Cowboy protocol and set of utility funs for building JSON/MsgPack APIs
First you should initialize protocol for cowboy
-include("sheep.hrl").
init(_Transport, Req, _Opts) ->
{upgrade, protocol, sheep_http, Req, []}.Second, the sheep_init/2 callback will be called where you can set options and state.
-spec sheep_init(#sheep_request{}, term()) -> {#sheep_options{}, term()}.
sheep_init(Request, Opts) ->
Options = #sheep_options{},
State = #{},
{Options, State}.-record(sheep_options, {
encode_spec :: undefined | map(),
decode_spec :: undefined | map(),
method_spec :: undefined | map()
}).Specification of callback for decode data for the appropriate content-type.
Default value is:
#{
<<"application/json">> =>
fun(Payload) ->
jiffy:decode(Payload, [return_maps])
end,
<<"application/x-msgpack">> =>
fun(Payload) ->
{ok, Data} = msgpack:unpack(Payload, [{map_format, map}]),
Data
end
}.See encode_decode_handler.erl as example.
Specification of callback for encode data for the appropriate accept.
Default value is:
#{
<<"application/json">> =>
fun(Payload) ->
jiffy:encode(Payload, [pretty])
end,
<<"application/x-msgpack">> =>
fun(Payload) ->
msgpack:pack(Payload, [{map_format, map}])
end
}.Specifications for methods. Default value is:
#{
<<"POST">> => [create],
<<"GET">> => [read],
<<"PUT">> => [update],
<<"DELETE">> => [delete]
}.For each http method (GET, POST, PUT etc) you can specify list of functions that must be called.
Each function should return one of the following values:
- {continue, State} - in this case the next function from list will be called
- {continue, Response, State} - same as above
- #sheep_response{} - This result will be considered as final and returned as response
For example if you specify method_spec in following way:
#sheep_options{
method_spec = #{
<<"POST">> => [authorization, validation, create],
<<"GET">> => [authorization, fun http_helpers:pagination/2, read],
<<"PUT">> => [],
<<"DELETE">> => []
}
}then GET and POST requests will be processed by list of functions but PUT or DELETE will get 204 (no content) response.
See pipeline_handler.erl as example.