{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ViewPatterns      #-}
{- |
   Module      : Text.Pandoc.Writers.Muse
   Copyright   : Copyright (C) 2017-2020 Alexander Krotov
   License     : GNU GPL, version 2 or above

   Maintainer  : Alexander Krotov <ilabdsf@gmail.com>
   Stability   : stable
   Portability : portable

Conversion of 'Pandoc' documents to Muse.

This module is mostly intended for <https://amusewiki.org/ Amusewiki> markup support,
as described by <https://amusewiki.org/library/manual Text::Amuse markup manual>.
Original <https://www.gnu.org/software/emacs-muse/ Emacs Muse> markup support
is a secondary goal.

Where Text::Amuse markup
<https://metacpan.org/pod/Text::Amuse#DIFFERENCES-WITH-THE-ORIGINAL-EMACS-MUSE-MARKUP differs>
from <https://www.gnu.org/software/emacs-muse/manual/ Emacs Muse markup>,
Text::Amuse markup is supported.
For example, native tables are always used instead of Org Mode tables.
However, @\<literal style="html">@ tag is used for HTML raw blocks
even though it is supported only in Emacs Muse.
-}
module Text.Pandoc.Writers.Muse (writeMuse) where
import Control.Monad.Except (throwError)
import Control.Monad.Reader
import Control.Monad.State.Strict
import Data.Char (isAlphaNum, isAsciiLower, isAsciiUpper, isDigit, isSpace)
import Data.Default
import Data.List (intersperse, transpose)
import Data.List.NonEmpty (nonEmpty, NonEmpty(..))
import qualified Data.Set as Set
import qualified Data.Text as T
import Data.Text (Text)
import System.FilePath (takeExtension)
import Text.Pandoc.Class.PandocMonad (PandocMonad)
import Text.Pandoc.Definition
import Text.Pandoc.Error
import Text.Pandoc.ImageSize
import Text.Pandoc.Options
import Text.DocLayout
import Text.Pandoc.Shared
import Text.Pandoc.Templates (renderTemplate)
import Text.Pandoc.Writers.Math
import Text.Pandoc.Writers.Shared

type Notes = [[Block]]

type Muse m = ReaderT WriterEnv (StateT WriterState m)

data WriterEnv =
  WriterEnv { envOptions               :: WriterOptions
            , envTopLevel              :: Bool
            , envInsideBlock           :: Bool
            , envInlineStart           :: Bool -- ^ True if there is only whitespace since last newline
            , envInsideLinkDescription :: Bool -- ^ Escape ] if True
            , envAfterSpace            :: Bool -- ^ There is whitespace (not just newline) before
            , envOneLine               :: Bool -- ^ True if newlines are not allowed
            , envInsideAsterisks       :: Bool -- ^ True if outer element is emphasis with asterisks
            , envNearAsterisks         :: Bool -- ^ Rendering inline near asterisks
            }

data WriterState =
  WriterState { stNotes   :: Notes
              , stNoteNum :: Int
              , stIds     :: Set.Set Text
              , stUseTags :: Bool -- ^ Use tags for emphasis, for example because previous character is a letter
              }

instance Default WriterState
  where def = WriterState { stNotes = []
                          , stNoteNum = 1
                          , stIds = Set.empty
                          , stUseTags = False
                          }

evalMuse :: PandocMonad m => Muse m a -> WriterEnv -> WriterState -> m a
evalMuse document env = evalStateT $ runReaderT document env

-- | Convert Pandoc to Muse.
writeMuse :: PandocMonad m
          => WriterOptions
          -> Pandoc
          -> m Text
writeMuse opts document =
  evalMuse (pandocToMuse document) env def
  where env = WriterEnv { envOptions = opts
                        , envTopLevel = True
                        , envInsideBlock = False
                        , envInlineStart = True
                        , envInsideLinkDescription = False
                        , envAfterSpace = False
                        , envOneLine = False
                        , envInsideAsterisks = False
                        , envNearAsterisks = False
                        }

