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|
-- |
-- Copyright : (c) Sam Truzjan 2013
-- License : BSD3
-- Maintainer : pxqr.sta@gmail.com
-- Stability : provisional
-- Portability : portable
--
-- URN is pesistent location-independent identifier for
-- resources. In particular, URNs are used represent torrent names
-- as a part of magnet link, see 'Data.Torrent.Magnet.Magnet' for
-- more info.
--
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE DeriveDataTypeable #-}
module Data.Torrent.URN
( -- * Namespaces
NamespaceId
, btih
-- * URN
, URN (..)
-- ** Construction
, infohashURN
-- ** Conversion
, parseURN
, renderURN
) where
import Control.Applicative
import Data.Convertible
import Data.Default
import Data.List as L
import Data.String
import Data.Text as T
import Data.Typeable
import Network.HTTP.Types.QueryLike
import Text.PrettyPrint
import Text.PrettyPrint.Class
import Data.Torrent.InfoHash
-- | Namespace identifier determines the syntactic interpretation of
-- namespace-specific string.
type NamespaceId = [Text]
-- | BitTorrent Info Hash (hence the name) namespace
-- identifier. Namespace-specific string /should/ be a base16\/base32
-- encoded SHA1 hash of the corresponding torrent /info/ dictionary.
--
btih :: NamespaceId
btih = ["btih"]
-- | Uniform Resource Name - location-independent, resource
-- identifier.
--
data URN = URN
{ urnNamespace :: NamespaceId -- ^ a namespace identifier;
, urnString :: Text -- ^ a corresponding
-- namespace-specific string.
} deriving (Eq, Ord, Typeable)
{-----------------------------------------------------------------------
-- Infohash convertion
-----------------------------------------------------------------------}
instance Convertible URN InfoHash where
safeConvert u @ URN {..}
| urnNamespace /= btih = convError "invalid namespace" u
| otherwise = safeConvert urnString
-- | Make resource name for torrent with corresponding
-- infohash. Infohash is base16 (hex) encoded.
--
infohashURN :: InfoHash -> URN
infohashURN = URN btih . longHex
-- | Meaningless placeholder value.
instance Default URN where
def = infohashURN def
{-----------------------------------------------------------------------
-- Rendering
-----------------------------------------------------------------------}
-- | Render URN to its text representation.
renderURN :: URN -> Text
renderURN URN {..}
= T.intercalate ":" $ "urn" : urnNamespace ++ [urnString]
instance Pretty URN where
pretty = text . T.unpack . renderURN
instance Show URN where
showsPrec n = showsPrec n . T.unpack . renderURN
instance QueryValueLike URN where
toQueryValue = toQueryValue . renderURN
{-# INLINE toQueryValue #-}
{-----------------------------------------------------------------------
-- Parsing
-----------------------------------------------------------------------}
unsnoc :: [a] -> Maybe ([a], a)
unsnoc [] = Nothing
unsnoc xs = Just (L.init xs, L.last xs)
instance Convertible Text URN where
safeConvert t = case T.split (== ':') t of
uriScheme : body
| T.toLower uriScheme == "urn" ->
case unsnoc body of
Just (namespace, val) -> pure URN
{ urnNamespace = namespace
, urnString = val
}
Nothing -> convError "missing URN string" body
| otherwise -> convError "invalid URN scheme" uriScheme
[] -> convError "missing URN scheme" t
instance IsString URN where
fromString = either (error . prettyConvertError) id
. safeConvert . T.pack
-- | Try to parse an URN from its text representation.
--
-- Use 'safeConvert' for detailed error messages.
--
parseURN :: Text -> Maybe URN
parseURN = either (const Nothing) pure . safeConvert
|
