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module Text.Hakyll.Internal.Template
( Template (..)
, fromString
, readTemplate
, substitute
, regularSubstitute
, finalSubstitute
) where
import Control.Arrow ((>>>))
import Control.Applicative ((<$>))
import Data.List (isPrefixOf)
import Data.Char (isAlphaNum)
import Data.Maybe (fromMaybe)
import System.FilePath ((</>))
import qualified Data.Map as M
import Text.Hakyll.Context (Context (..))
import Text.Hakyll.HakyllMonad (Hakyll)
import Text.Hakyll.HakyllAction
import Text.Hakyll.Pandoc
import Text.Hakyll.Internal.Cache
import Text.Hakyll.Internal.Page
import Text.Hakyll.Internal.Template.Template
import Text.Hakyll.Internal.Template.Hamlet
-- | Construct a @Template@ from a string.
--
fromString :: String -> Template
fromString = Template . fromString'
where
fromString' [] = []
fromString' string
| "$$" `isPrefixOf` string =
EscapeCharacter : (fromString' $ drop 2 string)
| "$" `isPrefixOf` string =
let (key, rest) = span isAlphaNum $ drop 1 string
in Identifier key : fromString' rest
| otherwise =
let (chunk, rest) = break (== '$') string
in Chunk chunk : fromString' rest
-- | Read a @Template@ from a file. This function might fetch the @Template@
-- from the cache, if available.
readTemplate :: FilePath -> Hakyll Template
readTemplate path = do
isCacheMoreRecent' <- isCacheMoreRecent fileName [path]
if isCacheMoreRecent'
then getFromCache fileName
else do
template <- if isHamletRTFile path
then readHamletTemplate
else readDefaultTemplate
storeInCache template fileName
return template
where
fileName = "templates" </> path
readDefaultTemplate = do
page <- unContext <$>
runHakyllAction (readPageAction path >>> renderAction)
let body = fromMaybe (error $ "No body in template " ++ fileName)
(M.lookup "body" page)
return $ fromString body
readHamletTemplate = fromHamletRT <$> readHamletRT path
-- | Substitutes @$identifiers@ in the given @Template@ by values from the given
-- "Context". When a key is not found, it is left as it is. You can specify
-- the characters used to replace escaped dollars (@$$@) here.
substitute :: String -> Template -> Context -> String
substitute escaper template context = substitute' =<< unTemplate template
where
substitute' (Chunk chunk) = chunk
substitute' (Identifier key) =
fromMaybe ('$' : key) $ M.lookup key $ unContext context
substitute' (EscapeCharacter) = escaper
-- | @substitute@ for use during a chain. This will leave escaped characters as
-- they are.
regularSubstitute :: Template -> Context -> String
regularSubstitute = substitute "$$"
-- | @substitute@ for the end of a chain (just before writing). This renders
-- escaped characters.
finalSubstitute :: Template -> Context -> String
finalSubstitute = substitute "$"
|