-----------------------------------------------------------------------------
-- Copyright 2011, Open Universiteit Nederland. This file is distributed
-- under the terms of the GNU General Public License. For more information,
-- see the file "LICENSE.txt", which is included in the distribution.
-----------------------------------------------------------------------------
-- |
-- Maintainer  :  bastiaan.heeren@ou.nl
-- Stability   :  provisional
-- Portability :  portable (depends on ghc)
--
-----------------------------------------------------------------------------
module Domain.Math.Equation.CoverUpExercise
   ( coverUpExercise, coverUpStrategy
   ) where

import Common.Library
import Data.Maybe
import Domain.Math.CleanUp (cleanUpExpr, cleanUpView)
import Domain.Math.Data.OrList
import Domain.Math.Data.Relation
import Domain.Math.Equation.CoverUpRules
import Domain.Math.Equation.Examples
import Domain.Math.Equation.Views
import Domain.Math.Expr

------------------------------------------------------------
-- Exercise

coverUpExercise :: Exercise (OrList (Equation Expr))
coverUpExercise = makeExercise
   { exerciseId   = describe "solve an equation by covering up" $
                       newId "algebra.equations.coverup"
   , status       = Provisional
   , parser       = parseOrsEqExpr
   , equivalence  = withoutContext eqCoverUp
   , similarity   = withoutContext myEq
   , ready        = predicateView equationsSolvedForm
   , extraRules   = coverUpRulesOr
   , strategy     = coverUpStrategy
   , navigation   = termNavigator
   , examples     = level Medium $ map singleton (concat (fillInResult ++ coverUpEquations))
   }

------------------------------------------------------------
-- Strategy and rules

coverUpStrategy :: LabeledStrategy (Context (OrList (Equation Expr)))
coverUpStrategy = cleanUpStrategyAfter (applyTop $ fmap $ fmap cleanUpExpr) $
   label "Cover-up" $
   repeatS $ somewhere $ alternatives coverUpRulesOr

eqCoverUp :: OrList (Equation Expr) -> OrList (Equation Expr) -> Bool
eqCoverUp a b = myEq (f a) (f b)
 where
   inc = inContext coverUpExercise
   f x = fromMaybe x $ fromContext $ applyD coverUpStrategy $ inc x

myEq :: OrList (Equation Expr) -> OrList (Equation Expr) -> Bool
myEq = viewEquivalent (traverseView (traverseView cleanUpView))