{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleInstances #-}
module Text.Hamlet.Parse
    ( Result (..)
    , Content (..)
    , Doc (..)
    , parseDoc
    , HamletSettings (..)
    , defaultHamletSettings
    , xhtmlHamletSettings
    , CloseStyle (..)
    , Binding (..)
    , NewlineStyle (..)
    , specialOrIdent
    , DataConstr (..)
    , Module (..)
    )
    where

import Text.Shakespeare.Base
import Control.Applicative ((<$>), Applicative (..))
import Control.Monad
import Control.Arrow
import Data.Char (isUpper)
import Data.Data
import Text.ParserCombinators.Parsec hiding (Line)
import Data.Set (Set)
import qualified Data.Set as Set
import Data.Maybe (mapMaybe, fromMaybe, isNothing)
import Language.Haskell.TH.Syntax (Lift (..))

data Result v = Error String | Ok v
    deriving (Show, Eq, Read, Data, Typeable)
instance Monad Result where
    return = Ok
    Error s >>= _ = Error s
    Ok v >>= f = f v
    fail = Error
instance Functor Result where
    fmap = liftM
instance Applicative Result where
    pure = return
    (<*>) = ap

data Content = ContentRaw String
             | ContentVar Deref
             | ContentUrl Bool Deref -- ^ bool: does it include params?
             | ContentEmbed Deref
             | ContentMsg Deref
             | ContentAttrs Deref
    deriving (Show, Eq, Read, Data, Typeable)

data Line = LineForall Deref Binding
          | LineIf Deref
          | LineElseIf Deref
          | LineElse
          | LineWith [(Deref, Binding)]
          | LineMaybe Deref Binding
          | LineNothing
          | LineCase Deref
          | LineOf Binding
          | LineTag
            { _lineTagName :: String
            , _lineAttr :: [(Maybe Deref, String, Maybe [Content])]
            , _lineContent :: [Content]
            , _lineClasses :: [(Maybe Deref, [Content])]
            , _lineAttrs :: [Deref]
            , _lineNoNewline :: Bool
            }
          | LineContent [Content] Bool -- ^ True == avoid newlines
    deriving (Eq, Show, Read)

parseLines :: HamletSettings -> String -> Result (Maybe NewlineStyle, HamletSettings, [(Int, Line)])
parseLines set s =
    case parse parser s s of
        Left e -> Error $ show e
        Right x -> Ok x
  where
    parser = do
        mnewline <- parseNewline
        let set' =
                case mnewline of
                    Nothing ->
                        case hamletNewlines set of
                            DefaultNewlineStyle -> set { hamletNewlines = AlwaysNewlines }
                            _ -> set
                    Just n -> set { hamletNewlines = n }
        res <- many (parseLine set')
        return (mnewline, set', res)

    parseNewline =
        (try (many eol' >> spaceTabs >> string "$newline ") >> parseNewline' >>= \nl -> eol' >> return nl) <|>
        return Nothing
    parseNewline' =
        (try (string "always") >> return (Just AlwaysNewlines)) <|>
        (try (string "never") >> return (Just NoNewlines)) <|>
        (try (string "text") >> return (Just NewlinesText))

    eol' = (char '\n' >> return ()) <|> (string "\r\n" >> return ())

