63 lines
2.3 KiB
Haskell
63 lines
2.3 KiB
Haskell
--------------------------------------------------------------------------------
|
|
module Hakyll.Core.Metadata
|
|
( Metadata
|
|
, MonadMetadata (..)
|
|
, getMetadataField
|
|
, getMetadataField'
|
|
, makePatternDependency
|
|
) where
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
import Control.Monad (forM)
|
|
import Data.Map (Map)
|
|
import qualified Data.Map as M
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
import Hakyll.Core.Dependencies
|
|
import Hakyll.Core.Identifier
|
|
import Hakyll.Core.Identifier.Pattern
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
type Metadata = Map String String
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
class Monad m => MonadMetadata m where
|
|
getMetadata :: Identifier -> m Metadata
|
|
getMatches :: Pattern -> m [Identifier]
|
|
|
|
getAllMetadata :: Pattern -> m [(Identifier, Metadata)]
|
|
getAllMetadata pattern = do
|
|
matches' <- getMatches pattern
|
|
forM matches' $ \id' -> do
|
|
metadata <- getMetadata id'
|
|
return (id', metadata)
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
getMetadataField :: MonadMetadata m => Identifier -> String -> m (Maybe String)
|
|
getMetadataField identifier key = do
|
|
metadata <- getMetadata identifier
|
|
return $ M.lookup key metadata
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
-- | Version of 'getMetadataField' which throws an error if the field does not
|
|
-- exist.
|
|
getMetadataField' :: MonadMetadata m => Identifier -> String -> m String
|
|
getMetadataField' identifier key = do
|
|
field <- getMetadataField identifier key
|
|
case field of
|
|
Just v -> return v
|
|
Nothing -> fail $ "Hakyll.Core.Metadata.getMetadataField': " ++
|
|
"Item " ++ show identifier ++ " has no metadata field " ++ show key
|
|
|
|
|
|
--------------------------------------------------------------------------------
|
|
makePatternDependency :: MonadMetadata m => Pattern -> m Dependency
|
|
makePatternDependency pattern = do
|
|
matches' <- getMatches pattern
|
|
return $ PatternDependency pattern matches'
|