{-#LANGUAGE ScopedTypeVariables#-}
module Utils where
import Control.Exception (SomeException, bracket, bracket_, evaluate, try)
import System.IO.Unsafe (unsafePerformIO)
import Debug.Trace (trace)
import Data.Bits ((.&.))
import Data.Char (chr)
import Data.String (IsString, fromString)
import System.Random (Random (..), RandomGen)
import Test.QuickCheck hiding ((.&.))
import Test.QuickCheck.Monadic (assert, monadicIO, run)
import qualified Data.ByteString as B
import Pipes.Text.Internal





-- Ensure that two potentially bottom values (in the sense of crashing
-- for some inputs, not looping infinitely) either both crash, or both
-- give comparable results for some input.
(=^=) :: (Eq a, Show a) => a -> a -> Bool
i =^= j = unsafePerformIO $ do
  x <- try (evaluate i)
  y <- try (evaluate j)
  case (x,y) of
    (Left (_ :: SomeException), Left (_ :: SomeException))
                       -> return True
    (Right a, Right b) -> return (a == b)
    e                  -> trace ("*** Divergence: " ++ show e) return False
infix 4 =^=
{-# NOINLINE (=^=) #-}

-- Do two functions give the same answer?
eq :: (Eq a, Show a) => (t -> a) -> (t -> a) -> t -> Bool
eq a b s  = a s =^= b s

-- What about with the RHS packed?
-- eqP :: (Eq a, Show a, Stringy s) =>
--        (String -> a) -> (s -> a) -> String -> Word8 -> Bool
-- eqP f g s w  = eql "orig" (f s) (g t) &&
--                eql "mini" (f s) (g mini) &&
--                eql "head" (f sa) (g ta) &&
--                eql "tail" (f sb) (g tb)
--     where t             = packS s
--           mini          = packSChunkSize 10 s
--           (sa,sb)       = splitAt m s
--           (ta,tb)       = splitAtS m t
--           l             = length s
--           m | l == 0    = n
--             | otherwise = n `mod` l
--           n             = fromIntegral w
--           eql d a b
--             | a =^= b   = True
--             | otherwise = trace (d ++ ": " ++ show a ++ " /= " ++ show b) False


instance Arbitrary B.ByteString where
    arbitrary     = B.pack `fmap` arbitrary

genUnicode :: IsString a => Gen a
genUnicode = fmap fromString string where
    string = sized $ \n ->
        do k <- choose (0,n)
           sequence [ char | _ <- [1..k] ]

    excluding :: [a -> Bool] -> Gen a -> Gen a
    excluding bad gen = loop
      where
        loop = do
          x <- gen
          if or (map ($ x) bad)
            then loop
            else return x

    reserved = [lowSurrogate, highSurrogate, noncharacter]
    lowSurrogate c = c >= 0xDC00 && c <= 0xDFFF
    highSurrogate c = c >= 0xD800 && c <= 0xDBFF
    noncharacter c = masked == 0xFFFE || masked == 0xFFFF
      where
        masked = c .&. 0xFFFF

    ascii = choose (0,0x7F)
    plane0 = choose (0xF0, 0xFFFF)
    plane1 = oneof [ choose (0x10000, 0x10FFF)
                   , choose (0x11000, 0x11FFF)
                   , choose (0x12000, 0x12FFF)
                   , choose (0x13000, 0x13FFF)
                   , choose (0x1D000, 0x1DFFF)
                   , choose (0x1F000, 0x1FFFF)
                   ]
    plane2 = oneof [ choose (0x20000, 0x20FFF)
                   , choose (0x21000, 0x21FFF)
                   , choose (0x22000, 0x22FFF)
                   , choose (0x23000, 0x23FFF)
                   , choose (0x24000, 0x24FFF)
                   , choose (0x25000, 0x25FFF)
                   , choose (0x26000, 0x26FFF)
                   , choose (0x27000, 0x27FFF)
                   , choose (0x28000, 0x28FFF)
                   , choose (0x29000, 0x29FFF)
                   , choose (0x2A000, 0x2AFFF)
                   , choose (0x2B000, 0x2BFFF)
                   , choose (0x2F000, 0x2FFFF)
                   ]
    plane14 = choose (0xE0000, 0xE0FFF)
    planes = [ascii, plane0, plane1, plane2, plane14]

    char = chr `fmap` excluding reserved (oneof planes)