-- | Return Muse representation of document.
pandocToMuse :: PandocMonad m
             => Pandoc
             -> Muse m Text
pandocToMuse (Pandoc meta blocks) = do
  opts <- asks envOptions
  let colwidth = if writerWrapText opts == WrapAuto
                    then Just $ writerColumns opts
                    else Nothing
  metadata <- metaToContext opts
               blockListToMuse
               (fmap chomp . inlineListToMuse)
               meta
  body <- blockListToMuse blocks
  notes <- currentNotesToMuse
  let main = body $+$ notes
  let context = defField "body" main metadata
  return $ render colwidth $
    case writerTemplate opts of
       Nothing  -> main
       Just tpl -> renderTemplate tpl context

-- | Helper function for flatBlockListToMuse
-- | Render all blocks and insert blank lines between the first two
catWithBlankLines :: PandocMonad m
                  => [Block]       -- ^ List of block elements
                  -> Int           -- ^ Number of blank lines
                  -> Muse m (Doc Text)
catWithBlankLines (b : bs) n = do
  b' <- blockToMuseWithNotes b
  bs' <- flatBlockListToMuse bs
  return $ b' <> blanklines n <> bs'
catWithBlankLines _ _ = error "Expected at least one block"

-- | Convert list of Pandoc block elements to Muse
-- | without setting envTopLevel.
flatBlockListToMuse :: PandocMonad m
                => [Block]       -- ^ List of block elements
                -> Muse m (Doc Text)
flatBlockListToMuse bs@(BulletList _ : BulletList _ : _) = catWithBlankLines bs 2
flatBlockListToMuse bs@(OrderedList (_, style1, _) _ : OrderedList (_, style2, _) _ : _) =
  catWithBlankLines bs (if style1' == style2' then 2 else 0)
    where
      style1' = normalizeStyle style1
      style2' = normalizeStyle style2
      normalizeStyle DefaultStyle = Decimal
      normalizeStyle s            = s
flatBlockListToMuse bs@(DefinitionList _ : DefinitionList _ : _) = catWithBlankLines bs 2
flatBlockListToMuse bs@(_ : _) = catWithBlankLines bs 0
flatBlockListToMuse [] = return mempty

simpleTable :: PandocMonad m
            => [Inline]
            -> [[Block]]
            -> [[[Block]]]
            -> Muse m (Doc Text)
simpleTable caption headers rows = do
  topLevel <- asks envTopLevel
  caption' <- inlineListToMuse caption
  headers' <- mapM blockListToMuse headers
  rows' <- mapM (mapM blockListToMuse) rows
  let widthsInChars = maybe 0 maximum . nonEmpty . map offset <$>
                       transpose (headers' : rows')
  let hpipeBlocks sep blocks = hcat $ intersperse sep' blocks
        where sep' = lblock (T.length sep) $ literal sep
  let makeRow sep = hpipeBlocks sep . zipWith lblock widthsInChars
  let head' = makeRow " || " headers'
  rows'' <- mapM (\row -> makeRow rowSeparator <$> mapM blockListToMuse row) rows
  let body = vcat rows''
  return $ (if topLevel then nest 1 else id) ((if noHeaders then empty else head')
                                             $$ body
                                             $$ (if null caption then empty else "|+ " <> caption' <> " +|"))
         $$ blankline
  where noHeaders = all null headers
        rowSeparator = if noHeaders then " | " else " |  "

-- | Convert list of Pandoc block elements to Muse.
blockListToMuse :: PandocMonad m
                => [Block]       -- ^ List of block elements
                -> Muse m (Doc Text)
blockListToMuse =
  local (\env -> env { envTopLevel = not (envInsideBlock env)
                     , envInsideBlock = True
                     }) . flatBlockListToMuse

