{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE PackageImports #-}

module HSE.All(
    module X,
    CppFlags(..), ParseFlags(..), defaultParseFlags,
    parseFlagsAddFixities, parseFlagsSetLanguage,
    parseModuleEx, ParseError(..), ParsedModuleResults(..),
    freeVars, vars, varss, pvars
    ) where

import Language.Haskell.Exts.Util hiding (freeVars, Vars(..))
import qualified Language.Haskell.Exts.Util as X
import HSE.Util as X
import HSE.Reduce as X
import HSE.Type as X
import HSE.Match as X
import HSE.Scope as X
import Util
import Data.Char
import Data.List.Extra
import Data.Maybe
import Timing
import Language.Preprocessor.Cpphs
import Data.Set (Set)
import qualified Data.Map as Map
import qualified Data.Set as Set
import System.IO.Extra
import Data.Functor
import Prelude

import GHC.Util
import qualified "ghc-lib-parser" Lexer
import qualified "ghc-lib-parser" HsSyn

vars :: FreeVars a => a -> [String]
freeVars :: FreeVars a => a -> Set String
varss, pvars :: AllVars a => a -> [String]
vars  = Set.toList . Set.map prettyPrint . X.freeVars
varss = Set.toList . Set.map prettyPrint . X.free . X.allVars
pvars = Set.toList . Set.map prettyPrint . X.bound . X.allVars
freeVars = Set.map prettyPrint . X.freeVars

-- | What C pre processor should be used.
data CppFlags
    = NoCpp -- ^ No pre processing is done.
    | CppSimple -- ^ Lines prefixed with @#@ are stripped.
    | Cpphs CpphsOptions -- ^ The @cpphs@ library is used.

-- | Created with 'defaultParseFlags', used by 'parseModuleEx'.
data ParseFlags = ParseFlags
    {cppFlags :: CppFlags -- ^ How the file is preprocessed (defaults to 'NoCpp').
    ,hseFlags :: ParseMode -- ^ How the file is parsed (defaults to all fixities in the @base@ package and most non-conflicting extensions).
    }

lensFixities :: [Fixity]
lensFixities = concat
    -- List as provided at https://github.com/ndmitchell/hlint/issues/416
    [infixr_ 4 ["%%@~","<%@~","%%~","<+~","<*~","<-~","<//~","<^~","<^^~","<**~"]
    ,infix_ 4 ["%%@=","<%@=","%%=","<+=","<*=","<-=","<//=","<^=","<^^=","<**="]
    ,infixr_ 2 ["<<~"]
    ,infixr_ 9 ["#."]
    ,infixl_ 8 [".#"]
    ,infixr_ 8 ["^!","^@!"]
    ,infixl_ 1 ["&","<&>","??"]
    ,infixl_ 8 ["^.","^@."]
    ,infixr_ 9 ["<.>","<.",".>"]
    ,infixr_ 4 ["%@~",".~","+~","*~","-~","//~","^~","^^~","**~","&&~","<>~","||~","%~"]
    ,infix_ 4 ["%@=",".=","+=","*=","-=","//=","^=","^^=","**=","&&=","<>=","||=","%="]
    ,infixr_ 2 ["<~"]
    ,infixr_ 2 ["`zoom`","`magnify`"]
    ,infixl_ 8 ["^..","^?","^?!","^@..","^@?","^@?!"]
    ,infixl_ 8 ["^#"]
    ,infixr_ 4 ["<#~","#~","#%~","<#%~","#%%~"]
    ,infix_ 4 ["<#=","#=","#%=","<#%=","#%%="]
    ,infixl_ 9 [":>"]
    ,infixr_ 4 ["</>~","<</>~","<.>~","<<.>~"]
    ,infix_ 4 ["</>=","<</>=","<.>=","<<.>="]
    ,infixr_ 4 [".|.~",".&.~","<.|.~","<.&.~"]
    ,infix_ 4 [".|.=",".&.=","<.|.=","<.&.="]
    ]

otherFixities :: [Fixity]
otherFixities = concat
    -- hspec
    [infix_ 1 ["`shouldBe`","`shouldSatisfy`","`shouldStartWith`","`shouldEndWith`","`shouldContain`","`shouldMatchList`"
              ,"`shouldReturn`","`shouldNotBe`","`shouldNotSatisfy`","`shouldNotContain`","`shouldNotReturn`","`shouldThrow`"]
    -- quickcheck
    ,infixr_ 0 ["==>"]
    ,infix_ 4 ["==="]
    -- esqueleto
    ,infix_ 4 ["==."]
    -- lattices
    ,infixr_ 5 ["\\/"] -- \/
    ,infixr_ 6 ["/\\"] -- /\
    ]

