module Compiler where

import qualified Ast as A
import Control.Monad.State
import Env
import Error
import System.Environment (getEnv, getEnvironment)
import Text.Parsec (ParseError, SourcePos)
import Text.Read (Lexeme (String))

toFuncType :: [A.FuncParam] -> Maybe A.Type -> A.Type
toFuncType params rtyp =
  A.FuncType (map (\(_, t, _) -> t) params) rtyp

type CompState = (Env, [Error])

type CompResult = Either [Error] ()

startState :: CompState
startState = (emptyEnv, [])

compile :: [A.Expr] -> State CompState CompResult
compile (x : xs) = do
  case x of
    (A.Module name pos) -> return $ Right ()
    (A.BinOp _ a b) -> compile [a, b]
    (A.Func ident params ret body priv pos) -> do
      -- current env
      (ev, errs) <- get
      -- with function and parameters
      (nev, nerrs) <-
        return $ case addSymUniq ev (ident, toFuncType params ret, pos) of
          Left e -> (ev, e : errs)
          Right fev ->
            foldl
              ( \(ev, errs) (id, typ, pos) -> case addSymUniq ev (id, typ, pos) of
                  Right ev -> (ev, errs)
                  Left nerr -> (ev, nerr : errs)
              )
              (addEnv fev, errs)
              params
      put (nev, nerrs)
      r <- compile body
      (_, errs) <- get
      put (ev, errs)
      return r
    (A.Call ident args pos) -> do
      id <- compile [ident]
      return $ Right ()
    (A.Return value pos) -> case value of
      Nothing -> return $ Right ()
      Just v -> compile [v]
    (A.Var ident pos) -> do
      (ev, errs) <- get
      if existsSym ev ident
        then return $ Right ()
        else do
          put (ev, Error ("undefined variable \"" ++ ident ++ "\"") pos : errs)
          return $ Right ()
    _ -> compile []
  compile xs
compile [] = do
  (_, errs) <- get
  case errs of
    [] -> return $ Right ()
    _ -> return $ Left errs