-- | Convert Pandoc block element to Muse.
blockToMuse :: PandocMonad m
            => Block         -- ^ Block element
            -> Muse m (Doc Text)
blockToMuse (Plain inlines) = inlineListToMuse' inlines
blockToMuse (Para inlines) = do
  contents <- inlineListToMuse' inlines
  return $ contents <> blankline
blockToMuse (LineBlock lns) = do
  lns' <- local (\env -> env { envOneLine = True }) $ mapM inlineListToMuse lns
  return $ nowrap $ vcat (map (literal "> " <>) lns') <> blankline
blockToMuse (CodeBlock (_,_,_) str) =
  return $ "<example>" $$ literal str $$ "</example>" $$ blankline
blockToMuse (RawBlock (Format format) str) =
  return $ blankline $$ "<literal style=\"" <> literal format <> "\">" $$
           literal str $$ "</literal>" $$ blankline
blockToMuse (BlockQuote blocks) = do
  contents <- flatBlockListToMuse blocks
  return $ blankline
        <> "<quote>"
        $$ nest 0 contents -- nest 0 to remove trailing blank lines
        $$ "</quote>"
        <> blankline
blockToMuse (OrderedList (start, style, _) items) = do
  let markers = take (length items) $ orderedListMarkers
                                      (start, style, Period)
  contents <- zipWithM orderedListItemToMuse markers items
  topLevel <- asks envTopLevel
  return $ (if topLevel then nest 1 else id) (vcat contents) $$ blankline
  where orderedListItemToMuse :: PandocMonad m
                              => Text     -- ^ marker for list item
                              -> [Block]  -- ^ list item (list of blocks)
                              -> Muse m (Doc Text)
        orderedListItemToMuse marker item = hang (T.length marker + 1) (literal marker <> space)
          <$> blockListToMuse item
blockToMuse (BulletList items) = do
  contents <- mapM bulletListItemToMuse items
  topLevel <- asks envTopLevel
  return $ (if topLevel then nest 1 else id) (vcat contents) $$ blankline
  where bulletListItemToMuse :: PandocMonad m
                             => [Block]
                             -> Muse m (Doc Text)
        bulletListItemToMuse item = do
          modify $ \st -> st { stUseTags = False }
          hang 2 "- " <$> blockListToMuse item
blockToMuse (DefinitionList items) = do
  contents <- mapM definitionListItemToMuse items
  topLevel <- asks envTopLevel
  return $ (if topLevel then nest 1 else id) (vcat contents) $$ blankline
  where definitionListItemToMuse :: PandocMonad m
                                 => ([Inline], [[Block]])
                                 -> Muse m (Doc Text)
        definitionListItemToMuse (label, defs) = do
          modify $ \st -> st { stUseTags = False }
          label' <- local (\env -> env { envOneLine = True, envAfterSpace = True }) $ inlineListToMuse' label
          let ind = offset' label' -- using Text.DocLayout.offset results in round trip failures
          hang ind (nowrap label') . vcat <$> mapM descriptionToMuse defs
          where offset' d = maximum (0 :| map T.length
                                         (T.lines $ render Nothing d))
        descriptionToMuse :: PandocMonad m
                          => [Block]
                          -> Muse m (Doc Text)
        descriptionToMuse desc = hang 4 " :: " <$> blockListToMuse desc
blockToMuse (Header level (ident,_,_) inlines) = do
  opts <- asks envOptions
  topLevel <- asks envTopLevel
  contents <- local (\env -> env { envOneLine = True }) $ inlineListToMuse' inlines
  ids <- gets stIds
  let autoId = uniqueIdent (writerExtensions opts) inlines ids
  modify $ \st -> st{ stIds = Set.insert autoId ids }

  let attr' = if T.null ident || (isEnabled Ext_auto_identifiers opts && ident == autoId)
                 then empty
                 else "#" <> literal ident <> cr
  let header' = if topLevel then literal (T.replicate level "*") <> space else mempty
  return $ blankline <> attr' $$ nowrap (header' <> contents) <> blankline
-- https://www.gnu.org/software/emacs-muse/manual/muse.html#Horizontal-Rules-and-Anchors
blockToMuse HorizontalRule = return $ blankline $$ "----" $$ blankline
blockToMuse (Table _ blkCapt specs thead tbody tfoot) =
  if isSimple && numcols > 1
    then simpleTable caption headers rows
    else do
      opts <- asks envOptions
      gridTable opts blocksToDoc True (map (const AlignDefault) aligns) widths headers rows
  where
    (caption, aligns, widths, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
    blocksToDoc opts blocks =
      local (\env -> env { envOptions = opts }) $ blockListToMuse blocks
    numcols = maximum
              (length aligns :| length widths : map length (headers:rows))
    isSimple = onlySimpleTableCells (headers : rows) && all (== 0) widths
blockToMuse (Div _ bs) = flatBlockListToMuse bs
blockToMuse Null = return empty

