{-# LANGUAGE OverloadedStrings, TemplateHaskell, UndecidableInstances, FlexibleInstances, DerivingVia, PolyKinds, DeriveAnyClass #-}

module ReadMeExamples where

import Data.Text
import GHC.Generics (Generic1)
import Generics.Constraints (makeDerivings)
import Hyper
import Hyper.Class.ZipMatch
import Hyper.Diff
import Hyper.Type.AST.App
import Hyper.Type.AST.Var
import Hyper.Type.AST.TypedLam

import Prelude

data Expr h
    = EVar Text
    | EApp (h :# Expr) (h :# Expr)
    | ELam Text (h :# Typ) (h :# Expr)
    deriving Generic

data Typ h
    = TInt
    | TFunc (h :# Typ) (h :# Typ)
    deriving Generic

makeDerivings [''Eq, ''Ord, ''Show] [''Expr, ''Typ]
makeHTraversableAndBases ''Expr
makeHTraversableAndBases ''Typ
makeZipMatch ''Expr
makeZipMatch ''Typ

instance RNodes Expr
instance RNodes Typ
instance (c Expr, c Typ) => Recursively c Expr
instance c Typ => Recursively c Typ
instance RTraversable Expr
instance RTraversable Typ

data RExpr h
    = RVar (Var Text RExpr h)
    | RApp (App RExpr h)
    | RLam (TypedLam Text Typ RExpr h)
    deriving
    ( Generic, Generic1
    , HNodes, HFunctor, HFoldable, HTraversable, ZipMatch
    , RNodes, Recursively c, RTraversable
    )

makeHasHPlain [''Expr, ''Typ, ''RExpr]

verboseExpr :: Pure # Expr
verboseExpr = Pure (ELam "x" (Pure TInt) (Pure (EVar "x")))

exprA, exprB :: HPlain RExpr
exprA = RLamP "x" TIntP (RVarP "x")
exprB = RLamP "x" (TFuncP TIntP TIntP) (RVarP "x")

d :: DiffP # RExpr
d = diffP exprA exprB

formatDiff :: (Show a, Show b) => w -> a -> b -> String
formatDiff _ x y = "- " <> show x <> "\n+ " <> show y <> "\n"