-------------------------------------------------------------------------------- {-# LANGUAGE CPP #-} {-# LANGUAGE ExistentialQuantification #-} module Hakyll.Web.Template.Context ( ContextField (..) , Context (..) , field , boolField , constField , listField , listFieldWith , functionField , mapContext , defaultContext , bodyField , metadataField , urlField , pathField , titleField , dateField , dateFieldWith , getItemUTC , getItemModificationTime , modificationTimeField , modificationTimeFieldWith , teaserField , teaserFieldWithSeparator , missingField ) where -------------------------------------------------------------------------------- import Control.Applicative (Alternative (..)) import Control.Monad (msum) import Data.List (intercalate) import Data.Time.Clock (UTCTime (..)) import Data.Time.Format (formatTime) import qualified Data.Time.Format as TF import Data.Time.Locale.Compat (TimeLocale, defaultTimeLocale) import Hakyll.Core.Compiler import Hakyll.Core.Compiler.Internal import Hakyll.Core.Identifier import Hakyll.Core.Item import Hakyll.Core.Metadata import Hakyll.Core.Provider import Hakyll.Core.Util.String (needlePrefix, splitAll) import Hakyll.Web.Html import System.FilePath (splitDirectories, takeBaseName) -------------------------------------------------------------------------------- -- | Mostly for internal usage data ContextField = StringField String | forall a. ListField (Context a) [Item a] -------------------------------------------------------------------------------- -- | The 'Context' monoid. Please note that the order in which you -- compose the items is important. For example in -- -- > field "A" f1 <> field "A" f2 -- -- the first context will overwrite the second. This is especially -- important when something is being composed with -- 'metadataField' (or 'defaultContext'). If you want your context to be -- overwritten by the metadata fields, compose it from the right: -- -- @ -- 'metadataField' \<\> field \"date\" fDate -- @ -- newtype Context a = Context { unContext :: String -> [String] -> Item a -> Compiler ContextField } -------------------------------------------------------------------------------- instance Monoid (Context a) where mempty = missingField mappend (Context f) (Context g) = Context $ \k a i -> f k a i <|> g k a i -------------------------------------------------------------------------------- field' :: String -> (Item a -> Compiler ContextField) -> Context a field' key value = Context $ \k _ i -> if k == key then value i else empty -------------------------------------------------------------------------------- -- | Constructs a new field in the 'Context.' field :: String -- ^ Key -> (Item a -> Compiler String) -- ^ Function that constructs a value based -- on the item -> Context a field key value = field' key (fmap StringField . value) -------------------------------------------------------------------------------- -- | Creates a 'field' to use with the @$if()$@ template macro. boolField :: String -> (Item a -> Bool) -> Context a boolField name f = field name (\i -> if f i then pure (error $ unwords ["no string value for bool field:",name]) else empty) -------------------------------------------------------------------------------- -- | Creates a 'field' that does not depend on the 'Item' constField :: String -> String -> Context a constField key = field key . const . return -------------------------------------------------------------------------------- listField :: String -> Context a -> Compiler [Item a] -> Context b listField key c xs = listFieldWith key c (const xs) -------------------------------------------------------------------------------- listFieldWith :: String -> Context a -> (Item b -> Compiler [Item a]) -> Context b listFieldWith key c f = field' key $ fmap (ListField c) . f -------------------------------------------------------------------------------- functionField :: String -> ([String] -> Item a -> Compiler String) -> Context a functionField name value = Context $ \k args i -> if k == name then StringField <$> value args i else empty -------------------------------------------------------------------------------- mapContext :: (String -> String) -> Context a -> Context a mapContext f (Context c) = Context $ \k a i -> do fld <- c k a i case fld of StringField str -> return $ StringField (f str) ListField _ _ -> fail $ "Hakyll.Web.Template.Context.mapContext: " ++ "can't map over a ListField!" -------------------------------------------------------------------------------- -- | A context that contains (in that order) -- -- 1. A @$body$@ field -- -- 2. Metadata fields -- -- 3. A @$url$@ 'urlField' -- -- 4. A @$path$@ 'pathField' -- -- 5. A @$title$@ 'titleField' defaultContext :: Context String defaultContext = bodyField "body" `mappend` metadataField `mappend` urlField "url" `mappend` pathField "path" `mappend` titleField "title" `mappend` missingField -------------------------------------------------------------------------------- teaserSeparator :: String teaserSeparator = "" -------------------------------------------------------------------------------- -- | Constructs a 'field' that contains the body of the item. bodyField :: String -> Context String bodyField key = field key $ return . itemBody -------------------------------------------------------------------------------- -- | Map any field to its metadata value, if present metadataField :: Context a metadataField = Context $ \k _ i -> do value <- getMetadataField (itemIdentifier i) k maybe empty (return . StringField) value -------------------------------------------------------------------------------- -- | Absolute url to the resulting item urlField :: String -> Context a urlField key = field key $ fmap (maybe empty toUrl) . getRoute . itemIdentifier -------------------------------------------------------------------------------- -- | Filepath of the underlying file of