-- | Return Muse representation of notes collected so far.
currentNotesToMuse :: PandocMonad m
                   => Muse m (Doc Text)
currentNotesToMuse = do
  notes <- reverse <$> gets stNotes
  modify $ \st -> st { stNotes = mempty }
  notesToMuse notes

-- | Return Muse representation of notes.
notesToMuse :: PandocMonad m
            => Notes
            -> Muse m (Doc Text)
notesToMuse notes = do
  n <- gets stNoteNum
  modify $ \st -> st { stNoteNum = stNoteNum st + length notes }
  vsep <$> zipWithM noteToMuse [n ..] notes

-- | Return Muse representation of a note.
noteToMuse :: PandocMonad m
           => Int
           -> [Block]
           -> Muse m (Doc Text)
noteToMuse num note = do
  res <- hang (T.length marker) (literal marker) <$>
    local (\env -> env { envInsideBlock = True
                       , envInlineStart = True
                       , envAfterSpace = True
                       }) (blockListToMuse note)
  return $ res <> blankline
  where
    marker = "[" <> tshow num <> "] "

-- | Return Muse representation of block and accumulated notes.
blockToMuseWithNotes :: PandocMonad m
                     => Block
                     -> Muse m (Doc Text)
blockToMuseWithNotes blk = do
  topLevel <- asks envTopLevel
  opts <- asks envOptions
  let hdrToMuse hdr@Header{} = do
        b <- blockToMuse hdr
        if topLevel && writerReferenceLocation opts == EndOfSection
          then do
            notes <- currentNotesToMuse
            return $ notes $+$ b
          else
            return b
      hdrToMuse b = blockToMuse b
  b <- hdrToMuse blk
  if topLevel && writerReferenceLocation opts == EndOfBlock
    then do
           notes <- currentNotesToMuse
           return $ b $+$ notes <> blankline
    else return b

-- | Escape special characters for Muse.
escapeText :: Text -> Text
escapeText s =
  "<verbatim>" <>
  T.replace "</verbatim>" "<</verbatim><verbatim>/verbatim>" s <>
  "</verbatim>"

-- | Replace newlines with spaces
replaceNewlines :: Text -> Text
replaceNewlines = T.map $ \c ->
  if c == '\n' then ' ' else c

startsWithMarker :: (Char -> Bool) -> Text -> Bool
startsWithMarker f t = case T.uncons $ T.dropWhile f' t of
  Just ('.', xs) -> T.null xs || isSpace (T.head xs)
  _              -> False
  where
    f' c = c == ' ' || f c

containsNotes :: Char -> Char -> Text -> Bool
containsNotes left right = p . T.unpack -- This ought to be a parser
  where p (left':xs)
          | left' == left = q xs || p xs
          | otherwise = p xs
        p ""       = False
        q (x:xs)
          | x `elem` ("123456789"::String) = r xs || p xs
          | otherwise = p xs
        q [] = False
        r ('0':xs) = r xs || p xs
        r xs       = s xs || q xs || p xs
        s (right':xs)
          | right' == right = True
          | otherwise = p xs
        s []      = False

-- | Return True if string should be escaped with <verbatim> tags
shouldEscapeText :: PandocMonad m
                   => Text
                   -> Muse m Bool
shouldEscapeText s = do
  insideLink <- asks envInsideLinkDescription
  return $ T.null s ||
           T.any (`elem` ("#*<=|" :: String)) s ||
           "::" `T.isInfixOf` s ||
           "~~" `T.isInfixOf` s ||
           "[[" `T.isInfixOf` s ||
           ">>>" `T.isInfixOf` s ||
           ("]" `T.isInfixOf` s && insideLink) ||
           containsNotes '[' ']' s ||
           containsNotes '{' '}' s

