Org reader: add basic file inclusion mechanism

Support for the `#+INCLUDE:` file inclusion mechanism was added.
Recognized include types are *example*, *export*, *src*, and normal org
file inclusion.  Advanced features like line numbers and level selection
are not implemented yet.

Closes: #3510

3 files changed, 43 insertions, 5 deletions

diff --git a/src/Text/Pandoc/Readers/Org/Blocks.hs b/src/Text/Pandoc/Readers/Org/Blocks.hs
index 788ec26dc..e77a64efe 100644
--- a/src/Text/Pandoc/Readers/Org/Blocks.hs
+++ b/src/Text/Pandoc/Readers/Org/Blocks.hs
@@ -1,6 +1,3 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE RecordWildCards  #-}
-{-# LANGUAGE ViewPatterns     #-}
 {-
 Copyright (C) 2014-2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
 
@@ -18,7 +15,9 @@ 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
 -}
-
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE RecordWildCards  #-}
+{-# LANGUAGE ViewPatterns     #-}
 {- |
    Module      : Text.Pandoc.Readers.Org.Options
    Copyright   : Copyright (C) 2014-2017 Albert Krewinkel
@@ -274,6 +273,7 @@ block = choice [ mempty <$ blanklines
                , figure
                , example
                , genericDrawer
+               , include
                , specialLine
                , horizontalRule
                , list
@@ -717,6 +717,34 @@ exampleCode = B.codeBlockWith ("", ["example"], [])
 specialLine :: PandocMonad m => OrgParser m (F Blocks)
 specialLine = fmap return . try $ rawExportLine <|> metaLine <|> commentLine
 
+-- | Include the content of a file.
+include :: PandocMonad m => OrgParser m (F Blocks)
+include = try $ do
+  metaLineStart <* stringAnyCase "include:" <* skipSpaces
+  filename <- includeTarget
+  blockType <- optionMaybe $ skipSpaces *> many1 alphaNum
+  blocksParser <- case blockType of
+                    Just "example" -> do
+                      return $ pure . B.codeBlock <$> parseRaw
+                    Just "export" -> do
+                      format <- skipSpaces *> many (noneOf "\n\r\t ")
+                      return $ pure . B.rawBlock format <$> parseRaw
+                    Just "src" -> do
+                      language <- skipSpaces *> many (noneOf "\n\r\t ")
+                      let attr = (mempty, [language], mempty)
+                      return $ pure . B.codeBlockWith attr <$> parseRaw
+                    _ -> return $ pure . B.fromList <$> blockList
+  anyLine
+  insertIncludedFileF blocksParser ["."] filename
+ where
+  includeTarget :: PandocMonad m => OrgParser m FilePath
+  includeTarget = do
+    char '"'
+    manyTill (noneOf "\n\r\t") (char '"')
+
+  parseRaw :: PandocMonad m => OrgParser m String
+  parseRaw = many anyChar
+
 rawExportLine :: PandocMonad m => OrgParser m Blocks
 rawExportLine = try $ do
   metaLineStart
diff --git a/src/Text/Pandoc/Readers/Org/ParserState.hs b/src/Text/Pandoc/Readers/Org/ParserState.hs
index f530d1d03..51666fc64 100644
--- a/src/Text/Pandoc/Readers/Org/ParserState.hs
+++ b/src/Text/Pandoc/Readers/Org/ParserState.hs
@@ -66,7 +66,8 @@ import Text.Pandoc.Logging
 import Text.Pandoc.Parsing (HasHeaderMap (..), HasIdentifierList (..),
                             HasLogMessages (..),
                             HasLastStrPosition (..), HasQuoteContext (..),
-                            HasReaderOptions (..), ParserContext (..),
+                            HasReaderOptions (..), HasIncludeFiles (..),
+                            ParserContext (..),
                             QuoteContext (..), SourcePos, Future,
                             askF, asksF, returnF, runF, trimInlinesF)
 
@@ -106,6 +107,7 @@ data OrgParserState = OrgParserState
   , orgStateExportSettings       :: ExportSettings
   , orgStateHeaderMap            :: M.Map Inlines String
   , orgStateIdentifiers          :: Set.Set String
+  , orgStateIncludeFiles         :: [String]
   , orgStateLastForbiddenCharPos :: Maybe SourcePos
   , orgStateLastPreCharPos       :: Maybe SourcePos
   , orgStateLastStrPos           :: Maybe SourcePos
@@ -148,6 +150,12 @@ instance HasLogMessages OrgParserState where
   addLogMessage msg st = st{ orgLogMessages = msg : orgLogMessages st }
   getLogMessages st = reverse $ orgLogMessages st
 
+instance HasIncludeFiles OrgParserState where
+  getIncludeFiles = orgStateIncludeFiles
+  addIncludeFile f st = st { orgStateIncludeFiles = f : orgStateIncludeFiles st }
+  dropLatestIncludeFile st =
+    st { orgStateIncludeFiles = drop 1 $ orgStateIncludeFiles st }
+
 instance Default OrgParserState where
   def = defaultOrgParserState
 
@@ -159,6 +167,7 @@ defaultOrgParserState = OrgParserState
   , orgStateExportSettings = def
   , orgStateHeaderMap = M.empty
   , orgStateIdentifiers = Set.empty
+  , orgStateIncludeFiles = []
   , orgStateLastForbiddenCharPos = Nothing
   , orgStateLastPreCharPos = Nothing
   , orgStateLastStrPos = Nothing
diff --git a/src/Text/Pandoc/Readers/Org/Parsing.hs b/src/Text/Pandoc/Readers/Org/Parsing.hs
index 50f5ebae5..c25b215df 100644
--- a/src/Text/Pandoc/Readers/Org/Parsing.hs
+++ b/src/Text/Pandoc/Readers/Org/Parsing.hs
@@ -71,6 +71,7 @@ module Text.Pandoc.Readers.Org.Parsing
   , ellipses
   , citeKey
   , gridTableWith
+  , insertIncludedFileF
   -- * Re-exports from Text.Pandoc.Parsec
   , runParser
   , runParserT