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|
-----------------------------------------------------------------------------
-- |
-- Module : Network.HTTP.Headers
-- Copyright : See LICENSE file
-- License : BSD
--
-- Maintainer : Ganesh Sittampalam <ganesh@earth.li>
-- Stability : experimental
-- Portability : non-portable (not tested)
--
-- This module provides the data types for representing HTTP headers, and
-- operations for looking up header values and working with sequences of
-- header values in 'Request's and 'Response's. To avoid having to provide
-- separate set of operations for doing so, we introduce a type class 'HasHeaders'
-- to facilitate writing such processing using overloading instead.
--
-----------------------------------------------------------------------------
module Network.HTTP.Headers
( HasHeaders(..) -- type class
, Header(..)
, mkHeader -- :: HeaderName -> String -> Header
, hdrName -- :: Header -> HeaderName
, hdrValue -- :: Header -> String
, HeaderName(..)
, insertHeader -- :: HasHeaders a => HeaderName -> String -> a -> a
, insertHeaderIfMissing -- :: HasHeaders a => HeaderName -> String -> a -> a
, insertHeaders -- :: HasHeaders a => [Header] -> a -> a
, retrieveHeaders -- :: HasHeaders a => HeaderName -> a -> [Header]
, replaceHeader -- :: HasHeaders a => HeaderName -> String -> a -> a
, findHeader -- :: HasHeaders a => HeaderName -> a -> Maybe String
, lookupHeader -- :: HeaderName -> [Header] -> Maybe String
, parseHeader -- :: parseHeader :: String -> Result Header
, parseHeaders -- :: [String] -> Result [Header]
, headerMap -- :: [(String, HeaderName)]
, HeaderSetter
) where
import Data.Char (toLower)
import Network.Stream (Result, failParse)
import Network.HTTP.Utils ( trim, split, crlf )
-- | The @Header@ data type pairs header names & values.
data Header = Header HeaderName String
hdrName :: Header -> HeaderName
hdrName (Header h _) = h
hdrValue :: Header -> String
hdrValue (Header _ v) = v
-- | Header constructor as a function, hiding above rep.
mkHeader :: HeaderName -> String -> Header
mkHeader = Header
instance Show Header where
show (Header key value) = shows key (':':' ':value ++ crlf)
-- | HTTP @HeaderName@ type, a Haskell data constructor for each
-- specification-defined header, prefixed with @Hdr@ and CamelCased,
-- (i.e., eliding the @-@ in the process.) Should you require using
-- a custom header, there's the @HdrCustom@ constructor which takes
-- a @String@ argument.
--
-- Encoding HTTP header names differently, as Strings perhaps, is an
-- equally fine choice..no decidedly clear winner, but let's stick
-- with data constructors here.
--
data HeaderName
-- Generic Headers --
= HdrCacheControl
| HdrConnection
| HdrDate
| HdrPragma
| HdrTransferEncoding
| HdrUpgrade
| HdrVia
-- Request Headers --
| HdrAccept
| HdrAcceptCharset
| HdrAcceptEncoding
| HdrAcceptLanguage
| HdrAuthorization
| HdrCookie
| HdrExpect
| HdrFrom
| HdrHost
| HdrIfModifiedSince
| HdrIfMatch
| HdrIfNoneMatch
| HdrIfRange
| HdrIfUnmodifiedSince
| HdrMaxForwards
| HdrProxyAuthorization
| HdrRange
| HdrReferer
| HdrUserAgent
-- Response Headers
| HdrAge
| HdrLocation
| HdrProxyAuthenticate
| HdrPublic
| HdrRetryAfter
| HdrServer
| HdrSetCookie
| HdrTE
| HdrTrailer
| HdrVary
| HdrWarning
| HdrWWWAuthenticate
-- Entity Headers
| HdrAllow
| HdrContentBase
| HdrContentEncoding
| HdrContentLanguage
| HdrContentLength
| HdrContentLocation
| HdrContentMD5
| HdrContentRange
| HdrContentType
| HdrETag
| HdrExpires
| HdrLastModified
-- | MIME entity headers (for sub-parts)
| HdrContentTransferEncoding
-- | Allows for unrecognised or experimental headers.
| HdrCustom String -- not in header map below.
