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 lesson, suitable for any /time-slot/ in the generic /timetable/.

module WeekDaze.Model.Lesson(
-- * Types
-- ** Type-synonyms
-- ** Data-types
-- * Constants
--	resourceIdsCSSIdentifier,
--	tag
) where

import                  Control.Arrow((&&&))
import qualified        Control.DeepSeq
import qualified        Text.XHtml.Strict
import qualified        Text.XML.HXT.Arrow.Pickle       as HXT
import qualified        WeekDaze.Data.Subject           as Data.Subject
import qualified        WeekDaze.Text.CSS               as Text.CSS
import                  Text.XHtml.Strict((+++), (<<), (!))

-- | Used to qualify output.
resourceIdsCSSIdentifier :: Text.CSS.CSSIdentifier
resourceIdsCSSIdentifier        = "resourceIds" -- CAVEAT: coordinate with 'Data.Meeting.resourceIdsCSSIdentifier'.

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

{- |
	* Defines a potential /booking/ of the /resource/s required to teach a /subject/.

	* It doesn't specify the /time-slot/ at which it's to be booked, because that's defined by it's position within a /timetable/.

	* A /timetable/ composed from these /lesson/s, can be viewed by either a /location/, /student/ or /teacher/, so 'getResourceIds' is polymorphic.
data Lesson resourceIds level   = MkLesson {
        getResourceIds  :: resourceIds,                 -- ^ The concrete type depends on whether viewed from the perspective of the /location/, /student/ or /teacher/.
        getSubject      :: Data.Subject.Subject level   -- ^ The /subject/ to be taught.
} deriving (Eq, Ord, Show)

instance (Text.XHtml.Strict.HTML level, Text.XHtml.Strict.HTML resourceIds) => Text.XHtml.Strict.HTML (Lesson resourceIds level) where
        toHtml lesson   = Text.XHtml.Strict.thediv ! [
                Text.XHtml.Strict.theclass tag,
                Text.XHtml.Strict.title tag
         ] << (
                getSubject lesson +++ '.' +++ Text.XHtml.Strict.ulist ! [
                        Text.XHtml.Strict.theclass resourceIdsCSSIdentifier,
                        Text.XHtml.Strict.title resourceIdsCSSIdentifier
                ] << getResourceIds lesson

instance (HXT.XmlPickler level, HXT.XmlPickler resourceIds, Show level) => HXT.XmlPickler (Lesson resourceIds level) where
        xpickle = HXT.xpElem tag . HXT.xpWrap (
                uncurry MkLesson,               -- Construct from a Pair.
                getResourceIds &&& getSubject   -- Deconstruct to a Pair.
         ) $ HXT.xpickle `HXT.xpPair` HXT.xpickle

instance (Control.DeepSeq.NFData level, Control.DeepSeq.NFData resourceIds) => Control.DeepSeq.NFData (Lesson resourceIds level) where
        rnf     = Control.DeepSeq.rnf . (getResourceIds &&& getSubject)

-- | A potentially undefined /lesson/.
type GeneralisedLesson resourceIds level        = Maybe (Lesson resourceIds level)