module Minilang.Lambda.ParserSpec where

import Data.Text (Text, pack)
import Minilang.Lambda.Parser (AST (..), initialChars, parse, restChars)
import Test.Hspec (Spec, parallel, shouldBe)
import Test.Hspec.QuickCheck (prop)
import Test.QuickCheck (Arbitrary (..), elements, listOf)

spec :: Spec
spec = parallel $ do
  prop "parses an identifier as a variable" $ \(Identifier ident) ->
    parse ident `shouldBe` Right (Sym ident)
  prop "parses a lambda-expression as an abstraction" $ \(Identifier ident) (Identifier body) ->
    parse ("(lam (" <> ident <> ") " <> body <> ")") `shouldBe` Right (Abs ident (Sym body))

newtype Identifier = Identifier Text
  deriving (Eq, Show)

instance Arbitrary Identifier where
  arbitrary =
    Identifier . pack
      <$> ((:) <$> elements initialChars <*> listOf (elements restChars))