-module (ring).
-export ([start/2]).

start(N, M) ->
	statistics(runtime),
    statistics(wall_clock),
	Main_process = self(),
	io:format("Creating ~p ring processes~n", [N]),
	spawn(fun() -> ring(1, N, M, self(), Main_process) end),
	receive
		ended -> void
	end,
	{_, Time1} = statistics(runtime),
    {_, Time2} = statistics(wall_clock),
    U1 = Time1,
    U2 = Time2,
    io:format("Ring benchmark for ~p processes and ~p messages = ~p (~p) milliseconds~n", [N, M, U1, U2]).

ring(_, N, _, _, _) when(N =< 0)->
	io:format("Empty ring~n"),
	erlang:error(emptyRing);
ring(_, _, M, _, _) when(M =< 0)->
	io:format("No messages to send~n"),
	erlang:error(noMessagesToSend);
ring(N, N, M, First_process, Main_process) ->
	io:format("Ring process ~p (~p) created~n", [N, self()]),
	io:format("Sending ~p messages through the ring~n", [M]),
	First_process ! {send, main_process, Main_process},
	loop(M, N, N, First_process, Main_process);
ring(I, N, M, First_process, Main_process) ->
	io:format("Ring process ~p (~p) created~n", [I, self()]),
	Next_process = spawn(fun() -> ring(I+1, N, M, First_process, Main_process) end),
	loop(M, I, N, Next_process, Main_process).

loop(0, N, N, _, Main_process) ->
	io:format("Ring process ~p (~p) finished~n", [N, self()]),
	Main_process ! ended;
loop(0, I, _, _, _) -> 
	io:format("Ring process ~p (~p) finished~n", [I, self()]);
loop(M, I, N, Next_process, Main_process) ->
	receive
		{send, From, From_process} ->
			io:format("Process ~p (~p) received message ~p from process ~p (~p) ~n", [I, self(), M, From, From_process]),
			Next_process ! {send, I, self()},
			loop(M-1, I, N, Next_process, Main_process)
	end.