Org reader: move parser state into separate module

The org reader code has become large and confusing.  Extracting smaller
parts into submodules should help to clean things up.

3 files changed, 233 insertions, 158 deletions

diff --git a/pandoc.cabal b/pandoc.cabal
index e8252293b..d38754dcd 100644
--- a/pandoc.cabal
+++ b/pandoc.cabal
@@ -393,6 +393,7 @@ Library
                    Text.Pandoc.Readers.Odt.Generic.XMLConverter,
                    Text.Pandoc.Readers.Odt.Arrows.State,
                    Text.Pandoc.Readers.Odt.Arrows.Utils,
+                   Text.Pandoc.Readers.Org.ParserState,
                    Text.Pandoc.Writers.Shared,
                    Text.Pandoc.Asciify,
                    Text.Pandoc.MIME,
diff --git a/src/Text/Pandoc/Readers/Org.hs b/src/Text/Pandoc/Readers/Org.hs
index 5a50a8f34..610397d58 100644
--- a/src/Text/Pandoc/Readers/Org.hs
+++ b/src/Text/Pandoc/Readers/Org.hs
@@ -1,6 +1,5 @@
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE MultiParamTypeClasses, FlexibleContexts, FlexibleInstances #-}
 {-
 Copyright (C) 2014-2016 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
 
@@ -31,8 +30,7 @@ Conversion of org-mode formatted plain text to 'Pandoc' document.
 module Text.Pandoc.Readers.Org ( readOrg ) where
 
 import qualified Text.Pandoc.Builder as B
-import           Text.Pandoc.Builder ( Inlines, Blocks, HasMeta(..),
-                                       trimInlines )
+import           Text.Pandoc.Builder ( Inlines, Blocks )
 import           Text.Pandoc.Definition
 import           Text.Pandoc.Compat.Monoid ((<>))
 import           Text.Pandoc.Error
@@ -43,153 +41,33 @@ import           Text.Pandoc.Parsing hiding ( F, unF, askF, asksF, runF
                                             , parseFromString, blanklines
                                             )
 import           Text.Pandoc.Readers.LaTeX (inlineCommand, rawLaTeXInline)
+import           Text.Pandoc.Readers.Org.ParserState
 import           Text.Pandoc.Shared (compactify', compactify'DL)
 import           Text.TeXMath (readTeX, writePandoc, DisplayType(..))
 import qualified Text.TeXMath.Readers.MathML.EntityMap as MathMLEntityMap
 
 import           Control.Arrow (first)
-import           Control.Monad (foldM, guard, liftM, liftM2, mplus, mzero, when)
-import           Control.Monad.Reader (Reader, runReader, ask, asks, local)
+import           Control.Monad (foldM, guard, mplus, mzero, when)
+import           Control.Monad.Reader ( Reader, runReader )
 import           Data.Char (isAlphaNum, isSpace, toLower)
-import           Data.Default
 import           Data.List (intersperse, isPrefixOf, isSuffixOf)
 import qualified Data.Map as M
-import qualified Data.Set as Set
 import           Data.Maybe (fromMaybe, isJust)
 import           Network.HTTP (urlEncode)
 
+
 -- | Parse org-mode string and return a Pandoc document.
 readOrg :: ReaderOptions -- ^ Reader options
         -> String        -- ^ String to parse (assuming @'\n'@ line endings)
         -> Either PandocError Pandoc
 readOrg opts s = flip runReader def $ readWithM parseOrg def{ orgStateOptions = opts } (s ++ "\n\n")
 
-data OrgParserLocal = OrgParserLocal { orgLocalQuoteContext :: QuoteContext }
-
+-- | The parser used to read org files.
 type OrgParser = ParserT [Char] OrgParserState (Reader OrgParserLocal)
 
