{-# LANGUAGE InstanceSigs #-}
{-# LANGUAGE DerivingStrategies #-}
module Arbitrary.InvalidBrainfuckText (InvalidBrainfuckText(..)) where

import Data.Text (Text)
import Test.QuickCheck.Gen (Gen)
import Test.QuickCheck.Arbitrary (Arbitrary (arbitrary))

import qualified Data.Text as Text
import qualified Test.QuickCheck.Gen as Gen
import qualified Arbitrary.ValidBrainfuckText as ValidBrainfuckText

newtype InvalidBrainfuckText = InvalidBrainfuckText { get :: Text }
  deriving stock Show

instance Arbitrary InvalidBrainfuckText where
  arbitrary :: Gen InvalidBrainfuckText
  arbitrary = do
    validText <- ValidBrainfuckText.get <$> arbitrary

    index <- Gen.choose (0, Text.length validText)
    badBrace <- Gen.oneof $ map pure "[]"
    let (prefix, suffix) = Text.splitAt index validText
    
    pure . InvalidBrainfuckText $ Text.concat [prefix, Text.singleton badBrace, suffix]