parseLine :: HamletSettings -> Parser (Int, Line)
parseLine set = do
    ss <- fmap sum $ many ((char ' ' >> return 1) <|>
                           (char '\t' >> fail "Tabs are not allowed in Hamlet indentation"))
    x <- doctype <|>
         doctypeDollar <|>
         comment <|>
         ssiInclude <|>
         htmlComment <|>
         doctypeRaw <|>
         backslash <|>
         controlIf <|>
         controlElseIf <|>
         (try (string "$else") >> spaceTabs >> eol >> return LineElse) <|>
         controlMaybe <|>
         (try (string "$nothing") >> spaceTabs >> eol >> return LineNothing) <|>
         controlForall <|>
         controlWith <|>
         controlCase <|>
         controlOf <|>
         angle <|>
         invalidDollar <|>
         (eol' >> return (LineContent [] True)) <|>
         (do
            (cs, avoidNewLines) <- content InContent
            isEof <- (eof >> return True) <|> return False
            if null cs && ss == 0 && isEof
                then fail "End of Hamlet template"
                else return $ LineContent cs avoidNewLines)
    return (ss, x)
  where
    eol' = (char '\n' >> return ()) <|> (string "\r\n" >> return ())
    eol = eof <|> eol'
    doctype = do
        try $ string "!!!" >> eol
        return $ LineContent [ContentRaw $ hamletDoctype set ++ "\n"] True
    doctypeDollar = do
        _ <- try $ string "$doctype "
        name <- many $ noneOf "\r\n"
        eol
        case lookup name $ hamletDoctypeNames set of
            Nothing -> fail $ "Unknown doctype name: " ++ name
            Just val -> return $ LineContent [ContentRaw $ val ++ "\n"] True

    doctypeRaw = do
        x <- try $ string "<!"
        y <- many $ noneOf "\r\n"
        eol
        return $ LineContent [ContentRaw $ concat [x, y, "\n"]] True

    invalidDollar = do
        _ <- char '$'
        fail "Received a command I did not understand. If you wanted a literal $, start the line with a backslash."
    comment = do
        _ <- try $ string "$#"
        _ <- many $ noneOf "\r\n"
        eol
        return $ LineContent [] True
    ssiInclude = do
        x <- try $ string "<!--#"
        y <- many $ noneOf "\r\n"
        eol
        return $ LineContent [ContentRaw $ x ++ y] False
    htmlComment = do
        _ <- try $ string "<!--"
        _ <- manyTill anyChar $ try $ string "-->"
        x <- many nonComments
        eol
        return $ LineContent [ContentRaw $ concat x] False {- FIXME -} -- FIXME handle variables?
    nonComments = (many1 $ noneOf "\r\n<") <|> (do
        _ <- char '<'
        (do
            _ <- try $ string "!--"
            _ <- manyTill anyChar $ try $ string "-->"
            return "") <|> return "<")
    backslash = do
        _ <- char '\\'
        (eol >> return (LineContent [ContentRaw "\n"] True))
            <|> (uncurry LineContent <$> content InContent)
    controlIf = do
        _ <- try $ string "$if"
        spaces
        x <- parseDeref
        _ <- spaceTabs
        eol
        return $ LineIf x
    controlElseIf = do
        _ <- try $ string "$elseif"
        spaces
        x <- parseDeref
        _ <- spaceTabs
        eol
        return $ LineElseIf x
    binding = do
        y <- identPattern
        spaces
        _ <- string "<-"
        spaces
        x <- parseDeref
        _ <- spaceTabs
        return (x,y)
    bindingSep = char ',' >> spaceTabs
    controlMaybe = do
        _ <- try $ string "$maybe"
        spaces
        (x,y) <- binding
        eol
        return $ LineMaybe x y
    controlForall = do
        _ <- try $ string "$forall"
        spaces
        (x,y) <- binding
        eol
        return $ LineForall x y
    controlWith = do
        _ <- try $ string "$with"
        spaces
        bindings <- (binding `sepBy` bindingSep) `endBy` eol
        return $ LineWith $ concat bindings -- concat because endBy returns a [[(Deref,Ident)]]
    controlCase = do
        _ <- try $ string "$case"
        spaces
        x <- parseDeref
        _ <- spaceTabs
        eol
        return $ LineCase x
    controlOf = do
        _   <- try $ string "$of"
        spaces
        x <- identPattern
        _   <- spaceTabs
        eol
        return $ LineOf x
    content cr = do
        x <- many $ content' cr
        case cr of
            InQuotes -> void $ char '"'
            NotInQuotes -> return ()
            NotInQuotesAttr -> return ()
            InContent -> eol
        return (cc $ map fst x, any snd x)
      where
        cc [] = []
        cc (ContentRaw a:ContentRaw b:c) = cc $ ContentRaw (a ++ b) : c
        cc (a:b) = a : cc b
    content' cr = contentHash <|> contentAt <|> contentCaret
                              <|> contentUnder
                              <|> contentReg' cr
    contentHash = do
        x <- parseHash
        case x of
            Left str -> return (ContentRaw str, null str)
            Right deref -> return (ContentVar deref, False)
    contentAt = do
        x <- parseAt
        return $ case x of
                    Left str -> (ContentRaw str, null str)
                    Right (s, y) -> (ContentUrl y s, False)
    contentCaret = do
        x <- parseCaret
        case x of
            Left str -> return (ContentRaw str, null str)
            Right deref -> return (ContentEmbed deref, False)
    contentUnder = do
        x <- parseUnder
        case x of
            Left str -> return (ContentRaw str, null str)
            Right deref -> return (ContentMsg deref, False)
    contentReg' x = (flip (,) False) <$> contentReg x
    contentReg InContent = (ContentRaw . return) <$> noneOf "#@^\r\n"
    contentReg NotInQuotes = (ContentRaw . return) <$> noneOf "@^#. \t\n\r>"
    contentReg NotInQuotesAttr = (ContentRaw . return) <$> noneOf "@^ \t\n\r>"
    contentReg InQuotes = (ContentRaw . return) <$> noneOf "#@^\"\n\r"
    tagAttribValue notInQuotes = do
        cr <- (char '"' >> return InQuotes) <|> return notInQuotes
        fst <$> content cr
    tagIdent = char '#' >> TagIdent <$> tagAttribValue NotInQuotes
    tagCond = do
        d <- between (char ':') (char ':') parseDeref
        tagClass (Just d) <|> tagAttrib (Just d)
    tagClass x = do
        clazz <- char '.' >> tagAttribValue NotInQuotes
        let hasHash (ContentRaw s) = any (== '#') s
            hasHash _ = False
        if any hasHash clazz
            then fail $ "Invalid class: " ++ show clazz ++ ". Did you want a space between a class and an ID?"
            else return (TagClass (x, clazz))
    tagAttrib cond = do
        s <- many1 $ noneOf " \t=\r\n><"
        v <- (char '=' >> Just <$> tagAttribValue NotInQuotesAttr) <|> return Nothing
        return $ TagAttrib (cond, s, v)

