1 files changed, 57 insertions, 0 deletions
diff --git a/learn-you-some-erlang/kitty_gen_server.erl b/learn-you-some-erlang/kitty_gen_server.erl
new file mode 100644
index 0000000..c906a6a
--- /dev/null
+++ b/learn-you-some-erlang/kitty_gen_server.erl
@@ -0,0 +1,57 @@
+-module(kitty_gen_server).
+-behaviour(gen_server).
+
+-export([start_link/0, order_cat/4, return_cat/2, close_shop/1]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+         terminate/2, code_change/3]).
+
+-record(cat, {name, color=green, description}).
+
+%%% Client API
+start_link() ->
+    gen_server:start_link(?MODULE, [], []).
+
+%% Synchronous call
+order_cat(Pid, Name, Color, Description) ->
+   gen_server:call(Pid, {order, Name, Color, Description}).
+
+%% This call is asynchronous
+return_cat(Pid, Cat = #cat{}) ->
+    gen_server:cast(Pid, {return, Cat}).
+
+%% Synchronous call
+close_shop(Pid) ->
+    gen_server:call(Pid, terminate).
+
+%%% Server functions
+init([]) -> {ok, []}. %% no treatment of info here!
+
+handle_call({order, Name, Color, Description}, _From, Cats) ->
+    if Cats =:= [] ->
+        {reply, make_cat(Name, Color, Description), Cats};
+       Cats =/= [] ->
+        {reply, hd(Cats), tl(Cats)}
+    end;
+handle_call(terminate, _From, Cats) ->
+    {stop, normal, ok, Cats}.
+
+handle_cast({return, Cat = #cat{}}, Cats) ->
+    {noreply, [Cat|Cats]}.
+
+handle_info(Msg, Cats) ->
+    io:format("Unexpected message: ~p~n",[Msg]),
+    {noreply, Cats}.
+
+terminate(normal, Cats) ->
+    [io:format("~p was set free.~n",[C#cat.name]) || C <- Cats],
+    ok.
+
+code_change(_OldVsn, State, _Extra) ->
+    %% No change planned. The function is there for the behaviour,
+    %% but will not be used. Only a version on the next
+    {ok, State}. 
+
+%%% Private functions
+make_cat(Name, Col, Desc) ->
+    #cat{name=Name, color=Col, description=Desc}.
+