ring.erl

-module(ring).

-export([start/0]).

% start/0 top function to run.
% c(ring).
% ring:start().

start() -> 
    % trace who (process) called the func (mod:func)
    dbg:tracer(),
    dbg:p(all, c),
    dbg:tpl(?MODULE, x),
    run_ring(3, 2).

run_ring(RingSize, MsgRepeatCount) ->
    start_ring_element(self(), RingSize, MsgRepeatCount).
    
start_ring_element(StartRingPid, 1, MsgRepeatCount) ->
    StartRingPid ! {self(), StartRingPid},
    ring_last_element(StartRingPid, MsgRepeatCount);
start_ring_element(StartRingPid, NumberOfRingElemetsLeft, MsgRepeatCount) ->
    NextPid = spawn(fun() -> start_ring_element(StartRingPid, NumberOfRingElemetsLeft - 1, MsgRepeatCount) end),
    ring_element(NextPid).

ring_element(NextPid) ->
    receive
        stop -> 
            NextPid ! stop;
        {From, To} ->
            io:format("Msg from = ~p \t to: ~p\n", [From, To]),
            NextPid ! {self(), NextPid},
            ring_element(NextPid)
    end.

ring_last_element(NextPid, 0) ->
    NextPid ! stop;
ring_last_element(NextPid, MsgRepeatCount) ->
    receive
        stop -> NextPid ! stop;
        Msg -> NextPid ! Msg,
        ring_last_element(NextPid, MsgRepeatCount - 1)
    end.