Entities (
                     charToEntity,
                     charToNumericalEntity,
                     decodeEntities,
                     escapeSGMLChar,
                     escapeSGMLString,
                     characterEntity
                    ) where
import Data.Char ( chr, ord )
import Text.ParserCombinators.Parsec
import Data.Maybe ( fromMaybe )

-- | Returns a string containing an entity reference for the character.
charToEntity :: Char -> String
charToEntity char = 
  let matches = filter (\(entity, character) -> (character == char)) 
                       entityTable in
  if (length matches) == 0
     then charToNumericalEntity char
     else fst (head matches)

-- | Returns a string containing a numerical entity reference for the char.
charToNumericalEntity :: Char -> String
charToNumericalEntity ch = "&#" ++ show (ord ch) ++ ";"

-- | Parse SGML character entity.
characterEntity :: GenParser Char st Char
characterEntity = namedEntity <|> hexEntity <|> decimalEntity <?> "SGML entity"

-- | Parse SGML character entity.
namedEntity :: GenParser Char st Char
namedEntity = try $ do
  st <- char '&'
  body <- many1 alphaNum
  end <- char ';'
  let entity = "&" ++ body ++ ";"
  return $ case (lookup entity entityTable) of
             Just ch -> ch
             Nothing -> '?'
   
-- | Parse SGML hexadecimal entity.
hexEntity :: GenParser Char st Char
hexEntity = try $ do
  st <- string "&#"
  hex <- oneOf "Xx"
  body <- many1 (oneOf "0123456789ABCDEFabcdef")
  end <- char ';'
  return $ chr $ read ('0':'x':body)

-- | Parse SGML decimal entity.
decimalEntity :: GenParser Char st Char
decimalEntity = try $ do
  st <- string "&#"
  body <- many1 digit
  end <- char ';'
  return $ chr $ read body

-- | Escape one character as needed for SGML.
escapeSGMLChar :: Char -> String
escapeSGMLChar x = 
  case x of
    '&'  -> "&amp;"
    '<'  -> "&lt;"
    '>'  -> "&gt;"
    '"'  -> "&quot;"
    c    -> [c] 

-- | True if the character needs to be escaped.
needsEscaping :: Char -> Bool
needsEscaping c = c `elem` "&<>\""

-- | Escape string as needed for SGML.  Entity references are not preserved.
escapeSGMLString :: String -> String
escapeSGMLString ""  = ""
escapeSGMLString str = 
  case break needsEscaping str of
    (okay, "")     -> okay
    (okay, (c:cs)) -> okay ++ escapeSGMLChar c ++ escapeSGMLString cs 

-- | Convert entities in a string to characters.
decodeEntities :: String -> String
decodeEntities str = 
  case parse (many (characterEntity <|> anyChar)) str str of
	Left err        -> error $ "\nError: " ++ show err
	Right result    -> result