instance Eq HeaderName where
HdrCustom a == HdrCustom b = (fmap toLower a) == (fmap toLower b)
HdrCacheControl == HdrCacheControl = True
HdrCacheControl == _ = False
_ == HdrCacheControl = False
HdrConnection == HdrConnection = True
HdrConnection == _ = False
_ == HdrConnection = False
HdrDate == HdrDate = True
HdrDate == _ = False
_ == HdrDate = False
HdrPragma == HdrPragma = True
HdrPragma == _ = False
_ == HdrPragma = False
HdrTransferEncoding == HdrTransferEncoding = True
HdrTransferEncoding == _ = False
_ == HdrTransferEncoding = False
HdrUpgrade == HdrUpgrade = True
HdrUpgrade == _ = False
_ == HdrUpgrade = False
HdrVia == HdrVia = True
HdrVia == _ = False
_ == HdrVia = False
HdrAccept == HdrAccept = True
HdrAccept == _ = False
_ == HdrAccept = False
HdrAcceptCharset == HdrAcceptCharset = True
HdrAcceptCharset == _ = False
_ == HdrAcceptCharset = False
HdrAcceptEncoding == HdrAcceptEncoding = True
HdrAcceptEncoding == _ = False
_ == HdrAcceptEncoding = False
HdrAcceptLanguage == HdrAcceptLanguage = True
HdrAcceptLanguage == _ = False
_ == HdrAcceptLanguage = False
HdrAuthorization == HdrAuthorization = True
HdrAuthorization == _ = False
_ == HdrAuthorization = False
HdrCookie == HdrCookie = True
HdrCookie == _ = False
_ == HdrCookie = False
HdrExpect == HdrExpect = True
HdrExpect == _ = False
_ == HdrExpect = False
HdrFrom == HdrFrom = True
HdrFrom == _ = False
_ == HdrFrom = False
HdrHost == HdrHost = True
HdrHost == _ = False
_ == HdrHost = False
HdrIfModifiedSince == HdrIfModifiedSince = True
HdrIfModifiedSince == _ = False
_ == HdrIfModifiedSince = False
HdrIfMatch == HdrIfMatch = True
HdrIfMatch == _ = False
_ == HdrIfMatch = False
HdrIfNoneMatch == HdrIfNoneMatch = True
HdrIfNoneMatch == _ = False
_ == HdrIfNoneMatch = False
HdrIfRange == HdrIfRange = True
HdrIfRange == _ = False
_ == HdrIfRange = False
HdrIfUnmodifiedSince == HdrIfUnmodifiedSince = True
HdrIfUnmodifiedSince == _ = False
_ == HdrIfUnmodifiedSince = False
HdrMaxForwards == HdrMaxForwards = True
HdrMaxForwards == _ = False
_ == HdrMaxForwards = False
HdrProxyAuthorization == HdrProxyAuthorization = True
HdrProxyAuthorization == _ = False
_ == HdrProxyAuthorization = False
HdrRange == HdrRange = True
HdrRange == _ = False
_ == HdrRange = False
HdrReferer == HdrReferer = True
HdrReferer == _ = False
_ == HdrReferer = False
HdrUserAgent == HdrUserAgent = True
HdrUserAgent == _ = False
_ == HdrUserAgent = False
HdrAge == HdrAge = True
HdrAge == _ = False
_ == HdrAge = False
HdrLocation == HdrLocation = True
HdrLocation == _ = False
_ == HdrLocation = False
HdrProxyAuthenticate == HdrProxyAuthenticate = True
HdrProxyAuthenticate == _ = False
_ == HdrProxyAuthenticate = False
HdrPublic == HdrPublic = True
HdrPublic == _ = False
_ == HdrPublic = False
HdrRetryAfter == HdrRetryAfter = True
HdrRetryAfter == _ = False
_ == HdrRetryAfter = False
HdrServer == HdrServer = True
HdrServer == _ = False
_ == HdrServer = False
HdrSetCookie == HdrSetCookie = True
HdrSetCookie == _ = False
_ == HdrSetCookie = False
HdrTE == HdrTE = True
HdrTE == _ = False
_ == HdrTE = False
HdrTrailer == HdrTrailer = True
HdrTrailer == _ = False
_ == HdrTrailer = False
HdrVary == HdrVary = True
HdrVary == _ = False
_ == HdrVary = False
HdrWarning == HdrWarning = True
HdrWarning == _ = False
_ == HdrWarning = False
HdrWWWAuthenticate == HdrWWWAuthenticate = True
HdrWWWAuthenticate == _ = False
