----------------------------------------------------------------------------- -- | -- Module : Haddock.Backends.Html -- Copyright : (c) Simon Marlow 2003-2006, -- David Waern 2006-2009, -- Mark Lentczner 2010, -- Mateusz Kowalczyk 2013 -- License : BSD-like -- -- Maintainer : haddock@projects.haskell.org -- Stability : experimental -- Portability : portable ----------------------------------------------------------------------------- {-# LANGUAGE CPP, NamedFieldPuns #-} module Haddock.Backends.Xhtml ( ppHtml, copyHtmlBits, ppHtmlIndex, ppHtmlContents, ) where import Prelude hiding (div) import Haddock.Backends.Xhtml.Decl import Haddock.Backends.Xhtml.DocMarkup import Haddock.Backends.Xhtml.Layout import Haddock.Backends.Xhtml.Names import Haddock.Backends.Xhtml.Themes import Haddock.Backends.Xhtml.Types import Haddock.Backends.Xhtml.Utils import Haddock.ModuleTree import Haddock.Types import Haddock.Version import Haddock.Utils import Haddock.Utils.Json import Text.XHtml hiding ( name, title, p, quote ) import Haddock.GhcUtils import Control.Monad ( when, unless ) import qualified Data.ByteString.Builder as Builder import Data.Char ( toUpper, isSpace ) import Data.List ( sortBy, isPrefixOf, intercalate, intersperse ) import Data.Maybe import System.Directory import System.FilePath hiding ( () ) import qualified System.IO as IO import Data.Map ( Map ) import qualified Data.Map as Map hiding ( Map ) import qualified Data.Set as Set hiding ( Set ) import Data.Ord ( comparing ) import DynFlags (Language(..)) import GHC hiding ( NoLink, moduleInfo,LexicalFixity(..) ) import Name -------------------------------------------------------------------------------- -- * Generating HTML documentation -------------------------------------------------------------------------------- ppHtml :: DynFlags -> String -- ^ Title -> Maybe String -- ^ Package -> [Interface] -> [InstalledInterface] -- ^ Reexported interfaces -> FilePath -- ^ Destination directory -> Maybe (MDoc GHC.RdrName) -- ^ Prologue text, maybe -> Themes -- ^ Themes -> Maybe String -- ^ The mathjax URL (--mathjax) -> SourceURLs -- ^ The source URL (--source) -> WikiURLs -- ^ The wiki URL (--wiki) -> Maybe String -- ^ The contents URL (--use-contents) -> Maybe String -- ^ The index URL (--use-index) -> Bool -- ^ Whether to use unicode in output (--use-unicode) -> QualOption -- ^ How to qualify names -> Bool -- ^ Output pretty html (newlines and indenting) -> Bool -- ^ Also write Quickjump index -> IO () ppHtml dflags doctitle maybe_package ifaces reexported_ifaces odir prologue themes maybe_mathjax_url maybe_source_url maybe_wiki_url maybe_contents_url maybe_index_url unicode qual debug withQuickjump = do let visible_ifaces = filter visible ifaces visible i = OptHide `notElem` ifaceOptions i when (isNothing maybe_contents_url) $ ppHtmlContents dflags odir doctitle maybe_package themes maybe_mathjax_url maybe_index_url maybe_source_url maybe_wiki_url (map toInstalledIface visible_ifaces ++ reexported_ifaces) False -- we don't want to display the packages in a single-package contents prologue debug (makeContentsQual qual) when (isNothing maybe_index_url) $ do ppHtmlIndex odir doctitle maybe_package themes maybe_mathjax_url maybe_contents_url maybe_source_url maybe_wiki_url (map toInstalledIface visible_ifaces ++ reexported_ifaces) debug when withQuickjump $ ppJsonIndex odir maybe_source_url maybe_wiki_url unicode qual visible_ifaces mapM_ (ppHtmlModule odir doctitle themes maybe_mathjax_url maybe_source_url maybe_wiki_url maybe_contents_url maybe_index_url unicode qual debug) visible_ifaces copyHtmlBits :: FilePath -> FilePath -> Themes -> Bool -> IO () copyHtmlBits odir libdir themes withQuickjump = do let libhtmldir = joinPath [libdir, "html"] copyCssFile f = copyFile f (combine