-----------------------------------------------------------------------------
-- Copyright 2015, 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)
--
-----------------------------------------------------------------------------
--  $Id: Generator.hs 7527 2015-04-08 07:58:06Z bastiaan $

module Domain.RelationAlgebra.Generator (templateGenerator) where

import Control.Monad
import Domain.RelationAlgebra.Formula
import Test.QuickCheck

instance Arbitrary RelAlg where
   arbitrary = sized (arbRelAlg . min 8)

arbRelAlg :: Int -> Gen RelAlg
arbRelAlg 0 = frequency [(8, liftM Var (elements relAlgVars)), (1, return V), (1, return empty), (1, return I)]
arbRelAlg n = oneof [ arbRelAlg 0, binop (:.:), binop (:+:), binop (:&&:), binop (:||:)
                    , unop Not, unop Inv
                    ]
 where
   binop op = liftM2 op rec rec
   unop op  = liftM op rec
   rec      = arbRelAlg (n `div` 2)

relAlgVars :: [String]
relAlgVars = ["q", "r", "s"]

-------------------------------------------------------------------
-- Templates

template1, template2, template3, template4, template7, template8 ::
   RelAlg -> RelAlg -> RelAlg -> RelAlg

template5 :: RelAlg -> RelAlg -> RelAlg -> RelAlg -> RelAlg
template6 :: Maybe RelAlg -> RelAlg -> RelAlg -> Maybe RelAlg -> RelAlg

template1 x y z = x :||: (y :&&: z)
template2 x y z = Not(x :&&: (y :||: z))
template3 x y z = Inv(x :||: (y :&&: z))
template4 x y z = Inv (Not(x :&&: (y :||: z)))
template5 x y z v = Inv (Not((x :||: v) :&&: (y :||: z)))
template6 mp a b mq = f1 (f2 (a :&&: b))
 where f1 x = maybe x (:.: x) mp
       f2 x = maybe x (x :.:) mq
template7 x y z = x :.: (y :||:z)
template8 x y z = x :||: Not (Inv (y :.: z) :&&: Not (Inv y :.: Inv z))

-------------------------------------------------------------------
-- Template generators

templateGenerator :: Int -> Gen RelAlg
templateGenerator n = oneof (map ($ n) [gen1,gen2,gen3,gen4,gen5,gen6,gen7,gen8,gen9])

gen1, gen2, gen3, gen4, gen5, gen6, gen7, gen8, gen9 :: Int -> Gen RelAlg
gen1 = use3 template1 arbInvNotMol arbInvNotMol arbInvNotMol
gen2 = use3 template2 arbInvNotMol arbInvNotMol arbInvNotMol
gen3 = use3 template3 arbInvNotMol arbInvNotMol arbInvNotMol
gen4 = use3 template4 arbInvNotMol arbInvNotMol arbInvNotMol
gen5 = use4 template5 arbInvNotMol arbInvNotMol arbInvNotMol arbInvNotMol
gen6 = use3 template1 hulpgen1 arbInvNotMol arbInvNotMol
gen7 = use3 template1 arbInvNotMol hulpgen1 arbInvNotMol
gen8 = use3 template2 arbInvNotMol hulpgen1 arbInvNotMol
gen9 = use3 template8 hulpgen2 arbInvNotMol arbInvNotMol

use3 :: (a -> b -> c -> d) -> (t -> Gen a) -> (t -> Gen b) -> (t -> Gen c) -> t -> Gen d
use3 temp f g h   n = liftM3 temp (f n) (g n) (h n)

use4 :: (a -> b -> c -> d -> e) -> (t -> Gen a) -> (t -> Gen b) -> (t -> Gen c) -> (t -> Gen d) -> t -> Gen e
use4 temp f g h k n = liftM4 temp (f n) (g n) (h n) (k n)

hulpgen1 :: Int -> Gen RelAlg
hulpgen1 n = liftM4 template6 (arbMaybeInvNotMol n) arbVar arbVar (arbMaybeInvNotMol n)

hulpgen2 :: Int -> Gen RelAlg
hulpgen2 n = liftM3 template7 (arbInvNotMol 1) (arbRelAlg n) (arbRelAlg n)

arbInvNotMol :: Int -> Gen RelAlg
arbInvNotMol 0 = frequency [(10, liftM Var (elements relAlgVars)), (1, return V), (1, return empty), (1, return I)]
arbInvNotMol n = frequency [ (10, arbInvNotMol 0), (4, binop (:.:)), (4, binop (:+:)), (2, unop Not), (2, unop Inv) ]
 where
   binop op = liftM2 op rec rec
   unop op  = liftM op rec
   rec      = arbInvNotMol (n `div` 2)

arbMaybeInvNotMol :: Int -> Gen (Maybe RelAlg)
arbMaybeInvNotMol n = frequency [(3, liftM Just (arbInvNotMol n)), (1, return Nothing)]

arbVar :: Gen RelAlg
arbVar = liftM Var (elements relAlgVars)