{-# LANGUAGE NoImplicitPrelude #-}
{-
Copyright (C) 2015-2018 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) 2015-2018 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 Prelude
import CMarkGFM
import Control.Monad.State
import Data.Char (isAlphaNum, isLetter, isSpace, toLower)
import Data.List (groupBy)
import qualified Data.Map as Map
import Data.Maybe (mapMaybe)
import Data.Text (Text, unpack)
import Text.Pandoc.Asciify (toAsciiChar)
import Text.Pandoc.Class (PandocMonad)
import Text.Pandoc.Definition
import Text.Pandoc.Emoji (emojiToInline)
import Text.Pandoc.Options
import Text.Pandoc.Shared (stringify)
import Text.Pandoc.Walk (walkM)

-- | Parse a CommonMark formatted string into a 'Pandoc' structure.
readCommonMark :: PandocMonad m => ReaderOptions -> Text -> m Pandoc
readCommonMark opts s = return $
  (if isEnabled Ext_gfm_auto_identifiers opts
      then addHeaderIdentifiers opts
      else id) $
  nodeToPandoc opts $ commonmarkToNode opts' exts s
  where opts' = [ optSmart | isEnabled Ext_smart opts ]
        exts = [ extStrikethrough | isEnabled Ext_strikeout opts ] ++
               [ extTable | isEnabled Ext_pipe_tables opts ] ++
               [ extAutolink | isEnabled Ext_autolink_bare_uris opts ]

convertEmojis :: String -> [Inline]
convertEmojis s@(':':xs) =
   case break (==':') xs of
        (ys,':':zs) ->
           case emojiToInline ys of
                Just em -> em : convertEmojis zs
                Nothing -> Str (':' : ys) : convertEmojis (':':zs)
        _ -> [Str s]
convertEmojis s =
  case break (==':') s of
    ("","") -> []
    (_,"") -> [Str s]
    (xs,ys) -> Str xs:convertEmojis ys

addHeaderIdentifiers :: ReaderOptions -> Pandoc -> Pandoc
addHeaderIdentifiers opts doc = evalState (walkM (addHeaderId opts) doc) mempty

addHeaderId :: ReaderOptions -> Block -> State (Map.Map String Int) Block
addHeaderId opts (Header lev (_,classes,kvs) ils) = do
  idmap <- get
  let ident = toIdent opts ils
  ident' <- case Map.lookup ident idmap of
                 Nothing -> do
                   put (Map.insert ident 1 idmap)
                   return ident
                 Just i -> do
                   put (Map.adjust (+ 1) ident idmap)
                   return (ident ++ "-" ++ show i)
  return $ Header lev (ident',classes,kvs) ils
addHeaderId _ x = return x

toIdent :: ReaderOptions -> [Inline] -> String
toIdent opts = map (\c -> if isSpace c then '-' else c)
               . filterer
               . map toLower . stringify
  where filterer = if isEnabled Ext_ascii_identifiers opts
                   then mapMaybe toAsciiChar
                   else filter (\c -> isLetter c || isAlphaNum c || isSpace c ||
                                      c == '_' || c == '-')

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

addBlocks :: ReaderOptions -> [Node] -> [Block]
addBlocks opts = foldr (addBlock opts) []

addBlock :: ReaderOptions -> Node -> [Block] -> [Block]
addBlock opts (Node _ PARAGRAPH nodes) =
  (Para (addInlines opts nodes) :)
addBlock _ (Node _ THEMATIC_BREAK _) =
  (HorizontalRule :)
addBlock opts (Node _ BLOCK_QUOTE nodes) =
  (BlockQuote (addBlocks opts nodes) :)
addBlock opts (Node _ (HTML_BLOCK t) _)
  | isEnabled Ext_raw_html opts = (RawBlock (Format "html") (unpack t) :)
  | otherwise                 = id
-- 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 opts (Node _ (HEADING lev) nodes) =
  (Header lev ("",[],[]) (addInlines opts nodes) :)
addBlock opts (Node _ (LIST listAttrs) nodes) =
  (constructor (map (setTightness . addBlocks opts . 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 opts (Node _ (TABLE alignments) nodes) =
  (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 opts (n:ns)
          | otherwise     = [Plain (addInlines opts (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 :: ReaderOptions -> [Node] -> [Inline]
addInlines opts = foldr (addInline opts) []

addInline :: ReaderOptions -> Node -> [Inline] -> [Inline]
addInline opts (Node _ (TEXT t) _) = (foldr ((++) . toinl) [] clumps ++)
  where raw = unpack t
        clumps = groupBy samekind raw
        samekind ' ' ' ' = True
        samekind ' ' _   = False
        samekind _   ' ' = False
        samekind _  _    = True
        toinl (' ':_) = [Space]
        toinl xs      = if isEnabled Ext_emoji opts
                        then convertEmojis xs
                        else [Str xs]
addInline _ (Node _ LINEBREAK _) = (LineBreak :)
addInline opts (Node _ SOFTBREAK _)
  | isEnabled Ext_hard_line_breaks opts = (LineBreak :)
  | otherwise                           = (SoftBreak :)
addInline opts (Node _ (HTML_INLINE t) _)
  | isEnabled Ext_raw_html opts = (RawInline (Format "html") (unpack t) :)
  | otherwise                 = id
-- 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 opts (Node _ EMPH nodes) =
  (Emph (addInlines opts nodes) :)
addInline opts (Node _ STRONG nodes) =
  (Strong (addInlines opts nodes) :)
addInline opts (Node _ STRIKETHROUGH nodes) =
  (Strikeout (addInlines opts nodes) :)
addInline opts (Node _ (LINK url title) nodes) =
  (Link nullAttr (addInlines opts nodes) (unpack url, unpack title) :)
addInline opts (Node _ (IMAGE url title) nodes) =
  (Image nullAttr (addInlines opts nodes) (unpack url, unpack title) :)
addInline _ _ = id