    tagAttrs = do
        _ <- char '*'
        d <- between (char '{') (char '}') parseDeref
        return $ TagAttribs d

    tag' = foldr tag'' ("div", [], [], [])
    tag'' (TagName s) (_, y, z, as) = (s, y, z, as)
    tag'' (TagIdent s) (x, y, z, as) = (x, (Nothing, "id", Just s) : y, z, as)
    tag'' (TagClass s) (x, y, z, as) = (x, y, s : z, as)
    tag'' (TagAttrib s) (x, y, z, as) = (x, s : y, z, as)
    tag'' (TagAttribs s) (x, y, z, as) = (x, y, z, s : as)

    ident :: Parser Ident
    ident = do
      i <- many1 (alphaNum <|> char '_' <|> char '\'')
      white
      return (Ident i)
     <?> "identifier"

    parens = between (char '(' >> white) (char ')' >> white)

    brackets = between (char '[' >> white) (char ']' >> white)

    braces = between (char '{' >> white) (char '}' >> white)

    comma = char ',' >> white

    atsign = char '@' >> white

    equals = char '=' >> white

    white = skipMany $ char ' '

    wildDots = string ".." >> white

    isVariable (Ident (x:_)) = not (isUpper x)
    isVariable (Ident []) = error "isVariable: bad identifier"

    isConstructor (Ident (x:_)) = isUpper x
    isConstructor (Ident []) = error "isConstructor: bad identifier"

    identPattern :: Parser Binding
    identPattern = gcon True <|> apat
      where
      apat = choice
        [ varpat
        , gcon False
        , parens tuplepat
        , brackets listpat
        ]