_ == HdrWWWAuthenticate = False
HdrAllow == HdrAllow = True
HdrAllow == _ = False
_ == HdrAllow = False
HdrContentBase == HdrContentBase = True
HdrContentBase == _ = False
_ == HdrContentBase = False
HdrContentEncoding == HdrContentEncoding = True
HdrContentEncoding == _ = False
_ == HdrContentEncoding = False
HdrContentLanguage == HdrContentLanguage = True
HdrContentLanguage == _ = False
_ == HdrContentLanguage = False
HdrContentLength == HdrContentLength = True
HdrContentLength == _ = False
_ == HdrContentLength = False
HdrContentLocation == HdrContentLocation = True
HdrContentLocation == _ = False
_ == HdrContentLocation = False
HdrContentMD5 == HdrContentMD5 = True
HdrContentMD5 == _ = False
_ == HdrContentMD5 = False
HdrContentRange == HdrContentRange = True
HdrContentRange == _ = False
_ == HdrContentRange = False
HdrContentType == HdrContentType = True
HdrContentType == _ = False
_ == HdrContentType = False
HdrETag == HdrETag = True
HdrETag == _ = False
_ == HdrETag = False
HdrExpires == HdrExpires = True
HdrExpires == _ = False
_ == HdrExpires = False
HdrLastModified == HdrLastModified = True
HdrLastModified == _ = False
_ == HdrLastModified = False
HdrContentTransferEncoding == HdrContentTransferEncoding = True
HdrContentTransferEncoding == _ = False
_ == HdrContentTransferEncoding = False
-- | @headerMap@ is a straight assoc list for translating between header names
-- and values.
headerMap :: [ (String,HeaderName) ]
headerMap =
[ p "Cache-Control" HdrCacheControl
, p "Connection" HdrConnection
, p "Date" HdrDate
, p "Pragma" HdrPragma
, p "Transfer-Encoding" HdrTransferEncoding
, p "Upgrade" HdrUpgrade
, p "Via" HdrVia
, p "Accept" HdrAccept
, p "Accept-Charset" HdrAcceptCharset
, p "Accept-Encoding" HdrAcceptEncoding
, p "Accept-Language" HdrAcceptLanguage
, p "Authorization" HdrAuthorization
, p "Cookie" HdrCookie
, p "Expect" HdrExpect
, p "From" HdrFrom
, p "Host" HdrHost
, p "If-Modified-Since" HdrIfModifiedSince
, p "If-Match" HdrIfMatch
, p "If-None-Match" HdrIfNoneMatch
, p "If-Range" HdrIfRange
, p "If-Unmodified-Since" HdrIfUnmodifiedSince
, p "Max-Forwards" HdrMaxForwards
, p "Proxy-Authorization" HdrProxyAuthorization
, p "Range" HdrRange
, p "Referer" HdrReferer
, p "User-Agent" HdrUserAgent
, p "Age" HdrAge
, p "Location" HdrLocation
, p "Proxy-Authenticate" HdrProxyAuthenticate
, p "Public" HdrPublic
, p "Retry-After" HdrRetryAfter
, p "Server" HdrServer
, p "Set-Cookie" HdrSetCookie
, p "TE" HdrTE
, p "Trailer" HdrTrailer
, p "Vary" HdrVary
, p "Warning" HdrWarning
, p "WWW-Authenticate" HdrWWWAuthenticate
, p "Allow" HdrAllow
, p "Content-Base" HdrContentBase
, p "Content-Encoding" HdrContentEncoding
, p "Content-Language" HdrContentLanguage
, p "Content-Length" HdrContentLength
, p "Content-Location" HdrContentLocation
, p "Content-MD5" HdrContentMD5
, p "Content-Range" HdrContentRange
, p "Content-Type" HdrContentType
, p "ETag" HdrETag
, p "Expires" HdrExpires
, p "Last-Modified" HdrLastModified
, p "Content-Transfer-Encoding" HdrContentTransferEncoding
]
where
p a b = (a,b)
instance Show HeaderName where
show (HdrCustom s) = s
show x = case filter ((==x).snd) headerMap of
[] -> error "headerMap incomplete"
(h:_) -> fst h
-- | @HasHeaders@ is a type class for types containing HTTP headers, allowing
-- you to write overloaded header manipulation functions
-- for both 'Request' and 'Response' data types, for instance.
