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+{-# LANGUAGE OverloadedStrings #-}
+{-
+Copyright (C) 2014 Albert Krewinkel <tarleb@moltkeplatz.de>
+
+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.Readers.Org
+   Copyright   : Copyright (C) 2014 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb@moltkeplatz.de>
+
+Conversion of Org-Mode to 'Pandoc' document.
+-}
+module Text.Pandoc.Readers.Org ( readOrg ) where
+
+import qualified Text.Pandoc.Builder as B
+import           Text.Pandoc.Builder (Inlines, Blocks, trimInlines, (<>))
+import           Text.Pandoc.Definition
+import           Text.Pandoc.Options
+import           Text.Pandoc.Parsing hiding (orderedListMarker)
+import           Text.Pandoc.Shared (compactify')
+
+import           Control.Applicative (pure, (<$>), (<$), (<*>), (<*), (*>), (<**>))
+import           Control.Monad (guard, mzero)
+import           Data.Char (toLower)
+import           Data.List (foldl')
+import           Data.Maybe (listToMaybe, fromMaybe)
+import           Data.Monoid (mconcat, mempty, mappend)
+
+-- | Parse org-mode string and return a Pandoc document.
+readOrg :: ReaderOptions -- ^ Reader options
+        -> String        -- ^ String to parse (assuming @'\n'@ line endings)
+        -> Pandoc
+readOrg opts s = (readWith parseOrg) def{ stateOptions = opts } (s ++ "\n\n")
+
+type OrgParser = Parser [Char] ParserState
+
+parseOrg:: OrgParser Pandoc
+parseOrg = do
+  blocks' <- B.toList <$> parseBlocks
+  st <- getState
+  let meta = stateMeta st
+  return $ Pandoc meta $ filter (/= Null) blocks'
+
+--
+-- parsing blocks
+--
+
+parseBlocks :: OrgParser Blocks
+parseBlocks = mconcat <$> manyTill block eof
+
+block :: OrgParser Blocks
+block = choice [ mempty <$ blanklines
+               , orgBlock
+               , example
+               , drawer
+               , specialLine
+               , header
+               , hline
+               , list
+               , table
+               , paraOrPlain
+               ] <?> "block"
+
+--
+-- Org Blocks (#+BEGIN_... / #+END_...)
+--
+
+orgBlock :: OrgParser Blocks
+orgBlock = try $ do
+  (indent, blockType, args) <- blockHeader
+  blockStr <- rawBlockContent indent blockType
+  let classArgs = [ translateLang . fromMaybe [] $ listToMaybe args ]
+  case blockType of
+    "comment" -> return mempty
+    "src"     -> return $ B.codeBlockWith ("", classArgs, []) blockStr
+    _         -> B.divWith ("", [blockType], [])
+                            <$> (parseFromString parseBlocks blockStr)
+
+blockHeader :: OrgParser (Int, String, [String])
+blockHeader = (,,) <$> blockIndent
+                   <*> blockType
+                   <*> (skipSpaces *> blockArgs)
+ where blockIndent = length <$> many spaceChar
+       blockType = map toLower <$> (stringAnyCase "#+begin_" *> many letter)
+       blockArgs = manyTill (many nonspaceChar <* skipSpaces) newline
+
+rawBlockContent :: Int -> String -> OrgParser String
+rawBlockContent indent blockType =
+  unlines . map commaEscaped <$> manyTill indentedLine blockEnder
+ where
+   indentedLine = try $ choice [ blankline         *> pure "\n"
+                               , indentWith indent *> anyLine
+                               ]
+   blockEnder = try $ indentWith indent *> stringAnyCase ("#+end_" <> blockType)
+
+-- indent by specified number of spaces (or equiv. tabs)
+indentWith :: Int -> OrgParser String
+indentWith num = do
+  tabStop <- getOption readerTabStop
+  if (num < tabStop)
+     then count num (char ' ')
+     else choice [ try (count num (char ' '))
+                 , try (char '\t' >> count (num - tabStop) (char ' ')) ]
+
+translateLang :: String -> String
+translateLang "sh" = "bash"
+translateLang cs = cs
+
+commaEscaped :: String -> String
+commaEscaped (',':cs@('*':_))     = cs
