{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ViewPatterns #-}

module HsInspect.Imports
  ( imports,
    Qualified,
  )
where

import Data.List (sort)
import Data.Maybe (fromJust)
import qualified GHC as GHC
import HscTypes (TargetId(..))
import HsInspect.Sexp
import HsInspect.Util
import HsInspect.Workarounds
import RdrName (GlobalRdrElt(..), ImpDeclSpec(..), ImportSpec(..),
                globalRdrEnvElts)

imports :: GHC.GhcMonad m => FilePath -> m [Qualified]
imports file = do
  (fromJust -> m, target) <- importsOnly mempty file

  GHC.removeTarget $ TargetModule m
  GHC.addTarget target

  -- performance can be very bad here if the user hasn't compiled recently. We
  -- could do the Index hack and only load things that have .hi files but that
  -- will result in very bizarre behaviour and we don't expect the user's code
  -- to be compilable at this point.
  _ <- GHC.load $ GHC.LoadUpTo m

  rdr_env <- minf_rdr_env' m
  pure . sort $ describe =<< globalRdrEnvElts rdr_env

describe :: GlobalRdrElt -> [Qualified]
describe GRE {gre_name, gre_imp} = describe' <$> gre_imp
  where
    describe' ImpSpec {is_decl = ImpDeclSpec {is_mod, is_as, is_qual}} =
      let ln =
            if is_qual
              then Nothing
              else Just $ showGhc gre_name
          lqn =
            if is_mod == is_as
              then Nothing
              else Just $ showGhc is_as ++ "." ++ showGhc gre_name
          fqn = showGhc is_mod ++ "." ++ showGhc gre_name
       in Qualified ln lqn fqn

-- 1. local name
-- 2. locally qualified name
-- 3. fully qualified name
data Qualified
  = Qualified
      (Maybe String)
      (Maybe String)
      String
  deriving (Eq, Ord, Show)

instance ToSexp Qualified where
  toSexp (Qualified ln lqn fqn) =
    alist
      [ ("local", toSexp ln),
        ("qual", toSexp lqn),
        ("full", toSexp fqn)
      ]