      varpat = do
        v <- try $ do v <- ident
                      guard (isVariable v)
                      return v
        option (BindVar v) $ do
          atsign
          b <- apat
          return (BindAs v b)
       <?> "variable"

      gcon :: Bool -> Parser Binding
      gcon allowArgs = do
        c <- try $ do c <- dataConstr
                      return c
        choice
          [ record c
          , fmap (BindConstr c) (guard allowArgs >> many apat)
          , return (BindConstr c [])
          ]
       <?> "constructor"

      dataConstr = do
        p <- dcPiece
        ps <- many dcPieces
        return $ toDataConstr p ps

      dcPiece = do
        x@(Ident y) <- ident
        guard $ isConstructor x
        return y

      dcPieces = do
        _ <- char '.'
        dcPiece

      toDataConstr x [] = DCUnqualified $ Ident x
      toDataConstr x (y:ys) =
          go (x:) y ys
        where
          go front next [] = DCQualified (Module $ front []) (Ident next)
          go front next (rest:rests) = go (front . (next:)) rest rests

      record c = braces $ do
        (fields, wild) <- option ([], False) $ go
        return (BindRecord c fields wild)
        where
        go = (wildDots >> return ([], True))
           <|> (do x         <- recordField
                   (xs,wild) <- option ([],False) (comma >> go)
                   return (x:xs,wild))

      recordField = do
        field <- ident
        p <- option (BindVar field) -- support punning
                    (equals >> identPattern)
        return (field,p)

      tuplepat = do
        xs <- identPattern `sepBy` comma
        return $ case xs of
          [x] -> x
          _   -> BindTuple xs

      listpat = BindList <$> identPattern `sepBy` comma

    angle = do
        _ <- char '<'
        name' <- many  $ noneOf " \t.#\r\n!>"
        let name = if null name' then "div" else name'
        xs <- many $ try ((many $ oneOf " \t\r\n") >>
              (tagIdent <|> tagCond <|> tagClass Nothing <|> tagAttrs <|> tagAttrib Nothing))
        _ <- many $ oneOf " \t\r\n"
        _ <- char '>'
        (c, avoidNewLines) <- content InContent
        let (tn, attr, classes, attrsd) = tag' $ TagName name : xs
        if '/' `elem` tn
          then fail "A tag name may not contain a slash. Perhaps you have a closing tag in your HTML."
          else return $ LineTag tn attr c classes attrsd avoidNewLines

data TagPiece = TagName String
              | TagIdent [Content]
              | TagClass (Maybe Deref, [Content])
              | TagAttrib (Maybe Deref, String, Maybe [Content])
              | TagAttribs Deref
    deriving Show

data ContentRule = InQuotes | NotInQuotes | NotInQuotesAttr | InContent

data Nest = Nest Line [Nest]

nestLines :: [(Int, Line)] -> [Nest]
nestLines [] = []
nestLines ((i, l):rest) =
    let (deeper, rest') = span (\(i', _) -> i' > i) rest
     in Nest l (nestLines deeper) : nestLines rest'

data Doc = DocForall Deref Binding [Doc]
         | DocWith [(Deref, Binding)] [Doc]
         | DocCond [(Deref, [Doc])] (Maybe [Doc])
         | DocMaybe Deref Binding [Doc] (Maybe [Doc])
         | DocCase Deref [(Binding, [Doc])]
         | DocContent Content
    deriving (Show, Eq, Read, Data, Typeable)