-- | Escape special characters for Muse if needed.
conditionalEscapeText :: PandocMonad m
                        => Text
                        -> Muse m Text
conditionalEscapeText s = do
  shouldEscape <- shouldEscapeText s
  return $ if shouldEscape
             then escapeText s
             else s

-- Expand Math and Cite before normalizing inline list
preprocessInlineList :: PandocMonad m
                     => [Inline]
                     -> m [Inline]
preprocessInlineList (Math t str:xs) = (++) <$> texMathToInlines t str <*> preprocessInlineList xs
-- Amusewiki does not support <cite> tag,
-- and Emacs Muse citation support is limited
-- (https://www.gnu.org/software/emacs-muse/manual/html_node/Citations.html#Citation)
-- so just fallback to expanding inlines.
preprocessInlineList (Cite _  lst:xs) = (lst ++) <$> preprocessInlineList xs
preprocessInlineList (x:xs) = (x:) <$> preprocessInlineList xs
preprocessInlineList [] = return []

replaceSmallCaps :: Inline -> Inline
replaceSmallCaps (SmallCaps lst) = Emph lst
replaceSmallCaps x               = x

removeKeyValues :: Inline -> Inline
removeKeyValues (Code (i, cls, _) xs) = Code (i, cls, []) xs
-- Do not remove attributes from Link
-- Do not remove attributes, such as "width", from Image
-- Do not remove attributes, such as "dir", from Span
removeKeyValues x                     = x

normalizeInlineList :: [Inline] -> [Inline]
normalizeInlineList (Str "" : xs)
  = normalizeInlineList xs
normalizeInlineList (x : Str "" : xs)
  = normalizeInlineList (x:xs)
normalizeInlineList (Str x1 : Str x2 : xs)
  = normalizeInlineList $ Str (x1 <> x2) : xs
normalizeInlineList (Emph x1 : Emph x2 : ils)
  = normalizeInlineList $ Emph (x1 <> x2) : ils
normalizeInlineList (Strong x1 : Strong x2 : ils)
  = normalizeInlineList $ Strong (x1 <> x2) : ils
normalizeInlineList (Strikeout x1 : Strikeout x2 : ils)
  = normalizeInlineList $ Strikeout (x1 <> x2) : ils
normalizeInlineList (Superscript x1 : Superscript x2 : ils)
  = normalizeInlineList $ Superscript (x1 <> x2) : ils
normalizeInlineList (Subscript x1 : Subscript x2 : ils)
  = normalizeInlineList $ Subscript (x1 <> x2) : ils
normalizeInlineList (SmallCaps x1 : SmallCaps x2 : ils)
  = normalizeInlineList $ SmallCaps (x1 <> x2) : ils
normalizeInlineList (Code _ x1 : Code _ x2 : ils)
  = normalizeInlineList $ Code nullAttr (x1 <> x2) : ils
normalizeInlineList (RawInline f1 x1 : RawInline f2 x2 : ils) | f1 == f2
  = normalizeInlineList $ RawInline f1 (x1 <> x2) : ils
-- Do not join Span's during normalization
normalizeInlineList (x:xs) = x : normalizeInlineList xs
normalizeInlineList [] = []

fixNotes :: [Inline] -> [Inline]
fixNotes []                            = []
fixNotes (Space : n@Note{} : rest)     = Str " " : n : fixNotes rest
fixNotes (SoftBreak : n@Note{} : rest) = Str " " : n : fixNotes rest
fixNotes (x:xs)                        = x : fixNotes xs

startsWithSpace :: [Inline] -> Bool
startsWithSpace (Space:_)     = True
startsWithSpace (SoftBreak:_) = True
startsWithSpace (Str s:_)     = stringStartsWithSpace s
startsWithSpace _             = False

endsWithSpace :: [Inline] -> Bool
endsWithSpace [Space]     = True
endsWithSpace [SoftBreak] = True
endsWithSpace [Str s]     = stringEndsWithSpace s
endsWithSpace (_:xs)      = endsWithSpace xs
endsWithSpace []          = False

urlEscapeBrackets :: Text -> Text
urlEscapeBrackets = T.concatMap $ \c -> case c of
  ']' -> "%5D"
  _   -> T.singleton c