class HasHeaders x where
getHeaders :: x -> [Header]
setHeaders :: x -> [Header] -> x
-- Header manipulation functions
type HeaderSetter a = HeaderName -> String -> a -> a
-- | @insertHeader hdr val x@ inserts a header with the given header name
-- and value. Does not check for existing headers with same name, allowing
-- duplicates to be introduce (use 'replaceHeader' if you want to avoid this.)
insertHeader :: HasHeaders a => HeaderSetter a
insertHeader name value x = setHeaders x newHeaders
where
newHeaders = (Header name value) : getHeaders x
-- | @insertHeaderIfMissing hdr val x@ adds the new header only if no previous
-- header with name @hdr@ exists in @x@.
insertHeaderIfMissing :: HasHeaders a => HeaderSetter a
insertHeaderIfMissing name value x = setHeaders x (newHeaders $ getHeaders x)
where
newHeaders list@(h@(Header n _): rest)
| n == name = list
| otherwise = h : newHeaders rest
newHeaders [] = [Header name value]
-- | @replaceHeader hdr val o@ replaces the header @hdr@ with the
-- value @val@, dropping any existing
replaceHeader :: HasHeaders a => HeaderSetter a
replaceHeader name value h = setHeaders h newHeaders
where
newHeaders = Header name value : [ x | x@(Header n _) <- getHeaders h, name /= n ]
-- | @insertHeaders hdrs x@ appends multiple headers to @x@'s existing
-- set.
insertHeaders :: HasHeaders a => [Header] -> a -> a
insertHeaders hdrs x = setHeaders x (getHeaders x ++ hdrs)
-- | @retrieveHeaders hdrNm x@ gets a list of headers with 'HeaderName' @hdrNm@.
retrieveHeaders :: HasHeaders a => HeaderName -> a -> [Header]
retrieveHeaders name x = filter matchname (getHeaders x)
where
matchname (Header n _) = n == name
-- | @findHeader hdrNm x@ looks up @hdrNm@ in @x@, returning the first
-- header that matches, if any.
findHeader :: HasHeaders a => HeaderName -> a -> Maybe String
findHeader n x = lookupHeader n (getHeaders x)
-- | @lookupHeader hdr hdrs@ locates the first header matching @hdr@ in the
-- list @hdrs@.
lookupHeader :: HeaderName -> [Header] -> Maybe String
lookupHeader _ [] = Nothing
lookupHeader v (Header n s:t)
| v == n = Just s
| otherwise = lookupHeader v t
-- | @parseHeader headerNameAndValueString@ tries to unscramble a
-- @header: value@ pairing and returning it as a 'Header'.
parseHeader :: String -> Result Header
parseHeader str =
case split ':' str of
Nothing -> failParse ("Unable to parse header: " ++ str)
Just (k,v) -> return $ Header (fn k) (trim $ drop 1 v)
where
fn k = case map snd $ filter (match k . fst) headerMap of
[] -> (HdrCustom k)
(h:_) -> h
match :: String -> String -> Bool
match s1 s2 = map toLower s1 == map toLower s2
-- | @parseHeaders hdrs@ takes a sequence of strings holding header
-- information and parses them into a set of headers (preserving their
-- order in the input argument.) Handles header values split up over
-- multiple lines.
parseHeaders :: [String] -> Result [Header]
parseHeaders = catRslts [] .
map (parseHeader . clean) .
joinExtended ""
where
-- Joins consecutive lines where the second line
-- begins with ' ' or '\t'.
joinExtended old [] = [old]
joinExtended old (h : t)
| isLineExtension h = joinExtended (old ++ ' ' : tail h) t
| otherwise = old : joinExtended h t
isLineExtension (x:_) = x == ' ' || x == '\t'
isLineExtension _ = False
clean [] = []
clean (h:t) | h `elem` "\t\r\n" = ' ' : clean t
| otherwise = h : clean t
-- tolerant of errors? should parse
-- errors here be reported or ignored?
-- currently ignored.
catRslts :: [a] -> [Result a] -> Result [a]
catRslts list (h:t) =
case h of
Left _ -> catRslts list t
Right v -> catRslts (v:list) t
catRslts list [] = Right $ reverse list
|