odir (takeFileName f)) copyLibFile f = copyFile (joinPath [libhtmldir, f]) (joinPath [odir, f]) mapM_ copyCssFile (cssFiles themes) copyLibFile haddockJsFile copyCssFile (joinPath [libhtmldir, quickJumpCssFile]) when withQuickjump (copyLibFile jsQuickJumpFile) return () headHtml :: String -> Themes -> Maybe String -> Html headHtml docTitle themes mathjax_url = header << [ meta ! [httpequiv "Content-Type", content "text/html; charset=UTF-8"], thetitle << docTitle, styleSheet themes, thelink ! [ rel "stylesheet", thetype "text/css", href quickJumpCssFile] << noHtml, script ! [src haddockJsFile, emptyAttr "async", thetype "text/javascript"] << noHtml, script ! [src mjUrl, thetype "text/javascript"] << noHtml ] where mjUrl = maybe "https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS-MML_HTMLorMML" id mathjax_url srcButton :: SourceURLs -> Maybe Interface -> Maybe Html srcButton (Just src_base_url, _, _, _) Nothing = Just (anchor ! [href src_base_url] << "Source") srcButton (_, Just src_module_url, _, _) (Just iface) = let url = spliceURL (Just $ ifaceOrigFilename iface) (Just $ ifaceMod iface) Nothing Nothing src_module_url in Just (anchor ! [href url] << "Source") srcButton _ _ = Nothing wikiButton :: WikiURLs -> Maybe Module -> Maybe Html wikiButton (Just wiki_base_url, _, _) Nothing = Just (anchor ! [href wiki_base_url] << "User Comments") wikiButton (_, Just wiki_module_url, _) (Just mdl) = let url = spliceURL Nothing (Just mdl) Nothing Nothing wiki_module_url in Just (anchor ! [href url] << "User Comments") wikiButton _ _ = Nothing contentsButton :: Maybe String -> Maybe Html contentsButton maybe_contents_url = Just (anchor ! [href url] << "Contents") where url = fromMaybe contentsHtmlFile maybe_contents_url indexButton :: Maybe String -> Maybe Html indexButton maybe_index_url = Just (anchor ! [href url] << "Index") where url = fromMaybe indexHtmlFile maybe_index_url bodyHtml :: String -> Maybe Interface -> SourceURLs -> WikiURLs -> Maybe String -> Maybe String -> Html -> Html bodyHtml doctitle iface maybe_source_url maybe_wiki_url maybe_contents_url maybe_index_url pageContent = body << [ divPackageHeader << [ unordList (catMaybes [ srcButton maybe_source_url iface, wikiButton maybe_wiki_url (ifaceMod <$> iface), contentsButton maybe_contents_url, indexButton maybe_index_url]) ! [theclass "links", identifier "page-menu"], nonEmptySectionName << doctitle ], divContent << pageContent, divFooter << paragraph << ( "Produced by " +++ (anchor ! [href projectUrl] << toHtml projectName) +++ (" version " ++ projectVersion) ) ] moduleInfo :: Interface -> Html moduleInfo iface = let info = ifaceInfo iface doOneEntry :: (String, HaddockModInfo GHC.Name -> Maybe String) -> Maybe HtmlTable doOneEntry (fieldName, field) = field info >>= \a -> return (th << fieldName <-> td << a) entries :: [HtmlTable] entries = maybeToList copyrightsTable ++ mapMaybe doOneEntry [ ("License",hmi_license), ("Maintainer",hmi_maintainer), ("Stability",hmi_stability), ("Portability",hmi_portability), ("Safe Haskell",hmi_safety), ("Language", lg) ] ++ extsForm where lg inf = case hmi_language inf of Nothing -> Nothing Just Haskell98 -> Just "Haskell98" Just Haskell2010 -> Just "Haskell2010" multilineRow :: String -> [String] -> HtmlTable multilineRow title xs = (th ! [valign "top"]) << title <-> td << (toLines xs) where toLines = mconcat . intersperse br . map toHtml copyrightsTable :: Maybe HtmlTable copyrightsTable = fmap (multilineRow "Copyright" . split) (hmi_copyright info) where split = map (trim . filter (/= ',')) . lines extsForm | OptShowExtensions `elem` ifaceOptions iface = let fs = map (dropOpt . show) (hmi_extensions info) in case map stringToHtml fs of [] -> [] [x] -> extField x -- don't use a list for a single extension xs -> extField $ unordList xs ! [theclass "extension-list"] | otherwise = [] where extField x = return $ th << "Extensions" <-> td << x dropOpt x = if "Opt_" `isPrefixOf` x then drop 4 x else x in case entries of [] -> noHtml _ -> table ! [theclass "info"] << aboves entries -------------------------------------------------------------------------------- -- * Generate the module contents -------------------------------------------------------------------------------- ppHtmlContents :: DynFlags -> FilePath -> String -> Maybe String -> Themes -> Maybe String -> Maybe String -> SourceURLs -> WikiURLs -> [InstalledInterface] -> Bool -> Maybe (MDoc GHC.RdrName) -> Bool -> Qualification -- ^ How to qualify names -> IO () ppHtmlContents dflags odir doctitle _maybe_package themes mathjax_url maybe_index_url maybe_source_url maybe_wiki_url ifaces showPkgs prologue debug qual = do let tree = mkModuleTree dflags showPkgs [(instMod iface, toInstalledDescription iface) | iface <- ifaces , not (instIsSig iface)] sig_tree = mkModuleTree dflags showPkgs [(instMod iface, toInstalledDescription iface) | iface <- ifaces , instIsSig iface] html = headHtml doctitle themes mathjax_url +++ bodyHtml doctitle Nothing maybe_source_url maybe_wiki_url Nothing maybe_index_url << [ ppPrologue qual doctitle prologue, ppSignatureTree qual sig_tree, ppModuleTree qual tree ] createDirectoryIfMissing True odir writeFile (joinPath [odir, contentsHtmlFile]) (renderToString debug html) ppPrologue :: Qualification -> String -> Maybe (MDoc GHC.RdrName) -> Html ppPrologue _ _ Nothing = noHtml ppPrologue qual title (Just doc) = divDescription << (h1 << title +++ docElement thediv (rdrDocToHtml qual doc)) ppSignatureTree :: Qualification -> [ModuleTree] -> Html ppSignatureTree qual ts = divModuleList << (sectionName << "Signatures" +++ mkNodeList qual [] "n" ts) ppModuleTree :: Qualification -> [ModuleTree] -> Html ppModuleTree _ [] = mempty ppModuleTree qual ts = divModuleList << (sectionName << "Modules" +++ mkNodeList qual [] "n" ts) mkNodeList :: Qualification -> [String] -> String -> [ModuleTree] -> Html mkNodeList qual ss p ts = case ts of [] -> noHtml _ -> unordList (zipWith (mkNode qual ss) ps ts) where ps = [ p ++ '.' : show i | i <- [(1::Int)..]] mkNode :: Qualification -> [String] -> String -> ModuleTree -> Html mkNode qual ss p (Node s leaf _pkg srcPkg short ts) = htmlModule <+> shortDescr +++ htmlPkg +++ subtree where modAttrs = case (ts, leaf) of (_:_, Nothing) -> collapseControl p "module" (_, _ ) -> [theclass "module"] cBtn = case (ts, leaf) of (_:_, Just _) -> thespan ! collapseControl p "" << spaceHtml (_, _ ) -> noHtml -- We only need an explicit collapser button when the module name -- is also a leaf, and so is a link to a module page. Indeed, the -- spaceHtml is a minor hack and does upset the layout a fraction. htmlModule = thespan ! modAttrs << (cBtn +++ case leaf of Just m -> ppModule m Nothing -> toHtml s ) shortDescr = maybe noHtml (origDocToHtml qual) short htmlPkg = maybe noHtml (thespan ! [theclass "package"] <<) srcPkg subtree = if null ts then noHtml else collapseDetails p DetailsOpen ( thesummary ! [ theclass "hide-when-js-enabled" ] << "Submodules" +++ mkNodeList qual (s:ss) p ts ) -------------------------------------------------------------------------------- -- * Generate the index -------------------------------------------------------------------------------- ppJsonIndex :: FilePath -> SourceURLs -- ^ The source URL (--source) -> WikiURLs -- ^ The wiki URL (--wiki) -> Bool -> QualOption -> [Interface] -> IO () ppJsonIndex odir maybe_source_url maybe_wiki_url unicode qual_opt ifaces = do createDirectoryIfMissing True odir IO.withBinaryFile (joinPath [odir, indexJsonFile]) IO.WriteMode $ \h -> do Builder.hPutBuilder h (encodeToBuilder modules) where modules :: Value modules = Array (concatMap goInterface ifaces) goInterface :: Interface -> [Value] goInterface iface = concatMap (goExport mdl qual) (ifaceRnExportItems iface) where aliases = ifaceModuleAliases iface qual = makeModuleQual qual_opt aliases mdl mdl = ifaceMod iface goExport :: Module -> Qualification -> ExportItem DocNameI -> [Value] goExport mdl qual item | Just item_html <- processExport True links_info unicode qual item = [ Object [ "display_html" .