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module Text.Hakyll.Page
( Page,
fromContext,
getBody,
readPage,
writePage
) 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 Control.Monad
import System.FilePath
import System.IO
import Text.Hakyll.File
import Text.Hakyll.Util
import Text.Hakyll.Renderable
import Text.Pandoc
-- | A Page is basically key-value mapping. Certain keys have special
-- meanings, like for example url, body and title.
data Page = Page (M.Map B.ByteString B.ByteString)
-- | Create a Page from a key-value mapping.
fromContext :: (M.Map B.ByteString B.ByteString) -> Page
fromContext = Page
-- | Auxiliary function to pack a pair.
packPair :: (String, String) -> (B.ByteString, B.ByteString)
packPair (a, b) = (B.pack a, B.pack b)
-- | Get the URL for a certain page. This should always be defined. If
-- not, it will return trash.html.
getPageURL :: Page -> String
getPageURL (Page page) =
let result = M.lookup (B.pack "url") page
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 -> B.ByteString
getBody (Page page) = fromMaybe B.empty $ M.lookup (B.pack "body") page
-- | The default writer options for pandoc rendering.
writerOptions :: WriterOptions
writerOptions = defaultWriterOptions
-- | Get a render function for a given extension.
renderFunction :: String -> (String -> String)
renderFunction ".html" = id
renderFunction ext = writeHtmlString writerOptions .
readFunction ext defaultParserState
where readFunction ".markdown" = readMarkdown
readFunction ".md" = readMarkdown
readFunction ".tex" = readLaTeX
readFunction _ = readMarkdown
-- | Read metadata header from a file handle.
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)
-- | Check if the given string is a metadata delimiter.
isDelimiter :: String -> Bool
isDelimiter = L.isPrefixOf "---"
-- | Used for caching of files.
cachePage :: Page -> IO ()
cachePage page@(Page mapping) = do
let destination = toCache $ getURL page
makeDirectories destination
handle <- openFile destination WriteMode
hPutStrLn handle "---"
mapM_ (writePair handle) $ M.toList $ M.delete (B.pack "body") mapping
hPutStrLn handle "---"
B.hPut handle $ getBody page
hClose handle
where writePair h (k, v) = B.hPut h k >>
B.hPut h (B.pack ": ") >>
B.hPut h v >>
hPutStrLn h ""
-- | 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 pagePath = do
-- Check cache.
getFromCache <- isCacheValid cacheFile [pagePath]
let path = if getFromCache then cacheFile else pagePath
-- Read file.
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)
-- Render file
let rendered = B.pack $ (renderFunction $ takeExtension path) body
seq rendered $ hClose handle
let page = fromContext $ M.fromList $
[(B.pack "body", rendered), packPair ("url", url)] ++ map packPair context
-- Cache if needed
if getFromCache then return () else cachePage page
return page
where url = toURL pagePath
cacheFile = toCache url
-- | Write a page to the site destination.
writePage :: Page -> IO ()
writePage page = do
let destination = toDestination $ getURL page
makeDirectories destination
B.writeFile destination (getBody page)
-- Make pages renderable.
instance Renderable Page where
getDependencies = (:[]) . flip addExtension ".html" . dropExtension . getPageURL
getURL = getPageURL
toContext (Page mapping) = return mapping
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