the item pathField :: String -> Context a pathField key = field key $ return . toFilePath . itemIdentifier -------------------------------------------------------------------------------- -- | This title 'field' takes the basename of the underlying file by default titleField :: String -> Context a titleField = mapContext takeBaseName . pathField -------------------------------------------------------------------------------- -- | When the metadata has a field called @published@ in one of the -- following formats then this function can render the date. -- -- * @Mon, 06 Sep 2010 00:01:00 +0000@ -- -- * @Mon, 06 Sep 2010 00:01:00 UTC@ -- -- * @Mon, 06 Sep 2010 00:01:00@ -- -- * @2010-09-06T00:01:00+0000@ -- -- * @2010-09-06T00:01:00Z@ -- -- * @2010-09-06T00:01:00@ -- -- * @2010-09-06 00:01:00+0000@ -- -- * @2010-09-06 00:01:00@ -- -- * @September 06, 2010 00:01 AM@ -- -- Following date-only formats are supported too (@00:00:00@ for time is -- assumed) -- -- * @2010-09-06@ -- -- * @September 06, 2010@ -- -- Alternatively, when the metadata has a field called @path@ in a -- @folder/yyyy-mm-dd-title.extension@ format (the convention for pages) -- and no @published@ metadata field set, this function can render -- the date. This pattern matches the file name or directory names -- that begins with @yyyy-mm-dd@ . For example: -- @folder//yyyy-mm-dd-title//dist//main.extension@ . -- In case of multiple matches, the rightmost one is used. dateField :: String -- ^ Key in which the rendered date should be placed -> String -- ^ Format to use on the date -> Context a -- ^ Resulting context dateField = dateFieldWith defaultTimeLocale -------------------------------------------------------------------------------- -- | This is an extended version of 'dateField' that allows you to -- specify a time locale that is used for outputting the date. For more -- details, see 'dateField'. dateFieldWith :: TimeLocale -- ^ Output time locale -> String -- ^ Destination key -> String -- ^ Format to use on the date -> Context a -- ^ Resulting context dateFieldWith locale key format = field key $ \i -> do time <- getItemUTC locale $ itemIdentifier i return $ formatTime locale format time -------------------------------------------------------------------------------- -- | Parser to try to extract and parse the time from the @published@ -- field or from the filename. See 'dateField' for more information. -- Exported for user convenience. getItemUTC :: MonadMetadata m => TimeLocale -- ^ Output time locale -> Identifier -- ^ Input page -> m UTCTime -- ^ Parsed UTCTime getItemUTC locale id' = do metadata <- getMetadata id' let tryField k fmt = lookupString k metadata >>= parseTime' fmt paths = splitDirectories $ toFilePath id' maybe empty' return $ msum $ [tryField "published" fmt | fmt <- formats] ++ [tryField "date" fmt | fmt <- formats] ++ [parseTime' "%Y-%m-%d" $ intercalate "-" $ take 3 $ splitAll "-" fnCand | fnCand <- reverse paths] where empty' = fail $ "Hakyll.Web.Template.Context.getItemUTC: " ++ "could not parse time for " ++ show id' parseTime' = parseTimeM True locale formats = [ "%a, %d %b %Y %H:%M:%S %Z" , "%Y-%m-%dT%H:%M:%S%Z" , "%Y-%m-%d %H:%M:%S%Z" , "%Y-%m-%d" , "%B %e, %Y %l:%M %p" , "%B %e, %Y" , "%b %d, %Y" ] -------------------------------------------------------------------------------- -- | Get the time on which the actual file was last modified. This only works if -- there actually is an underlying file, of couse. getItemModificationTime :: Identifier -> Compiler UTCTime getItemModificationTime identifier = do provider <- compilerProvider <$> compilerAsk return $ resourceModificationTime provider identifier -------------------------------------------------------------------------------- modificationTimeField :: String -- ^ Key -> String -- ^ Format -> Context a -- ^ Resuting context modificationTimeField = modificationTimeFieldWith defaultTimeLocale -------------------------------------------------------------------------------- modificationTimeFieldWith :: TimeLocale -- ^ Time output locale -> String -- ^ Key -> String -- ^ Format -> Context a -- ^ Resulting context modificationTimeFieldWith locale key fmt = field key $ \i -> do mtime <- getItemModificationTime $ itemIdentifier i return $ formatTime locale fmt mtime -------------------------------------------------------------------------------- -- | A context with "teaser" key which contain a teaser of the item. -- The item is loaded from the given snapshot (which should be saved -- in the user code before any templates are applied). teaserField :: String -- ^ Key to use -> Snapshot -- ^ Snapshot to load -> Context String -- ^ Resulting context teaserField = teaserFieldWithSeparator teaserSeparator -------------------------------------------------------------------------------- -- | A context with "teaser" key which contain a teaser of the item, defined as -- the snapshot content before the teaser separator. The item is loaded from the -- given snapshot (which should be saved in the user code before any templates -- are applied). teaserFieldWithSeparator :: String -- ^ Separator to use -> String -- ^ Key to use -> Snapshot -- ^ Snapshot to load -> Context String -- ^ Resulting context teaserFieldWithSeparator separator key snapshot = field key $ \item -> do body <- itemBody <$> loadSnapshot (itemIdentifier item) snapshot case needlePrefix separator body of Nothing -> fail $ "Hakyll.Web.Template.Context: no teaser defined for " ++ show (itemIdentifier item) Just t -> return t -------------------------------------------------------------------------------- missingField :: Context a missingField = Context $ \k _ i -> fail $ "Missing field $" ++ k ++ "$ in context for item " ++ show (itemIdentifier i) parseTimeM :: Bool -> TimeLocale -> String -> String -> Maybe UTCTime #if MIN_VERSION_time(1,5,0) parseTimeM = TF.parseTimeM #else parseTimeM _ = TF.parseTime #endif