+commaEscaped (',':cs@('#':'+':_)) = cs
+commaEscaped cs                   = cs
+
+example :: OrgParser Blocks
+example = try $
+  B.codeBlockWith ("", ["example"], []) . unlines <$> many1 exampleLine
+
+exampleLine :: OrgParser String
+exampleLine = try $ string ": " *> anyLine
+
+-- Drawers for properties or a logbook
+drawer :: OrgParser Blocks
+drawer = try $ do
+  drawerStart
+  manyTill drawerLine (try drawerEnd)
+  return mempty
+
+drawerStart :: OrgParser String
+drawerStart = try $
+  skipSpaces *> drawerName <* skipSpaces <* newline
+ where drawerName = try $  char ':' *> validDrawerName <* char ':'
+       validDrawerName =  stringAnyCase "PROPERTIES"
+                          <|> stringAnyCase "LOGBOOK"
+
+drawerLine :: OrgParser String
+drawerLine = try $ anyLine
+
+drawerEnd :: OrgParser String
+drawerEnd = try $
+  skipSpaces *> stringAnyCase ":END:" <* skipSpaces <* newline
+
+
+-- Comments, Options and Metadata
+specialLine :: OrgParser Blocks
+specialLine = try $ metaLine <|> commentLine
+
+metaLine :: OrgParser Blocks
+metaLine = try $ metaLineStart *> declarationLine
+
+commentLine :: OrgParser Blocks
+commentLine = try $ commentLineStart *> anyLine *> pure mempty
+
+-- The order, in which blocks are tried, makes sure that we're not looking at
+-- the beginning of a block, so we don't need to check for it
+metaLineStart :: OrgParser String
+metaLineStart = try $ mappend <$> many spaceChar <*> string "#+"
+
+commentLineStart :: OrgParser String
+commentLineStart = try $ mappend <$> many spaceChar <*> string "# "
+
+declarationLine :: OrgParser Blocks
+declarationLine = try $ do
+  meta' <- B.setMeta <$> metaKey <*> metaValue <*> pure nullMeta
+  updateState $ \st -> st { stateMeta = stateMeta st <> meta' }
+  return mempty
+
+metaValue :: OrgParser MetaValue
+metaValue = MetaInlines . B.toList . trimInlines <$> restOfLine
+
+metaKey :: OrgParser [Char]
+metaKey = map toLower <$> many1 (noneOf ": \n\r")
+                      <*  char ':'
+                      <*  skipSpaces
+
+-- | Headers
+header :: OrgParser Blocks
+header = try $
+  B.header <$> headerStart
+           <*> (trimInlines <$> restOfLine)
+
+headerStart :: OrgParser Int
+headerStart = try $
+  (length <$> many1 (char '*')) <* many1 (char ' ')
+
+-- Horizontal Line (five dashes or more)
+hline :: OrgParser Blocks
+hline = try $ do
+  skipSpaces
+  string "-----"
+  many (char '-')
+  skipSpaces
+  newline
+  return B.horizontalRule
+
+--
+-- Tables
+--
+
+data OrgTableRow = OrgContentRow [Blocks]
+                 | OrgAlignRow [Alignment]
+                 | OrgHlineRow
+ deriving (Eq, Show)
+
+type OrgTableContent = (Int, [Alignment], [Double], [Blocks], [[Blocks]])
+
+table :: OrgParser Blocks
+table = try $ do
+  lookAhead tableStart
+  (_, aligns, widths, heads, lns) <- normalizeTable . tableContent <$> tableRows
+  return $ B.table "" (zip aligns widths) heads lns
+
+tableStart :: OrgParser Char
+tableStart = try $ skipSpaces *> char '|'
+
+tableRows :: OrgParser [OrgTableRow]
+tableRows = try $ many (tableAlignRow <|> tableHline <|> tableContentRow)
+
+tableContentRow :: OrgParser OrgTableRow
+tableContentRow = try $
+  OrgContentRow <$> (tableStart *> manyTill tableContentCell newline)
+
+tableContentCell :: OrgParser Blocks
+tableContentCell = try $
+  B.plain . trimInlines . mconcat <$> many1Till inline (try endOfCell)
+
+endOfCell :: OrgParser Char
+-- endOfCell =  char '|' <|> newline
+endOfCell = try $ char '|' <|> lookAhead newline
+
+tableAlignRow :: OrgParser OrgTableRow
+tableAlignRow = try $
+  OrgAlignRow <$> (tableStart *> manyTill tableAlignCell newline)
+
+tableAlignCell :: OrgParser Alignment
+tableAlignCell =
+  choice [ try $ emptyCell *> return (AlignDefault)
+         , try $ skipSpaces