-- Fixites from the `base` package which are currently
-- missing from `haskell-src-exts`'s baseFixities.
-- see https://github.com/haskell-suite/haskell-src-exts/pull/400
baseNotYetInHSE :: [Fixity]
baseNotYetInHSE = concat
    [infixr_ 9 ["`Compose`"]
    ,infixr_ 6 ["<>"]
    ,infixr_ 5 ["<|"]
    ,infixl_ 4 ["<$!>","<$","$>"]
    ,infix_ 4 [":~:", ":~~:"]
    ]

customFixities :: [Fixity]
customFixities =
    infixl_ 1 ["`on`"]
        -- see https://github.com/ndmitchell/hlint/issues/425
        -- otherwise GTK apps using `on` at a different fixity have spurious warnings

-- | Default value for 'ParseFlags'.
defaultParseFlags :: ParseFlags
defaultParseFlags = ParseFlags NoCpp defaultParseMode
    {fixities = Just $ customFixities ++ baseFixities ++ baseNotYetInHSE ++ lensFixities ++ otherFixities
    ,ignoreLinePragmas = False
    ,ignoreFunctionArity = True
    ,extensions = defaultExtensions}

parseFlagsNoLocations :: ParseFlags -> ParseFlags
parseFlagsNoLocations x = x{cppFlags = case cppFlags x of Cpphs y -> Cpphs $ f y; y -> y}
    where f x = x{boolopts = (boolopts x){locations=False}}

-- | Given some fixities, add them to the existing fixities in 'ParseFlags'.
parseFlagsAddFixities :: [Fixity] -> ParseFlags -> ParseFlags
parseFlagsAddFixities fx x = x{hseFlags=hse{fixities = Just $ fx ++ fromMaybe [] (fixities hse)}}
    where hse = hseFlags x

parseFlagsSetLanguage :: (Language, [Extension]) -> ParseFlags -> ParseFlags
parseFlagsSetLanguage (l, es) x = x{hseFlags=(hseFlags x){baseLanguage = l, extensions = es}}


runCpp :: CppFlags -> FilePath -> String -> IO String
runCpp NoCpp _ x = return x
runCpp CppSimple _ x = return $ unlines [if "#" `isPrefixOf` trimStart x then "" else x | x <- lines x]
runCpp (Cpphs o) file x = dropLine <$> runCpphs o file x
    where
        -- LINE pragmas always inserted when locations=True
        dropLine (line1 -> (a,b)) | "{-# LINE " `isPrefixOf` a = b
        dropLine x = x

---------------------------------------------------------------------
-- PARSING

-- | A parse error.
data ParseError = ParseError
    {parseErrorLocation :: SrcLoc -- ^ Location of the error.
    ,parseErrorMessage :: String  -- ^ Message about the cause of the error.
    ,parseErrorContents :: String -- ^ Snippet of several lines (typically 5) including a @>@ character pointing at the faulty line.
    ,parseErrorSDocs :: [SDoc]    -- ^ Parse error messages as reported by ghc-lib.
    }

-- | Combined 'hs-src-ext' and 'ghc-lib-parser' parse trees.
data ParsedModuleResults = ParsedModuleResults {
    pm_hsext  :: (Module SrcSpanInfo, [Comment]) -- hs-src-ext result.
  , pm_ghclib :: Maybe (Located (HsSyn.HsModule HsSyn.GhcPs)) -- ghc-lib-parser result.
}

-- | Utility called from 'parseModuleEx' and 'failOpModuleEx'.
mkMode :: ParseFlags -> String -> ParseMode
mkMode flags file = (hseFlags flags){parseFilename = file,fixities = Nothing }

