%%  Inspired by  "Programming Erlang",
%%  published by The Pragmatic Bookshelf.
%%  Copyrights apply to this code.
%%  We make no guarantees that this code is fit for any purpose.
%%  Visit http://www.pragmaticprogrammer.com/titles/jaerlang for more book information.

-module(server).
-export([start/2, start/3, rpc/2, swap_code/2]).

start(Name, Mod) ->
    register(Name, spawn(fun() -> loop(Name, Mod, Mod:init()) end)).

start(Name, Mod, State) ->
    register(Name, spawn(fun() -> loop(Name, Mod, State) end)).

swap_code(Name, Mod) -> rpc(Name, {swap_code, Mod}).

rpc(Name, Request) ->
    Name ! {self(), Request},
    receive
        {Name, crash} -> exit(rpc);
        {Name, ok, Response} -> Response
    end.

loop(Name, Mod, OldState) ->
    receive
        {From, {swap_code, NewCallbackMod}} ->
            From ! {Name, ok, ack},
            loop(Name, NewCallbackMod, OldState);
        {From, Request} ->
	    {Response, NewState} = Mod:handle(From, Request, OldState),
	    From ! {Name, ok, Response},
	    loop(Name, Mod, NewState)
            %% try Mod:handle(From, Request, OldState) of
            %%     {Response, NewState} ->
            %%         From ! {Name, ok, Response},
            %%         loop(Name, Mod, NewState)
            %% catch
            %%     _: Why ->
            %%         log_the_error(Name, Request, Why),
            %%         From ! {Name, crash},
            %%         loop(Name, Mod, OldState)
            %% end
    end.

log_the_error(Name, Request, Why) ->
    io:format("Server ~p request ~p ~n"
              "caused exception ~p~n",
              [Name, Request, Why]).