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module Text.Hakyll.Page
( Page,
PageValue,
addContext,
getURL,
getBody,
readPage,
pageFromList,
concatPages,
concatPagesWith
) where
import qualified Data.Map as M
import qualified Data.List as L
import qualified Data.ByteString.Lazy.Char8 as B
import Data.Maybe
import System.FilePath
import System.IO
import Text.Hakyll.Util
import Text.Pandoc
-- | A Page is basically key-value mapping. Certain keys have special
-- meanings, like for example url, body and title.
type Page = M.Map String PageValue
-- | We use a ByteString for obvious reasons.
type PageValue = B.ByteString
-- | Add a key-value mapping to the Page.
addContext :: String -> String -> Page -> Page
addContext key value = M.insert key (B.pack value)
-- | Get the URL for a certain page. This should always be defined. If
-- not, it will return trash.html.
getURL :: Page -> String
getURL context = let result = M.lookup "url" context
in case result of (Just url) -> B.unpack url
Nothing -> error "URL is not defined."
-- | Get the body for a certain page. When not defined, the body will be
-- empty.
getBody :: Page -> PageValue
getBody context = fromMaybe B.empty $ M.lookup "body" context
writerOptions :: WriterOptions
writerOptions = defaultWriterOptions
renderFunction :: String -> (String -> String)
renderFunction ".html" = id
renderFunction ext = writeHtmlString writerOptions .
renderFunction' ext defaultParserState
where renderFunction' ".markdown" = readMarkdown
renderFunction' ".md" = readMarkdown
renderFunction' ".tex" = readLaTeX
renderFunction' _ = readMarkdown
readMetaData :: Handle -> IO [(String, String)]
readMetaData handle = do
line <- hGetLine handle
if isDelimiter line then return []
else do others <- readMetaData handle
return $ (trimPair . break (== ':')) line : others
where trimPair (key, value) = (trim key, trim $ tail value)
isDelimiter :: String -> Bool
isDelimiter = L.isPrefixOf "---"
-- | Read a page from a file. Metadata is supported, and if the filename
-- has a .markdown extension, it will be rendered using pandoc. Note that
-- pages are not templates, so they should not contain $identifiers.
readPage :: FilePath -> IO Page
readPage path = do
handle <- openFile path ReadMode
line <- hGetLine handle
(context, body) <- if isDelimiter line
then do md <- readMetaData handle
c <- hGetContents handle
return (md, c)
else hGetContents handle >>= \b -> return ([], line ++ b)
let rendered = B.pack $ (renderFunction $ takeExtension path) body
url = addExtension (dropExtension path) ".html"
seq rendered $ hClose handle
return $ M.insert "body" rendered $ addContext "url" url $ pageFromList context
-- | Create a key-value mapping page from an association list.
pageFromList :: [(String, String)] -> Page
pageFromList = M.fromList . map packPair
where packPair (k, v) = let pv = B.pack v
in seq pv (k, pv)
-- | Concat the bodies of pages, and return the result.
concatPages :: [Page] -> PageValue
concatPages = concatPagesWith "body"
-- | Concat certain values of pages, and return the result.
concatPagesWith :: String -- ^ Key of which to concat the values.
-> [Page] -- ^ Pages to get the values from.
-> PageValue -- ^ The concatenation.
concatPagesWith key = B.concat . map (fromMaybe B.empty . M.lookup key)
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