{-# LANGUAGE PatternGuards #-}

{-
Copyright (C) 2014 Jesse Rosenthal <jrosenthal@jhu.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.TeXMath.Readers.OMML
 Copyright : Copyright (C) 2014 Jesse Rosenthal
 License : GNU GPL, version 2 or above

 Maintainer : Jesse Rosenthal <jrosenthal@jhu.edu>
 Stability : alpha
 Portability : portable

Types and functions for conversion of OMML into TeXMath 'Exp's.
-}

module Text.TeXMath.Readers.OMML (readOMML) where

import Text.XML.Light
import Data.Maybe (isJust, mapMaybe, fromMaybe)
import Data.List (intercalate)
import Data.Char (isDigit, readLitChar)
import Text.TeXMath.Types
import Text.TeXMath.Shared (fixTree, getSpaceWidth, getOperator)
import Text.TeXMath.Unicode.ToTeX (getSymbolType)
import Control.Applicative ((<$>))
import Text.TeXMath.Unicode.Fonts (getUnicode, stringToFont)

readOMML :: String -> Either String [Exp]
readOMML s | Just e <- parseXMLDoc s =
  case elemToOMML e of
    Just exs -> Right $ map fixTree $ unGroup exs
    Nothing   -> Left "xml file was not an <m:oMathPara> or <m:oMath> element."
readOMML _ = Left "Couldn't parse OMML file"

unGroup :: [Exp] -> [Exp]
unGroup [EGrouped exps] = exps
unGroup exps = exps

elemToOMML :: Element -> Maybe [Exp]
elemToOMML element  | isElem "m" "oMathPara" element = do
  let expList = mapMaybe elemToOMML (elChildren element)
  return $ map (\l -> if length l == 1 then (head l) else EGrouped l) expList
elemToOMML element  | isElem "m" "oMath" element =
  Just $ concat $ mapMaybe (elemToExps) (elChildren element)
elemToOMML _ = Nothing

isElem :: String -> String -> Element -> Bool
isElem prefix name element =
  let qp = fromMaybe "" (qPrefix (elName element))
  in
   qName (elName element) == name &&
   qp == prefix

hasElemName:: String -> String -> QName -> Bool
hasElemName prefix name qn =
  let qp = fromMaybe "" (qPrefix qn)
  in
   qName qn == name &&
   qp       == prefix

data OMathRunElem = TextRun String
                  | LnBrk
                  | Tab
                    deriving Show

data OMathRunTextStyle = NoStyle
                       | Normal
                       | Styled { oMathScript :: Maybe OMathTextScript
                                , oMathStyle  :: Maybe OMathTextStyle }
                       deriving Show

data OMathTextScript = ORoman
                     | OScript
                     | OFraktur
                     | ODoubleStruck
                     | OSansSerif
                     | OMonospace
                     deriving (Show, Eq)

data OMathTextStyle = OPlain
                    | OBold
                    | OItalic
                    | OBoldItalic
                    deriving (Show, Eq)

elemToBase :: Element -> Maybe Exp
elemToBase element | isElem "m" "e" element = do
  bs <- elemToBases element
  return $ case bs of
    (e : []) -> e
    exps     -> EGrouped exps
elemToBase _ = Nothing

elemToBases :: Element -> Maybe [Exp]
elemToBases element | isElem "m" "e" element =
  return $ concat $ mapMaybe elemToExps' (elChildren element)
elemToBases _ = Nothing


-- TODO: The right way to do this is to use the ampersand to break the
-- text lines into multiple columns. That's tricky, though, and this
-- will get us most of the way for the time being.
filterAmpersand :: Exp -> Exp
filterAmpersand (EIdentifier s)   = EIdentifier (filter ('&' /=) s)
filterAmpersand (EText tt s)      = EText tt (filter ('&' /=) s)
filterAmpersand (EStyled tt exps) = EStyled tt (map filterAmpersand exps)
filterAmpersand (EGrouped exps)   = EGrouped (map filterAmpersand exps)
filterAmpersand e                    = e

elemToOMathRunTextStyle :: Element -> OMathRunTextStyle
elemToOMathRunTextStyle element
  | Just mrPr <- filterChildName (hasElemName"m" "rPr") element
  , Just _    <- filterChildName (hasElemName"m" "nor") mrPr =
    Normal
  | Just mrPr <- filterChildName (hasElemName"m" "rPr") element =
    let scr =
          case
            filterChildName (hasElemName"m" "scr") mrPr >>=
            findAttrBy (hasElemName"m" "val")
          of
            Just "roman"         -> Just ORoman
            Just "script"        -> Just OScript
            Just "fraktur"       -> Just OFraktur
            Just "double-struck" -> Just ODoubleStruck
            Just "sans-serif"    -> Just OSansSerif
            Just "monospace"     -> Just OMonospace
            _                    -> Nothing

