module ParserSpec (spec) where

import Parser (Expr (Abstraction, Application, Variable), parse)
import Test.Hspec

spec :: Spec
spec = do
  describe "Parser" $ do
    it "can parse variable" $
      (parse "x") `shouldBe` Right (Variable "x")
    it "can parse identity abstraction" $
      (parse "λx.x") `shouldBe` Right (Abstraction ("x", Variable "x"))
    it "can parse mockingbird of identity" $
      (parse "(λx.x x) (λx.x)") -- (λx.x) (λx.x) -> (λx.x)
        `shouldBe` Right
          ( Application
              ( Abstraction
                  ( "x",
                    Application
                      ( Variable "x",
                        Variable "x"
                      )
                  ),
                Abstraction ("x", Variable "x")
              )
          )
    it "it can parse successor" $
      (parse "λn.λf.λx.f (n f x)")
        `shouldBe` Right
          ( Abstraction
              ( "n",
                Abstraction
                  ( "f",
                    Abstraction
                      ( "x",
                        Application
                          ( Variable "f",
                            Application
                              ( Application
                                  ( Variable "n",
                                    Variable "f"
                                  ),
                                Variable "x"
                              )
                          )
                      )
                  )
              )
          )