/
Metadata.hs
138 lines (106 loc) · 4.92 KB
/
Metadata.hs
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--------------------------------------------------------------------------------
module Hakyll.Core.Metadata
( Metadata
, lookupString
, lookupStringList
, MonadMetadata (..)
, getMetadataField
, getMetadataField'
, makePatternDependency
, BinaryMetadata (..)
) where
--------------------------------------------------------------------------------
import Control.Arrow (second)
import Control.Monad (forM)
import Data.Binary (Binary (..), getWord8,
putWord8, Get)
import qualified Data.HashMap.Strict as HMS
import qualified Data.Set as S
import qualified Data.Text as T
import qualified Data.Vector as V
import qualified Data.Yaml.Extended as Yaml
import Hakyll.Core.Dependencies
import Hakyll.Core.Identifier
import Hakyll.Core.Identifier.Pattern
--------------------------------------------------------------------------------
type Metadata = Yaml.Object
--------------------------------------------------------------------------------
lookupString :: String -> Metadata -> Maybe String
lookupString key meta = HMS.lookup (T.pack key) meta >>= Yaml.toString
--------------------------------------------------------------------------------
lookupStringList :: String -> Metadata -> Maybe [String]
lookupStringList key meta =
HMS.lookup (T.pack key) meta >>= Yaml.toList >>= mapM Yaml.toString
--------------------------------------------------------------------------------
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 $ lookupString 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 (S.fromList matches')
--------------------------------------------------------------------------------
-- | Newtype wrapper for serialization.
newtype BinaryMetadata = BinaryMetadata
{unBinaryMetadata :: Metadata}
instance Binary BinaryMetadata where
put (BinaryMetadata obj) = put (BinaryYaml $ Yaml.Object obj)
get = do
BinaryYaml (Yaml.Object obj) <- get
return $ BinaryMetadata obj
--------------------------------------------------------------------------------
newtype BinaryYaml = BinaryYaml {unBinaryYaml :: Yaml.Value}
--------------------------------------------------------------------------------
instance Binary BinaryYaml where
put (BinaryYaml yaml) = case yaml of
Yaml.Object obj -> do
putWord8 0
let list :: [(T.Text, BinaryYaml)]
list = map (second BinaryYaml) $ HMS.toList obj
put list
Yaml.Array arr -> do
putWord8 1
let list = map BinaryYaml (V.toList arr) :: [BinaryYaml]
put list
Yaml.String s -> putWord8 2 >> put s
Yaml.Number n -> putWord8 3 >> put n
Yaml.Bool b -> putWord8 4 >> put b
Yaml.Null -> putWord8 5
get = do
tag <- getWord8
case tag of
0 -> do
list <- get :: Get [(T.Text, BinaryYaml)]
return $ BinaryYaml $ Yaml.Object $
HMS.fromList $ map (second unBinaryYaml) list
1 -> do
list <- get :: Get [BinaryYaml]
return $ BinaryYaml $
Yaml.Array $ V.fromList $ map unBinaryYaml list
2 -> BinaryYaml . Yaml.String <$> get
3 -> BinaryYaml . Yaml.Number <$> get
4 -> BinaryYaml . Yaml.Bool <$> get
5 -> return $ BinaryYaml Yaml.Null
_ -> fail "Data.Binary.get: Invalid Binary Metadata"