module Elaborator where

import Data.List (elemIndex)
import Expr (Expr)
import qualified Expr as E
import IR (IRExpr)
import qualified IR as I

type Binders = [Text]

elaborate :: IRExpr -> State Binders Expr
elaborate (I.Var n) = do
    binders <- get
    pure $ E.Var n . fromIntegral <$> elemIndex n binders ?: E.Free n
elaborate (I.Level level) = pure $ E.Level level
elaborate (I.App m n) = E.App <$> elaborate m <*> elaborate n
elaborate (I.Abs x t b) = do
    t' <- elaborate t
    modify (x :)
    E.Abs x t' <$> elaborate b
elaborate (I.Pi x t b) = do
    t' <- elaborate t
    modify (x :)
    E.Pi x t' <$> elaborate b
elaborate (I.Let name Nothing val body) = E.Let name Nothing <$> elaborate val <*> elaborate body
elaborate (I.Let name (Just t) val body) = E.Let name . Just <$> elaborate t <*> elaborate val <*> elaborate body