{-# LANGUAGE PatternGuards, ScopedTypeVariables #-}
module Main where

import Prelude hiding ( mod, id, mapM )
import GHC
--import Packages
import HscTypes         ( isBootSummary )
import Digraph          ( flattenSCCs )
import DriverPhases     ( isHaskellSrcFilename )
import HscTypes         ( msHsFilePath )
import Name             ( getOccString )
--import ErrUtils         ( printBagOfErrors )
import Panic            ( panic )
import DynFlags         ( defaultFatalMessager, defaultFlushOut )
import Bag
import Exception
import FastString
import MonadUtils       ( liftIO )
import SrcLoc

import Distribution.Simple.GHC ( componentGhcOptions )
import Distribution.Simple.Configure ( getPersistBuildConfig )
import Distribution.Simple.Compiler ( compilerVersion )
import Distribution.Simple.Program.GHC ( renderGhcOptions )
import Distribution.PackageDescription ( library, libBuildInfo )
import Distribution.Simple.LocalBuildInfo
import qualified Distribution.Verbosity as V

import Control.Monad hiding (mapM)
import System.Environment
import System.Console.GetOpt
import System.Exit
import System.IO
import Data.List as List hiding ( group )
import Data.Traversable (mapM)
import Data.Map ( Map )
import qualified Data.Map as M

--import UniqFM
--import Debug.Trace

-- search for definitions of things 
-- we do this by parsing the source and grabbing top-level definitions

-- We generate both CTAGS and ETAGS format tags files
-- The former is for use in most sensible editors, while EMACS uses ETAGS

----------------------------------
---- CENTRAL DATA TYPES ----------

type FileName = String
type ThingName = String -- name of a defined entity in a Haskell program

-- A definition we have found (we know its containing module, name, and location)
data FoundThing = FoundThing ModuleName ThingName RealSrcLoc

-- Data we have obtained from a file (list of things we found)
data FileData = FileData FileName [FoundThing] (Map Int String)
--- invariant (not checked): every found thing has a source location in that file?


------------------------------
-------- MAIN PROGRAM --------

main :: IO ()
main = do
  progName <- getProgName
  let usageString =
        "Usage: " ++ progName ++ " [OPTION...] [-- GHC OPTION... --] [files...]"
  args <- getArgs
  let (ghcArgs', ourArgs, unbalanced) = splitArgs args
  let (flags, filenames, errs) = getOpt Permute options ourArgs
  let (hsfiles, otherfiles) = List.partition isHaskellSrcFilename filenames

  let ghc_topdir = case [ d | FlagTopDir d <- flags ] of
                          [] -> ""
                          (x:_) -> x
  mapM_ (\n -> putStr $ "Warning: ignoring non-Haskellish file " ++ n ++ "\n")
        otherfiles
  if unbalanced || errs /= [] || elem FlagHelp flags || hsfiles == []
   then do
     putStr $ unlines errs
     putStr $ usageInfo usageString options
     exitWith (ExitFailure 1)
   else return ()

  ghcArgs <- case [ d | FlagUseCabalConfig d <- flags ] of
               [distPref] -> do
                  cabalOpts <- flagsFromCabal distPref
                  return (cabalOpts ++ ghcArgs')
               [] ->
                  return ghcArgs'
               _ -> error "Too many --use-cabal-config flags"
  print ghcArgs

  let modes = getMode flags
  let openFileMode = if elem FlagAppend flags
                     then AppendMode
                     else WriteMode
  ctags_hdl <-  if CTags `elem` modes
                     then Just `liftM` openFile "tags" openFileMode
                     else return Nothing
  etags_hdl <- if ETags `elem` modes
                     then Just `liftM` openFile "TAGS" openFileMode
                     else return Nothing