entityTable :: [(String, Char)]
entityTable =  [
	("&quot;", chr 34),
	("&amp;", chr 38),
	("&lt;", chr 60),
	("&gt;", chr 62),
	("&nbsp;", chr 160),
	("&iexcl;", chr 161),
	("&cent;", chr 162),
	("&pound;", chr 163),
	("&curren;", chr 164),
	("&yen;", chr 165),
	("&brvbar;", chr 166),
	("&sect;", chr 167),
	("&uml;", chr 168),
	("&copy;", chr 169),
	("&ordf;", chr 170),
	("&laquo;", chr 171),
	("&not;", chr 172),
	("&shy;", chr 173),
	("&reg;", chr 174),
	("&macr;", chr 175),
	("&deg;", chr 176),
	("&plusmn;", chr 177),
	("&sup2;", chr 178),
	("&sup3;", chr 179),
	("&acute;", chr 180),
	("&micro;", chr 181),
	("&para;", chr 182),
	("&middot;", chr 183),
	("&cedil;", chr 184),
	("&sup1;", chr 185),
	("&ordm;", chr 186),
	("&raquo;", chr 187),
	("&frac14;", chr 188),
	("&frac12;", chr 189),
	("&frac34;", chr 190),
	("&iquest;", chr 191),
	("&Agrave;", chr 192),
	("&Aacute;", chr 193),
	("&Acirc;", chr 194),
	("&Atilde;", chr 195),
	("&Auml;", chr 196),
	("&Aring;", chr 197),
	("&AElig;", chr 198),
	("&Ccedil;", chr 199),
	("&Egrave;", chr 200),
	("&Eacute;", chr 201),
	("&Ecirc;", chr 202),
	("&Euml;", chr 203),
	("&Igrave;", chr 204),
	("&Iacute;", chr 205),
	("&Icirc;", chr 206),
	("&Iuml;", chr 207),
	("&ETH;", chr 208),
	("&Ntilde;", chr 209),
	("&Ograve;", chr 210),
	("&Oacute;", chr 211),
	("&Ocirc;", chr 212),
	("&Otilde;", chr 213),
	("&Ouml;", chr 214),
	("&times;", chr 215),
	("&Oslash;", chr 216),
	("&Ugrave;", chr 217),
	("&Uacute;", chr 218),
	("&Ucirc;", chr 219),
	("&Uuml;", chr 220),
	("&Yacute;", chr 221),
	("&THORN;", chr 222),
	("&szlig;", chr 223),
	("&agrave;", chr 224),
	("&aacute;", chr 225),
	("&acirc;", chr 226),
	("&atilde;", chr 227),
	("&auml;", chr 228),
	("&aring;", chr 229),
	("&aelig;", chr 230),
	("&ccedil;", chr 231),
	("&egrave;", chr 232),
	("&eacute;", chr 233),
	("&ecirc;", chr 234),
	("&euml;", chr 235),
	("&igrave;", chr 236),
	("&iacute;", chr 237),
	("&icirc;", chr 238),
	("&iuml;", chr 239),
	("&eth;", chr 240),
	("&ntilde;", chr 241),
	("&ograve;", chr 242),
	("&oacute;", chr 243),
	("&ocirc;", chr 244),
	("&otilde;", chr 245),
	("&ouml;", chr 246),
	("&divide;", chr 247),
	("&oslash;", chr 248),
	("&ugrave;", chr 249),
	("&uacute;", chr 250),
	("&ucirc;", chr 251),
	("&uuml;", chr 252),
	("&yacute;", chr 253),
	("&thorn;", chr 254),
	("&yuml;", chr 255),
	("&OElig;", chr 338),
	("&oelig;", chr 339),
	("&Scaron;", chr 352),
	("&scaron;", chr 353),
	("&Yuml;", chr 376),
	("&fnof;", chr 402),
	("&circ;", chr 710),
	("&tilde;", chr 732),
	("&Alpha;", chr 913),
	("&Beta;", chr 914),
	("&Gamma;", chr 915),
	("&Delta;", chr 916),
	("&Epsilon;", chr 917),
	("&Zeta;", chr 918),
	("&Eta;", chr 919),
	("&Theta;", chr 920),
	("&Iota;", chr 921),
	("&Kappa;", chr 922),
	("&Lambda;", chr 923),
	("&Mu;", chr 924),
	("&Nu;", chr 925),
	("&Xi;", chr 926),
	("&Omicron;", chr 927),
	("&Pi;", chr 928),
	("&Rho;", chr 929),
	("&Sigma;", chr 931),