+                   *> char '<'
+                   *> tableAlignFromChar
+                   <* many digit
+                   <* char '>'
+                   <* emptyCell
+         ] <?> "alignment info"
+    where emptyCell = try $ skipSpaces *> endOfCell
+
+tableAlignFromChar :: OrgParser Alignment
+tableAlignFromChar = try $ choice [ char 'l' *> return AlignLeft
+                                  , char 'c' *> return AlignCenter
+                                  , char 'r' *> return AlignRight
+                                  ]
+
+tableHline :: OrgParser OrgTableRow
+tableHline = try $
+  OrgHlineRow <$ (tableStart *> char '-' *> anyLine)
+
+tableContent :: [OrgTableRow]
+             -> OrgTableContent
+tableContent = foldl' (flip rowToContent) (0, mempty, repeat 0, mempty, mempty)
+
+normalizeTable :: OrgTableContent
+               -> OrgTableContent
+normalizeTable (cols, aligns, widths, heads, lns) =
+  let aligns' = fillColumns aligns AlignDefault
+      widths' = fillColumns widths 0.0
+      heads'  = if heads == mempty
+                then heads
+                else fillColumns heads  (B.plain mempty)
+      lns'    = map (flip fillColumns (B.plain mempty)) lns
+      fillColumns base padding = take cols $ base ++ repeat padding
+  in (cols, aligns', widths', heads', lns')
+
+
+-- One or more horizontal rules after the first content line mark the previous
+-- line as a header.  All other horizontal lines are discarded.
+rowToContent :: OrgTableRow
+             -> OrgTableContent
+             -> OrgTableContent
+rowToContent OrgHlineRow        = maybeBodyToHeader
+rowToContent (OrgContentRow rs) = setLongestRow rs . appendToBody rs
+rowToContent (OrgAlignRow as)   = setLongestRow as . setAligns as
+
+setLongestRow :: [a]
+              -> OrgTableContent
+              -> OrgTableContent
+setLongestRow r (cols, aligns, widths, heads, lns) =
+  (max cols (length r), aligns, widths, heads, lns)
+
+maybeBodyToHeader :: OrgTableContent
+                  -> OrgTableContent
+maybeBodyToHeader (cols, aligns, widths, [], b:[]) = (cols, aligns, widths, b, [])
+maybeBodyToHeader content                          = content
+
+appendToBody :: [Blocks]
+             -> OrgTableContent
+             -> OrgTableContent
+appendToBody r (cols, aligns, widths, heads, lns) =
+  (cols, aligns, widths, heads, lns ++ [r])
+
+setAligns :: [Alignment]
+          -> OrgTableContent
+          -> OrgTableContent
+setAligns aligns (cols, _, widths, heads, lns) =
+   (cols, aligns, widths, heads, lns)
+
+-- Paragraphs or Plain text
+paraOrPlain :: OrgParser Blocks
+paraOrPlain = try $
+  trimInlines . mconcat
+    <$> many1 inline
+    <**> option B.plain
+                (try $ newline *> pure B.para)
+
+restOfLine :: OrgParser Inlines
+restOfLine = mconcat <$> manyTill inline newline
+
+
+--
+-- list blocks
+--
+
+list :: OrgParser Blocks
+list = choice [ bulletList, orderedList ] <?> "list"
+
+bulletList :: OrgParser Blocks
+bulletList = B.bulletList . compactify' <$> many1 (listItem bulletListStart)
+
+orderedList :: OrgParser Blocks
+orderedList = B.orderedList . compactify' <$> many1 (listItem orderedListStart)
+
+genericListStart :: OrgParser String
+                 -> OrgParser Int
+genericListStart listMarker = try $
+  (+) <$> (length <$> many spaceChar)
+      <*> (length <$> listMarker <* many1 spaceChar)
+
+-- parses bullet list start and returns its length (excl. following whitespace)
+bulletListStart :: OrgParser Int
+bulletListStart = genericListStart bulletListMarker
+  where bulletListMarker = pure <$> oneOf "*-+"
+
+orderedListStart :: OrgParser Int
+orderedListStart = genericListStart orderedListMarker
+  -- Ordered list markers allowed in org-mode
+  where orderedListMarker = mappend <$> many1 digit <*> (pure <$> oneOf ".)")