nestToDoc :: HamletSettings -> [Nest] -> Result [Doc]
nestToDoc _set [] = Ok []
nestToDoc set (Nest (LineForall d i) inside:rest) = do
    inside' <- nestToDoc set inside
    rest' <- nestToDoc set rest
    Ok $ DocForall d i inside' : rest'
nestToDoc set (Nest (LineWith dis) inside:rest) = do
    inside' <- nestToDoc set inside
    rest' <- nestToDoc set rest
    Ok $ DocWith dis inside' : rest'
nestToDoc set (Nest (LineIf d) inside:rest) = do
    inside' <- nestToDoc set inside
    (ifs, el, rest') <- parseConds set ((:) (d, inside')) rest
    rest'' <- nestToDoc set rest'
    Ok $ DocCond ifs el : rest''
nestToDoc set (Nest (LineMaybe d i) inside:rest) = do
    inside' <- nestToDoc set inside
    (nothing, rest') <-
        case rest of
            Nest LineNothing ninside:x -> do
                ninside' <- nestToDoc set ninside
                return (Just ninside', x)
            _ -> return (Nothing, rest)
    rest'' <- nestToDoc set rest'
    Ok $ DocMaybe d i inside' nothing : rest''
nestToDoc set (Nest (LineCase d) inside:rest) = do
    let getOf (Nest (LineOf x) insideC) = do
            insideC' <- nestToDoc set insideC
            Ok (x, insideC')
        getOf _ = Error "Inside a $case there may only be $of.  Use '$of _' for a wildcard."
    cases <- mapM getOf inside
    rest' <- nestToDoc set rest
    Ok $ DocCase d cases : rest'
nestToDoc set (Nest (LineTag tn attrs content classes attrsD avoidNewLine) inside:rest) = do
    let attrFix (x, y, z) = (x, y, [(Nothing, z)])
    let takeClass (a, "class", b) = Just (a, fromMaybe [] b)
        takeClass _ = Nothing
    let clazzes = classes ++ mapMaybe takeClass attrs
    let notClass (_, x, _) = x /= "class"
    let noclass = filter notClass attrs
    let attrs' =
            case clazzes of
              [] -> map attrFix noclass
              _ -> (testIncludeClazzes clazzes, "class", map (second Just) clazzes)
                       : map attrFix noclass
    let closeStyle =
            if not (null content) || not (null inside)
                then CloseSeparate
                else hamletCloseStyle set tn
    let end = case closeStyle of
                CloseSeparate ->
                    DocContent $ ContentRaw $ "</" ++ tn ++ ">"
                _ -> DocContent $ ContentRaw ""
        seal = case closeStyle of
                 CloseInside -> DocContent $ ContentRaw "/>"
                 _ -> DocContent $ ContentRaw ">"
        start = DocContent $ ContentRaw $ "<" ++ tn
        attrs'' = concatMap attrToContent attrs'
        newline' = DocContent $ ContentRaw
                 $ case hamletNewlines set of { AlwaysNewlines | not avoidNewLine -> "\n"; _ -> "" }
    inside' <- nestToDoc set inside
    rest' <- nestToDoc set rest
    Ok $ start
       : attrs''
      ++ map (DocContent . ContentAttrs) attrsD
      ++ seal
       : map DocContent content
      ++ inside'
      ++ end
       : newline'
       : rest'
nestToDoc set (Nest (LineContent content avoidNewLine) inside:rest) = do
    inside' <- nestToDoc set inside
    rest' <- nestToDoc set rest
    let newline' = DocContent $ ContentRaw
                   $ case hamletNewlines set of { NoNewlines -> ""; _ -> if nextIsContent && not avoidNewLine then "\n" else "" }
        nextIsContent =
            case (inside, rest) of
                ([], Nest LineContent{} _:_) -> True
                ([], Nest LineTag{} _:_) -> True
                _ -> False
    Ok $ map DocContent content ++ newline':inside' ++ rest'
nestToDoc _set (Nest (LineElseIf _) _:_) = Error "Unexpected elseif"
nestToDoc _set (Nest LineElse _:_) = Error "Unexpected else"
nestToDoc _set (Nest LineNothing _:_) = Error "Unexpected nothing"
nestToDoc _set (Nest (LineOf _) _:_) = Error "Unexpected 'of' (did you forget a $case?)"

