--(C) 2018, Functional Programming Course at University of Koblenz-Landau.
module Fancy where

import Test.HUnit (runTestTT,Test(TestLabel,TestList),(~?=))
import Data.Char

-- An 'arbitrary' datastructure that consists of two stack-like parts
data FancyPart a = Add a (FancyPart a)| End deriving (Show,Eq)
data Fancy a = Fancy (FancyPart a) (FancyPart a) deriving (Show,Eq)

-- Implement fmap for the datastructure Fancy
instance Functor Fancy
    where
      fmap f (Fancy a b) = Fancy (fmap f a) (fmap f b)

instance Functor FancyPart
  where
    fmap f (Add a rest) = Add (f a) (fmap f rest)
    fmap f (End) = End

-- Implement foldr for the datastructure Fancy
instance Foldable Fancy
    where
      foldr f z (Fancy a b) = (foldr f (foldr f z b) a)

instance Foldable FancyPart
  where
    foldr f z (Add a rest) = (f a (foldr f z rest))
    foldr f z (End) = z


-- Here are two samples for testing later
sample1 :: Fancy Int
sample1 = Fancy (Add 3 $ Add 4 $ Add 5 $ Add 6 End)
                (Add 9 $ Add 8 $ Add 7 End)
sample1' = Fancy (Add 4 $ Add 5 $ Add 6 $ Add 7 End)
                (Add 10 $ Add 9 $ Add 8 End)
sample2 :: Fancy String
sample2 = Fancy (Add "I" $ Add "want" $ Add "to" End)
                (Add "programmer" $ Add "a" $ Add "be" End)
sample2' = Fancy (Add "I" $ Add "WANT" $ Add "TO" End)
                (Add "PROGRAMMER" $ Add "A" $ Add "BE" End)

-- | Tests 'permutations' on a few examples.
main :: IO ()
main = do
    testresults <- runTestTT tests
    print testresults

-- | A few tests for 'permutations'.
tests :: Test
tests = TestLabel "Fancy" (TestList [
        fmap (+1) sample1 ~?= sample1',
        fmap (map toUpper) sample2 ~?= sample2',
        foldr (+) 0 sample1 ~?= 42,
        foldr (\s1 s2 -> s1 ++ " " ++ s2) "" sample2 ~?= "I want to programmer a be ",
        fmap ((flip mod) 2) sample1 ~?= Fancy (Add 1 $ Add 0 $ Add 1 $ Add 0 End)
                                        (Add 1 $ Add 0 $ Add 1 End)
    ])