+
+listItem :: OrgParser Int
+         -> OrgParser Blocks
+listItem start = try $ do
+  (markerLength, first) <- try (start >>= rawListItem)
+  rest <- many (listContinuation markerLength)
+  parseFromString parseBlocks $ concat (first:rest)
+
+-- parse raw text for one list item, excluding start marker and continuations
+rawListItem :: Int
+            -> OrgParser (Int, String)
+rawListItem markerLength = try $ do
+  firstLine <- anyLine
+  restLines <- many (listLine markerLength)
+  return (markerLength, (firstLine ++ "\n" ++ (concat restLines)))
+
+-- continuation of a list item - indented and separated by blankline or endline.
+-- Note: nested lists are parsed as continuations.
+listContinuation :: Int
+                 -> OrgParser String
+listContinuation markerLength = try $
+  mappend <$> many blankline
+          <*> (concat <$> many1 (listLine markerLength))
+
+-- parse a line of a list item
+listLine :: Int
+         -> OrgParser String
+listLine markerLength = try $
+  indentWith markerLength *> anyLine
+    <**> pure (++ "\n")
+
+
+--
+-- inline
+--
+
+inline :: OrgParser Inlines
+inline = choice inlineParsers <?> "inline"
+  where inlineParsers = [ whitespace
+                        , link
+                        , str
+                        , endline
+                        , emph
+                        , strong
+                        , strikeout
+                        , underline
+                        , code
+                        , verbatim
+                        , subscript
+                        , superscript
+                        , symbol
+                        ]
+
+-- treat these as potentially non-text when parsing inline:
+specialChars :: [Char]
+specialChars = "\"$'()*+-./:<=>[\\]^_{|}~"
+
+
+whitespace :: OrgParser Inlines
+whitespace = B.space <$ skipMany1 spaceChar <?> "whitespace"
+
+str :: OrgParser Inlines
+str = B.str <$> many1 (noneOf $ specialChars ++ "\n\r ")
+            <* updateLastStrPos
+
+-- an endline character that can be treated as a space, not a structural break
+endline :: OrgParser Inlines
+endline = try $ do
+  newline
+  notFollowedBy blankline
+  notFollowedBy' exampleLine
+  notFollowedBy' hline
+  notFollowedBy' tableStart
+  notFollowedBy' drawerStart
+  notFollowedBy' headerStart
+  notFollowedBy' metaLineStart
+  notFollowedBy' commentLineStart
+  notFollowedBy' bulletListStart
+  notFollowedBy' orderedListStart
+  return B.space
+
+link :: OrgParser Inlines
+link = explicitLink <|> selfLink <?> "link"
+
+explicitLink :: OrgParser Inlines
+explicitLink = try $ do
+  char '['
+  src   <- enclosedRaw     (char '[') (char ']')
+  title <- enclosedInlines (char '[') (char ']')
+  char ']'
+  return $ B.link src "" title
+
+selfLink :: OrgParser Inlines
+selfLink = try $ do
+  src <- enclosedRaw (string "[[") (string "]]")
+  return $ B.link src "" (B.str src)
+
+emph      :: OrgParser Inlines
+emph      = B.emph         <$> inlinesEnclosedBy '/'
+
+strong    :: OrgParser Inlines
+strong    = B.strong       <$> inlinesEnclosedBy '*'
+
+strikeout :: OrgParser Inlines
+strikeout = B.strikeout    <$> inlinesEnclosedBy '+'
+
+-- There is no underline, so we use strong instead.