isHorizontalRule :: Text -> Bool
isHorizontalRule s = T.length s >= 4 && T.all (== '-') s

stringStartsWithSpace :: Text -> Bool
stringStartsWithSpace = maybe False (isSpace . fst) . T.uncons

stringEndsWithSpace :: Text -> Bool
stringEndsWithSpace = maybe False (isSpace . snd) . T.unsnoc

fixOrEscape :: Bool -> Inline -> Bool
fixOrEscape b (Str s) = fixOrEscapeStr b s
  where
    fixOrEscapeStr sp t = case T.uncons t of
      Just ('-', xs)
        | T.null xs -> sp
        | otherwise -> (sp && isSpace (T.head xs)) || isHorizontalRule t
      Just (';', xs)
        | T.null xs -> not sp
        | otherwise -> not sp && isSpace (T.head xs)
      Just ('>', xs)
        | T.null xs -> True
        | otherwise -> isSpace (T.head xs)
      _             -> (sp && (startsWithMarker isDigit s ||
                               startsWithMarker isAsciiLower s ||
                               startsWithMarker isAsciiUpper s))
                       || stringStartsWithSpace s
fixOrEscape _ Space = True
fixOrEscape _ SoftBreak = True
fixOrEscape _ _ = False

inlineListStartsWithAlnum :: PandocMonad m
                          => [Inline]
                          -> Muse m Bool
inlineListStartsWithAlnum (Str s:_) = do
  esc <- shouldEscapeText s
  return $ esc || isAlphaNum (T.head s)
inlineListStartsWithAlnum _ = return False

-- | Convert list of Pandoc inline elements to Muse
renderInlineList :: PandocMonad m
                 => [Inline]
                 -> Muse m (Doc Text)
renderInlineList [] = pure ""
renderInlineList (x:xs) = do
  start <- asks envInlineStart
  afterSpace <- asks envAfterSpace
  topLevel <- asks envTopLevel
  insideAsterisks <- asks envInsideAsterisks
  nearAsterisks <- asks envNearAsterisks
  useTags <- gets stUseTags
  alnumNext <- inlineListStartsWithAlnum xs
  let newUseTags = useTags || alnumNext
  modify $ \st -> st { stUseTags = newUseTags }

  r <- local (\env -> env { envInlineStart = False
                          , envInsideAsterisks = False
                          , envNearAsterisks = nearAsterisks || (null xs && insideAsterisks)
                          }) $ inlineToMuse x
  opts <- asks envOptions
  let isNewline = (x == SoftBreak && writerWrapText opts == WrapPreserve) || x == LineBreak
  lst' <- local (\env -> env { envInlineStart = isNewline
                             , envAfterSpace = x == Space || (not topLevel && isNewline)
                             , envNearAsterisks = False
                             }) $ renderInlineList xs
  if start && fixOrEscape afterSpace x
    then pure (literal "<verbatim></verbatim>" <> r <> lst')
    else pure (r <> lst')

-- | Normalize and convert list of Pandoc inline elements to Muse.
inlineListToMuse :: PandocMonad m
                 => [Inline]
                 -> Muse m (Doc Text)
inlineListToMuse lst = do
  lst' <- normalizeInlineList . fixNotes <$> preprocessInlineList (map (removeKeyValues . replaceSmallCaps) lst)
  insideAsterisks <- asks envInsideAsterisks
  start <- asks envInlineStart
  modify $ \st -> st { stUseTags = False } -- Previous character is likely a '>' or some other markup
  if start && null lst'
    then pure "<verbatim></verbatim>"
    else local (\env -> env { envNearAsterisks = insideAsterisks }) $ renderInlineList lst'

inlineListToMuse' :: PandocMonad m => [Inline] -> Muse m (Doc Text)
inlineListToMuse' lst = do
  topLevel <- asks envTopLevel
  afterSpace <- asks envAfterSpace
  local (\env -> env { envInlineStart = True
                     , envAfterSpace = afterSpace || not topLevel
                     }) $ inlineListToMuse lst

emphasis :: PandocMonad m => Text -> Text -> [Inline] -> Muse m (Doc Text)
emphasis b e lst = do
  contents <- local (\env -> env { envInsideAsterisks = inAsterisks }) $ inlineListToMuse lst
  modify $ \st -> st { stUseTags = useTags }
  return $ literal b <> contents <> literal e
  where inAsterisks = T.last b == '*' || T.head e == '*'
        useTags = T.last e /= '>'