        sty =
          case
            filterChildName (hasElemName"m" "sty") mrPr >>=
            findAttrBy (hasElemName"m" "val")
          of
            Just "p"             -> Just OPlain
            Just "b"             -> Just OBold
            Just "i"             -> Just OItalic
            Just "bi"            -> Just OBoldItalic
            _                    -> Nothing
    in
     Styled { oMathScript = scr, oMathStyle = sty }
  | otherwise = NoStyle

elemToOMathRunElem :: Element -> Maybe OMathRunElem
elemToOMathRunElem element
  | isElem "w" "t" element
    || isElem "m" "t" element
    || isElem "w" "delText" element = Just $ TextRun $ strContent element
  | isElem "w" "br" element = Just LnBrk
  | isElem "w" "tab" element = Just Tab
  | isElem "w" "sym" element = Just $ TextRun $ getSymChar element
  | otherwise = Nothing

elemToOMathRunElems :: Element -> Maybe [OMathRunElem]
elemToOMathRunElems element
  | isElem "w" "r" element
    || isElem "m" "r" element =
      Just $ mapMaybe (elemToOMathRunElem) (elChildren element)
elemToOMathRunElems _ = Nothing

----- And now the TeXMath Creation

oMathRunElemToString :: OMathRunElem -> String
oMathRunElemToString (TextRun s) = s
oMathRunElemToString (LnBrk) = ['\n']
oMathRunElemToString (Tab) = ['\t']

oMathRunElemsToString :: [OMathRunElem] -> String
oMathRunElemsToString = concatMap oMathRunElemToString

oMathRunTextStyleToTextType :: OMathRunTextStyle -> Maybe TextType
oMathRunTextStyleToTextType (Normal) = Just $ TextNormal
oMathRunTextStyleToTextType (NoStyle) = Nothing
oMathRunTextStyleToTextType (Styled scr sty)
  | Just OBold <- sty
  , Just OSansSerif <- scr =
    Just $ TextSansSerifBold
  | Just OBoldItalic <- sty
  , Just OSansSerif <- scr =
    Just $ TextSansSerifBoldItalic
  | Just OBold <- sty
  , Just OScript <- scr =
    Just $ TextBoldScript
  | Just OBold <- sty
  , Just OFraktur <- scr =
    Just $ TextBoldFraktur
  | Just OItalic <- sty
  , Just OSansSerif <- scr =
    Just $ TextSansSerifItalic
  | Just OBold <- sty =
    Just $ TextBold
  | Just OItalic <- sty =
    Just $ TextItalic
  | Just OMonospace <- scr =
    Just $ TextMonospace
  | Just OSansSerif <- scr =
    Just $ TextSansSerif
  | Just ODoubleStruck <- scr =
    Just $ TextDoubleStruck
  | Just OScript <- scr =
    Just $ TextScript
  | Just OFraktur <- scr =
    Just $ TextFraktur
  | Just OBoldItalic <- sty =
    Just $ TextBoldItalic
  | otherwise = Nothing

elemToExps :: Element -> Maybe [Exp]
elemToExps element = unGroup <$> elemToExps' element

