127 lines
4.5 KiB
Haskell
127 lines
4.5 KiB
Haskell
{-# LANGUAGE NoImplicitPrelude #-}
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{-
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Copyright (C) 2017–2018 John MacFarlane <jgm@berkeley.edu>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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-}
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{- |
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Module : Text.Pandoc.BCP47
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Copyright : Copyright (C) 2017–2018 John MacFarlane
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License : GNU GPL, version 2 or above
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Maintainer : John MacFarlane <jgm@berkeley.edu>
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Stability : alpha
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Portability : portable
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Functions for parsing and rendering BCP47 language identifiers.
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-}
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module Text.Pandoc.BCP47 (
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getLang
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, parseBCP47
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, Lang(..)
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, renderLang
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)
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where
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import Prelude
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import Control.Monad (guard)
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import Data.Char (isAlphaNum, isAscii, isLetter, isLower, isUpper, toLower,
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toUpper)
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import Data.List (intercalate)
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import Text.Pandoc.Definition
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import Text.Pandoc.Options
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import qualified Text.Parsec as P
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-- | Represents BCP 47 language/country code.
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data Lang = Lang{ langLanguage :: String
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, langScript :: String
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, langRegion :: String
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, langVariants :: [String] }
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deriving (Eq, Ord, Show)
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-- | Render a Lang as BCP 47.
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renderLang :: Lang -> String
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renderLang lang = intercalate "-" (langLanguage lang : filter (not . null)
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([langScript lang, langRegion lang] ++ langVariants lang))
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-- | Get the contents of the `lang` metadata field or variable.
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getLang :: WriterOptions -> Meta -> Maybe String
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getLang opts meta =
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case lookup "lang" (writerVariables opts) of
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Just s -> Just s
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_ ->
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case lookupMeta "lang" meta of
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Just (MetaInlines [Str s]) -> Just s
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Just (MetaString s) -> Just s
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_ -> Nothing
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-- | Parse a BCP 47 string as a Lang. Currently we parse
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-- extensions and private-use fields as "variants," even
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-- though officially they aren't.
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parseBCP47 :: String -> Either String Lang
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parseBCP47 lang =
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case P.parse bcp47 "lang" lang of
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Right r -> Right r
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Left e -> Left $ show e
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where bcp47 = do
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language <- pLanguage
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script <- P.option "" pScript
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region <- P.option "" pRegion
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variants <- P.many (pVariant P.<|> pExtension P.<|> pPrivateUse)
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P.eof
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return Lang{ langLanguage = language
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, langScript = script
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, langRegion = region
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, langVariants = variants }
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asciiLetter = P.satisfy (\c -> isAscii c && isLetter c)
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pLanguage = do
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cs <- P.many1 asciiLetter
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let lcs = length cs
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guard $ lcs == 2 || lcs == 3
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return $ map toLower cs
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pScript = P.try $ do
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P.char '-'
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x <- P.satisfy (\c -> isAscii c && isLetter c && isUpper c)
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xs <- P.count 3
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(P.satisfy (\c -> isAscii c && isLetter c && isLower c))
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return $ map toLower (x:xs)
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pRegion = P.try $ do
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P.char '-'
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cs <- P.many1 asciiLetter
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let lcs = length cs
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guard $ lcs == 2 || lcs == 3
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return $ map toUpper cs
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pVariant = P.try $ do
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P.char '-'
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ds <- P.option "" (P.count 1 P.digit)
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cs <- P.many1 asciiLetter
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let var = ds ++ cs
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guard $ if null ds
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then length var >= 5 && length var <= 8
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else length var == 4
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return $ map toLower var
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pExtension = P.try $ do
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P.char '-'
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cs <- P.many1 $ P.satisfy (\c -> isAscii c && isAlphaNum c)
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guard $ length cs >= 2 && length cs <= 8
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return $ map toLower cs
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pPrivateUse = P.try $ do
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P.char '-'
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P.char 'x'
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P.char '-'
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cs <- P.many1 $ P.satisfy (\c -> isAscii c && isAlphaNum c)
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guard $ not (null cs) && length cs <= 8
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let var = "x-" ++ cs
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return $ map toLower var
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