{-
Copyright (C) 2015 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  02111-1307  USA
-}

{- |
   Module      : Text.Pandoc.Readers.CommonMark
   Copyright   : Copyright (C) 2015 John MacFarlane
   License     : GNU GPL, version 2 or above

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

Conversion of CommonMark-formatted plain text to 'Pandoc' document.

CommonMark is a strongly specified variant of Markdown: http://commonmark.org.
-}
module Text.Pandoc.Readers.CommonMark (readCommonMark)
where

import CMarkGFM
import Data.List (groupBy)
import Data.Text (Text, unpack)
import Text.Pandoc.Class (PandocMonad)
import Text.Pandoc.Definition
import Text.Pandoc.Options

-- | Parse a CommonMark formatted string into a 'Pandoc' structure.
readCommonMark :: PandocMonad m => ReaderOptions -> Text -> m Pandoc
readCommonMark opts s = return $
  nodeToPandoc $ commonmarkToNode opts' exts s
  where opts' = [ optSmart | enabled Ext_smart ]
        exts = [ extStrikethrough | enabled Ext_strikeout ] ++
               [ extTable | enabled Ext_pipe_tables ] ++
               [ extAutolink | enabled Ext_autolink_bare_uris ]
        enabled x = extensionEnabled x (readerExtensions opts)

nodeToPandoc :: Node -> Pandoc
nodeToPandoc (Node _ DOCUMENT nodes) =
  Pandoc nullMeta $ foldr addBlock [] nodes
nodeToPandoc n =  -- shouldn't happen
  Pandoc nullMeta $ foldr addBlock [] [n]

addBlocks :: [Node] -> [Block]
addBlocks = foldr addBlock []

addBlock :: Node -> [Block] -> [Block]
addBlock (Node _ PARAGRAPH nodes) =
  (Para (addInlines nodes) :)
addBlock (Node _ THEMATIC_BREAK _) =
  (HorizontalRule :)
addBlock (Node _ BLOCK_QUOTE nodes) =
  (BlockQuote (addBlocks nodes) :)
addBlock (Node _ (HTML_BLOCK t) _) =
  (RawBlock (Format "html") (unpack t) :)
-- Note:  the cmark parser will never generate CUSTOM_BLOCK,
-- so we don't need to handle it:
addBlock (Node _ (CUSTOM_BLOCK _onEnter _onExit) _nodes) =
  id
addBlock (Node _ (CODE_BLOCK info t) _) =
  (CodeBlock ("", take 1 (words (unpack info)), []) (unpack t) :)
addBlock (Node _ (HEADING lev) nodes) =
  (Header lev ("",[],[]) (addInlines nodes) :)
addBlock (Node _ (LIST listAttrs) nodes) =
  (constructor (map (setTightness . addBlocks . children) nodes) :)
  where constructor = case listType listAttrs of
                       BULLET_LIST  -> BulletList
                       ORDERED_LIST -> OrderedList
                                         (start, DefaultStyle, delim)
        start = listStart listAttrs
        setTightness = if listTight listAttrs
                           then map paraToPlain
                           else id
        paraToPlain (Para xs) = Plain (xs)
        paraToPlain x         = x
        delim = case listDelim listAttrs of
                     PERIOD_DELIM -> Period
                     PAREN_DELIM  -> OneParen
addBlock (Node _ (TABLE alignments) nodes) = do
  (Table [] aligns widths headers rows :)
  where aligns = map fromTableCellAlignment alignments
        fromTableCellAlignment NoAlignment   = AlignDefault
        fromTableCellAlignment LeftAligned   = AlignLeft
        fromTableCellAlignment RightAligned  = AlignRight
        fromTableCellAlignment CenterAligned = AlignCenter
        widths = replicate numcols 0.0
        numcols = if null rows'
                     then 0
                     else maximum $ map length rows'
        rows' = map toRow $ filter isRow nodes
        (headers, rows) = case rows' of
                               (h:rs) -> (h, rs)
                               []     -> ([], [])
        isRow (Node _ TABLE_ROW _) = True
        isRow _ = False
        isCell (Node _ TABLE_CELL _) = True
        isCell _ = False
        toRow (Node _ TABLE_ROW ns) = map toCell $ filter isCell ns
        toRow (Node _ t _) = error $ "toRow encountered non-row " ++ show t
        toCell (Node _ TABLE_CELL []) = []
        toCell (Node _ TABLE_CELL (n:ns))
          | isBlockNode n = addBlocks (n:ns)
          | otherwise     = [Plain (addInlines (n:ns))]
        toCell (Node _ t _) = error $ "toCell encountered non-cell " ++ show t
addBlock (Node _ TABLE_ROW _) = id -- handled in TABLE
addBlock (Node _ TABLE_CELL _) = id -- handled in TABLE
addBlock _ = id

isBlockNode :: Node -> Bool
isBlockNode (Node _ nodetype _) =
  case nodetype of
       DOCUMENT -> True
       THEMATIC_BREAK -> True
       PARAGRAPH -> True
       BLOCK_QUOTE -> True
       HTML_BLOCK _ -> True
       CUSTOM_BLOCK _ _ -> True
       CODE_BLOCK _ _ -> True
       HEADING _ -> True
       LIST _ -> True
       ITEM -> True
       TEXT _ -> False
       SOFTBREAK -> False
       LINEBREAK -> False
       HTML_INLINE _ -> False
       CUSTOM_INLINE _ _ -> False
       CODE _ -> False
       EMPH -> False
       STRONG -> False
       LINK _ _ -> False
       IMAGE _ _ -> False
       STRIKETHROUGH -> False
       TABLE _ -> False
       TABLE_ROW -> False
       TABLE_CELL -> False

children :: Node -> [Node]
children (Node _ _ ns) = ns

addInlines :: [Node] -> [Inline]
addInlines = foldr addInline []

addInline :: Node -> [Inline] -> [Inline]
addInline (Node _ (TEXT t) _) = (map toinl clumps ++)
  where raw = unpack t
        clumps = groupBy samekind raw
        samekind ' ' ' ' = True
        samekind ' ' _   = False
        samekind _   ' ' = False
        samekind _  _    = True
        toinl (' ':_) = Space
        toinl xs      = Str xs
addInline (Node _ LINEBREAK _) = (LineBreak :)
addInline (Node _ SOFTBREAK _) = (SoftBreak :)
addInline (Node _ (HTML_INLINE t) _) =
  (RawInline (Format "html") (unpack t) :)
-- Note:  the cmark parser will never generate CUSTOM_BLOCK,
-- so we don't need to handle it:
addInline (Node _ (CUSTOM_INLINE _onEnter _onExit) _nodes) =
  id
addInline (Node _ (CODE t) _) =
  (Code ("",[],[]) (unpack t) :)
addInline (Node _ EMPH nodes) =
  (Emph (addInlines nodes) :)
addInline (Node _ STRONG nodes) =
  (Strong (addInlines nodes) :)
addInline (Node _ STRIKETHROUGH nodes) =
  (Strikeout (addInlines nodes) :)
addInline (Node _ (LINK url title) nodes) =
  (Link nullAttr (addInlines nodes) (unpack url, unpack title) :)
addInline (Node _ (IMAGE url title) nodes) =
  (Image nullAttr (addInlines nodes) (unpack url, unpack title) :)
addInline _ = id