-module(hello_handler).
-behaviour(cowboy_http_handler).

-export([init/3]).
-export([handle/2]).
-export([terminate/3]).

-record(state, {
}).

init(_, Req, _Opts) ->
    {ok, Req, #state{}}.

handle(Req, State=#state{}) ->
    {QueryBin, Req1} = cowboy_req:qs(Req),
    QueryStr = binary_to_list(QueryBin),
    QueryTokens = string:tokens(QueryStr, "%20"),
    ReplyStr = string:split(QueryTokens, "&", all),
    Op = lists:nth(1, ReplyStr),

    Result = case Op of
        "sum" -> integer_to_binary(list_to_integer(lists:nth(2, ReplyStr)) + list_to_integer(lists:nth(3, ReplyStr)));
        "sub" -> integer_to_binary(list_to_integer(lists:nth(2, ReplyStr)) - list_to_integer(lists:nth(3, ReplyStr)));
        "mul" -> integer_to_binary(list_to_integer(lists:nth(2, ReplyStr)) * list_to_integer(lists:nth(3, ReplyStr)));
        "div" -> float_to_binary(list_to_integer(lists:nth(2, ReplyStr)) / list_to_integer(lists:nth(3, ReplyStr)))
    end,

    io:fwrite("~p~n",[Result]),

    {ok, Req2} = cowboy_req:reply(200,
        [{<<"content-type">>, <<"text/plain">>}],
        [Result],
        Req1),
    {ok, Req2, State}.

terminate(_Reason, _Req, _State) ->
    ok.