{-# LANGUAGE CPP, Rank2Types, TupleSections #-}

module Info (infoExpr, typeExpr) where

import Cabal
import Control.Applicative
import CoreUtils
import Data.Function
import Data.Generics
import Data.List
import Data.Maybe
import Data.Ord as O
import Desugar
import GHC
import GHC.SYB.Utils
import GHCApi
import qualified Gap
import HscTypes
import NameSet
import Outputable
import PprTyThing
import System.Time
import TcRnTypes
import Types

----------------------------------------------------------------

type Expression = String
type ModuleString = String

----------------------------------------------------------------

infoExpr :: Options -> ModuleString -> Expression -> FilePath -> IO String
infoExpr opt modstr expr file = (++ "\n") <$> info opt file modstr expr

info :: Options -> FilePath -> ModuleString -> FilePath -> IO String
info opt fileName modstr expr = inModuleContext opt fileName modstr exprToInfo
  where
    exprToInfo = infoThing expr

----------------------------------------------------------------

typeExpr :: Options -> ModuleString -> Int -> Int -> FilePath -> IO String
typeExpr opt modstr lineNo colNo file = Info.typeOf opt file modstr lineNo colNo

typeOf :: Options -> FilePath -> ModuleString -> Int -> Int -> IO String
typeOf opt fileName modstr lineNo colNo = inModuleContext opt fileName modstr exprToType
  where
    exprToType = do
      modSum <- getModSummary $ mkModuleName modstr
      p <- parseModule modSum
      tcm <- typecheckModule p
      let es = findExpr tcm lineNo colNo
      ts <- catMaybes <$> mapM (getType tcm) es
      let sss = map toTup $ sortBy (cmp `on` fst) ts
      return $ convert opt sss

    toTup :: (SrcSpan, Type) -> ((Int,Int,Int,Int),String)
    toTup (spn, typ) = (fourInts spn, pretty typ)

    fourInts :: SrcSpan -> (Int,Int,Int,Int)
    fourInts = fromMaybe (0,0,0,0) . Gap.getSrcSpan

    cmp a b
      | a `isSubspanOf` b = O.LT
      | b `isSubspanOf` a = O.GT
      | otherwise = O.EQ

findExpr :: TypecheckedModule -> Int -> Int -> [LHsExpr Id]
findExpr tcm line col =
  let src = tm_typechecked_source tcm
  in listifyStaged TypeChecker f src
  where
    f :: LHsExpr Id -> Bool
    f (L spn _) = isGoodSrcSpan spn && spn `spans` (line, col)

listifyStaged :: Typeable r => Stage -> (r -> Bool) -> GenericQ [r]
listifyStaged s p = everythingStaged s (++) [] ([] `mkQ` (\x -> [x | p x]))

getType :: GhcMonad m => TypecheckedModule -> LHsExpr Id -> m (Maybe (SrcSpan, Type))
getType tcm e = do
  hs_env <- getSession
  (_, mbe) <- Gap.liftIO $ deSugarExpr hs_env modu rn_env ty_env e
  return $ (getLoc e, ) <$> CoreUtils.exprType <$> mbe
  where
    modu = ms_mod $ pm_mod_summary $ tm_parsed_module tcm
    rn_env = tcg_rdr_env $ fst $ tm_internals_ tcm
    ty_env = tcg_type_env $ fst $ tm_internals_ tcm

pretty :: Type -> String
pretty = showSDocForUser neverQualify . pprTypeForUser False

----------------------------------------------------------------
-- from ghc/InteractiveUI.hs

infoThing :: String -> Ghc String
infoThing str = do
    names <- parseName str
    mb_stuffs <- mapM getInfo names
    let filtered = filterOutChildren (\(t,_f,_i) -> t) (catMaybes mb_stuffs)
    unqual <- getPrintUnqual
    return $ showSDocForUser unqual $ vcat (intersperse (text "") $ map (pprInfo False) filtered)

filterOutChildren :: (a -> TyThing) -> [a] -> [a]
filterOutChildren get_thing xs
  = [x | x <- xs, not (getName (get_thing x) `elemNameSet` implicits)]
  where
      implicits = mkNameSet [getName t | x <- xs, t <- implicitTyThings (get_thing x)]

pprInfo :: PrintExplicitForalls -> (TyThing, GHC.Fixity, [Instance]) -> SDoc
pprInfo pefas (thing, fixity, insts)
    = pprTyThingInContextLoc pefas thing
   $$ show_fixity fixity
   $$ vcat (map pprInstance insts)
  where
    show_fixity fx
        | fx == defaultFixity = Outputable.empty
        | otherwise           = ppr fx <+> ppr (getName thing)

----------------------------------------------------------------

inModuleContext :: Options -> FilePath -> ModuleString -> Ghc String -> IO String
inModuleContext opt fileName modstr action = withGHC valid
  where
    valid = do
        (file,_) <- initializeGHC opt fileName ["-w"] False
        setTargetFile file
        load LoadAllTargets
        mif setContextFromTarget action invalid
    invalid = do
        initializeGHC opt fileName ["-w"] False
        setTargetBuffer
        load LoadAllTargets
        mif setContextFromTarget action (return errorMessage)
    setTargetBuffer = do
        modgraph <- depanal [mkModuleName modstr] True
        let imports = concatMap (map (showSDoc . ppr . unLoc)) $
                      map ms_imps modgraph ++ map ms_srcimps modgraph
            moddef = "module " ++ sanitize modstr ++ " where"
            header = moddef : imports
        importsBuf <- Gap.toStringBuffer header
        clkTime <- Gap.liftIO getClockTime
        setTargets [Target (TargetModule $ mkModuleName modstr) True (Just (importsBuf, clkTime))]
    mif m t e = m >>= \ok -> if ok then t else e
    sanitize = fromMaybe "SomeModule" . listToMaybe . words
    errorMessage = "Couldn't determine type"

setContextFromTarget :: Ghc Bool
setContextFromTarget = depanal [] False >>= Gap.setCtx