{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE PatternGuards #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE RankNTypes #-}
-- | Some helpers for parsing data out of a raw WAI 'Request'.
--
-- copy from wai-extra 3.0.3.

module Network.Wai.Parse
    ( parseHttpAccept
    , parseRequestBody
    , RequestBodyType (..)
    , getRequestBodyType
    , sinkRequestBody
    , BackEnd
    , lbsBackEnd
    , Param
    , File
    , FileInfo (..)
    , parseContentType
#if TEST
    , Bound (..)
    , findBound
    , sinkTillBound
    , killCR
    , killCRLF
    , takeLine
#endif
    ) where

import qualified Data.ByteString.Search as Search
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Char8 as S8
import Data.Word (Word8)
import Data.Maybe (fromMaybe)
import Data.List (sortBy)
import Data.Function (on)
import Network.Wai
import qualified Network.HTTP.Types as H
import Control.Monad (when, unless)
import Data.IORef

breakDiscard :: Word8 -> S.ByteString -> (S.ByteString, S.ByteString)
breakDiscard w s =
    let (x, y) = S.break (== w) s
     in (x, S.drop 1 y)

-- | Parse the HTTP accept string to determine supported content types.
parseHttpAccept :: S.ByteString -> [S.ByteString]
parseHttpAccept = map fst
                . sortBy (rcompare `on` snd)
                . map (addSpecificity . grabQ)
                . S.split 44 -- comma
  where
    rcompare :: (Double,Int) -> (Double,Int) -> Ordering
    rcompare = flip compare
    addSpecificity (s, q) =
        -- Prefer higher-specificity types
        let semicolons = S.count 0x3B s
            stars = S.count 0x2A s
        in (s, (q, semicolons - stars))
    grabQ s =
        -- Stripping all spaces may be too harsh.
        -- Maybe just strip either side of semicolon?
        let (s', q) = S.breakSubstring ";q=" (S.filter (/=0x20) s) -- 0x20 is space
            q' = S.takeWhile (/=0x3B) (S.drop 3 q) -- 0x3B is semicolon
         in (s', readQ q')
    readQ s = case reads $ S8.unpack s of
                (x, _):_ -> x
                _ -> 1.0

-- | Store uploaded files in memory
lbsBackEnd :: Monad m => ignored1 -> ignored2 -> m S.ByteString -> m L.ByteString
lbsBackEnd _ _ popper =
    loop id
  where
    loop front = do
        bs <- popper
        if S.null bs
            then return $ L.fromChunks $ front []
            else loop $ front . (bs:)

-- | Information on an uploaded file.
data FileInfo c = FileInfo
    { fileName :: S.ByteString
    , fileContentType :: S.ByteString
    , fileContent :: c
    }
    deriving (Eq, Show)

-- | Post parameter name and value.
type Param = (S.ByteString, S.ByteString)

-- | Post parameter name and associated file information.
type File y = (S.ByteString, FileInfo y)

-- | A file uploading backend. Takes the parameter name, file name, and a
-- stream of data.
type BackEnd a = S.ByteString -- ^ parameter name
              -> FileInfo ()
              -> IO S.ByteString
              -> IO a

data RequestBodyType = UrlEncoded | Multipart S.ByteString

getRequestBodyType :: Request -> Maybe RequestBodyType
getRequestBodyType req = do
    ctype' <- lookup "Content-Type" $ requestHeaders req
    let (ctype, attrs) = parseContentType ctype'
    case ctype of
        "application/x-www-form-urlencoded" -> return UrlEncoded
        "multipart/form-data" | Just bound <- lookup "boundary" attrs -> return $ Multipart bound
        _ -> Nothing

-- | Parse a content type value, turning a single @ByteString@ into the actual
-- content type and a list of pairs of attributes.
--
-- Since 1.3.2
parseContentType :: S.ByteString -> (S.ByteString, [(S.ByteString, S.ByteString)])
parseContentType a = do
    let (ctype, b) = S.break (== semicolon) a
        attrs = goAttrs id $ S.drop 1 b
     in (ctype, attrs)
  where
    semicolon = 59
    equals = 61
    space = 32
    goAttrs front bs
        | S.null bs = front []
        | otherwise =
            let (x, rest) = S.break (== semicolon) bs
             in goAttrs (front . (goAttr x:)) $ S.drop 1 rest
    goAttr bs =
        let (k, v') = S.break (== equals) bs
            v = S.drop 1 v'
         in (strip k, strip v)
    strip = S.dropWhile (== space) . fst . S.breakEnd (/= space)

