{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# OPTIONS_GHC -fno-warn-missing-signatures #-}
module Expr.If.Test where

import Test.Tasty
import Test.Tasty.HUnit

import Control.Arrow (left)
import Data.Proxy (Proxy(..))
import Data.Type.Equality ((:~:)(Refl))
import Prelude hiding (maybe, not)

import Language.LOL.Symantic.Repr
import Language.LOL.Symantic.AST
import Language.LOL.Symantic.Expr
import Language.LOL.Symantic.Type

-- * Expressions
e1 = if_ (bool True)
         (bool False)
         (bool True)

-- * Tests
(==>)
 :: forall h ast root.
 ( Eq h, Eq ast, Show h, Show ast
 , root ~ Expr_Lambda_If_Bool IO
 , Expr_from ast (Expr_Lambda IO root)
 , Expr_from ast (Expr_Bool      root)
 , Expr_from ast (Expr_If        root)
 ) => ast
 -> Either (Proxy h, Error_of_Expr ast root)
           (Type_Root_of_Expr (Expr_Lambda_If_Bool IO) h, h, String)
 -> TestTree
(==>) ast expected =
	testCase (show ast) $
	case expr_lambda_if_bool_from (Proxy::Proxy IO) ast of
	 Left err -> Left err @?= snd `left` expected
	 Right (Exists_Type_and_Repr ty (Forall_Repr r)) ->
		case expected of
		 Left (_, err) -> Right ("…"::String) @?= Left err
		 Right (ty_expected::Type_Root_of_Expr (Expr_Lambda_If_Bool IO) h, _::h, _::String) ->
			(>>= (@?= (\(_::Proxy h, err) -> err) `left` expected)) $
			case ty `type_eq` ty_expected of
			 Nothing -> return $ Left $
				error_expr (Proxy::Proxy (Expr_Lambda_If_Bool IO)) $
				Error_Expr_Type_mismatch ast
				 (Exists_Type ty)
				 (Exists_Type ty_expected)
			 Just Refl -> do
				h <- host_from_expr r
				return $
					Right
					 ( ty
					 , h
					 , string_from_expr r
					 -- , (string_from_expr :: Repr_String IO h -> String) r
					 )

tests :: TestTree
tests = testGroup "If"
 [ AST "if"
	 [ AST "bool" [AST "True" []]
	 , AST "bool" [AST "False" []]
	 , AST "bool" [AST "True" []]
	 ] ==> Right
	 ( type_bool
	 , False
	 , "if True then False else True" )
 ]