elemToExps' :: Element -> Maybe [Exp]
elemToExps' element | isElem "m" "acc" element = do
  let chr = filterChildName (hasElemName "m" "accPr") element >>=
            filterChildName (hasElemName "m" "chr") >>=
            findAttrBy (hasElemName "m" "val") >>=
            Just . head
      chr' = case chr of
        Just c -> c
        Nothing -> '^'       -- default to hat.
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return $ [EOver False baseExp (ESymbol Accent [chr'])]
elemToExps' element | isElem "m" "bar" element = do
  pos <- filterChildName (hasElemName "m" "barPr") element >>=
            filterChildName (hasElemName "m" "pos") >>=
            findAttrBy (hasElemName "m" "val")
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  case pos of
    "top" -> Just [EOver False baseExp (ESymbol Accent "\175")]
    "bot" -> Just [EUnder False baseExp (ESymbol Accent "\818")]
    _     -> Nothing
elemToExps' element | isElem "m" "box" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return [baseExp]
elemToExps' element | isElem "m" "borderBox" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return [EBoxed baseExp]
elemToExps' element | isElem "m" "d" element =
  let baseExps  = mapMaybe
                  elemToBases
                  (elChildren element)
      inDelimExps = map (map Right) baseExps
      dPr = filterChildName (hasElemName "m" "dPr") element
      begChr = dPr >>=
               filterChildName (hasElemName "m" "begChr") >>=
               findAttrBy (hasElemName "m" "val") >>=
               (\c -> if null c then (Just ' ') else (Just $ head c))
      sepChr = dPr >>=
               filterChildName (hasElemName "m" "sepChr") >>=
               findAttrBy (hasElemName "m" "val") >>=
               (\c -> if null c then (Just ' ') else (Just $ head c))
      endChr = dPr >>=
               filterChildName (hasElemName "m" "endChr") >>=
               findAttrBy (hasElemName "m" "val") >>=
               (\c -> if null c then (Just ' ') else (Just $ head c))
      beg = fromMaybe '(' begChr
      end = fromMaybe ')' endChr
      sep = fromMaybe '|' sepChr
      exps = intercalate [Left [sep]] inDelimExps
  in
   Just [EDelimited [beg] [end] exps]
elemToExps' element | isElem "m" "eqArr" element =
  let expLst = mapMaybe elemToBases (elChildren element)
      expLst' = map (\es -> [map filterAmpersand es]) expLst
  in
   return [EArray [] expLst']
elemToExps' element | isElem "m" "f" element = do
  num <- filterChildName (hasElemName "m" "num") element
  den <- filterChildName (hasElemName "m" "den") element
  let numExp = EGrouped $ concat $ mapMaybe (elemToExps) (elChildren num)
      denExp = EGrouped $ concat $ mapMaybe (elemToExps) (elChildren den)
  return $ [EFraction NormalFrac numExp denExp]
elemToExps' element | isElem "m" "func" element = do
  fName <- filterChildName (hasElemName "m" "fName") element
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
          elemToBase
  -- We need a string for the fname, but omml gives it to us as a
  -- series of oMath elems. We're going to filter out the oMathRuns,
  -- which should work for us most of the time.
  let fnameString = concatMap expToString $
                    concat $ mapMaybe (elemToExps) (elChildren fName)
  return [EMathOperator fnameString, baseExp]
elemToExps' element | isElem "m" "groupChr" element = do
  let gPr = filterChildName (hasElemName "m" "groupChrPr") element
      chr = gPr >>=
            filterChildName (hasElemName "m" "chr") >>=
            findAttrBy (hasElemName "m" "val")
      pos = gPr >>=
            filterChildName (hasElemName "m" "pos") >>=
            findAttrBy (hasElemName "m" "val")
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  case pos of
    Just "top" ->
      let chr' = case chr of
            Just (c:_) -> c
            _           -> '\65079'   -- default to overbrace
      in
       return [EOver False baseExp (ESymbol Accent [chr'])]
    Just "bot" ->
      let chr' = case chr of
            Just (c:_) -> c
            _           -> '\65080'   -- default to underbrace
      in
       return [EUnder False baseExp (ESymbol Accent [chr'])]
    _          -> Nothing
elemToExps' element | isElem "m" "limLow" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element
          >>= elemToBase
  limExp <- filterChildName (hasElemName "m" "lim") element
            >>= (\e -> Just $ concat $ mapMaybe (elemToExps) (elChildren e))
            >>= (return . EGrouped)
  return [EUnder True baseExp limExp]
elemToExps' element | isElem "m" "limUpp" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element
          >>= elemToBase
  limExp <- filterChildName (hasElemName "m" "lim") element
            >>= (\e -> Just $ concat $ mapMaybe (elemToExps) (elChildren e))
            >>= (return . EGrouped)
  return [EOver True baseExp limExp]
elemToExps' element | isElem "m" "m" element =
  let rows = filterChildrenName (hasElemName "m" "mr") element
      rowExps = map
                (\mr -> mapMaybe
                        elemToBases
                        (elChildren mr))
                rows
  in
   return [EArray [AlignCenter] rowExps]
elemToExps' element | isElem "m" "nary" element = do
  let naryPr = filterChildName (hasElemName "m" "naryPr") element
      naryChr = naryPr >>=
                filterChildName (hasElemName "m" "chr") >>=
                findAttrBy (hasElemName "m" "val")
      opChr = case naryChr of
        Just (c:_) -> c
        _          -> '\8747'   -- default to integral
      limLoc = naryPr >>=
               filterChildName (hasElemName "m" "limLoc") >>=
               findAttrBy (hasElemName "m" "val")
  subExps <- filterChildName (hasElemName "m" "sub") element >>=
         (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  supExps <- filterChildName (hasElemName "m" "sup") element >>=
         (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  case limLoc of
    Just "undOvr" -> return [EUnderover True
                              (ESymbol Op [opChr])
                              (EGrouped subExps)
                              (EGrouped supExps)
                            , baseExp]
    _             -> return [ESubsup
                              (ESymbol Op [opChr])
                              (EGrouped subExps)
                              (EGrouped supExps)
                            , baseExp]