= String (showHtmlFragment item_html) , "name" .= String (intercalate " " (map nameString names)) , "module" .= String (moduleString mdl) , "link" .= String (fromMaybe "" (listToMaybe (map (nameLink mdl) names))) ] ] | otherwise = [] where names = exportName item ++ exportSubs item exportSubs :: ExportItem name -> [IdP name] exportSubs ExportDecl { expItemSubDocs } = map fst expItemSubDocs exportSubs _ = [] exportName :: ExportItem name -> [IdP name] exportName ExportDecl { expItemDecl } = getMainDeclBinder (unLoc expItemDecl) exportName ExportNoDecl { expItemName } = [expItemName] exportName _ = [] nameString :: NamedThing name => name -> String nameString = occNameString . nameOccName . getName nameLink :: NamedThing name => Module -> name -> String nameLink mdl = moduleNameUrl' (moduleName mdl) . nameOccName . getName links_info = (maybe_source_url, maybe_wiki_url) ppHtmlIndex :: FilePath -> String -> Maybe String -> Themes -> Maybe String -> Maybe String -> SourceURLs -> WikiURLs -> [InstalledInterface] -> Bool -> IO () ppHtmlIndex odir doctitle _maybe_package themes maybe_mathjax_url maybe_contents_url maybe_source_url maybe_wiki_url ifaces debug = do let html = indexPage split_indices Nothing (if split_indices then [] else index) createDirectoryIfMissing True odir when split_indices $ do mapM_ (do_sub_index index) initialChars -- Let's add a single large index as well for those who don't know exactly what they're looking for: let mergedhtml = indexPage False Nothing index writeFile (joinPath [odir, subIndexHtmlFile merged_name]) (renderToString debug mergedhtml) writeFile (joinPath [odir, indexHtmlFile]) (renderToString debug html) where indexPage showLetters ch items = headHtml (doctitle ++ " (" ++ indexName ch ++ ")") themes maybe_mathjax_url +++ bodyHtml doctitle Nothing maybe_source_url maybe_wiki_url maybe_contents_url Nothing << [ if showLetters then indexInitialLetterLinks else noHtml, if null items then noHtml else divIndex << [sectionName << indexName ch, buildIndex items] ] indexName ch = "Index" ++ maybe "" (\c -> " - " ++ [c]) ch merged_name = "All" buildIndex items = table << aboves (map indexElt items) -- an arbitrary heuristic: -- too large, and a single-page will be slow to load -- too small, and we'll have lots of letter-indexes with only one -- or two members in them, which seems inefficient or -- unnecessarily hard to use. split_indices = length index > 150 indexInitialLetterLinks = divAlphabet << unordList (map (\str -> anchor ! [href (subIndexHtmlFile str)] << str) $ [ [c] | c <- initialChars , any ((==c) . toUpper . head . fst) index ] ++ [merged_name]) -- todo: what about names/operators that start with Unicode -- characters? -- Exports beginning with '_' can be listed near the end, -- presumably they're not as important... but would be listed -- with non-split index! initialChars = [ 'A'..'Z' ] ++ ":!#$%&*+./<=>?