%% This Source Code Form is subject to the terms of the Mozilla Public
%% License, v. 2.0. If a copy of the MPL was not distributed with this
%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
%%
%% Copyright (c) 2007-2020 VMware, Inc. or its affiliates.  All rights reserved.
%%

-module(rabbit_shovel_status).
-behaviour(gen_server).

-export([start_link/0]).

-export([report/3, remove/1, status/0, lookup/1]).

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

-define(SERVER, ?MODULE).
-define(ETS_NAME, ?MODULE).
-define(CHECK_FREQUENCY, 60000).

-record(state, {timer}).
-record(entry, {name, type, info, timestamp}).

start_link() ->
    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

report(Name, Type, Info) ->
    gen_server:cast(?SERVER, {report, Name, Type, Info, calendar:local_time()}).

remove(Name) ->
    gen_server:cast(?SERVER, {remove, Name}).

status() ->
    gen_server:call(?SERVER, status, infinity).

lookup(Name) ->
    gen_server:call(?SERVER, {lookup, Name}, infinity).

init([]) ->
    ?ETS_NAME = ets:new(?ETS_NAME,
                        [named_table, {keypos, #entry.name}, private]),
    {ok, ensure_timer(#state{})}.

handle_call(status, _From, State) ->
    Entries = ets:tab2list(?ETS_NAME),
    {reply, [{Entry#entry.name, Entry#entry.type, Entry#entry.info,
              Entry#entry.timestamp}
             || Entry <- Entries], State};

handle_call({lookup, Name}, _From, State) ->
    Link = case ets:lookup(?ETS_NAME, Name) of
               [Entry] -> [{name, Name},
                           {type, Entry#entry.type},
                           {info, Entry#entry.info},
                           {timestamp, Entry#entry.timestamp}];
               [] -> not_found
           end,
    {reply, Link, State}.

handle_cast({report, Name, Type, Info, Timestamp}, State) ->
    true = ets:insert(?ETS_NAME, #entry{name = Name, type = Type, info = Info,
                                        timestamp = Timestamp}),
    rabbit_event:notify(shovel_worker_status,
                        split_name(Name) ++ split_status(Info)),
    {noreply, State};

handle_cast({remove, Name}, State) ->
    true = ets:delete(?ETS_NAME, Name),
    rabbit_event:notify(shovel_worker_removed, split_name(Name)),
    {noreply, State}.

handle_info(check, State) ->
    rabbit_shovel_dyn_worker_sup_sup:cleanup_specs(),
    {noreply, ensure_timer(State)};
handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, State) ->
    rabbit_misc:stop_timer(State, #state.timer),
    ok.

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

split_status({running, MoreInfo})         -> [{status, running} | MoreInfo];
split_status({terminated, Reason})        -> [{status, terminated},
                                              {reason, Reason}];
split_status(Status) when is_atom(Status) -> [{status, Status}].

split_name({VHost, Name})           -> [{name,  Name},
                                        {vhost, VHost}];
split_name(Name) when is_atom(Name) -> [{name, Name}].

ensure_timer(State0) ->
    State1 = rabbit_misc:stop_timer(State0, #state.timer),
    rabbit_misc:ensure_timer(State1, #state.timer, ?CHECK_FREQUENCY, check).