elemToExps' element | isElem "m" "phant" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return [EPhantom baseExp]
elemToExps' element | isElem "m" "rad" element = do
  degExps <- filterChildName (hasElemName "m" "deg") element >>=
              (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return $ case degExps of
    [] -> [ESqrt baseExp]
    ds -> [ERoot (EGrouped ds) baseExp]
elemToExps' element | isElem "m" "sPre" element = do
  subExps <- filterChildName (hasElemName "m" "sub") element >>=
            (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  supExps <- filterChildName (hasElemName "m" "sup") element >>=
            (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  return [ESubsup
          (EIdentifier "")
          (EGrouped subExps)
          (EGrouped supExps)
         , baseExp]
elemToExps' element | isElem "m" "sSub" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  subExps <- filterChildName (hasElemName "m" "sub") element >>=
            (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  return [ESub baseExp (EGrouped subExps)]
elemToExps' element | isElem "m" "sSubSup" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  subExps <- filterChildName (hasElemName "m" "sub") element >>=
             (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  supExps <- filterChildName (hasElemName "m" "sup") element >>=
             (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  return [ESubsup baseExp (EGrouped subExps) (EGrouped supExps)]
elemToExps' element | isElem "m" "sSup" element = do
  baseExp <- filterChildName (hasElemName "m" "e") element >>=
             elemToBase
  supExps <- filterChildName (hasElemName "m" "sup") element >>=
            (\e -> return $ concat $ mapMaybe (elemToExps) (elChildren e))
  return [ESuper baseExp (EGrouped supExps)]
elemToExps' element | isElem "m" "r" element = do
  let mrPr = filterChildName (hasElemName "m" "rPr") element
      lit = mrPr >>=
            filterChildName (hasElemName "m" "lit") >>=
            findAttrBy (hasElemName "m" "val")
      txtSty = elemToOMathRunTextStyle element
  mrElems <- elemToOMathRunElems element
  return $ case oMathRunTextStyleToTextType txtSty of
    Nothing -> interpretString $ oMathRunElemsToString mrElems
    Just textType ->
      case lit of
        Just "on" ->
          [EText textType (oMathRunElemsToString mrElems)]
        _         ->
          [EStyled textType $ interpretString $ oMathRunElemsToString mrElems]
elemToExps' _ = Nothing

interpretChar :: Char -> Exp
interpretChar c | isDigit c = ENumber [c]
interpretChar c = case getSymbolType c of
  Alpha           -> EIdentifier [c]
  Ord | isDigit c -> ENumber [c]
      | otherwise -> case getSpaceWidth c of
                           Just x  -> ESpace x
                           Nothing -> ESymbol Ord [c]
  symType         -> ESymbol symType [c]

interpretString :: String -> [Exp]
interpretString [c]       = [interpretChar c]
interpretString s
  | all isDigit s         = [ENumber s]
  | isJust (getOperator (EMathOperator s))
                          = [EMathOperator s]
  | otherwise             =
      case map interpretChar s of
            xs | all isIdentifierOrSpace xs -> [EText TextNormal s]
               | otherwise                  -> xs
  where isIdentifierOrSpace (EIdentifier _) = True
        isIdentifierOrSpace (ESpace _)      = True
        isIdentifierOrSpace _               = False

expToString :: Exp -> String
expToString (ENumber s) = s
expToString (EIdentifier s) = s
expToString (EMathOperator s) = s
expToString (ESymbol _ s) = s
expToString (EText _ s) = s
expToString (EGrouped exps) = concatMap expToString exps
expToString (EStyled _ exps) = concatMap expToString exps
expToString _ = ""

-- The char attribute is a hex string
getSymChar :: Element -> String
getSymChar element
  | Just s <- lowerFromPrivate <$> getCodepoint
  , Just font <- getFont =
  let [(char, _)] = readLitChar ("\\x" ++ s) in
    maybe "" (:[]) $ getUnicode font char
  where
    getCodepoint = findAttrBy (hasElemName "w" "char") element
    getFont = stringToFont =<< findAttrBy (hasElemName "w" "font") element
    lowerFromPrivate ('F':xs) = '0':xs
    lowerFromPrivate xs = xs
getSymChar _ = ""