-- |Defines types and utility functions related to namespaces, and
-- some predefined values for commonly used namespaces, such as
-- rdf, xsd, dublin core, etc.

module Data.RDF.Namespace(
  -- * Namespace types and functions
  Namespace(..), mkPlainNS, mkPrefixedNS, mkPrefixedNS',
  PrefixMapping(PrefixMapping), PrefixMappings(PrefixMappings), toPMList,
  mkUri,
  prefixOf, uriOf,
  -- * Predefined namespace values
  rdf, rdfs, dc, dct, owl, xml, xsd, skos, foaf, ex, ex2,
  standard_ns_mappings, ns_mappings
) where

import qualified Data.Text as T
import Data.RDF.Types
import qualified Data.Map as Map
import Data.Semigroup ((<>))

standard_namespaces :: [Namespace]
standard_namespaces = [rdf, rdfs, dc, dct, owl, xsd, skos, foaf, ex, ex2]

-- |The set of common predefined namespaces as a 'PrefixMappings' value.
standard_ns_mappings :: PrefixMappings
standard_ns_mappings  =  ns_mappings standard_namespaces

-- |Takes a list of 'Namespace's and returns 'PrefixMappings'.
ns_mappings :: [Namespace] -> PrefixMappings
ns_mappings ns =  PrefixMappings $ Map.fromList $
                     fmap (\(PrefixedNS pre uri) -> (pre, uri)) ns

-- |The RDF namespace.
rdf :: Namespace
rdf = mkPrefixedNS' "rdf" "http://www.w3.org/1999/02/22-rdf-syntax-ns#"

-- |The RDF Schema namespace.
rdfs :: Namespace
rdfs = mkPrefixedNS' "rdfs" "http://www.w3.org/2000/01/rdf-schema#"

-- |The Dublin Core namespace.
dc :: Namespace
dc = mkPrefixedNS' "dc" "http://purl.org/dc/elements/1.1/"

-- |The Dublin Core terms namespace.
dct :: Namespace
dct = mkPrefixedNS' "dct" "http://purl.org/dc/terms/"

-- |The OWL namespace.
owl :: Namespace
owl = mkPrefixedNS' "owl" "http://www.w3.org/2002/07/owl#"

-- |The XML Schema namespace.
xml :: Namespace
xml = mkPrefixedNS' "xml" "http://www.w3.org/XML/1998/namespace"

-- |The XML Schema namespace.
xsd :: Namespace
xsd = mkPrefixedNS' "xsd" "http://www.w3.org/2001/XMLSchema#"

-- |The SKOS namespace.
skos :: Namespace
skos = mkPrefixedNS' "skos" "http://www.w3.org/2004/02/skos/core#"

-- |The friend of a friend namespace.
foaf :: Namespace
foaf = mkPrefixedNS' "foaf" "http://xmlns.com/foaf/0.1/"

-- |Example namespace #1.
ex :: Namespace
ex = mkPrefixedNS' "ex" "http://www.example.org/"

-- |Example namespace #2.
ex2 :: Namespace
ex2 = mkPrefixedNS' "ex2" "http://www2.example.org/"

-- |View the prefix mappings as a list of key-value pairs. The PM in
-- in the name is to reduce name clashes if used without qualifying.
toPMList :: PrefixMappings -> [(T.Text, T.Text)]
toPMList (PrefixMappings m) = Map.toList m

-- |Make a URI consisting of the given namespace and the given localname.
mkUri :: Namespace -> T.Text -> T.Text
mkUri ns local = uriOf ns `T.append` local


-- |Make a namespace for the given URI reference.
mkPlainNS :: T.Text -> Namespace
mkPlainNS = PlainNS

-- |Make a namespace having the given prefix for the given URI reference,
-- respectively.
mkPrefixedNS :: T.Text -> T.Text -> Namespace
mkPrefixedNS = PrefixedNS

-- |Make a namespace having the given prefix for the given URI reference,
-- respectively, using strings which will be converted to bytestrings
-- automatically.
mkPrefixedNS' :: String -> String -> Namespace
mkPrefixedNS' s1 s2 = mkPrefixedNS (T.pack s1) (T.pack s2)

-- |Determine the URI of the given namespace.
uriOf :: Namespace -> T.Text
uriOf (PlainNS      uri) = uri
uriOf (PrefixedNS _ uri) = uri

-- |Determine the prefix of the given namespace, if it has one.
prefixOf :: Namespace -> Maybe T.Text
prefixOf (PlainNS      _) = Nothing
prefixOf (PrefixedNS p _) = Just p