Sheep

Cowboy protocol and set of utility funs for building JSON/MsgPack APIs

Initialization

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}.

Options

-record(sheep_options, {
    encode_spec :: undefined | map(),
    decode_spec :: undefined | map(),
    method_spec :: undefined | map()
}).

decode_spec

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.

encode_spec

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
}.

method_spec

Specifications for methods. Default value is:

 #{
    <<"POST">> => [create],
    <<"GET">> => [read],
    <<"PUT">> => [update],
    <<"DELETE">> => [delete]
}.

Handlers

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.