{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE BangPatterns #-}

module Network.Wai.Handler.Warp.RequestHeader (
      parseHeaderLines
    ) where

import Control.Exception (throwIO)
import Control.Monad (when)
import qualified Data.ByteString as S
import qualified Data.ByteString.Char8 as B (unpack)
import Data.ByteString.Internal (ByteString(..), memchr)
import qualified Data.CaseInsensitive as CI
import Data.Word (Word8)
import Foreign.ForeignPtr (withForeignPtr)
import Foreign.Ptr (Ptr, plusPtr, minusPtr, nullPtr)
import Foreign.Storable (peek)
import qualified Network.HTTP.Types as H
import Network.Wai.Handler.Warp.Types

-- $setup
-- >>> :set -XOverloadedStrings

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

parseHeaderLines :: [ByteString]
                 -> IO (H.Method
                       ,ByteString  --  Path
                       ,ByteString  --  Path, parsed
                       ,ByteString  --  Query
                       ,H.HttpVersion
                       ,H.RequestHeaders
                       )
parseHeaderLines [] = throwIO $ NotEnoughLines []
parseHeaderLines (firstLine:otherLines) = do
    (method, path', query, httpversion) <- parseRequestLine firstLine
    let path = H.extractPath path'
        hdr = map parseHeader otherLines
    return (method, path', path, query, httpversion, hdr)

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

-- |
--
-- >>> parseRequestLine "GET / HTTP/1.1"
-- ("GET","/","",HTTP/1.1)
-- >>> parseRequestLine "POST /cgi/search.cgi?key=foo HTTP/1.0"
-- ("POST","/cgi/search.cgi","?key=foo",HTTP/1.0)
-- >>> parseRequestLine "GET "
-- *** Exception: Warp: Invalid first line of request: "GET "
-- >>> parseRequestLine "GET /NotHTTP UNKNOWN/1.1"
-- *** Exception: Warp: Request line specified a non-HTTP request
-- >>> parseRequestLine "PRI * HTTP/2.0"
-- ("PRI","*","",HTTP/2.0)
parseRequestLine :: ByteString
                 -> IO (H.Method
                       ,ByteString -- Path
                       ,ByteString -- Query
                       ,H.HttpVersion)
parseRequestLine requestLine@(PS fptr off len) = withForeignPtr fptr $ \ptr -> do
    when (len < 14) $ throwIO baderr
    let methodptr = ptr `plusPtr` off
        limptr = methodptr `plusPtr` len
        lim0 = fromIntegral len

    pathptr0 <- memchr methodptr 32 lim0 -- ' '
    when (pathptr0 == nullPtr || (limptr `minusPtr` pathptr0) < 11) $
        throwIO baderr
    let pathptr = pathptr0 `plusPtr` 1
        lim1 = fromIntegral (limptr `minusPtr` pathptr0)

    httpptr0 <- memchr pathptr 32 lim1 -- ' '
    when (httpptr0 == nullPtr || (limptr `minusPtr` httpptr0) < 9) $
        throwIO baderr
    let httpptr = httpptr0 `plusPtr` 1
        lim2 = fromIntegral (httpptr0 `minusPtr` pathptr)

    checkHTTP httpptr
    !hv <- httpVersion httpptr
    queryptr <- memchr pathptr 63 lim2 -- '?'

    let !method = bs ptr methodptr pathptr0
        !path
          | queryptr == nullPtr = bs ptr pathptr httpptr0
          | otherwise           = bs ptr pathptr queryptr
        !query
          | queryptr == nullPtr = S.empty
          | otherwise           = bs ptr queryptr httpptr0

    return (method,path,query,hv)
  where
    baderr = BadFirstLine $ B.unpack requestLine
    check :: Ptr Word8 -> Int -> Word8 -> IO ()
    check p n w = do
        w0 <- peek $ p `plusPtr` n
        when (w0 /= w) $ throwIO NonHttp
    checkHTTP httpptr = do
        check httpptr 0 72 -- 'H'
        check httpptr 1 84 -- 'T'
        check httpptr 2 84 -- 'T'
        check httpptr 3 80 -- 'P'
        check httpptr 4 47 -- '/'
        check httpptr 6 46 -- '.'
    httpVersion httpptr = do
        major <- peek (httpptr `plusPtr` 5) :: IO Word8
        minor <- peek (httpptr `plusPtr` 7) :: IO Word8
        let version
              | major == 49 = if minor == 49 then H.http11 else H.http10
              | major == 50 && minor == 48 = H.HttpVersion 2 0
              | otherwise   = H.http10
        return version
    bs ptr p0 p1 = PS fptr o l
      where
        o = p0 `minusPtr` ptr
        l = p1 `minusPtr` p0

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

-- |
--
-- >>> parseHeader "Content-Length:47"
-- ("Content-Length","47")
-- >>> parseHeader "Accept-Ranges: bytes"
-- ("Accept-Ranges","bytes")
-- >>> parseHeader "Host:  example.com:8080"
-- ("Host","example.com:8080")
-- >>> parseHeader "NoSemiColon"
-- ("NoSemiColon","")

parseHeader :: ByteString -> H.Header
parseHeader s =
    let (k, rest) = S.break (== 58) s -- ':'
        rest' = S.dropWhile (\c -> c == 32 || c == 9) $ S.drop 1 rest
     in (CI.mk k, rest')