@\\^|-~" ++ "_" do_sub_index this_ix c = unless (null index_part) $ writeFile (joinPath [odir, subIndexHtmlFile [c]]) (renderToString debug html) where html = indexPage True (Just c) index_part index_part = [(n,stuff) | (n,stuff) <- this_ix, toUpper (head n) == c] index :: [(String, Map GHC.Name [(Module,Bool)])] index = sortBy cmp (Map.toAscList full_index) where cmp (n1,_) (n2,_) = comparing (map toUpper) n1 n2 -- for each name (a plain string), we have a number of original HsNames that -- it can refer to, and for each of those we have a list of modules -- that export that entity. Each of the modules exports the entity -- in a visible or invisible way (hence the Bool). full_index :: Map String (Map GHC.Name [(Module,Bool)]) full_index = Map.fromListWith (flip (Map.unionWith (++))) (concatMap getIfaceIndex ifaces) getIfaceIndex iface = [ (getOccString name , Map.fromList [(name, [(mdl, name `Set.member` visible)])]) | name <- instExports iface ] where mdl = instMod iface visible = Set.fromList (instVisibleExports iface) indexElt :: (String, Map GHC.Name [(Module,Bool)]) -> HtmlTable indexElt (str, entities) = case Map.toAscList entities of [(nm,entries)] -> td ! [ theclass "src" ] << toHtml str <-> indexLinks nm entries many_entities -> td ! [ theclass "src" ] << toHtml str <-> td << spaceHtml aboves (zipWith (curry doAnnotatedEntity) [1..] many_entities) doAnnotatedEntity :: (Integer, (Name, [(Module, Bool)])) -> HtmlTable doAnnotatedEntity (j,(nm,entries)) = td ! [ theclass "alt" ] << toHtml (show j) <+> parens (ppAnnot (nameOccName nm)) <-> indexLinks nm entries ppAnnot n | not (isValOcc n) = toHtml "Type/Class" | isDataOcc n = toHtml "Data Constructor" | otherwise = toHtml "Function" indexLinks nm entries = td ! [ theclass "module" ] << hsep (punctuate comma [ if visible then linkId mdl (Just nm) << toHtml (moduleString mdl) else toHtml (moduleString mdl) | (mdl, visible) <- entries ]) -------------------------------------------------------------------------------- -- * Generate the HTML page for a module -------------------------------------------------------------------------------- ppHtmlModule :: FilePath -> String -> Themes -> Maybe String -> SourceURLs -> WikiURLs -> Maybe String -> Maybe String -> Bool -> QualOption -> Bool -> Interface -> IO () ppHtmlModule odir doctitle themes maybe_mathjax_url maybe_source_url maybe_wiki_url maybe_contents_url maybe_index_url unicode qual debug iface = do let mdl = ifaceMod iface aliases = ifaceModuleAliases iface mdl_str = moduleString mdl mdl_str_annot = mdl_str ++ if ifaceIsSig iface then " (signature)" else "" mdl_str_linked | ifaceIsSig iface = mdl_str +++ " (signature" +++ sup << ("[" +++ anchor ! [href signatureDocURL] << "?" +++ "]" ) +++ ")" | otherwise = toHtml mdl_str real_qual = makeModuleQual qual aliases mdl html = headHtml mdl_str_annot themes maybe_mathjax_url +++ bodyHtml doctitle (Just iface) maybe_source_url maybe_wiki_url maybe_contents_url maybe_index_url << [ divModuleHeader << (moduleInfo iface +++ (sectionName << mdl_str_linked)), ifaceToHtml maybe_source_url maybe_wiki_url iface unicode real_qual ] createDirectoryIfMissing True odir writeFile (joinPath [odir, moduleHtmlFile mdl]) (renderToString debug html) signatureDocURL :: String signatureDocURL = "https://wiki.haskell.org/Module_signature" ifaceToHtml :: SourceURLs -> WikiURLs -> Interface -> Bool -> Qualification -> Html ifaceToHtml maybe_source_url maybe_wiki_url iface unicode qual = ppModuleContents qual exports (not . null $ ifaceRnOrphanInstances iface) +++ description +++ synopsis +++ divInterface (maybe_doc_hdr +++ bdy +++ orphans) where exports = numberSectionHeadings (ifaceRnExportItems iface) -- todo: if something has only sub-docs, or fn-args-docs, should -- it be measured here and thus prevent omitting the synopsis? has_doc ExportDecl { expItemMbDoc = (Documentation mDoc mWarning, _) } = isJust mDoc || isJust mWarning has_doc (ExportNoDecl _ _) = False has_doc (ExportModule _) = False has_doc _ = True no_doc_at_all = not (any has_doc exports) description | isNoHtml doc = doc | otherwise = divDescription $ sectionName << "Description" +++ doc where doc = docSection Nothing qual (ifaceRnDoc