%% @doc Websocket client to connect to grisp.io
-module(grisp_connect_ws).

-export([start_link/0]).
-export([connect/0]).
-export([connect/2]).
-export([is_connected/0]).
-export([send/1]).

-behaviour(gen_server).

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

-record(state, {
    gun_pid,
    gun_ref,
    ws_stream,
    ws_up = false,
    ping_timer
}).

-include_lib("kernel/include/logger.hrl").

%--- API Functions -------------------------------------------------------------

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

connect() ->
    {ok, Domain} = application:get_env(grisp_connect, domain),
    {ok, Port} = application:get_env(grisp_connect, port),
    connect(Domain, Port).

connect(Server, Port) ->
    gen_server:cast(?MODULE, {?FUNCTION_NAME, Server, Port}).

is_connected() ->
    gen_server:call(?MODULE, ?FUNCTION_NAME).

send(Payload) ->
    gen_server:cast(?MODULE, {?FUNCTION_NAME, Payload}).

% gen_server callbacks ---------------------------------------------------------

init([]) -> {ok, #state{}}.

handle_call(is_connected, _, #state{ws_up = Up} = S) ->
    {reply, Up, S}.

handle_cast({connect, Server, Port}, #state{gun_pid = undefined} = S) ->
    GunOpts = #{
        protocols => [http],
        transport => tls,
        retry => 0,
        tls_opts => grisp_cryptoauth_tls:options(Server)
    },
    case gun:open(Server, Port, GunOpts) of
        {ok, GunPid} ->
            GunRef = monitor(process, GunPid),
            {noreply, #state{gun_pid = GunPid, gun_ref = GunRef}};
        Error ->
            ?LOG_ERROR(#{event => connection_failure, reason => Error}),
            {noreply, S}
    end;
handle_cast({connect, _Server, _Port}, S) ->
    {noreply, S};
handle_cast({send, _}, #state{ws_up = false} = S) ->
    ?LOG_ERROR(#{event => ws_send, reason => ws_disconnected}),
    {noreply, S};
handle_cast({send, Payload},  #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    gun:ws_send(Pid, Stream, {text, Payload}),
    {noreply, S}.

handle_info({gun_up, GunPid, _}, #state{gun_pid = GunPid} = S) ->
    ?LOG_INFO(#{event => connection_enstablished}),
    WsStream = gun:ws_upgrade(GunPid, "/grisp-connect/ws",[],
                              #{silence_pings => false}),
    NewS = S#state{gun_pid = GunPid, ws_stream = WsStream},
    {noreply, NewS};
handle_info({gun_up, Pid, http}, #state{gun_pid = GunPid} = S) ->
    ?LOG_WARNING("Ignoring unexpected gun_up http message"
                 " from pid ~p, current pid is ~p", [Pid, GunPid]),
    {noreply, S};
handle_info({gun_upgrade, Pid, Stream, [<<"websocket">>], _},
            #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    ?LOG_INFO(#{event => ws_upgrade}),
    {noreply, S#state{ws_up = true, ping_timer = start_ping_timer()}};
handle_info({gun_response, Pid, Stream, _, Status, _Headers},
            #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    ?LOG_ERROR(#{event => ws_upgrade_failure, status => Status}),
    {noreply, shutdown_gun(S)};
handle_info({gun_ws, Pid, Stream, ping},
            #state{gun_pid = Pid, ws_stream = Stream,
                   ping_timer = PingTimer} = S) ->
    timer:cancel(PingTimer),
    {noreply, S#state{ping_timer = start_ping_timer()}};
handle_info({gun_ws, Pid, Stream, {text, Text}},
            #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    grisp_connect_client:handle_message(Text),
    {noreply, S};
handle_info({gun_ws, Pid, Stream, {close, Code, Message}},
            #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    ?LOG_WARNING(#{event => stream_closed, code => Code, reason => Message}),
    {noreply, S};
handle_info({gun_error, Pid, _Stream, Reason}, #state{gun_pid = Pid} = S) ->
    ?LOG_ERROR(#{event => ws_closed, reason => Reason}),
    grisp_connect_client:disconnected(),
    {noreply, shutdown_gun(S)};
handle_info({gun_down, Pid, ws, closed, [Stream]}, #state{gun_pid = Pid, ws_stream = Stream} = S) ->
    ?LOG_WARNING(#{event => ws_closed}),
    grisp_connect_client:disconnected(),
    {noreply, shutdown_gun(S)};
handle_info({gun_down, Pid, ws, normal, _}, #state{gun_pid = Pid} = S) ->
    ?LOG_INFO(#{event => ws_closed, reason => normal}),
    grisp_connect_client:disconnected(),
    {noreply, shutdown_gun(S)};
handle_info({'DOWN', _, process, Pid, Reason}, #state{gun_pid = Pid,
                                                      ping_timer = Tref} = S) ->
    ?LOG_WARNING(#{event => gun_crash, reason => Reason}),
    timer:cancel(Tref),
    grisp_connect_client:disconnected(),
    {noreply, disconnected_state(S)};
handle_info(ping_timeout, S) ->
    ?LOG_WARNING(#{event => ping_timeout}),
    grisp_connect_client:disconnected(),
    {noreply, shutdown_gun(S)};
handle_info(M, S) ->
    ?LOG_WARNING(#{event => unhandled_info, info => M, state => S}),
    {noreply, S}.

% internal functions -----------------------------------------------------------

shutdown_gun(#state{gun_pid = Pid, gun_ref = GunRef,
                    ping_timer = PingTimer} = S) ->
    timer:cancel(PingTimer),
    demonitor(GunRef),
    gun:shutdown(Pid),
    disconnected_state(S).

start_ping_timer() ->
    {ok, Timeout} = application:get_env(grisp_connect, ws_ping_timeout),
    {ok, Tref} = timer:send_after(Timeout, ping_timeout),
    Tref.

disconnected_state(S) ->
    S#state{gun_pid = undefined, gun_ref = undefined,
            ws_up = false, ping_timer = undefined}.