  GHC.defaultErrorHandler defaultFatalMessager defaultFlushOut $
    runGhc (Just ghc_topdir) $ do
      --liftIO $ print "starting up session"
      dflags <- getSessionDynFlags
      (pflags, unrec, warns) <- parseDynamicFlags dflags{ verbosity=1 }
                                          (map noLoc ghcArgs)
      unless (null unrec) $
        liftIO $ putStrLn $ "Unrecognised options:\n" ++ show (map unLoc unrec)
      liftIO $ mapM_ putStrLn (map unLoc warns)
      let dflags2 = pflags { hscTarget = HscNothing } -- don't generate anything
      -- liftIO $ print ("pkgDB", case (pkgDatabase dflags2) of Nothing -> 0
      --                                                        Just m -> sizeUFM m)
      _ <- setSessionDynFlags dflags2
      --liftIO $ print (length pkgs)

      GHC.defaultCleanupHandler dflags2 $ do

        targetsAtOneGo hsfiles (ctags_hdl,etags_hdl)
        mapM_ (mapM (liftIO . hClose)) [ctags_hdl, etags_hdl]

----------------------------------------------
----------  ARGUMENT PROCESSING --------------

data Flag
   = FlagETags
   | FlagCTags
   | FlagBoth
   | FlagAppend
   | FlagHelp
   | FlagTopDir FilePath
   | FlagUseCabalConfig FilePath
   | FlagFilesFromCabal
  deriving (Ord, Eq, Show)
  -- ^Represents options passed to the program

data Mode = ETags | CTags deriving Eq

getMode :: [Flag] -> [Mode]
getMode fs = go (concatMap modeLike fs)
 where go []     = [ETags,CTags]
       go [x]    = [x]
       go more   = nub more

       modeLike FlagETags = [ETags]
       modeLike FlagCTags = [CTags]
       modeLike FlagBoth  = [ETags,CTags]
       modeLike _         = []

splitArgs :: [String] -> ([String], [String], Bool)
-- ^Pull out arguments between -- for GHC
splitArgs args0 = split [] [] False args0
    where split ghc' tags' unbal ("--" : args) = split tags' ghc' (not unbal) args
          split ghc' tags' unbal (arg : args) = split ghc' (arg:tags') unbal args
          split ghc' tags' unbal [] = (reverse ghc', reverse tags', unbal)

options :: [OptDescr Flag]
-- supports getopt
options = [ Option "" ["topdir"]
            (ReqArg FlagTopDir "DIR") "root of GHC installation (optional)"
          , Option "c" ["ctags"]
            (NoArg FlagCTags) "generate CTAGS file (ctags)"
          , Option "e" ["etags"]
            (NoArg FlagETags) "generate ETAGS file (etags)"
          , Option "b" ["both"]
            (NoArg FlagBoth) ("generate both CTAGS and ETAGS")
          , Option "a" ["append"]
            (NoArg FlagAppend) ("append to existing CTAGS and/or ETAGS file(s)")
          , Option "" ["use-cabal-config"]
            (ReqArg FlagUseCabalConfig "DIR") "use local cabal configuration from dist dir"
          , Option "" ["files-from-cabal"]
            (NoArg FlagFilesFromCabal) "use files from cabal"
          , Option "h" ["help"] (NoArg FlagHelp) "This help"
          ]

flagsFromCabal :: FilePath -> IO [String]
flagsFromCabal distPref = do
  lbi <- getPersistBuildConfig distPref
  let pd = localPkgDescr lbi
      findLibraryConfig []                         = Nothing
      findLibraryConfig ((CLibName, clbi, _) :  _) = Just clbi
      findLibraryConfig (_                   : xs) = findLibraryConfig xs
      mLibraryConfig = findLibraryConfig (componentsConfigs lbi)
  case (library pd, mLibraryConfig) of
    (Just lib, Just clbi) ->
      let bi = libBuildInfo lib
          odir = buildDir lbi
          opts = componentGhcOptions V.normal lbi bi clbi odir
          version = compilerVersion (compiler lbi)
      in return $ renderGhcOptions version opts
    _ -> error "no library"