-- | Error handler called on HSE parse failure.
failOpParseModuleEx :: String
                   -> ParseFlags
                   -> FilePath
                   -> String
                   -> SrcLoc
                   -> String
                   -> Maybe Lexer.PState
                   -> IO (Either ParseError ParsedModuleResults)
failOpParseModuleEx ppstr flags file str sl msg maybePFailed = do
    flags <- return $ parseFlagsNoLocations flags
    ppstr2 <- runCpp (cppFlags flags) file str
    let pe = case parseFileContentsWithMode (mkMode flags file) ppstr2 of
               ParseFailed sl2 _ -> context (srcLine sl2) ppstr2
               _ -> context (srcLine sl) ppstr
    return $ Left $ ParseError sl msg pe
                            (case maybePFailed of
                              Just ps  ->
                                pprErrMsgBagWithLoc $ snd $ getMessages ps dynFlags
                              Nothing -> []
                            )

-- | Parse a Haskell module. Applies the C pre processor, and uses best-guess fixity resolution if there are ambiguities.
-- The filename @-@ is treated as @stdin@. Requires some flags (often 'defaultParseFlags'), the filename, and optionally the contents of that file.
-- This version uses both hs-src-exts AND ghc-lib. It's considered to be an unrecoverable error if one
-- parsing method succeeds whilst the other fails.
parseModuleEx :: ParseFlags -> FilePath -> Maybe String -> IO (Either ParseError ParsedModuleResults)
parseModuleEx flags file str = timedIO "Parse" file $ do
        str <- case str of
            Just x -> return x
            Nothing | file == "-" -> getContentsUTF8
                    | otherwise -> readFileUTF8' file
        str <- return $ fromMaybe str $ stripPrefix "\65279" str -- remove the BOM if it exists, see #130
        ppstr <- runCpp (cppFlags flags) file str
        case (parseFileContentsWithComments (mkMode flags file) ppstr, parseFileGhcLib file ppstr) of
            (ParseOk (x, cs), ghc) ->
                return $ Right (ParsedModuleResults (applyFixity fixity x, cs) $ fromPOk ghc)
            (ParseFailed sl msg, pfailed) ->
                failOpParseModuleEx ppstr flags file str sl msg $ fromPFailed pfailed
    where
        fromPFailed (PFailed x) = Just x
        fromPFailed _ = Nothing

        fromPOk (POk _ x) = Just x
        fromPOk _ = Nothing

        fixity = fromMaybe [] $ fixities $ hseFlags flags

-- | Given a line number, and some source code, put bird ticks around the appropriate bit.
context :: Int -> String -> String
context lineNo src =
    unlines $ dropWhileEnd (all isSpace) $ dropWhile (all isSpace) $
    zipWith (++) ticks $ take 5 $ drop (lineNo - 3) $ lines src ++ ["","","","",""]
    where ticks = ["  ","  ","> ","  ","  "]


---------------------------------------------------------------------
-- FIXITIES

-- resolve fixities later, so we don't ever get uncatchable ambiguity errors
-- if there are fixity errors, try the cheapFixities (which never fails)
applyFixity :: [Fixity] -> Module_ -> Module_
applyFixity base modu = descendBi f modu
    where
        f x = fromMaybe (cheapFixities fixs x) $ applyFixities fixs x :: Decl_
        fixs = concatMap getFixity (moduleDecls modu) ++ base


-- Apply fixities, but ignoring any ambiguous fixity errors and skipping qualified names,
-- local infix declarations etc. Only use as a backup, if HSE gives an error.
--
-- Inspired by the code at:
-- http://hackage.haskell.org/trac/haskell-prime/attachment/wiki/FixityResolution/resolve.hs
cheapFixities :: [Fixity] -> Decl_ -> Decl_
cheapFixities fixs = descendBi (transform f)
    where
        ask = askFixity fixs

        f o@(InfixApp s1 (InfixApp s2 x op1 y) op2 z)
                | p1 == p2 && (a1 /= a2 || isAssocNone a1) = o -- Ambiguous infix expression!
                | p1 > p2 || p1 == p2 && (isAssocLeft a1 || isAssocNone a2) = o
                | otherwise = InfixApp s1 x op1 (f $ InfixApp s1 y op2 z)
            where
                (a1,p1) = ask op1
                (a2,p2) = ask op2
        f x = x


askFixity :: [Fixity] -> QOp S -> (Assoc (), Int)
askFixity xs = \k -> Map.findWithDefault (AssocLeft (), 9) (fromNamed k) mp
    where
        mp = Map.fromList [(s,(a,p)) | Fixity a p x <- xs, let s = fromNamed $ fmap (const an) x, s /= ""]