-instance HasIdentifierList OrgParserState where
-  extractIdentifierList = orgStateIdentifiers
-  updateIdentifierList f s = s{ orgStateIdentifiers = f (orgStateIdentifiers s) }
-
-instance HasHeaderMap OrgParserState where
-  extractHeaderMap = orgStateHeaderMap
-  updateHeaderMap  f s = s{ orgStateHeaderMap = f (orgStateHeaderMap s) }
-
-parseOrg :: OrgParser Pandoc
-parseOrg = do
-  blocks' <- parseBlocks
-  st <- getState
-  let meta = runF (orgStateMeta' st) st
-  let removeUnwantedBlocks = dropCommentTrees . filter (/= Null)
-  return $ Pandoc meta $ removeUnwantedBlocks (B.toList $ runF blocks' st)
-
--- | Drop COMMENT headers and the document tree below those headers.
-dropCommentTrees :: [Block] -> [Block]
-dropCommentTrees [] = []
-dropCommentTrees (b:bs) =
-  maybe (b:dropCommentTrees bs)
-        (dropCommentTrees . flip dropUntilHeaderAboveLevel bs)
-        (commentHeaderLevel b)
-
--- | Return the level of a header starting a comment or :noexport: tree and
---  Nothing otherwise.
-commentHeaderLevel :: Block -> Maybe Int
-commentHeaderLevel blk =
-   case blk of
-     (Header level _ ((Str "COMMENT"):_))          -> Just level
-     (Header level _ title) | hasNoExportTag title -> Just level
-     _                                             -> Nothing
- where
-   hasNoExportTag :: [Inline] -> Bool
-   hasNoExportTag = any isNoExportTag
-
-   isNoExportTag :: Inline -> Bool
-   isNoExportTag (Span ("", ["tag"], [("data-tag-name", "noexport")]) []) = True
-   isNoExportTag _ = False
-
--- | Drop blocks until a header on or above the given level is seen
-dropUntilHeaderAboveLevel :: Int -> [Block] -> [Block]
-dropUntilHeaderAboveLevel n = dropWhile (not . isHeaderLevelLowerEq n)
-
-isHeaderLevelLowerEq :: Int -> Block -> Bool
-isHeaderLevelLowerEq n blk =
-  case blk of
-    (Header level _ _) -> n >= level
-    _                  -> False
-
 --
--- Parser State for Org
+-- Functions acting on the parser state
 --
-
-type OrgNoteRecord = (String, F Blocks)
-type OrgNoteTable = [OrgNoteRecord]
-
-type OrgBlockAttributes = M.Map String String
-
-type OrgLinkFormatters = M.Map String (String -> String)
-
--- | Org-mode parser state
-data OrgParserState = OrgParserState
-                      { orgStateOptions              :: ReaderOptions
-                      , orgStateAnchorIds            :: [String]
-                      , orgStateBlockAttributes      :: OrgBlockAttributes
-                      , orgStateEmphasisCharStack    :: [Char]
-                      , orgStateEmphasisNewlines     :: Maybe Int
-                      , orgStateLastForbiddenCharPos :: Maybe SourcePos
-                      , orgStateLastPreCharPos       :: Maybe SourcePos
-                      , orgStateLastStrPos           :: Maybe SourcePos
-                      , orgStateLinkFormatters       :: OrgLinkFormatters
-                      , orgStateMeta                 :: Meta
-                      , orgStateMeta'                :: F Meta
-                      , orgStateNotes'               :: OrgNoteTable
-                      , orgStateParserContext        :: ParserContext
-                      , orgStateIdentifiers          :: Set.Set String
-                      , orgStateHeaderMap            :: M.Map Inlines String
-                      }
-
-instance Default OrgParserLocal where
-  def = OrgParserLocal NoQuote
-
-instance HasReaderOptions OrgParserState where
-  extractReaderOptions = orgStateOptions
-
-instance HasMeta OrgParserState where
-  setMeta field val st =
-    st{ orgStateMeta = setMeta field val $ orgStateMeta st }
-  deleteMeta field st =
-    st{ orgStateMeta = deleteMeta field $ orgStateMeta st }
-
-instance HasLastStrPosition OrgParserState where
-  getLastStrPos = orgStateLastStrPos
-  setLastStrPos pos st = st{ orgStateLastStrPos = Just pos }
-
-instance HasQuoteContext st (Reader OrgParserLocal) where
-  getQuoteContext = asks orgLocalQuoteContext
-  withQuoteContext q = local (\s -> s{orgLocalQuoteContext = q})
-
-instance Default OrgParserState where
-  def = defaultOrgParserState
-
-defaultOrgParserState :: OrgParserState
-defaultOrgParserState = OrgParserState
-                        { orgStateOptions = def
-                        , orgStateAnchorIds = []
-                        , orgStateBlockAttributes = M.empty
-                        , orgStateEmphasisCharStack = []
-                        , orgStateEmphasisNewlines = Nothing
-                        , orgStateLastForbiddenCharPos = Nothing
-                        , orgStateLastPreCharPos = Nothing
-                        , orgStateLastStrPos = Nothing
-                        , orgStateLinkFormatters = M.empty
-                        , orgStateMeta = nullMeta
-                        , orgStateMeta' = return nullMeta
-                        , orgStateNotes' = []
-                        , orgStateParserContext = NullState
-                        , orgStateIdentifiers = Set.empty
-                        , orgStateHeaderMap = M.empty
-                        }
-
 recordAnchorId :: String -> OrgParser ()
 recordAnchorId i = updateState $ \s ->
   s{ orgStateAnchorIds = i : (orgStateAnchorIds s) }
@@ -243,44 +121,65 @@ addToNotesTable note = do
   oldnotes <- orgStateNotes' <$> getState
   updateState $ \s -> s{ orgStateNotes' = note:oldnotes }
 