----------------------------------------------------------------
--- LOADING HASKELL SOURCE
--- (these bits actually run the compiler and produce abstract syntax)

safeLoad :: LoadHowMuch -> Ghc SuccessFlag
-- like GHC.load, but does not stop process on exception
safeLoad mode = do
  _dflags <- getSessionDynFlags
  ghandle (\(e :: SomeException) -> liftIO (print e) >> return Failed ) $
    handleSourceError (\e -> printException e >> return Failed) $
      load mode


targetsAtOneGo :: [FileName] -> (Maybe Handle, Maybe Handle) -> Ghc ()
-- load a list of targets
targetsAtOneGo hsfiles handles = do
  targets <- mapM (\f -> guessTarget f Nothing) hsfiles
  setTargets targets
  modgraph <- depanal [] False
  let mods = flattenSCCs $ topSortModuleGraph False modgraph Nothing
  graphData mods handles

fileTarget :: FileName -> Target
fileTarget filename = Target (TargetFile filename Nothing) True Nothing

---------------------------------------------------------------
----- CRAWLING ABSTRACT SYNTAX TO SNAFFLE THE DEFINITIONS -----

graphData :: ModuleGraph -> (Maybe Handle, Maybe Handle) -> Ghc ()
graphData graph handles = do
    mapM_ foundthings graph
    where foundthings ms =
              let filename = msHsFilePath ms
                  modname = moduleName $ ms_mod ms
              in handleSourceError (\e -> do
                                       printException e
                                       liftIO $ exitWith (ExitFailure 1)) $
                  do liftIO $ putStrLn ("loading " ++ filename)
                     mod <- loadModule =<< typecheckModule =<< parseModule ms
                     case mod of
                       _ | isBootSummary ms -> return ()
                       _ | Just s <- renamedSource mod ->
                         liftIO (writeTagsData handles =<< fileData filename modname s)
                       _otherwise ->
                         liftIO $ exitWith (ExitFailure 1)

fileData :: FileName -> ModuleName -> RenamedSource -> IO FileData
fileData filename modname (group, _imports, _lie, _doc) = do
    -- lie is related to type checking and so is irrelevant
    -- imports contains import declarations and no definitions
    -- doc and haddock seem haddock-related; let's hope to ignore them
    ls <- lines `fmap` readFile filename
    let line_map = M.fromAscList $ zip [1..] ls
    line_map' <- evaluate line_map
    return $ FileData filename (boundValues modname group) line_map'

boundValues :: ModuleName -> HsGroup Name -> [FoundThing]
-- ^Finds all the top-level definitions in a module
boundValues mod group =
  let vals = case hs_valds group of
               ValBindsOut nest _sigs ->
                   [ x | (_rec, binds) <- nest
                       , bind <- bagToList binds
                       , x <- boundThings mod bind ]
               _other -> error "boundValues"
      tys = [ n | ns <- map hsLTyClDeclBinders (tyClGroupConcat (hs_tyclds group))
                , n <- map found ns ]
      fors = concat $ map forBound (hs_fords group)
             where forBound lford = case unLoc lford of
                                      ForeignImport n _ _ _ -> [found n]
                                      ForeignExport { } -> []
  in vals ++ tys ++ fors
  where found = foundOfLName mod

startOfLocated :: Located a -> RealSrcLoc
startOfLocated lHs = case getLoc lHs of
                     RealSrcSpan l -> realSrcSpanStart l
                     UnhelpfulSpan _ -> panic "startOfLocated UnhelpfulSpan"

foundOfLName :: ModuleName -> Located Name -> FoundThing
foundOfLName mod id = FoundThing mod (getOccString $ unLoc id) (startOfLocated id)

