{-# LANGUAGE CPP, MultiParamTypeClasses #-}
	Copyright (C) 2013-2015 Dr. Alistair Ward

	This file is part of WeekDaze.

	WeekDaze is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	WeekDaze is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with WeekDaze.  If not, see <http://www.gnu.org/licenses/>.
{- |
 [@AUTHOR@]	Dr. Alistair Ward

 [@DESCRIPTION@]	Defines a suitable type for its polymorphic namesake.

 [@CAVEAT@]	Exporting nothing but the type-constructor forces this to be used only as an interface, & therefore to be easily replaced; though a data-constructor is also exported for testing.

module WeekDaze.Identifiers.LocationId(
-- * Types
-- ** Data-types
-- * Constants
--	tag,
-- * Functions
-- ** Constructor
) where

import qualified        Control.Arrow
import qualified        Control.DeepSeq
import qualified        Text.XHtml.Strict
import                  Text.XHtml.Strict((<<))
import qualified        Text.XML.HXT.Arrow.Pickle       as HXT
import qualified        WeekDaze.Text.XHTML             as Text.XHTML

#ifdef USE_HDBC
import qualified        Data.Convertible
import qualified        Database.HDBC

instance Data.Convertible.Convertible Database.HDBC.SqlValue LocationId {-multi-parameter type-class-} where
        safeConvert     = fmap mkLocationId . Data.Convertible.safeConvert
#endif /* USE_HDBC */

-- | Used to qualify XML & CSS.
tag :: String
tag     = "locationId"

-- | Define a concrete type for the identifier for a /location/.
newtype LocationId      = MkLocationId {
        deconstruct     :: String       -- Could also be an Int.
} deriving (Eq, Ord)

-- | Constructor.
mkLocationId :: String -> LocationId
mkLocationId    = MkLocationId

instance Show LocationId where
        showsPrec _     = shows . deconstruct

instance Read LocationId where
        readsPrec _     = map (Control.Arrow.first mkLocationId) . reads

instance HXT.XmlPickler LocationId where
        xpickle = HXT.xpWrap (
                mkLocationId,   -- Construct from a String.
                deconstruct     -- Deconstruct to a String.
         ) $ HXT.xpTextAttr tag {-can't be null-}

instance Control.DeepSeq.NFData LocationId where
        rnf     = Control.DeepSeq.rnf . deconstruct

instance Text.XHtml.Strict.HTML LocationId where
        toHtml (MkLocationId s)         = Text.XHTML.mkXHTMLSpan tag << s