--- The version Text.Pandoc.Parsing cannot be used, as we need additional parts
--- of the state saved and restored.
-parseFromString :: OrgParser a -> String -> OrgParser a
-parseFromString parser str' = do
-  oldLastPreCharPos <- orgStateLastPreCharPos <$> getState
-  updateState $ \s -> s{ orgStateLastPreCharPos = Nothing }
-  result <- P.parseFromString parser str'
-  updateState $ \s -> s{ orgStateLastPreCharPos = oldLastPreCharPos }
-  return result
-
-
 --
--- Adaptions and specializations of parsing utilities
+-- Parser
 --
+parseOrg :: OrgParser Pandoc
+parseOrg = do
+  blocks' <- parseBlocks
+  st <- getState
+  let meta = runF (orgStateMeta' st) st
+  let removeUnwantedBlocks = dropCommentTrees . filter (/= Null)
+  return $ Pandoc meta $ removeUnwantedBlocks (B.toList $ runF blocks' st)
 
-newtype F a = F { unF :: Reader OrgParserState a
-                } deriving (Monad, Applicative, Functor)
+-- | Drop COMMENT headers and the document tree below those headers.
+dropCommentTrees :: [Block] -> [Block]
+dropCommentTrees [] = []
+dropCommentTrees (b:bs) =
+  maybe (b:dropCommentTrees bs)
+        (dropCommentTrees . flip dropUntilHeaderAboveLevel bs)
+        (commentHeaderLevel b)
 
-runF :: F a -> OrgParserState -> a
-runF = runReader . unF
+-- | Return the level of a header starting a comment or :noexport: tree and
+--  Nothing otherwise.
+commentHeaderLevel :: Block -> Maybe Int
+commentHeaderLevel blk =
+   case blk of
+     (Header level _ ((Str "COMMENT"):_))          -> Just level
+     (Header level _ title) | hasNoExportTag title -> Just level
+     _                                             -> Nothing
+ where
+   hasNoExportTag :: [Inline] -> Bool
+   hasNoExportTag = any isNoExportTag
 
-askF :: F OrgParserState
-askF = F ask
+   isNoExportTag :: Inline -> Bool
+   isNoExportTag (Span ("", ["tag"], [("data-tag-name", "noexport")]) []) = True
+   isNoExportTag _ = False
 
