%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%

%%
%% Description: User register for ssh_cli

-module(ssh_userreg).

-behaviour(gen_server).

%% API
-export([start_link/0,
	 register_user/2,
	 lookup_user/1,
	 delete_user/1]).

%% gen_server callbacks
-export([init/1,
	 handle_call/3,
	 handle_cast/2,
	 handle_info/2,
	 terminate/2,
	 code_change/3]).

-record(state, {user_db = []}).

%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description: Starts the server
%%--------------------------------------------------------------------
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

register_user(User, Cm) ->
    gen_server:cast(?MODULE, {register, {User, Cm}}).

delete_user(Cm) ->
    gen_server:cast(?MODULE, {delete, Cm}).

lookup_user(Cm) ->
    gen_server:call(?MODULE, {get_user, Cm}, infinity).

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([]) ->
    {ok, #state{}}.

%%--------------------------------------------------------------------
%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call({get_user, Cm}, _From, #state{user_db = Db} = State) ->
    User = lookup(Cm, Db),
    {reply, {ok, User}, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% Description: Handling cast messages
%%--------------------------------------------------------------------
handle_cast({register, UserCm}, State) ->
    {noreply, insert(UserCm, State)};
handle_cast({delete, UserCm}, State) ->
    {noreply, delete(UserCm, State)}.

%%--------------------------------------------------------------------
%% Function: handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% Description: Handling all non call/cast messages
%%--------------------------------------------------------------------
handle_info(_Info, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, State) -> void()
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
    ok.

%%--------------------------------------------------------------------
%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
insert({User, Cm}, #state{user_db = Db} = State) ->
    State#state{user_db = [{User, Cm} | Db]}.

delete(Cm, #state{user_db = Db} = State) ->
    State#state{user_db = lists:keydelete(Cm, 2, Db)}.

lookup(_, []) ->
    undefined;
lookup(Cm, [{User, Cm} | _Rest]) ->
    User;
lookup(Cm, [_ | Rest]) ->
    lookup(Cm, Rest).