example_echo_handler.erl

-module(example_echo_handler).

-include_lib("mixer/include/mixer.hrl").
-mixin([
        {example_default,
         [
          init/3,
          rest_init/2,
          content_types_accepted/2,
          content_types_provided/2,
          resource_exists/2
         ]}
       ]).

-export([ allowed_methods/2
        , handle_put/2
        , handle_get/2
        ]).

%trails
-behaviour(trails_handler).
-export([trails/0]).

trails() ->
  Metadata =
    #{get =>
      #{tags => ["echo"],
        description => "Gets echo var from the server",
        produces => ["text/plain"]
      },
      put =>
      #{tags => ["echo"],
        description => "Sets echo var in the server",
        produces => ["text/plain"],
        parameters => [
          #{name => <<"echo">>,
            description => <<"Echo message">>,
            in => <<"path">>,
            required => false,
            type => <<"string">>}
        ]
      }
    },
  [trails:trail("/message/[:echo]", example_echo_handler, [], Metadata)].

%% cowboy
allowed_methods(Req, State) ->
  {[<<"GET">>, <<"PUT">>, <<"HEAD">>], Req, State}.

%% internal
handle_get(Req, State) ->
  Echo = application:get_env(example, echo, ""),
  Body = [<<"You Get an echo!">> , Echo],
  {Body, Req, State}.

handle_put(Req, State) ->
  {Echo, Req1} = cowboy_req:binding(echo, Req, ""),
  application:set_env(example, echo, Echo),
  Body = [<<"You put an echo! ">> , Echo],
  Req2 = cowboy_req:set_resp_body(Body, Req1),
  {true, Req2, State}.