-module (gtd).
-export ([start/0, run/0, worker/1]).

-define(TCP_OPTIONS, [{packet, 0}, {active, false}, {reuseaddr, true}, {nodelay, false}]).
-define(PORT_NO, 5000).

receive_loop(ListenSocket) ->
    Worker = spawn(gtd,worker,[gen_tcp:accept(ListenSocket)]),
    receive_loop(ListenSocket).

run() ->
    case gen_tcp:listen(?PORT_NO,?TCP_OPTIONS) of
        {ok, ListenSocket} ->
            io:format("Listening on ~p...~n",[?PORT_NO]),
            receive_loop(ListenSocket),
            io:format("Connection closed.~n"),
            gen_tcp:close(ListenSocket);
        {error, Reason} ->
            io:format("Failed to listen on ~p: ~p~n",[?PORT_NO,Reason])
    end.

parse_request(Request)->
    {ok,TopHeader,Rest} = erlang:decode_packet(http,Request,[]),
    ParsedHeaders = parse_headers(erlang:decode_packet(httph,Rest,[]),[]),
    {TopHeader,ParsedHeaders}.

parse_headers({ok, http_eoh, Rest},Parsed_Headers)->
    Parsed_Headers;
parse_headers({ok,Header,Rest},Parsed_Headers) ->
    parse_headers(erlang:decode_packet(httph,Rest,[]),[Header | Parsed_Headers]).

worker({error, Reason}) ->
    {error, Reason};
worker({ok, TcpSocket}) ->
    {ok,Request} = gen_tcp:recv(TcpSocket,0),
    {{http_request, Method,{abs_path, Path},Version},Headers} = parse_request(list_to_binary(Request)),
    case Method of
        'PUT' ->
            {ok,Data} = gen_tcp:recv(TcpSocket,0);
        'POST' ->
            {ok,Data} = gen_tcp:recv(TcpSocket,0);
        'GET' ->
            Data = [];
        'DELETE' ->
            Data = []
    end,
    RequestObject = {{http_request, Method,{abs_path, Path},Version},Headers,Data},
    io:format("Worker ~p started for request ~p.~n",[self(),RequestObject]),
    Response = io_lib:format("HTTP/1.1 200 OK~n~nMethod: ~p~nPath: ~p~nHeaders: ~p~nData:~p",[Method,Path,Headers,Data]),
    gen_tcp:send(TcpSocket,Response),
    gen_tcp:close(TcpSocket).

start()->
    spawn(gtd,run,[]).