-module(fifo_s3_download_worker).
-behaviour(gen_server).
-behaviour(poolboy_worker).

-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
-endif.

-export([start_link/1]).

-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
         code_change/3]).

-record(state, {data=undefined, part=0, retries = 3}).

start_link(Args) ->
    gen_server:start_link(?MODULE, Args, []).

init(_Args) ->
    R = case application:get_env(fifo_s3, download_retry) of
            {ok, Rx} ->
                Rx;
            _ ->
                3
        end,
    {ok, #state{retries = R}}.

handle_call(get, _From, State = #state{data=R}) ->
    {reply, R, State#state{data=undefined}, hibernate};

handle_call(_Request, _From, State) ->
    {reply, ok, State}.

handle_cast({download, _From, P, B, K, Conf, C, Size},
            State = #state{data=undefined, retries = Tries}) ->
    {Start, End} = start_stop(P, C, Size),
    Range = build_range(Start, End),
    R = download(B, K, Range, Conf, Tries),
    {noreply, State#state{data=R, part=P}};

handle_cast({download, _From, _P, _, _, _Conf, _C, _Size}, State) ->
    {noreply, State#state{data = undefined}};

handle_cast(cancle, State) ->
    {noreply, State#state{data = undefined}};

handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

build_range(Start, Stop) when Start =< Stop ->
    lists:flatten(io_lib:format("bytes=~p-~p", [Start, Stop])).

start_stop(P, Size, Max) ->
    Start = P*Size,
    End = case (P+1)*Size of
              EndX when EndX > Max ->
                  Max;
              EndX ->
                  EndX
          end,
    {Start, End - 1}.



download(B, K, Range, Conf, 0) ->
    try erlcloud_s3:get_object(B, K, [{range, Range}], Conf) of
        Data ->
            case proplists:get_value(content, Data) of
                undefined ->
                    {error, content};
                D ->
                    {ok, D}
            end
    catch
        _:E ->
            {error, E}
    end;

download(B, K, Range, Conf, Try) ->
    try erlcloud_s3:get_object(B, K, [{range, Range}], Conf) of
        Data ->
            case proplists:get_value(content, Data) of
                undefined ->
                    download(B, K, Range, Conf, Try - 1);
                D ->
                    {ok, D}
            end
    catch
        _:_E ->
            download(B, K, Range, Conf, Try - 1)
    end.

%%%===================================================================
%%% Tests
%%%===================================================================

-ifdef(TEST).

start_stop_test() ->
    Size = 10,
    Max = 25,
    ?assertEqual({0, 0}, start_stop(0, 1, Max)),
    ?assertEqual({0, 9}, start_stop(0, Size, Max)),
    ?assertEqual({10, 19}, start_stop(1, Size, Max)),
    ?assertEqual({20, 24}, start_stop(2, Size, Max)).

-endif.