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|
--------------------------------------------------------------------------------
-- | An identifier is a type used to uniquely identify a resource, target...
--
-- One can think of an identifier as something similar to a file path. An
-- identifier is a path as well, with the different elements in the path
-- separated by @/@ characters. Examples of identifiers are:
--
-- * @posts/foo.markdown@
--
-- * @index@
--
-- * @error/404@
--
-- The most important difference between an 'Identifier' and a file path is that
-- the identifier for an item is not necesserily the file path.
--
-- For example, we could have an @index@ identifier, generated by Hakyll. The
-- actual file path would be @index.html@, but we identify it using @index@.
--
-- @posts/foo.markdown@ could be an identifier of an item that is rendered to
-- @posts/foo.html@. In this case, the identifier is the name of the source
-- file of the page.
--
-- An `Identifier` carries the type of the value it identifies. This basically
-- means that an @Identifier (Page String)@ refers to a page.
--
-- It is a phantom type parameter, meaning you can safely change this if you
-- know what you are doing. You can change the type using the 'castIdentifier'
-- function.
--
-- If the @a@ type is not known, Hakyll traditionally uses @Identifier ()@.
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Hakyll.Core.Identifier
( Identifier
, fromFilePath
, toFilePath
, identifierVersion
, setVersion
) where
--------------------------------------------------------------------------------
import Control.Applicative ((<$>), (<*>))
import Control.DeepSeq (NFData (..))
import Data.List (intercalate)
import System.FilePath (dropTrailingPathSeparator, splitPath)
--------------------------------------------------------------------------------
import Data.Binary (Binary (..))
import Data.Typeable (Typeable)
import GHC.Exts (IsString, fromString)
--------------------------------------------------------------------------------
-- | An identifier used to uniquely identify a value
data Identifier = Identifier
{ identifierVersion :: Maybe String
, identifierPath :: String
} deriving (Eq, Ord, Typeable)
--------------------------------------------------------------------------------
instance Binary Identifier where
put (Identifier v p) = put v >> put p
get = Identifier <$> get <*> get
--------------------------------------------------------------------------------
instance IsString Identifier where
fromString = fromFilePath
--------------------------------------------------------------------------------
instance NFData Identifier where
rnf (Identifier v p) = rnf v `seq` rnf p `seq` ()
--------------------------------------------------------------------------------
instance Show Identifier where
show i = case identifierVersion i of
Nothing -> toFilePath i
Just v -> toFilePath i ++ " (" ++ v ++ ")"
--------------------------------------------------------------------------------
-- | Parse an identifier from a string
fromFilePath :: String -> Identifier
fromFilePath = Identifier Nothing .
intercalate "/" . filter (not . null) . split'
where
split' = map dropTrailingPathSeparator . splitPath
--------------------------------------------------------------------------------
-- | Convert an identifier to a relative 'FilePath'
toFilePath :: Identifier -> FilePath
toFilePath = identifierPath
--------------------------------------------------------------------------------
setVersion :: Maybe String -> Identifier -> Identifier
setVersion v i = i {identifierVersion = v}
|