-asksF :: (OrgParserState -> a) -> F a
-asksF f = F $ asks f
+-- | Drop blocks until a header on or above the given level is seen
+dropUntilHeaderAboveLevel :: Int -> [Block] -> [Block]
+dropUntilHeaderAboveLevel n = dropWhile (not . isHeaderLevelLowerEq n)
 
-instance Monoid a => Monoid (F a) where
-  mempty = return mempty
-  mappend = liftM2 mappend
-  mconcat = fmap mconcat . sequence
+isHeaderLevelLowerEq :: Int -> Block -> Bool
+isHeaderLevelLowerEq n blk =
+  case blk of
+    (Header level _ _) -> n >= level
+    _                  -> False
 
-trimInlinesF :: F Inlines -> F Inlines
-trimInlinesF = liftM trimInlines
 
-returnF :: a -> OrgParser (F a)
-returnF = return . return
+--
+-- Adaptions and specializations of parsing utilities
+--
 
+-- The version Text.Pandoc.Parsing cannot be used, as we need additional parts
+-- of the state saved and restored.
+parseFromString :: OrgParser a -> String -> OrgParser a
+parseFromString parser str' = do
+  oldLastPreCharPos <- orgStateLastPreCharPos <$> getState
+  updateState $ \s -> s{ orgStateLastPreCharPos = Nothing }
+  result <- P.parseFromString parser str'
+  updateState $ \s -> s{ orgStateLastPreCharPos = oldLastPreCharPos }
+  return result
 