parseRequestBody :: BackEnd y
                 -> Request
                 -> IO ([Param], [File y])
parseRequestBody s r =
    case getRequestBodyType r of
        Nothing -> return ([], [])
        Just rbt -> sinkRequestBody s rbt (requestBody r)

sinkRequestBody :: BackEnd y
                -> RequestBodyType
                -> IO S.ByteString
                -> IO ([Param], [File y])
sinkRequestBody s r body = do
    ref <- newIORef (id, id)
    let add x = atomicModifyIORef ref $ \(y, z) ->
            case x of
                Left y' -> ((y . (y':), z), ())
                Right z' -> ((y, z . (z':)), ())
    conduitRequestBody s r body add
    (x, y) <- readIORef ref
    return (x [], y [])

conduitRequestBody :: BackEnd y
                   -> RequestBodyType
                   -> IO S.ByteString
                   -> (Either Param (File y) -> IO ())
                   -> IO ()
conduitRequestBody _ UrlEncoded rbody add = do
    -- NOTE: in general, url-encoded data will be in a single chunk.
    -- Therefore, I'm optimizing for the usual case by sticking with
    -- strict byte strings here.
    let loop front = do
            bs <- rbody
            if S.null bs
                then return $ S.concat $ front []
                else loop $ front . (bs:)
    bs <- loop id
    mapM_ (add . Left) $ H.parseSimpleQuery bs
conduitRequestBody backend (Multipart bound) rbody add =
    parsePieces backend (S8.pack "--" `S.append` bound) rbody add

takeLine :: Source -> IO (Maybe S.ByteString)
takeLine src =
    go id
  where
    go front = do
        bs <- readSource src
        if S.null bs
            then close front
            else push front bs

    close front = leftover src (front S.empty) >> return Nothing
    push front bs = do
        let (x, y) = S.break (== 10) $ front bs -- LF
         in if S.null y
                then go $ S.append x
                else do
                    when (S.length y > 1) $ leftover src $ S.drop 1 y
                    return $ Just $ killCR x

takeLines :: Source -> IO [S.ByteString]
takeLines src = do
    res <- takeLine src
    case res of
        Nothing -> return []
        Just l
            | S.null l -> return []
            | otherwise -> do
                ls <- takeLines src
                return $ l : ls

data Source = Source (IO S.ByteString) (IORef S.ByteString)

mkSource :: IO S.ByteString -> IO Source
mkSource f = do
    ref <- newIORef S.empty
    return $ Source f ref

readSource :: Source -> IO S.ByteString
readSource (Source f ref) = do
    bs <- atomicModifyIORef ref $ \bs -> (S.empty, bs)
    if S.null bs
        then f
        else return bs

leftover :: Source -> S.ByteString -> IO ()
leftover (Source _ ref) bs = writeIORef ref bs

parsePieces :: BackEnd y
            -> S.ByteString
            -> IO S.ByteString
            -> (Either Param (File y) -> IO ())
            -> IO ()
parsePieces sink bound rbody add =
    mkSource rbody >>= loop
  where
    loop src = do
        _boundLine <- takeLine src
        res' <- takeLines src
        unless (null res') $ do
            let ls' = map parsePair res'
            let x = do
                    cd <- lookup contDisp ls'
                    let ct = lookup contType ls'
                    let attrs = parseAttrs cd
                    name <- lookup "name" attrs
                    return (ct, name, lookup "filename" attrs)
            case x of
                Just (mct, name, Just filename) -> do
                    let ct = fromMaybe "application/octet-stream" mct
                        fi0 = FileInfo filename ct ()
                    (wasFound, y) <- sinkTillBound' bound name fi0 sink src
                    add $ Right (name, fi0 { fileContent = y })
                    when wasFound (loop src)
                Just (_ct, name, Nothing) -> do
                    let seed = id
                    let iter front bs = return $ front . (:) bs
                    (wasFound, front) <- sinkTillBound bound iter seed src
                    let bs = S.concat $ front []
                    let x' = (name, bs)
                    add $ Left x'
                    when wasFound (loop src)
                _ -> do
                    -- ignore this part
                    let seed = ()
                        iter () _ = return ()
                    (wasFound, ()) <- sinkTillBound bound iter seed src
                    when wasFound (loop src)
      where
        contDisp = S8.pack "Content-Disposition"
        contType = S8.pack "Content-Type"
        parsePair s =
            let (x, y) = breakDiscard 58 s -- colon
             in (x, S.dropWhile (== 32) y) -- space