iface) -- omit the synopsis if there are no documentation annotations at all synopsis | no_doc_at_all = noHtml | otherwise = divSynopsis $ collapseDetails "syn" DetailsClosed ( thesummary << "Synopsis" +++ shortDeclList ( mapMaybe (processExport True linksInfo unicode qual) exports ) ! collapseToggle "syn" "" ) -- if the documentation doesn't begin with a section header, then -- add one ("Documentation"). maybe_doc_hdr = case exports of [] -> noHtml ExportGroup {} : _ -> noHtml _ -> h1 << "Documentation" bdy = foldr (+++) noHtml $ mapMaybe (processExport False linksInfo unicode qual) exports orphans = ppOrphanInstances linksInfo (ifaceRnOrphanInstances iface) False unicode qual linksInfo = (maybe_source_url, maybe_wiki_url) ppModuleContents :: Qualification -> [ExportItem DocNameI] -> Bool -- ^ Orphans sections -> Html ppModuleContents qual exports orphan | null sections && not orphan = noHtml | otherwise = contentsDiv where contentsDiv = divTableOfContents << ( sectionName << "Contents" +++ unordList (sections ++ orphanSection)) (sections, _leftovers{-should be []-}) = process 0 exports orphanSection | orphan = [ linkedAnchor "section.orphans" << "Orphan instances" ] | otherwise = [] process :: Int -> [ExportItem DocNameI] -> ([Html],[ExportItem DocNameI]) process _ [] = ([], []) process n items@(ExportGroup lev id0 doc : rest) | lev <= n = ( [], items ) | otherwise = ( html:secs, rest2 ) where html = linkedAnchor (groupId id0) << docToHtmlNoAnchors (Just id0) qual (mkMeta doc) +++ mk_subsections ssecs (ssecs, rest1) = process lev rest (secs, rest2) = process n rest1 process n (_ : rest) = process n rest mk_subsections [] = noHtml mk_subsections ss = unordList ss -- we need to assign a unique id to each section heading so we can hyperlink -- them from the contents: numberSectionHeadings :: [ExportItem DocNameI] -> [ExportItem DocNameI] numberSectionHeadings = go 1 where go :: Int -> [ExportItem DocNameI] -> [ExportItem DocNameI] go _ [] = [] go n (ExportGroup lev _ doc : es) = ExportGroup lev (show n) doc : go (n+1) es go n (other:es) = other : go n es processExport :: Bool -> LinksInfo -> Bool -> Qualification -> ExportItem DocNameI -> Maybe Html processExport _ _ _ _ ExportDecl { expItemDecl = L _ (InstD _) } = Nothing -- Hide empty instances processExport summary _ _ qual (ExportGroup lev id0 doc) = nothingIf summary $ groupHeading lev id0 << docToHtml (Just id0) qual (mkMeta doc) processExport summary links unicode qual (ExportDecl decl pats doc subdocs insts fixities splice) = processDecl summary $ ppDecl summary links decl pats doc insts fixities subdocs splice unicode qual processExport summary _ _ qual (ExportNoDecl y []) = processDeclOneLiner summary $ ppDocName qual Prefix True y processExport summary _ _ qual (ExportNoDecl y subs) = processDeclOneLiner summary $ ppDocName qual Prefix True y +++ parenList (map (ppDocName qual Prefix True) subs) processExport summary _ _ qual (ExportDoc doc) = nothingIf summary $ docSection_ Nothing qual doc processExport summary _ _ _ (ExportModule mdl) = processDeclOneLiner summary $ toHtml "module" <+> ppModule mdl nothingIf :: Bool -> a -> Maybe a nothingIf True _ = Nothing nothingIf False a = Just a processDecl :: Bool -> Html -> Maybe Html processDecl True = Just processDecl False = Just . divTopDecl trim :: String -> String trim = f . f where f = reverse . dropWhile isSpace processDeclOneLiner :: Bool -> Html -> Maybe Html processDeclOneLiner True = Just processDeclOneLiner False = Just . divTopDecl . declElem groupHeading :: Int -> String -> Html -> Html groupHeading lev id0 = linkedAnchor grpId . groupTag lev ! [identifier grpId] where grpId = groupId id0 groupTag :: Int -> Html -> Html groupTag lev | lev == 1 = h1 | lev == 2 = h2 | lev == 3 = h3 | otherwise = h4