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-- | Test ogma-extra internals.
module Main where

-- External imports
import Data.Either                          ( isLeft, isRight )
import Test.Framework                       ( Test, defaultMainWithOpts )
import Test.Framework.Providers.QuickCheck2 ( testProperty )
import Test.QuickCheck                      ( Property, (==>), Fun (Fun) )

-- Internal imports
import Data.List.Extra ( headEither, toHead, toTail )

-- | Run all unit tests on Ogma's core.
main :: IO ()
main =
  defaultMainWithOpts tests mempty

-- | All unit tests for Ogma's core.
tests :: [Test.Framework.Test]
tests =
  [ testProperty "Data.List.Extra.toHead (diag commutativity)" propToHead
  , testProperty "Data.List.Extra.toHead (identity)"           propToHeadId
  , testProperty "Data.List.Extra.toHead (composition)"        propToHeadCmp
  , testProperty "Data.List.Extra.toHead (length)"             propToHeadSameLength
  , testProperty "Data.List.Extra.toTail (diag commutativity)" propToTail
  , testProperty "Data.List.Extra.toTail (identity)"           propToTailId
  , testProperty "Data.List.Extra.toTail (composition)"        propToTailCmp
  , testProperty "Data.List.Extra.toTail (length)"             propToTailSameLength
  , testProperty "Data.List.Extra.headEither (Right case)"     propHeadEitherRight
  , testProperty "Data.List.Extra.headEither (Left case)"      propHeadEitherLeft
  ]

-- * Data.List.Extra

-- | Test that 'toHead' applies a transformation to the head of a list.
propToHead :: [Int] -> Fun Int Int -> Property
propToHead xs (Fun _ f) = not (null xs) ==> f (head xs) == head (toHead f xs)

-- | Test that 'toHead' preserves the identity.
propToHeadId :: [Int] -> Bool
propToHeadId xs = toHead id xs == xs

-- | Test that 'toHead' preserves function composition.
propToHeadCmp :: [Int] -> Fun Int Int -> Fun Int Int -> Bool
propToHeadCmp xs (Fun _ f) (Fun _ g) = toHead (f . g) xs == toHead f (toHead g xs)

-- | Test that 'toHead' does not alter the length of the list.
propToHeadSameLength :: [Int] -> Fun Int Int -> Bool
propToHeadSameLength xs (Fun _ f) = length xs == length (toHead f xs)

-- | Test that 'toTail' applies a transformation to the tail of a list.
propToTail :: [Int] -> Fun Int Int -> Property
propToTail xs (Fun _ f) = not (null xs) ==> fmap f (tail xs) == tail (toTail f xs)

-- | Test that 'toTail' preserves the identity.
propToTailId :: [Int] -> Bool
propToTailId xs = toTail id xs == xs

-- | Test that 'toHead' preserves function composition.
propToTailCmp :: [Int] -> Fun Int Int -> Fun Int Int -> Bool
propToTailCmp xs (Fun _ f) (Fun _ g) = toTail (f . g) xs == toTail f (toTail g xs)

-- | Test that 'toTail' does not alter the length of the list.
propToTailSameLength :: [Int] -> Fun Int Int -> Bool
propToTailSameLength xs (Fun _ f) = length xs == length (toTail f xs)

-- | Test that 'headEither' returns a 'Right' value if applied to a non-empty
-- list.
propHeadEitherRight :: [Int] -> Property
propHeadEitherRight xs = not (null xs) ==> isRight (headEither xs)

-- | Test that 'headEither' returns a 'Left' value if applied to an empty list.
propHeadEitherLeft :: [Int] -> Property
propHeadEitherLeft xs = null xs ==> isLeft (headEither xs)