%%%=============================================================================
%%% Copyright (c) 2012 Lindenbaum GmbH
%%%
%%% Permission to use, copy, modify, and/or distribute this software for any
%%% purpose with or without fee is hereby granted, provided that the above
%%% copyright notice and this permission notice appear in all copies.
%%%
%%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%%%
%%% @doc
%%% A server that periodically polls information for a specific IPMI target.
%%% The server monitors its corresponding {@link eipmi_session} process and
%%% exits as soon as the session gets down. The server itself will report
%%% unavailability of the target when the SEL can't be read for longer than 30
%%% seconds.
%%%
%%% Currently only polling of the target's System Event Log (SEL) is supported.
%%% All entries retrieved from the SEL will be forwarded as messages
%%% to the session owner.
%%% @end
%%%=============================================================================
-module(eipmi_poll).

-behaviour(gen_server).

%% API
-export([start_link/3]).

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

-include("eipmi.hrl").

%%------------------------------------------------------------------------------
%% Polling server defaults modifyable by the user.
%%------------------------------------------------------------------------------
-define(DEFAULTS, [
    {read_sel, 500},
    {clear_sel, true}
]).

%%%=============================================================================
%%% API
%%%=============================================================================

%%------------------------------------------------------------------------------
%% @doc
%% Start a polling server for the given session process.
%% @end
%%------------------------------------------------------------------------------
-spec start_link(pid(), eipmi:session(), [eipmi:option()]) ->
    {ok, pid()} | {error, term()}.
start_link(SessionPid, Session, Options) ->
    gen_server:start_link(?MODULE, [SessionPid, Session, Options], []).

%%%=============================================================================
%%% gen_server Callbacks
%%%=============================================================================

-record(state, {
    pid :: pid(),
    owner :: pid(),
    last_sucess :: erlang:timestamp() | undefined,
    session :: eipmi:session(),
    address :: inet:ip4_address(),
    properties :: [eipmi:option()]
}).

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
init([Pid, Session = {session, {Addr, _}, {Owner, _}}, Options]) ->
    erlang:monitor(process, Pid),
    Opts = eipmi_util:merge_vals(Options, ?DEFAULTS),
    {ok,
        start_timers(
            on_success(#state{
                pid = Pid,
                session = Session,
                owner = Owner,
                address = Addr,
                properties = Opts
            })
        )}.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
handle_call(Request, _From, State) ->
    {reply, undef, fire({unhandled, {call, Request}}, State)}.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
handle_cast(Request, State) ->
    {noreply, fire({unhandled, {cast, Request}}, State)}.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
handle_info({'DOWN', _, process, P, _}, State = #state{pid = P}) ->
    {stop, normal, State};
handle_info(read_sel, State) ->
    {noreply, start_timer(read_sel, read_sel(State))};
handle_info(Info, State) ->
    {noreply, fire({unhandled, {info, Info}}, State)}.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
terminate(_Reason, _State) ->
    ok.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%%=============================================================================
%%% Internal functions
%%%=============================================================================

-define(is_timer(I), is_integer(I) andalso I > 0).

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
read_sel(State = #state{pid = Pid, properties = Ps}) ->
    case catch eipmi_sel:read(Pid, proplists:get_value(clear_sel, Ps)) of
        {ok, Entries} ->
            lists:foldl(fun fire/2, on_success(State), Entries);
        {error, Reason} ->
            on_failure(Reason, State);
        Catch ->
            on_failure(Catch, State)
    end.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
start_timers(State = #state{properties = Ps}) ->
    Actions = [Action || {Action, Interval} <- Ps, ?is_timer(Interval)],
    lists:foldl(fun start_timer/2, State, Actions).

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
start_timer(Message, State = #state{properties = Ps}) ->
    erlang:send_after(proplists:get_value(Message, Ps), self(), Message),
    State.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
on_success(State) -> State#state{last_sucess = os:timestamp()}.

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
on_failure(Reason, State = #state{pid = Pid, last_sucess = T1}) ->
    case timer:now_diff(os:timestamp(), T1) of
        Tdiff when Tdiff > 30 * 1000 * 1000 ->
            eipmi_session:stop(Pid, lost_connection);
        _ ->
            ok
    end,
    fire({sel_read_error, Reason}, State).

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
fire(Event, State = #state{session = Session, address = Address}) ->
    State#state.owner ! {ipmi, Session, Address, Event},
    State.