module Language.Haskell.GhcMod.Browse (
    browseModule
  , browse
  , browseAll)
  where

import Control.Applicative ((<$>))
import Control.Monad (void)
import Data.Char (isAlpha)
import Data.List (sort)
import Data.Maybe (catMaybes)
import FastString (mkFastString)
import GHC (Ghc, GhcException(CmdLineError), ModuleInfo, Name, TyThing, DynFlags, Type, TyCon, Module)
import qualified GHC as G
import Language.Haskell.GhcMod.Doc (showPage, showOneLine, styleUnqualified)
import Language.Haskell.GhcMod.GHCApi
import Language.Haskell.GhcMod.Gap
import Language.Haskell.GhcMod.Types
import Name (getOccString)
import Outputable (ppr, Outputable)
import Panic (throwGhcException)
import TyCon (isAlgTyCon)
import Type (dropForAlls, splitFunTy_maybe, mkFunTy, isPredTy)

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

-- | Getting functions, classes, etc from a module.
--   If 'detailed' is 'True', their types are also obtained.
--   If 'operators' is 'True', operators are also returned.
browseModule :: Options
             -> Cradle
             -> ModuleString -- ^ A module name. (e.g. \"Data.List\")
             -> IO String
browseModule opt cradle mdlName = convert opt . sort <$> withGHCDummyFile (browse opt cradle mdlName)

-- | Getting functions, classes, etc from a module.
--   If 'detailed' is 'True', their types are also obtained.
--   If 'operators' is 'True', operators are also returned.
browse :: Options
       -> Cradle
       -> ModuleString -- ^ A module name. (e.g. \"Data.List\")
       -> Ghc [String]
browse opt cradle mdlName = do
    void $ initializeFlagsWithCradle opt cradle [] False
    getModule >>= G.getModuleInfo >>= listExports
  where
    getModule = G.findModule mdlname mpkgid `G.gcatch` fallback
    mdlname = G.mkModuleName mdlName
    mpkgid = mkFastString <$> packageId opt
    listExports Nothing       = return []
    listExports (Just mdinfo) = processExports opt mdinfo
    -- findModule works only for package modules, moreover,
    -- you cannot load a package module. On the other hand,
    -- to browse a local module you need to load it first.
    -- If CmdLineError is signalled, we assume the user
    -- tried browsing a local module.
    fallback (CmdLineError _) = loadAndFind
    fallback e                = throwGhcException e
    loadAndFind = do
      setTargetFiles [mdlName]
      void $ G.load G.LoadAllTargets
      G.findModule mdlname Nothing

processExports :: Options -> ModuleInfo -> Ghc [String]
processExports opt minfo = mapM (showExport opt minfo) $ removeOps $ G.modInfoExports minfo
  where
    removeOps
      | operators opt = id
      | otherwise = filter (isAlpha . head . getOccString)

showExport :: Options -> ModuleInfo -> Name -> Ghc String
showExport opt minfo e = do
  mtype' <- mtype
  return $ concat $ catMaybes [mqualified, Just $ formatOp $ getOccString e, mtype']
  where
    mqualified = (G.moduleNameString (G.moduleName $ G.nameModule e) ++ ".") `justIf` qualified opt
    mtype
      | detailed opt = do
        tyInfo <- G.modInfoLookupName minfo e
        -- If nothing found, load dependent module and lookup global
        tyResult <- maybe (inOtherModule e) (return . Just) tyInfo
        dflag <- G.getSessionDynFlags
        return $ do
          typeName <- tyResult >>= showThing dflag
          (" :: " ++ typeName) `justIf` detailed opt
      | otherwise = return Nothing
    formatOp nm@(n:_)
      | isAlpha n = nm
      | otherwise = "(" ++ nm ++ ")"
    formatOp "" = error "formatOp"
    inOtherModule :: Name -> Ghc (Maybe TyThing)
    inOtherModule nm = G.getModuleInfo (G.nameModule nm) >> G.lookupGlobalName nm
    justIf :: a -> Bool -> Maybe a
    justIf x True = Just x
    justIf _ False = Nothing

showThing :: DynFlags -> TyThing -> Maybe String
showThing dflag tything = showThing' dflag (fromTyThing tything)

showThing' :: DynFlags -> GapThing -> Maybe String
showThing' dflag (GtA a) = Just $ formatType dflag a
showThing' _     (GtT t) = unwords . toList <$> tyType t
  where
    toList t' = t' : getOccString t : map getOccString (G.tyConTyVars t)
showThing' _     _       = Nothing

formatType :: DynFlags -> Type -> String
formatType dflag a = showOutputable dflag (removeForAlls a)

tyType :: TyCon -> Maybe String
tyType typ
    | isAlgTyCon typ
      && not (G.isNewTyCon typ)
      && not (G.isClassTyCon typ) = Just "data"
    | G.isNewTyCon typ            = Just "newtype"
    | G.isClassTyCon typ          = Just "class"
    | G.isSynTyCon typ            = Just "type"
    | otherwise                   = Nothing

removeForAlls :: Type -> Type
removeForAlls ty = removeForAlls' ty' tty'
  where
    ty'  = dropForAlls ty
    tty' = splitFunTy_maybe ty'

removeForAlls' :: Type -> Maybe (Type, Type) -> Type
removeForAlls' ty Nothing = ty
removeForAlls' ty (Just (pre, ftype))
    | isPredTy pre        = mkFunTy pre (dropForAlls ftype)
    | otherwise           = ty

showOutputable :: Outputable a => DynFlags -> a -> String
showOutputable dflag = unwords . lines . showPage dflag styleUnqualified . ppr

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

-- | Browsing all functions in all system/user modules.
browseAll :: DynFlags -> Ghc [(String,String)]
browseAll dflag = do
    ms <- G.packageDbModules True
    is <- mapM G.getModuleInfo ms
    return $ concatMap (toNameModule dflag) (zip ms is)

toNameModule :: DynFlags -> (Module, Maybe ModuleInfo) -> [(String,String)]
toNameModule _     (_,Nothing)  = []
toNameModule dflag (m,Just inf) = map (\name -> (toStr name, mdl)) names
  where
    mdl = G.moduleNameString (G.moduleName m)
    names = G.modInfoExports inf
    toStr = showOneLine dflag styleUnqualified . ppr