boundThings :: ModuleName -> LHsBind Name -> [FoundThing]
boundThings modname lbinding =
  case unLoc lbinding of
    FunBind { fun_id = id } -> [thing id]
    PatBind { pat_lhs = lhs } -> patThings lhs []
    VarBind { var_id = id } -> [FoundThing modname (getOccString id) (startOfLocated lbinding)]
    AbsBinds { } -> [] -- nothing interesting in a type abstraction
  where thing = foundOfLName modname
        patThings lpat tl =
          let loc = startOfLocated lpat
              lid id = FoundThing modname (getOccString id) loc
          in case unLoc lpat of
               WildPat _ -> tl
               VarPat name -> lid name : tl
               LazyPat p -> patThings p tl
               AsPat id p -> patThings p (thing id : tl)
               ParPat p -> patThings p tl
               BangPat p -> patThings p tl
               ListPat ps _ _ -> foldr patThings tl ps
               TuplePat ps _ _ -> foldr patThings tl ps
               PArrPat ps _ -> foldr patThings tl ps
               ConPatIn _ conargs -> conArgs conargs tl
               ConPatOut _ _ _ _ conargs _ -> conArgs conargs tl
               LitPat _ -> tl
               NPat _ _ _ -> tl -- form of literal pattern?
               NPlusKPat id _ _ _ -> thing id : tl
               SigPatIn p _ -> patThings p tl
               SigPatOut p _ -> patThings p tl
               _ -> error "boundThings"
        conArgs (PrefixCon ps) tl = foldr patThings tl ps
        conArgs (RecCon (HsRecFields { rec_flds = flds })) tl
             = foldr (\f tl' -> patThings (hsRecFieldArg f) tl') tl flds
        conArgs (InfixCon p1 p2) tl = patThings p1 $ patThings p2 tl


-- stuff for dealing with ctags output format

writeTagsData :: (Maybe Handle, Maybe Handle) -> FileData -> IO ()
writeTagsData (mb_ctags_hdl, mb_etags_hdl) fd = do
  maybe (return ()) (\hdl -> writectagsfile hdl fd) mb_ctags_hdl
  maybe (return ()) (\hdl -> writeetagsfile hdl fd) mb_etags_hdl

writectagsfile :: Handle -> FileData -> IO ()
writectagsfile ctagsfile filedata = do
        let things = getfoundthings filedata
        mapM_ (\x -> hPutStrLn ctagsfile $ dumpthing False x) things
        mapM_ (\x -> hPutStrLn ctagsfile $ dumpthing True  x) things

getfoundthings :: FileData -> [FoundThing]
getfoundthings (FileData _filename things _src_lines) = things

dumpthing :: Bool -> FoundThing -> String
dumpthing showmod (FoundThing modname name loc) =
        fullname ++ "\t" ++ filename ++ "\t" ++ (show line)
    where line = srcLocLine loc
          filename = unpackFS $ srcLocFile loc
          fullname = if showmod then moduleNameString modname ++ "." ++ name
                     else name

-- stuff for dealing with etags output format

writeetagsfile :: Handle -> FileData -> IO ()
writeetagsfile etagsfile = hPutStr etagsfile . e_dumpfiledata

e_dumpfiledata :: FileData -> String
e_dumpfiledata (FileData filename things line_map) =
        "\x0c\n" ++ filename ++ "," ++ (show thingslength) ++ "\n" ++ thingsdump
        where
                thingsdump = concat $ map (e_dumpthing line_map) things
                thingslength = length thingsdump

e_dumpthing :: Map Int String -> FoundThing -> String
e_dumpthing src_lines (FoundThing modname name loc) =
    tagline name ++ tagline (moduleNameString modname ++ "." ++ name)
    where tagline n = src_code ++ "\x7f"
                      ++ n ++ "\x01"
                      ++ (show line) ++ "," ++ (show $ column) ++ "\n"
          line = srcLocLine loc
          column = srcLocCol loc
          src_code = case M.lookup line src_lines of
                       Just l -> take (column + length name) l
                       Nothing -> --trace (show ("not found: ", moduleNameString modname, name, line, column))
                                  name