data Bound = FoundBound S.ByteString S.ByteString
           | NoBound
           | PartialBound
    deriving (Eq, Show)

findBound :: S.ByteString -> S.ByteString -> Bound
findBound b bs = handleBreak $ Search.breakOn b bs
  where
    handleBreak (h, t)
        | S.null t = go [lowBound..S.length bs - 1]
        | otherwise = FoundBound h $ S.drop (S.length b) t

    lowBound = max 0 $ S.length bs - S.length b

    go [] = NoBound
    go (i:is)
        | mismatch [0..S.length b - 1] [i..S.length bs - 1] = go is
        | otherwise =
            let endI = i + S.length b
             in if endI > S.length bs
                    then PartialBound
                    else FoundBound (S.take i bs) (S.drop endI bs)
    mismatch [] _ = False
    mismatch _ [] = False
    mismatch (x:xs) (y:ys)
        | S.index b x == S.index bs y = mismatch xs ys
        | otherwise = True

sinkTillBound' :: S.ByteString
               -> S.ByteString
               -> FileInfo ()
               -> BackEnd y
               -> Source
               -> IO (Bool, y)
sinkTillBound' bound name fi sink src = do
    (next, final) <- wrapTillBound bound src
    y <- sink name fi next
    b <- final
    return (b, y)

data WTB = WTBWorking (S.ByteString -> S.ByteString)
         | WTBDone Bool
wrapTillBound :: S.ByteString -- ^ bound
              -> Source
              -> IO (IO S.ByteString, IO Bool) -- ^ Bool indicates if the bound was found
wrapTillBound bound src = do
    ref <- newIORef $ WTBWorking id
    return (go ref, final ref)
  where
    final ref = do
        x <- readIORef ref
        case x of
            WTBWorking _ -> error "wrapTillBound did not finish"
            WTBDone y -> return y

    go ref = do
        state <- readIORef ref
        case state of
            WTBDone _ -> return S.empty
            WTBWorking front -> do
                bs <- readSource src
                if S.null bs
                    then do
                        writeIORef ref $ WTBDone False
                        return $ front bs
                    else push $ front bs
      where
        push bs =
            case findBound bound bs of
                FoundBound before after -> do
                    let before' = killCRLF before
                    leftover src after
                    writeIORef ref $ WTBDone True
                    return before'
                NoBound -> do
                    -- don't emit newlines, in case it's part of a bound
                    let (toEmit, front') =
                            if not (S8.null bs) && S8.last bs `elem` "\r\n"
                                then let (x, y) = S.splitAt (S.length bs - 2) bs
                                      in (x, S.append y)
                                else (bs, id)
                    writeIORef ref $ WTBWorking front'
                    if S.null toEmit
                        then go ref
                        else return toEmit
                PartialBound -> do
                    writeIORef ref $ WTBWorking $ S.append bs
                    go ref

sinkTillBound :: S.ByteString
              -> (x -> S.ByteString -> IO x)
              -> x
              -> Source
              -> IO (Bool, x)
sinkTillBound bound iter seed0 src = do
    (next, final) <- wrapTillBound bound src
    let loop seed = do
            bs <- next
            if S.null bs
                then return seed
                else iter seed bs >>= loop
    seed <- loop seed0
    b <- final
    return (b, seed)

parseAttrs :: S.ByteString -> [(S.ByteString, S.ByteString)]
parseAttrs = map go . S.split 59 -- semicolon
  where
    tw = S.dropWhile (== 32) -- space
    dq s = if S.length s > 2 && S.head s == 34 && S.last s == 34 -- quote
                then S.tail $ S.init s
                else s
    go s =
        let (x, y) = breakDiscard 61 s -- equals sign
         in (tw x, dq $ tw y)

killCRLF :: S.ByteString -> S.ByteString
killCRLF bs
    | S.null bs || S.last bs /= 10 = bs -- line feed
    | otherwise = killCR $ S.init bs

killCR :: S.ByteString -> S.ByteString
killCR bs
    | S.null bs || S.last bs /= 13 = bs -- carriage return
    | otherwise = S.init bs