-- | Convert Pandoc inline element to Muse.
inlineToMuse :: PandocMonad m
             => Inline
             -> Muse m (Doc Text)
inlineToMuse (Str str) = do
  escapedStr <- conditionalEscapeText $ replaceNewlines str
  let useTags = isAlphaNum $ T.last escapedStr -- escapedStr is never empty because empty strings are escaped
  modify $ \st -> st { stUseTags = useTags }
  return $ literal escapedStr
inlineToMuse (Emph [Strong lst]) = do
  useTags <- gets stUseTags
  let lst' = normalizeInlineList lst
  if useTags
    then emphasis "<em>**" "**</em>" lst'
    else if null lst' || startsWithSpace lst' || endsWithSpace lst'
           then emphasis "*<strong>" "</strong>*" lst'
           else emphasis "***" "***" lst'
inlineToMuse (Emph lst) = do
  useTags <- gets stUseTags
  let lst' = normalizeInlineList lst
  if useTags || null lst' || startsWithSpace lst' || endsWithSpace lst'
    then emphasis "<em>" "</em>" lst'
    else emphasis "*" "*" lst'
inlineToMuse (Strong [Emph lst]) = do
  useTags <- gets stUseTags
  let lst' = normalizeInlineList lst
  if useTags
    then emphasis "<strong>*" "*</strong>" lst'
    else if null lst' || startsWithSpace lst' || endsWithSpace lst'
           then emphasis "**<em>" "</em>**" lst'
           else emphasis "***" "***" lst'
-- | Underline is only supported in Emacs Muse mode.
inlineToMuse (Underline lst) = do
  opts <- asks envOptions
  contents <- inlineListToMuse lst
  if isEnabled Ext_amuse opts
     then return $ "_" <> contents <> "_"
     else inlineToMuse (Emph lst)
inlineToMuse (Strong lst) = do
  useTags <- gets stUseTags
  let lst' = normalizeInlineList lst
  if useTags || null lst' || startsWithSpace lst' || endsWithSpace lst'
    then emphasis "<strong>" "</strong>" lst'
    else emphasis "**" "**" lst'
inlineToMuse (Strikeout lst) = do
  contents <- inlineListToMuse lst
  modify $ \st -> st { stUseTags = False }
  return $ "<del>" <> contents <> "</del>"
inlineToMuse (Superscript lst) = do
  contents <- inlineListToMuse lst
  modify $ \st -> st { stUseTags = False }
  return $ "<sup>" <> contents <> "</sup>"
inlineToMuse (Subscript lst) = do
  contents <- inlineListToMuse lst
  modify $ \st -> st { stUseTags = False }
  return $ "<sub>" <> contents <> "</sub>"
inlineToMuse SmallCaps {} =
  throwError $ PandocShouldNeverHappenError
    "SmallCaps should be expanded before normalization"
inlineToMuse (Quoted SingleQuote lst) = do
  contents <- inlineListToMuse lst
  modify $ \st -> st { stUseTags = False }
  return $ "‘" <> contents <> "’"
inlineToMuse (Quoted DoubleQuote lst) = do
  contents <- inlineListToMuse lst
  modify $ \st -> st { stUseTags = False }
  return $ "“" <> contents <> "”"
inlineToMuse Cite {} =
  throwError $ PandocShouldNeverHappenError
               "Citations should be expanded before normalization"
inlineToMuse (Code _ str) = do
  useTags <- gets stUseTags
  modify $ \st -> st { stUseTags = False }
  return $ if useTags || T.null str || T.any (== '=') str
              || isSpace (T.head str) || isSpace (T.last str)
             then "<code>" <> literal (T.replace "</code>" "<</code><code>/code>" str) <> "</code>"
             else "=" <> literal str <> "="
inlineToMuse Math{} =
  throwError $ PandocShouldNeverHappenError
    "Math should be expanded before normalization"
inlineToMuse (RawInline (Format f) str) = do
  modify $ \st -> st { stUseTags = False }
  return $ "<literal style=\"" <> literal f <> "\">" <> literal str <> "</literal>"
inlineToMuse LineBreak = do
  oneline <- asks envOneLine
