%% @author alexeikrasnopolski
%% @doc @todo Add description to monad_test.


-module(maybe_monad_test).

-include_lib("eunit/include/eunit.hrl").

%% ====================================================================
%% API functions
%% ====================================================================
-export([continuation/1, f1/1, f2/1, f3/1]).

bind(F, C) -> fun(nothing) -> nothing; (A) -> C(F(A)) end.
return() -> fun(A) -> A end.
  
%% continuation([f1, f2, f3]) ->
%%   bind(f1, 
%%            bind(f2, 
%%                     bind(f3, 
%%                               return)
%%                )
%%       )
%% .

continuation([]) -> return();
continuation([F | RF]) ->
  bind(F, continuation(RF))
.

f_test() ->
  Cont = continuation([fun f1/1,fun f2/1,fun f3/1]),
  io:format(user, "*** Result = ~p~n", [Cont(0)]),
  io:format(user, "*** Result = ~p~n", [Cont(1)]),
  io:format(user, "*** Result = ~p~n", [Cont(2)]),
  io:format(user, "*** Result = ~p~n", [Cont(3)])
.
%% ====================================================================
%% Internal functions
%% ====================================================================

f1(A) ->
  io:format(user, "f1 >>> ~p~n", [A]),
  case A of
    3 -> nothing;
    _ -> A + 1
  end
.

f2(A) ->
  io:format(user, "f2 >>> ~p~n", [A]),
  case A of
    3 -> nothing;
    _ -> A + 1
  end
.

f3(A) ->
  io:format(user, "f3 >>> ~p~n", [A]),
  case A of
    3 -> nothing;
    _ -> A + 1
  end
.