Added CommonMark reader using cmark (libcmark bindings).

- Added commonmark as an input format.
- Added `Text.Pandoc.Readers.CommonMark.readCommonMark`.
- For now, we use the markdown writer to generate benchmark
  text for the CommonMark reader.  We can change this when we
  get a writer.

5 files changed, 150 insertions, 18 deletions

diff --git a/README b/README
index 41bf0e4db..81e3f877b 100644
--- a/README
+++ b/README
@@ -12,17 +12,18 @@ Description
 
 Pandoc is a [Haskell] library for converting from one markup format to
 another, and a command-line tool that uses this library. It can read
-[markdown] and (subsets of) [Textile], [reStructuredText], [HTML],
-[LaTeX], [MediaWiki markup], [TWiki markup], [Haddock markup], [OPML],
-[Emacs Org-mode], [DocBook], [txt2tags], [EPUB] and [Word docx]; and
-it can write plain text, [markdown], [reStructuredText], [XHTML],
-[HTML 5], [LaTeX] (including [beamer] slide shows), [ConTeXt], [RTF],
-[OPML], [DocBook], [OpenDocument], [ODT], [Word docx], [GNU Texinfo],
-[MediaWiki markup], [DokuWiki markup], [Haddock markup], [EPUB] (v2 or v3),
-[FictionBook2], [Textile], [groff man] pages, [Emacs Org-Mode], [AsciiDoc],
-[InDesign ICML], and [Slidy], [Slideous], [DZSlides], [reveal.js] or
-[S5] HTML slide shows. It can also produce [PDF] output on systems where
-LaTeX is installed.
+[Markdown], [CommonMark], and (subsets of) [Textile],
+[reStructuredText], [HTML], [LaTeX], [MediaWiki markup], [TWiki
+markup], [Haddock markup], [OPML], [Emacs Org-mode], [DocBook],
+[txt2tags], [EPUB] and [Word docx]; and it can write plain text,
+[Markdown], [reStructuredText], [XHTML], [HTML 5], [LaTeX] (including
+[beamer] slide shows), [ConTeXt], [RTF], [OPML], [DocBook],
+[OpenDocument], [ODT], [Word docx], [GNU Texinfo], [MediaWiki markup],
+[DokuWiki markup], [Haddock markup], [EPUB] (v2 or v3),
+[FictionBook2], [Textile], [groff man] pages, [Emacs Org-Mode],
+[AsciiDoc], [InDesign ICML], and [Slidy], [Slideous], [DZSlides],
+[reveal.js] or [S5] HTML slide shows. It can also produce [PDF] output
+on systems where LaTeX is installed.
 
 Pandoc's enhanced version of markdown includes syntax for footnotes,
 tables, flexible ordered lists, definition lists, fenced code blocks,
@@ -159,6 +160,7 @@ General options
     extended markdown), `markdown_strict` (original unextended markdown),
     `markdown_phpextra` (PHP Markdown Extra extended markdown),
     `markdown_github` (github extended markdown),
+    `commonmark` (CommonMark markdown),
     `textile` (Textile), `rst` (reStructuredText), `html` (HTML),
     `docbook` (DocBook), `t2t` (txt2tags), `docx` (docx), `epub` (EPUB),
     `opml` (OPML), `org` (Emacs Org-mode), `mediawiki` (MediaWiki markup),
@@ -3238,3 +3240,4 @@ Rosenthal.
 [EPUB]: http://idpf.org/epub
 [EPUBspine]: http://www.idpf.org/epub/301/spec/epub-publications.html#sec-spine-elem
 [KaTeX]: https://github.com/Khan/KaTeX
+[CommonMark]: http://commonmark.org
diff --git a/benchmark/benchmark-pandoc.hs b/benchmark/benchmark-pandoc.hs
index bf67eaa4d..2a34696b9 100644
--- a/benchmark/benchmark-pandoc.hs
+++ b/benchmark/benchmark-pandoc.hs
@@ -26,12 +26,18 @@ import Debug.Trace (trace)
 readerBench :: Pandoc
             -> (String, ReaderOptions -> String -> IO Pandoc)
             -> Maybe Benchmark
-readerBench doc (name, reader) = case lookup name writers of
-  Just (PureStringWriter writer) ->
-    let inp = writer def{ writerWrapText = True} doc
-    in return $ bench (name ++ " reader") $ nfIO $
-                 (reader def{ readerSmart = True }) inp
-  _ -> trace ("\nCould not find writer for " ++ name ++ "\n") Nothing
+readerBench doc (name, reader) =
+  case lookup name writers of
+       Just (PureStringWriter writer) ->
+         let inp = writer def{ writerWrapText = True} doc
+         in return $ bench (name ++ " reader") $ nfIO $
+                      (reader def{ readerSmart = True }) inp
+       _ | name == "commonmark" ->
+           let inp = writeMarkdown def{ writerWrapText = True} doc
+           in return $ bench (name ++ " reader") $ nfIO $
+                        (reader def{ readerSmart = True }) inp
+         | otherwise -> trace ("\nCould not find writer for " ++ name ++
+                                 "\n") Nothing
 