  modify $ \st -> st { stUseTags = False }
  return $ if oneline then "<br>" else "<br>" <> cr
inlineToMuse Space = do
  modify $ \st -> st { stUseTags = False }
  return space
inlineToMuse SoftBreak = do
  oneline <- asks envOneLine
  wrapText <- asks $ writerWrapText . envOptions
  modify $ \st -> st { stUseTags = False }
  return $ if not oneline && wrapText == WrapPreserve then cr else space
inlineToMuse (Link _ txt (src, _)) =
  case txt of
        [Str x] | escapeURI x == src -> do
             modify $ \st -> st { stUseTags = False }
             return $ "[[" <> literal (escapeLink x) <> "]]"
        _ -> do contents <- local (\env -> env { envInsideLinkDescription = True }) $ inlineListToMuse txt
                modify $ \st -> st { stUseTags = False }
                return $ "[[" <> literal (escapeLink src) <> "][" <> contents <> "]]"
  where escapeLink lnk = if isImageUrl lnk then "URL:" <> urlEscapeBrackets lnk else urlEscapeBrackets lnk
        -- Taken from muse-image-regexp defined in Emacs Muse file lisp/muse-regexps.el
        imageExtensions = [".eps", ".gif", ".jpg", ".jpeg", ".pbm", ".png", ".tiff", ".xbm", ".xpm"]
        isImageUrl = (`elem` imageExtensions) . takeExtension . T.unpack
inlineToMuse (Image attr alt (source,T.stripPrefix "fig:" -> Just title)) =
  inlineToMuse (Image attr alt (source,title))
inlineToMuse (Image attr@(_, classes, _) inlines (source, title)) = do
  opts <- asks envOptions
  alt <- local (\env -> env { envInsideLinkDescription = True }) $ inlineListToMuse inlines
  title' <- if T.null title
            then if null inlines
                 then return ""
                 else return $ "[" <> alt <> "]"
            else do s <- local (\env -> env { envInsideLinkDescription = True }) $ conditionalEscapeText title
                    return $ "[" <> literal s <> "]"
  let width = case dimension Width attr of
                Just (Percent x) | isEnabled Ext_amuse opts -> " " <> tshow (round x :: Integer)
                _ -> ""
  let leftalign = if "align-left" `elem` classes
                  then " l"
                  else ""
  let rightalign = if "align-right" `elem` classes
                   then " r"
                   else ""
  modify $ \st -> st { stUseTags = False }
  return $ "[[" <> literal (urlEscapeBrackets source <> width <> leftalign <> rightalign) <> "]" <> title' <> "]"
inlineToMuse (Note contents) = do
  -- add to notes in state
  notes <- gets stNotes
  modify $ \st -> st { stNotes = contents:notes
                     , stUseTags = False
                     }
  n <- gets stNoteNum
  let ref = tshow $ n + length notes
  return $ "[" <> literal ref <> "]"
inlineToMuse (Span (anchor,names,kvs) inlines) = do
  contents <- inlineListToMuse inlines
  let (contents', hasDir) = case lookup "dir" kvs of
                              Just "rtl" -> ("<<<" <> contents <> ">>>", True)
                              Just "ltr" -> (">>>" <> contents <> "<<<", True)
                              _ -> (contents, False)
  let anchorDoc = if T.null anchor
                     then mempty
                     else literal ("#" <> anchor) <> space
  modify $ \st -> st { stUseTags = False }
  return $ anchorDoc <> (if null inlines && not (T.null anchor)
                         then mempty
                         else (if null names then (if hasDir then contents' else "<class>" <> contents' <> "</class>")
                               else "<class name=\"" <> literal (head names) <> "\">" <> contents' <> "</class>"))