compressDoc :: [Doc] -> [Doc]
compressDoc [] = []
compressDoc (DocForall d i doc:rest) =
    DocForall d i (compressDoc doc) : compressDoc rest
compressDoc (DocWith dis doc:rest) =
    DocWith dis (compressDoc doc) : compressDoc rest
compressDoc (DocMaybe d i doc mnothing:rest) =
    DocMaybe d i (compressDoc doc) (fmap compressDoc mnothing)
  : compressDoc rest
compressDoc (DocCond [(a, x)] Nothing:DocCond [(b, y)] Nothing:rest)
    | a == b = compressDoc $ DocCond [(a, x ++ y)] Nothing : rest
compressDoc (DocCond x y:rest) =
    DocCond (map (second compressDoc) x) (compressDoc `fmap` y)
    : compressDoc rest
compressDoc (DocCase d cs:rest) =
    DocCase d (map (second compressDoc) cs) : compressDoc rest
compressDoc (DocContent (ContentRaw ""):rest) = compressDoc rest
compressDoc ( DocContent (ContentRaw x)
            : DocContent (ContentRaw y)
            : rest
            ) = compressDoc $ (DocContent $ ContentRaw $ x ++ y) : rest
compressDoc (DocContent x:rest) = DocContent x : compressDoc rest

parseDoc :: HamletSettings -> String -> Result (Maybe NewlineStyle, [Doc])
parseDoc set s = do
    (mnl, set', ls) <- parseLines set s
    let notEmpty (_, LineContent [] _) = False
        notEmpty _ = True
    let ns = nestLines $ filter notEmpty ls
    ds <- nestToDoc set' ns
    return (mnl, compressDoc ds)

attrToContent :: (Maybe Deref, String, [(Maybe Deref, Maybe [Content])]) -> [Doc]
attrToContent (Just cond, k, v) =
    [DocCond [(cond, attrToContent (Nothing, k, v))] Nothing]
attrToContent (Nothing, k, []) = [DocContent $ ContentRaw $ ' ' : k]
attrToContent (Nothing, k, [(Nothing, Nothing)]) = [DocContent $ ContentRaw $ ' ' : k]
attrToContent (Nothing, k, [(Nothing, Just v)]) =
    DocContent (ContentRaw (' ' : k ++ "=\""))
  : map DocContent v
  ++ [DocContent $ ContentRaw "\""]
attrToContent (Nothing, k, v) = -- only for class
      DocContent (ContentRaw (' ' : k ++ "=\""))
    : concatMap go (init v)
    ++ go' (last v)
    ++ [DocContent $ ContentRaw "\""]
  where
    go (Nothing, x) = map DocContent (fromMaybe [] x) ++ [DocContent $ ContentRaw " "]
    go (Just b, x) =
        [ DocCond
            [(b, map DocContent (fromMaybe [] x) ++ [DocContent $ ContentRaw " "])]
            Nothing
        ]
    go' (Nothing, x) = maybe [] (map DocContent) x
    go' (Just b, x) =
        [ DocCond
            [(b, maybe [] (map DocContent) x)]
            Nothing
        ]

-- | Settings for parsing of a hamlet document.
data HamletSettings = HamletSettings
    {
      -- | The value to replace a \"!!!\" with. Do not include the trailing
      -- newline.
      hamletDoctype :: String
      -- | Should we add newlines to the output, making it more human-readable?
      --  Useful for client-side debugging but may alter browser page layout.
    , hamletNewlines :: NewlineStyle
      -- | How a tag should be closed. Use this to switch between HTML, XHTML
      -- or even XML output.
    , hamletCloseStyle :: String -> CloseStyle
      -- | Mapping from short names in \"$doctype\" statements to full doctype.
    , hamletDoctypeNames :: [(String, String)]
    }

data NewlineStyle = NoNewlines -- ^ never add newlines
                  | NewlinesText -- ^ add newlines between consecutive text lines
                  | AlwaysNewlines -- ^ add newlines everywhere
                  | DefaultNewlineStyle
    deriving Show

instance Lift NewlineStyle where
    lift NoNewlines = [|NoNewlines|]
    lift NewlinesText = [|NewlinesText|]
    lift AlwaysNewlines = [|AlwaysNewlines|]
    lift DefaultNewlineStyle = [|DefaultNewlineStyle|]