+underline :: OrgParser Inlines
+underline = B.strong       <$> inlinesEnclosedBy '_'
+
+code      :: OrgParser Inlines
+code      = B.code         <$> rawEnclosedBy '='
+
+verbatim  ::  OrgParser Inlines
+verbatim  = B.rawInline "" <$> rawEnclosedBy '~'
+
+subscript ::  OrgParser Inlines
+subscript = B.subscript    <$> (try $ char '_' *> maybeGroupedByBraces)
+
+superscript ::  OrgParser Inlines
+superscript = B.superscript <$> (try $ char '^' *> maybeGroupedByBraces)
+
+maybeGroupedByBraces :: OrgParser Inlines
+maybeGroupedByBraces = try $
+  choice [ try $ enclosedInlines (char '{') (char '}')
+         , B.str . (:"") <$> anyChar
+         ]
+
+symbol :: OrgParser Inlines
+symbol = B.str . (: "") <$> oneOf specialChars
+
+enclosedInlines :: OrgParser a
+                -> OrgParser b
+                -> OrgParser Inlines
+enclosedInlines start end = try $
+  trimInlines . mconcat <$> enclosed start end inline
+
+-- FIXME: This is a hack
+inlinesEnclosedBy :: Char
+                  -> OrgParser Inlines
+inlinesEnclosedBy c = enclosedInlines (atStart (char c) <* endsOnThisOrNextLine c)
+                                      (atEnd $ char c)
+
+enclosedRaw :: OrgParser a
+            -> OrgParser b
+            -> OrgParser String
+enclosedRaw start end = try $
+  start *> (onSingleLine <|> spanningTwoLines)
+ where onSingleLine = try $ many1Till (noneOf "\n\r") end
+       spanningTwoLines = try $
+         anyLine >>= \f -> mappend (f <> " ") <$> onSingleLine
+
+rawEnclosedBy :: Char
+              -> OrgParser String
+rawEnclosedBy c = enclosedRaw (atStart $ char c) (atEnd $ char c)
+
+-- succeeds only if we're not right after a str (ie. in middle of word)
+atStart :: OrgParser a -> OrgParser a
+atStart p = do
+  pos <- getPosition
+  st <- getState
+  guard $ stateLastStrPos st /= Just pos
+  p
+
+-- | succeeds only if we're at the end of a word
+atEnd :: OrgParser a -> OrgParser a
+atEnd p = try $ p <* lookingAtEndOfWord
+ where lookingAtEndOfWord = lookAhead . oneOf $ postWordChars
+
+postWordChars :: [Char]
+postWordChars = "\t\n\r !\"'),-.:?}"
+
+-- FIXME: These functions are hacks and should be replaced
+endsOnThisOrNextLine :: Char
+                     -> OrgParser ()
+endsOnThisOrNextLine c = do
+  inp <- getInput
+  let doOtherwise = \rest -> endsOnThisLine rest c (const mzero)
+  endsOnThisLine inp c doOtherwise
+
+endsOnThisLine :: [Char]
+               -> Char
+               -> ([Char] -> OrgParser ())
+               -> OrgParser ()
+endsOnThisLine input c doOnOtherLines = do
+  case break (`elem` c:"\n") input of
+    (_,'\n':rest)    -> doOnOtherLines rest
+    (_,_:rest@(n:_)) -> if n `elem` postWordChars
+                        then return ()
+                        else endsOnThisLine rest c doOnOtherLines
+    _                -> mzero
+