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-- | Internal module do some low-level rendering.
module Text.Hakyll.Render.Internal
( substitute
, regularSubstitute
, finalSubstitute
, pureRenderWith
, pureRenderAndConcatWith
, pureRenderChainWith
, writePage
) where
import qualified Data.Map as M
import Text.Hakyll.Context (Context, ContextManipulation)
import Control.Monad.Reader (liftIO)
import Data.List (isPrefixOf, foldl')
import Data.Char (isAlpha)
import Data.Maybe (fromMaybe)
import Control.Parallel.Strategies (rdeepseq, ($|))
import Text.Hakyll.Renderable
import Text.Hakyll.Page
import Text.Hakyll.File
import Text.Hakyll.Hakyll
-- | Substitutes @$identifiers@ in the given string by values from the given
-- "Context". When a key is not found, it is left as it is. You can here
-- specify the characters used to replace escaped dollars (@$$@).
substitute :: String -> String -> Context -> String
substitute _ [] _ = []
substitute escaper string context
| "$$" `isPrefixOf` string = escaper ++ substitute' (tail tail')
| "$" `isPrefixOf` string = substituteKey
| otherwise = (head string) : (substitute' tail')
where
tail' = tail string
(key, rest) = break (not . isAlpha) tail'
replacement = fromMaybe ('$' : key) $ M.lookup key context
substituteKey = replacement ++ substitute' rest
substitute' str = substitute escaper str context
-- | "substitute" for use during a chain.
regularSubstitute :: String -> Context -> String
regularSubstitute = substitute "$$"
-- | "substitute" for the end of a chain (just before writing).
finalSubstitute :: String -> Context -> String
finalSubstitute = substitute "$"
-- | A pure render function.
pureRenderWith :: ContextManipulation -- ^ Manipulation to apply on the context.
-> String -- ^ Template to use for rendering.
-> Context -- ^ Renderable object to render with given template.
-> Context -- ^ The body of the result will contain the render.
pureRenderWith manipulation template context =
-- Ignore $root when substituting here. We will only replace that in the
-- final render (just before writing).
let contextIgnoringRoot = M.insert "root" "$root" (manipulation context)
body = regularSubstitute template contextIgnoringRoot
-- Force the body to be rendered.
in ($|) id rdeepseq (M.insert "body" body context)
-- | A pure renderAndConcat function.
pureRenderAndConcatWith :: ContextManipulation
-> [String] -- ^ Templates to use.
-> [Context] -- ^ Different renderables.
-> String
pureRenderAndConcatWith manipulation templates contexts =
foldl' renderAndConcat [] contexts
where
renderAndConcat chunk context =
let rendered = pureRenderChainWith manipulation templates context
in chunk ++ fromMaybe "" (M.lookup "body" rendered)
-- | A pure renderChain function.
pureRenderChainWith :: ContextManipulation
-> [String]
-> Context
-> Context
pureRenderChainWith manipulation templates context =
let initial = manipulation context
in foldl' (flip $ pureRenderWith id) initial templates
-- | Write a page to the site destination. Final action after render
-- chains and such.
writePage :: Page -> Hakyll ()
writePage page = do
additionalContext' <- askHakyll additionalContext
let destination = toDestination url
context = additionalContext' `M.union` (M.singleton "root" $ toRoot url)
makeDirectories destination
-- Substitute $root here, just before writing.
liftIO $ writeFile destination $ finalSubstitute (getBody page) context
where
url = getURL page
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