 -- | Like @Text.Parsec.Char.newline@, but causes additional state changes.
 newline :: OrgParser Char
diff --git a/src/Text/Pandoc/Readers/Org/ParserState.hs b/src/Text/Pandoc/Readers/Org/ParserState.hs
new file mode 100644
index 000000000..680c469f3
--- /dev/null
+++ b/src/Text/Pandoc/Readers/Org/ParserState.hs
@@ -0,0 +1,175 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-
+Copyright (C) 2014-2016 Albert Krewinkel <tarleb+pandoc@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.Options
+   Copyright   : Copyright (C) 2014-2016 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+
+Define the Org-mode parser state.
+-}
+module Text.Pandoc.Readers.Org.ParserState
+  ( OrgParserState(..)
+  , OrgParserLocal(..)
+  , OrgNoteRecord
+  , F(..)
+  , askF
+  , asksF
+  , trimInlinesF
+  , runF
+  , returnF
+  ) where
+
+import           Control.Monad (liftM, liftM2)
+import           Control.Monad.Reader (Reader, runReader, ask, asks, local)
+
+import           Data.Default (Default(..))
+import qualified Data.Map as M
+import qualified Data.Set as Set
+
+import           Text.Pandoc.Builder ( Inlines, Blocks, HasMeta(..),
+                                       trimInlines )
+import           Text.Pandoc.Definition ( Meta(..), nullMeta )
+import           Text.Pandoc.Options ( ReaderOptions(..) )
+import           Text.Pandoc.Parsing ( HasHeaderMap(..)
+                                     , HasIdentifierList(..)
+                                     , HasLastStrPosition(..)
+                                     , HasQuoteContext(..)
+                                     , HasReaderOptions(..)
+                                     , ParserContext(..)
+                                     , QuoteContext(..)
+                                     , SourcePos )
+
+-- | An inline note / footnote containing the note key and its (inline) value.
+type OrgNoteRecord = (String, F Blocks)
+-- | Table of footnotes
+type OrgNoteTable = [OrgNoteRecord]
+-- | Map of org block attributes (e.g. LABEL, CAPTION, NAME, etc)
+type OrgBlockAttributes = M.Map String String
+-- | Map of functions for link transformations.  The map key is refers to the
+-- link-type, the corresponding function transforms the given link string.
+type OrgLinkFormatters = M.Map String (String -> String)
+
+-- | Org-mode parser state
+data OrgParserState = OrgParserState
+  { orgStateOptions              :: ReaderOptions
+  , orgStateAnchorIds            :: [String]
+  , orgStateBlockAttributes      :: OrgBlockAttributes
+  , orgStateEmphasisCharStack    :: [Char]
+  , orgStateEmphasisNewlines     :: Maybe Int
+  , orgStateLastForbiddenCharPos :: Maybe SourcePos
+  , orgStateLastPreCharPos       :: Maybe SourcePos
+  , orgStateLastStrPos           :: Maybe SourcePos
+  , orgStateLinkFormatters       :: OrgLinkFormatters
+  , orgStateMeta                 :: Meta
+  , orgStateMeta'                :: F Meta
+  , orgStateNotes'               :: OrgNoteTable
+  , orgStateParserContext        :: ParserContext
+  , orgStateIdentifiers          :: Set.Set String
+  , orgStateHeaderMap            :: M.Map Inlines String
+  }
+
+data OrgParserLocal = OrgParserLocal { orgLocalQuoteContext :: QuoteContext }
+
+instance Default OrgParserLocal where
+  def = OrgParserLocal NoQuote
+
+instance HasReaderOptions OrgParserState where
+  extractReaderOptions = orgStateOptions
+
+instance HasMeta OrgParserState where
+  setMeta field val st =
+    st{ orgStateMeta = setMeta field val $ orgStateMeta st }
+  deleteMeta field st =
+    st{ orgStateMeta = deleteMeta field $ orgStateMeta st }
+
+instance HasLastStrPosition OrgParserState where
+  getLastStrPos = orgStateLastStrPos
+  setLastStrPos pos st = st{ orgStateLastStrPos = Just pos }
+
+instance HasQuoteContext st (Reader OrgParserLocal) where
+  getQuoteContext = asks orgLocalQuoteContext
+  withQuoteContext q = local (\s -> s{orgLocalQuoteContext = q})
+
+instance HasIdentifierList OrgParserState where
+  extractIdentifierList = orgStateIdentifiers
+  updateIdentifierList f s = s{ orgStateIdentifiers = f (orgStateIdentifiers s) }
+
+instance HasHeaderMap OrgParserState where
+  extractHeaderMap = orgStateHeaderMap
+  updateHeaderMap  f s = s{ orgStateHeaderMap = f (orgStateHeaderMap s) }
+
+
+instance Default OrgParserState where
+  def = defaultOrgParserState
+
+defaultOrgParserState :: OrgParserState
+defaultOrgParserState = OrgParserState
+  { orgStateOptions = def
+  , orgStateAnchorIds = []
+  , orgStateBlockAttributes = M.empty
+  , orgStateEmphasisCharStack = []
+  , orgStateEmphasisNewlines = Nothing
+  , orgStateLastForbiddenCharPos = Nothing
+  , orgStateLastPreCharPos = Nothing
+  , orgStateLastStrPos = Nothing
+  , orgStateLinkFormatters = M.empty
+  , orgStateMeta = nullMeta
+  , orgStateMeta' = return nullMeta
+  , orgStateNotes' = []
+  , orgStateParserContext = NullState
+  , orgStateIdentifiers = Set.empty
+  , orgStateHeaderMap = M.empty
+  }
+
+
+--
+-- Parser state reader
+--
+
+-- | Reader monad wrapping the parser state.  This is used to delay evaluation
+-- until all relevant information has been parsed and made available in the
+-- parser state.  See also the newtype of the same name in
+-- Text.Pandoc.Parsing.
+newtype F a = F { unF :: Reader OrgParserState a
+                } deriving (Functor, Applicative, Monad)
+
+instance Monoid a => Monoid (F a) where
+  mempty = return mempty
+  mappend = liftM2 mappend
+  mconcat = fmap mconcat . sequence
+
+runF :: F a -> OrgParserState -> a
+runF = runReader . unF
+
+askF :: F OrgParserState
+askF = F ask
+
+asksF :: (OrgParserState -> a) -> F a
+asksF f = F $ asks f
+
+trimInlinesF :: F Inlines -> F Inlines
+trimInlinesF = liftM trimInlines
+
+returnF :: Monad m => a -> m (F a)
+returnF = return . return