89 lines
3.1 KiB
Haskell
89 lines
3.1 KiB
Haskell
-- from https://github.com/blaenk/blaenk.github.io
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE CPP #-}
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module TableOfContents (
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tableOfContents,
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ignoreTOC,
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collectHeaders,
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TOCAlignment(TOCOff,TOCLeft,TOCRight)
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) where
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import Text.Pandoc
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import Text.Pandoc.Walk (walk, query)
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import Text.Pandoc.Class (runPure)
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import Data.List (groupBy)
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import Data.Text (unpack)
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import Data.Tree (Forest, Tree(Node))
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#if !(MIN_VERSION_base(4,11,0))
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import Data.Monoid ((<>), mconcat)
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#endif
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import Data.Function (on)
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import Data.Maybe (fromMaybe)
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import Data.Text (unpack)
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import Text.Blaze.Html (preEscapedToHtml, (!))
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import Text.Blaze.Html.Renderer.String (renderHtml)
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import qualified Text.Blaze.Html5 as H
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import qualified Text.Blaze.Html5.Attributes as A
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data TOCAlignment = TOCOff | TOCLeft | TOCRight
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headerLevel :: Block -> Int
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headerLevel (Header level _ _) = level
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headerLevel _ = error "not a header"
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ignoreTOC :: Block -> Block
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ignoreTOC (Header level (ident, classes, params) inlines) =
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Header level (ident, "notoc" : classes, params) inlines
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ignoreTOC x = x
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collectHeaders :: Block -> [Block]
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collectHeaders header@(Header _ (_, classes, _) _) =
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if "notoc" `elem` classes
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then []
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else [header]
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collectHeaders _ = []
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groupByHierarchy :: [Block] -> Forest Block
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groupByHierarchy = map (\(x:xs) -> Node x (groupByHierarchy xs)) . groupBy ((<) `on` headerLevel)
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markupHeader :: Tree Block -> H.Html
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markupHeader n@(Node (Header _ (ident, _, keyvals) inlines) headers)
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| headers == [] = H.li $ link
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| otherwise = H.li $ link <> (H.ol $ markupHeaders headers)
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where render x = case runPure $ writeHtml5String def (Pandoc nullMeta [(Plain x)]) of
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Left _ -> error $ "Error building header.\n"
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++ " saw: " ++ show n
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Right txt -> txt
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section = fromMaybe (unpack $ render inlines) (lookup "toc" keyvals)
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link = H.a ! A.href (H.toValue $ "#" ++ ident) $ preEscapedToHtml section
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markupHeader n = error $ "'markupHeader' should only be passed a 'Node $ Header'\n"
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++ " saw: " ++ show n
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markupHeaders :: Forest Block -> H.Html
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markupHeaders = mconcat . map markupHeader
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createTable :: TOCAlignment -> Forest Block -> Block
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createTable _ [] = Null
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createTable alignment headers
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= render $ (H.nav ! (A.id "toc" <> alignmentAttr)) $ do
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H.p "Contents"
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H.ol $ markupHeaders headers
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where render = (RawBlock "html") . renderHtml
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alignmentAttr = case alignment of
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TOCRight -> A.class_ "right-toc"
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_ -> mempty
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generateTOC :: [Block] -> TOCAlignment -> Block -> Block
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generateTOC headers alignment x@(BulletList (( (( Plain ((Str "toc"):_)):_)):_))
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= createTable alignment . groupByHierarchy $ headers
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generateTOC _ _ x = x
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tableOfContents :: TOCAlignment -> Pandoc -> Pandoc
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tableOfContents TOCOff ast = walk ignoreTOC ast
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tableOfContents alignment ast = let headers = query collectHeaders ast
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in walk (generateTOC headers alignment) ast
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