% ag_server6.erl - (Silver) Adventure Game Server

-module(ag_server6).
-author('Alan G. Labouseur').

-type direction() :: north | south | east | west.

%--------
% Public 
%--------

-export([start/0, goToLocale/2, move/2]).

start() -> 
   io:fwrite("Starting AG server.~n",[]), 
   spawn(fun serverLoop/0).

goToLocale(ServerPid, Destination) -> 
   rpc(ServerPid, Destination).

-spec move(integer(), direction()) -> integer(). %  This is not enforced at runtime. It's for Dializer.
move(CurrentLocale, Direction) ->
   io:fwrite("Attempting to move ~w from location ~w.~n",[Direction, CurrentLocale]),
	NewLocaleNumber = mapper(CurrentLocale, Direction),
	NewLocaleDesciption = describe(NewLocaleNumber),
	io:fwrite("Moved to location ~w: ~s.~n",[NewLocaleNumber, NewLocaleDesciption]).


%---------
% Private 
%---------

mapper(0, north) -> 1;
mapper(0, south) -> 2;
mapper(0, west)  -> 5;
mapper(1, south) -> 0;
mapper(1, west)  -> 5;
mapper(2, north) -> 0;
mapper(2, east)  -> 4;
mapper(3, south) -> 4;
mapper(4, north) -> 3;
mapper(4, west)  -> 2;
mapper(5, north) -> 1;
mapper(5, east)  -> 0;
mapper(_, _)     -> -1.


describe(0)   -> "Inn of the Last Home";
describe(1)   -> "Yellow Brick Road";
describe(2)   -> "Depths of the Earth";
describe(3)   -> "Vault of the Drow";
describe(4)   -> "Mouth of the Yawning Cave";
describe(5)   -> "West Lake";
describe(-1)  -> "You cannot go that way";
describe(Loc) -> io:format("Oops! Unknown locale: ~w.", [Loc]).


rpc(ToPid, Request) -> 
   ToPid ! {self(), Request}, 
   receive                      
      {ToPid, Response} -> Response  % This waits for a response from ToPid.
   end.


serverLoop() -> 
  receive
     { FromPid, {0, L} } -> 
	     FromPid ! {self(), io:format("You are standing west of a house. Inventory: ~w.~n", [L])},
        serverLoop();

     { FromPid, {1, L} } -> 
	     FromPid ! {self(), io:format("You have come to the base of a large tree. Inventory: ~w.~n", [L])},
        serverLoop();

     { FromPid, {_, L} } -> 
	     FromPid ! {self(), io:format("You are lost in unknown locale. Good going, Indiana. Perhaps one of these items will help:~w.~n", [L])},
        serverLoop()
  end.