import Test.QuickCheck

basic :: Int -> [Int] -> Bool
basic _ [] = True
basic _ [h] = True
basic s (h1 : hs@(h2 : _)) = (r <= s') && basic (s' - (if (-r) > s' then 1 else 0)) hs
  where r = h2 - h1
        s' = max 0 s

f :: Int -> [Int] -> Bool
f _[_]=True;f s(h:j@(i:_))=(i-h<=s)&&f(max 0$s-fromEnum((h-i)>s))j


cases :: [((Int, [Int]), Bool, String)]
cases = [
  -- Truthy                                            	What is this testing?
  ((0, [1,1,1,1,1]), True,                              "Flat terrain with 0 stamina"),
  ((0, [50,45,20,19,18,10,1,1,1]), True,                "Drops with 0 stamina"),
  ((5, [1,6,11,16,21,26,31]), True,                     "Arduous climb, barely doable"),
  ((100, [500,1,100]), True,                            "Long drop, strong climber"),
  ((45, [20,50]), True,                                 "Short trek, excess stamina"),
  ((4, [6,2,1,2,5,6,1,2,3,5,1,1,1,3]), True,            "Example with a shorter cliff at the end"),
  ((17, [59,61,47,64,23,34,21,22,25,29,25]), True,      "Randomly generated"),

  -- Falsy 	                                            What is this testing?
  ((4, [6,2,1,2,5,6,1,2,3,5,1,1,1,4]), False,           "Example"),
  ((0, [1,1,2,1,1]), False,                             "Small hill with no stamina"),
  ((5, [30,28,22,18,13,9,7,9,11,14,22,23]), False,      "Valley with too many drops"),
  ((6, [40,47,49,55,61,66,69,70,50,55]), False,         "Early failure"),
  ((45, [79,48,41,70,76,85,27,12,31,66,13,17,94,77]), False, "Randomly generated"),
  ((31, [65,21,20,32,9,9,37,14,23,19,32,63]), False,    "Randomly generated")
  ]

testCase :: (Eq b) => (a -> b) -> (a, b, String) -> String
testCase f (args, ans, name) = if ans == f args
                               then "."
                               else "Failed \"" ++ name ++ "\""


main :: IO ()
main = do
  print $ testCase (uncurry f) <$> cases
  quickCheck (\(s, h1, hs) -> let s' = abs s
                                  hs' = abs <$> h1 : hs
                                  in basic s' hs' == f s' hs')