instance Lift (String -> CloseStyle) where
    lift _ = [|\s -> htmlCloseStyle s|]

instance Lift HamletSettings where
    lift (HamletSettings a b c d) = [|HamletSettings $(lift a) $(lift b) $(lift c) $(lift d)|]


htmlEmptyTags :: Set String
htmlEmptyTags = Set.fromAscList
    [ "area"
    , "base"
    , "basefont"
    , "br"
    , "col"
    , "frame"
    , "hr"
    , "img"
    , "input"
    , "isindex"
    , "link"
    , "meta"
    , "param"
    ]

-- | Defaults settings: HTML5 doctype and HTML-style empty tags.
defaultHamletSettings :: HamletSettings
defaultHamletSettings = HamletSettings "<!DOCTYPE html>" DefaultNewlineStyle htmlCloseStyle doctypeNames

xhtmlHamletSettings :: HamletSettings
xhtmlHamletSettings =
    HamletSettings doctype DefaultNewlineStyle xhtmlCloseStyle doctypeNames
  where
    doctype =
      "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" " ++
      "\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">"

htmlCloseStyle :: String -> CloseStyle
htmlCloseStyle s =
    if Set.member s htmlEmptyTags
        then NoClose
        else CloseSeparate

xhtmlCloseStyle :: String -> CloseStyle
xhtmlCloseStyle s =
    if Set.member s htmlEmptyTags
        then CloseInside
        else CloseSeparate

data CloseStyle = NoClose | CloseInside | CloseSeparate

parseConds :: HamletSettings
           -> ([(Deref, [Doc])] -> [(Deref, [Doc])])
           -> [Nest]
           -> Result ([(Deref, [Doc])], Maybe [Doc], [Nest])
parseConds set front (Nest LineElse inside:rest) = do
    inside' <- nestToDoc set inside
    Ok (front [], Just inside', rest)
parseConds set front (Nest (LineElseIf d) inside:rest) = do
    inside' <- nestToDoc set inside
    parseConds set (front . (:) (d, inside')) rest
parseConds _ front rest = Ok (front [], Nothing, rest)

doctypeNames :: [(String, String)]
doctypeNames =
    [ ("5", "<!DOCTYPE html>")
    , ("html", "<!DOCTYPE html>")
    , ("1.1", "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.1//EN\" \"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd\">")
    , ("strict", "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">")
    ]

data Binding = BindVar Ident
             | BindAs Ident Binding
             | BindConstr DataConstr [Binding]
             | BindTuple [Binding]
             | BindList [Binding]
             | BindRecord DataConstr [(Ident, Binding)] Bool
    deriving (Eq, Show, Read, Data, Typeable)

data DataConstr = DCQualified Module Ident
                | DCUnqualified Ident
    deriving (Eq, Show, Read, Data, Typeable)

newtype Module = Module [String]
    deriving (Eq, Show, Read, Data, Typeable)

spaceTabs :: Parser String
spaceTabs = many $ oneOf " \t"

-- | When using conditional classes, it will often be a single class, e.g.:
--
-- > <div :isHome:.homepage>
--
-- If isHome is False, we do not want any class attribute to be present.
-- However, due to combining multiple classes together, the most obvious
-- implementation would produce a class="". The purpose of this function is to
-- work around that. It does so by checking if all the classes on this tag are
-- optional. If so, it will only include the class attribute if at least one
-- conditional is true.
testIncludeClazzes :: [(Maybe Deref, [Content])] -> Maybe Deref
testIncludeClazzes cs
    | any (isNothing . fst) cs = Nothing
    | otherwise = Just $ DerefBranch (DerefIdent specialOrIdent) $ DerefList $ mapMaybe fst cs

-- | This funny hack is to allow us to refer to the 'or' function without
-- requiring the user to have it in scope. See how this function is used in
-- Text.Hamlet.
specialOrIdent :: Ident
specialOrIdent = Ident "__or__hamlet__special"