Network.HTTP.Media

A framework for parsing HTTP media type headers.

Media types

data MediaType

An HTTP media type, consisting of the type, subtype, and parameters.

Instances

Eq MediaType

Show MediaType

IsString MediaType

Match MediaType

(//) :: ByteString -> ByteString -> MediaType

Builds a MediaType without parameters. Can produce an error if either type is invalid.

(/:) :: MediaType -> (ByteString, ByteString) -> MediaType

Adds a parameter to a MediaType. Can produce an error if either string is invalid.

mainType :: MediaType -> ByteString

Retrieves the main type of a MediaType.

subType :: MediaType -> ByteString

Retrieves the sub type of a MediaType.

parameters :: MediaType -> Parameters

Retrieves the parameters of a MediaType.

(/?) :: MediaType -> ByteString -> Bool

Evaluates if a MediaType has a parameter of the given name.

(/.) :: MediaType -> ByteString -> Maybe ByteString

Retrieves a parameter from a MediaType.

data Quality a

Attaches a quality value to data.

Instances

Eq a => Eq (Quality a)

Show a => Show (Quality a)

Parsing

parseAccept :: ByteString -> Maybe [Quality MediaType]

Parses a full Accept header into a list of quality-valued media types.

Accept matching

matchAccept

Arguments

:: Match a

=> [a]

The server-side options

-> [Quality a]

The client-side preferences

-> Maybe a

Matches a list of server-side resource options against a quality-marked list of client-side preferences. A result of Nothing means that nothing matched (which should indicate a 406 error). If two or more results arise with the same quality level and specificity, then the first one in the server list is chosen.

The use of the Match type class allows the application of either MediaType for the standard Accept header or ByteString for any other Accept header which can be marked with a quality value. The standard application of this function for MediaType should be in conjunction with parseAccepts.

 parseAccepts header >>= matchQuality resourceTypeOptions

For more information on the matching process see RFC 2616, section 14.

mapAccept

Arguments

:: Match a

=> [(a, b)]

The map of server-side preferences to values

-> [Quality a]

The client-side preferences

-> Maybe b

The equivalent of matchAccept above, except the resulting choice is mapped to another value. Convenient for specifying how to translate the resource into each of its available formats.

 maybe render406Error renderResource $ parseAccepts header >>= mapQuality
     [ ("text/html",        asHtml)
     , ("application/json", asJson)
     ]

Content matching

matchContent

Arguments

:: Match a

=> a

The client's request value

-> [a]

The server-side response options

-> Maybe a

Matches a list of server-side parsing options against a the client-side content value. A result of Nothing means that nothing matched (which should indicate a 415 error).

As with the Accept parsing, he use of the Match type class allows the application of either MediaType or ByteString.

mapContent

Arguments

:: Match a

=> a

The client request's header value

-> [(a, b)]

The map of server-side responses

-> Maybe b

The equivalent of matchContent above, except the resulting choice is mapped to another value.

Match

class Match a where

Defines methods for a type whose values can be matched against each other in terms of a HTTP media header.

This allows functions to work on both the standard Accept header and others such as Accept-Language that still may use quality values.

Methods

matches :: a -> a -> Bool

Evaluates whether either the left argument matches the right one (order may be important).

moreSpecificThan :: a -> a -> Bool

Evaluates whether the left argument is more specific than the right.

Instances

Match ByteString

Match MediaType