{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE ScopedTypeVariables #-}
{- |
   Module      : Text.Pandoc.Readers.CommonMark
   Copyright   : Copyright (C) 2015-2021 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 Commonmark
import Commonmark.Extensions
import Commonmark.Pandoc
import Data.Text (Text)
import Text.Pandoc.Class.PandocMonad (PandocMonad)
import Text.Pandoc.Definition
import Text.Pandoc.Builder as B
import Text.Pandoc.Options
import Text.Pandoc.Error
import Text.Pandoc.Readers.Metadata (yamlMetaBlock)
import Control.Monad.Except
import Data.Functor.Identity (runIdentity)
import Data.Typeable
import Text.Pandoc.Parsing (runParserT, getPosition, sourceLine,
                            runF, defaultParserState, take1WhileP, option)
import qualified Data.Text as T

-- | Parse a CommonMark formatted string into a 'Pandoc' structure.
readCommonMark :: PandocMonad m => ReaderOptions -> Text -> m Pandoc
readCommonMark opts s
  | isEnabled Ext_yaml_metadata_block opts
  , "---" `T.isPrefixOf` s = do
       let metaValueParser = do
             inp <- option "" $ take1WhileP (const True)
             case runIdentity
                    (commonmarkWith (specFor opts) "metadata value" inp) of
                    Left _ -> mzero
                    Right (Cm bls :: Cm () Blocks)
                             -> return $ return $ B.toMetaValue bls
       res <- runParserT (do meta <- yamlMetaBlock metaValueParser
                             pos <- getPosition
                             return (meta, pos))
                         defaultParserState "YAML metadata" s
       case res of
         Left _ -> readCommonMarkBody opts s
         Right (meta, pos) -> do
           let dropLines 0 = id
               dropLines n = dropLines (n - 1) . T.drop 1 . T.dropWhile (/='\n')
           let metaLines = sourceLine pos - 1
           let body = T.replicate metaLines "\n" <> dropLines metaLines s
           Pandoc _ bs <- readCommonMarkBody opts body
           return $ Pandoc (runF meta defaultParserState) bs
  | otherwise = readCommonMarkBody opts s

readCommonMarkBody :: PandocMonad m => ReaderOptions -> Text -> m Pandoc
readCommonMarkBody opts s
  | isEnabled Ext_sourcepos opts =
    case runIdentity (commonmarkWith (specFor opts) "" s) of
      Left err -> throwError $ PandocParsecError s err
      Right (Cm bls :: Cm SourceRange Blocks) -> return $ B.doc bls
  | otherwise =
    case runIdentity (commonmarkWith (specFor opts) "" s) of
      Left err -> throwError $ PandocParsecError s err
      Right (Cm bls :: Cm () Blocks) -> return $ B.doc bls

specFor :: (Monad m, Typeable m, Typeable a,
            Rangeable (Cm a Inlines), Rangeable (Cm a Blocks))
        => ReaderOptions -> SyntaxSpec m (Cm a Inlines) (Cm a Blocks)
specFor opts = foldr ($) defaultSyntaxSpec exts
 where
  exts = [ (hardLineBreaksSpec <>) | isEnabled Ext_hard_line_breaks opts ] ++
         [ (smartPunctuationSpec <>) | isEnabled Ext_smart opts ] ++
         [ (strikethroughSpec <>) | isEnabled Ext_strikeout opts ] ++
         [ (superscriptSpec <>) | isEnabled Ext_superscript opts ] ++
         [ (subscriptSpec <>) | isEnabled Ext_subscript opts ] ++
         [ (mathSpec <>) | isEnabled Ext_tex_math_dollars opts ] ++
         [ (fancyListSpec <>) | isEnabled Ext_fancy_lists opts ] ++
         [ (fencedDivSpec <>) | isEnabled Ext_fenced_divs opts ] ++
         [ (bracketedSpanSpec <>) | isEnabled Ext_bracketed_spans opts ] ++
         [ (rawAttributeSpec <>) | isEnabled Ext_raw_attribute opts ] ++
         [ (attributesSpec <>) | isEnabled Ext_attributes opts ] ++
         [ (<> pipeTableSpec) | isEnabled Ext_pipe_tables opts ] ++
            -- see #6739
         [ (autolinkSpec <>) | isEnabled Ext_autolink_bare_uris opts ] ++
         [ (emojiSpec <>) | isEnabled Ext_emoji opts ] ++
         [ (autoIdentifiersSpec <>)
           | isEnabled Ext_gfm_auto_identifiers opts
           , not (isEnabled Ext_ascii_identifiers opts) ] ++
         [ (autoIdentifiersAsciiSpec <>)
           | isEnabled Ext_gfm_auto_identifiers opts
           , isEnabled Ext_ascii_identifiers opts ] ++
         [ (implicitHeadingReferencesSpec <>)
           | isEnabled Ext_implicit_header_references opts ] ++
         [ (footnoteSpec <>) | isEnabled Ext_footnotes opts ] ++
         [ (definitionListSpec <>) | isEnabled Ext_definition_lists opts ] ++
         [ (taskListSpec <>) | isEnabled Ext_task_lists opts ]