	("&Tau;", chr 932),
	("&Upsilon;", chr 933),
	("&Phi;", chr 934),
	("&Chi;", chr 935),
	("&Psi;", chr 936),
	("&Omega;", chr 937),
	("&alpha;", chr 945),
	("&beta;", chr 946),
	("&gamma;", chr 947),
	("&delta;", chr 948),
	("&epsilon;", chr 949),
	("&zeta;", chr 950),
	("&eta;", chr 951),
	("&theta;", chr 952),
	("&iota;", chr 953),
	("&kappa;", chr 954),
	("&lambda;", chr 955),
	("&mu;", chr 956),
	("&nu;", chr 957),
	("&xi;", chr 958),
	("&omicron;", chr 959),
	("&pi;", chr 960),
	("&rho;", chr 961),
	("&sigmaf;", chr 962),
	("&sigma;", chr 963),
	("&tau;", chr 964),
	("&upsilon;", chr 965),
	("&phi;", chr 966),
	("&chi;", chr 967),
	("&psi;", chr 968),
	("&omega;", chr 969),
	("&thetasym;", chr 977),
	("&upsih;", chr 978),
	("&piv;", chr 982),
	("&ensp;", chr 8194),
	("&emsp;", chr 8195),
	("&thinsp;", chr 8201),
	("&zwnj;", chr 8204),
	("&zwj;", chr 8205),
	("&lrm;", chr 8206),
	("&rlm;", chr 8207),
	("&ndash;", chr 8211),
	("&mdash;", chr 8212),
	("&lsquo;", chr 8216),
	("&rsquo;", chr 8217),
	("&sbquo;", chr 8218),
	("&ldquo;", chr 8220),
	("&rdquo;", chr 8221),
	("&bdquo;", chr 8222),
	("&dagger;", chr 8224),
	("&Dagger;", chr 8225),
	("&bull;", chr 8226),
	("&hellip;", chr 8230),
	("&permil;", chr 8240),
	("&prime;", chr 8242),
	("&Prime;", chr 8243),
	("&lsaquo;", chr 8249),
	("&rsaquo;", chr 8250),
	("&oline;", chr 8254),
	("&frasl;", chr 8260),
	("&euro;", chr 8364),
	("&image;", chr 8465),
	("&weierp;", chr 8472),
	("&real;", chr 8476),
	("&trade;", chr 8482),
	("&alefsym;", chr 8501),
	("&larr;", chr 8592),
	("&uarr;", chr 8593),
	("&rarr;", chr 8594),
	("&darr;", chr 8595),
	("&harr;", chr 8596),
	("&crarr;", chr 8629),
	("&lArr;", chr 8656),
	("&uArr;", chr 8657),
	("&rArr;", chr 8658),
	("&dArr;", chr 8659),
	("&hArr;", chr 8660),
	("&forall;", chr 8704),
	("&part;", chr 8706),
	("&exist;", chr 8707),
	("&empty;", chr 8709),
	("&nabla;", chr 8711),
	("&isin;", chr 8712),
	("&notin;", chr 8713),
	("&ni;", chr 8715),
	("&prod;", chr 8719),
	("&sum;", chr 8721),
	("&minus;", chr 8722),
	("&lowast;", chr 8727),
	("&radic;", chr 8730),
	("&prop;", chr 8733),
	("&infin;", chr 8734),
	("&ang;", chr 8736),
	("&and;", chr 8743),
	("&or;", chr 8744),
	("&cap;", chr 8745),
	("&cup;", chr 8746),
	("&int;", chr 8747),
	("&there4;", chr 8756),
	("&sim;", chr 8764),
	("&cong;", chr 8773),
	("&asymp;", chr 8776),
	("&ne;", chr 8800),
	("&equiv;", chr 8801),
	("&le;", chr 8804),
	("&ge;", chr 8805),
	("&sub;", chr 8834),
	("&sup;", chr 8835),
	("&nsub;", chr 8836),
	("&sube;", chr 8838),
	("&supe;", chr 8839),
	("&oplus;", chr 8853),
	("&otimes;", chr 8855),
	("&perp;", chr 8869),
	("&sdot;", chr 8901),
	("&lceil;", chr 8968),
	("&rceil;", chr 8969),
	("&lfloor;", chr 8970),
	("&rfloor;", chr 8971),
	("&lang;", chr 9001),
	("&rang;", chr 9002),
	("&loz;", chr 9674),
	("&spades;", chr 9824),
	("&clubs;", chr 9827),
	("&hearts;", chr 9829),
	("&diams;", chr 9830)
	]