 writerBench :: Pandoc
             -> (String, WriterOptions -> Pandoc -> String)
diff --git a/pandoc.cabal b/pandoc.cabal
index f4a8b4e69..823e92812 100644
--- a/pandoc.cabal
+++ b/pandoc.cabal
@@ -254,7 +254,8 @@ Library
                  old-time,
                  deepseq-generics >= 0.1 && < 0.2,
                  JuicyPixels >= 3.1.6.1 && < 3.3,
-                 filemanip >= 0.3 && < 0.4
+                 filemanip >= 0.3 && < 0.4,
+                 cmark >= 0.3 && < 0.4
   if flag(old-locale)
      Build-Depends: old-locale >= 1 && < 1.1,
                     time >= 1.2 && < 1.5
@@ -292,6 +293,7 @@ Library
                    Text.Pandoc.Readers.HTML,
                    Text.Pandoc.Readers.LaTeX,
                    Text.Pandoc.Readers.Markdown,
+                   Text.Pandoc.Readers.CommonMark,
                    Text.Pandoc.Readers.MediaWiki,
                    Text.Pandoc.Readers.RST,
                    Text.Pandoc.Readers.Org,
diff --git a/src/Text/Pandoc.hs b/src/Text/Pandoc.hs
index d2bb85699..435e60eb1 100644
--- a/src/Text/Pandoc.hs
+++ b/src/Text/Pandoc.hs
@@ -66,6 +66,7 @@ module Text.Pandoc
                , mkStringReader
                , readDocx
                , readMarkdown
+               , readCommonMark
                , readMediaWiki
                , readRST
                , readOrg
@@ -124,6 +125,7 @@ import Text.Pandoc.Definition
 import Text.Pandoc.Generic
 import Text.Pandoc.JSON
 import Text.Pandoc.Readers.Markdown
+import Text.Pandoc.Readers.CommonMark
 import Text.Pandoc.Readers.MediaWiki
 import Text.Pandoc.Readers.RST
 import Text.Pandoc.Readers.Org
@@ -225,6 +227,7 @@ readers = [ ("native"       , StringReader $ \_ s -> return $ readNative s)
            ,("markdown_phpextra" , mkStringReaderWithWarnings readMarkdownWithWarnings)
            ,("markdown_github" , mkStringReaderWithWarnings readMarkdownWithWarnings)
            ,("markdown_mmd",  mkStringReaderWithWarnings readMarkdownWithWarnings)
+           ,("commonmark"   , mkStringReader readCommonMark)
            ,("rst"          , mkStringReaderWithWarnings readRSTWithWarnings )
            ,("mediawiki"    , mkStringReader readMediaWiki)
            ,("docbook"      , mkStringReader readDocBook)
diff --git a/src/Text/Pandoc/Readers/CommonMark.hs b/src/Text/Pandoc/Readers/CommonMark.hs
new file mode 100644
index 000000000..dfad7adc2
--- /dev/null
+++ b/src/Text/Pandoc/Readers/CommonMark.hs
@@ -0,0 +1,118 @@
+{-
+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 CMark
+import Data.Text (unpack, pack)
+import Data.List (groupBy)
+import Text.Pandoc.Definition
+import Text.Pandoc.Options
+
+-- | Parse a CommonMark formatted string into a 'Pandoc' structure.
+readCommonMark :: ReaderOptions -> String -> Pandoc
+readCommonMark opts = nodeToPandoc . commonmarkToNode opts' . pack
+  where opts' = if readerSmart opts
+                   then [optNormalize, optSmart]
+                   else [optNormalize]
+
+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 _ HRULE _) =
+  (HorizontalRule :)
+addBlock (Node _ BLOCK_QUOTE nodes) =
+  (BlockQuote (addBlocks nodes) :)
+addBlock (Node _ (HTML t) _) =
+  (RawBlock (Format "html") (unpack t) :)
+addBlock (Node _ (CODE_BLOCK info t) _) =
+  (CodeBlock ("", take 1 (words (unpack info)), []) (unpack t) :)
+addBlock (Node _ (HEADER 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 _ ITEM nodes) = id -- handled in LIST
+addBlock _ = id
+
+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 _) = (Space :)
+addInline (Node _ (INLINE_HTML t) _) =
+  (RawInline (Format "html") (unpack t) :)
+addInline (Node _ (CODE t) _) =
+  (Code ("",[],[]) (unpack t) :)
+addInline (Node _ EMPH nodes) =
+  (Emph (addInlines nodes) :)
+addInline (Node _ STRONG nodes) =
+  (Strong (addInlines nodes) :)
+addInline (Node _ (LINK url title) nodes) =
+  (Link (addInlines nodes) (unpack url, unpack title) :)
+addInline (Node _ (IMAGE url title) nodes) =
+  (Image (addInlines nodes) (unpack url, unpack title) :)
+addInline _ = id