%%%-------------------------------------------------------------------
%%% @doc Endpoint diagnostic log.
%%%
%%% 当前用于记录 publish 时没有匹配到任何订阅者的数据，避免这类信息进入
%%% endpoint_subscription 的热路径同步磁盘写入。
%%%-------------------------------------------------------------------
-module(endpoint_log).

-behaviour(gen_server).

%% API
-export([start_link/0, unmatched_publish/2]).

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

-define(SERVER, ?MODULE).
-define(LOG_NAME, endpoint_unmatched_publish_log).
-define(DEFAULT_PATH_TEMPLATE, "${endpoint_root}/endpoint_log/unmatched_publish.log").
-define(DEFAULT_ENDPOINT_ROOT_DIR, "log").
-define(DEFAULT_MAX_BYTES, 10485760).
-define(DEFAULT_MAX_FILES, 10).
-define(MAX_LOG_CONTENT_BYTES, 32 * 1024).

-record(state, {
    enabled = false :: boolean(),
    log_name = ?LOG_NAME :: atom()
}).

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

-spec start_link() -> {ok, pid()} | ignore | {error, term()}.
start_link() ->
    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

-spec unmatched_publish(RouteKey :: binary(), Content :: binary()) -> ok.
unmatched_publish(RouteKey, Content) when is_binary(RouteKey), is_binary(Content) ->
    case erlang:whereis(?SERVER) of
        undefined ->
            ok;
        Pid when is_pid(Pid) ->
            gen_server:cast(Pid, {unmatched_publish, RouteKey, Content}),
            ok
    end.

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

-spec init(term()) -> {ok, #state{}}.
init([]) ->
    ok = endpoint_util:set_metadata(),
    case open_log() of
        ok ->
            {ok, #state{enabled = true}};
        {error, Reason} ->
            logger:warning("[endpoint_log] open disk_log failed, reason: ~p", [Reason]),
            {ok, #state{enabled = false}}
    end.

-spec handle_call(term(), gen_server:from(), #state{}) ->
    {reply, ok, #state{}}.
handle_call(_Request, _From, State) ->
    {reply, ok, State}.

-spec handle_cast(term(), #state{}) -> {noreply, #state{}}.
handle_cast({unmatched_publish, RouteKey, Content}, State = #state{enabled = true, log_name = LogName}) ->
    Entry = encode_unmatched_publish(RouteKey, Content),
    case disk_log:blog(LogName, Entry) of
        ok ->
            {noreply, State};
        {error, Reason} ->
            logger:warning("[endpoint_log] write unmatched publish log failed, reason: ~p", [Reason]),
            {noreply, State#state{enabled = false}}
    end;
handle_cast({unmatched_publish, _RouteKey, _Content}, State) ->
    {noreply, State};
handle_cast(_Request, State) ->
    {noreply, State}.

-spec handle_info(term(), #state{}) -> {noreply, #state{}}.
handle_info(Info, State) ->
    logger:debug("[endpoint_log] unknown info: ~p", [Info]),
    {noreply, State}.

-spec terminate(term(), #state{}) -> ok.
terminate(_Reason, #state{enabled = true, log_name = LogName}) ->
    _ = disk_log:close(LogName),
    ok;
terminate(_Reason, _State) ->
    ok.

-spec code_change(term() | {down, term()}, #state{}, term()) ->
    {ok, #state{}} | {error, term()}.
code_change(_OldVsn, State = #state{}, _Extra) ->
    {ok, State}.

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

-spec open_log() -> ok | {error, term()}.
open_log() ->
    Config = log_config(),
    Path = log_path(Config),
    ok = filelib:ensure_dir(Path),
    case disk_log:open([
        {name, ?LOG_NAME},
        {file, Path},
        {type, wrap},
        {format, external},
        {size, {config_pos_integer(max_bytes, Config, ?DEFAULT_MAX_BYTES),
                config_pos_integer(max_files, Config, ?DEFAULT_MAX_FILES)}},
        {linkto, self()},
        {repair, true}
    ]) of
        {ok, ?LOG_NAME} ->
            ok;
        {repaired, ?LOG_NAME, _Recovered, _BadBytes} ->
            ok;
        {error, Reason} ->
            {error, Reason}
    end.

-spec log_config() -> proplists:proplist().
log_config() ->
    case application:get_env(endpoint, endpoint_log) of
        {ok, Config} when is_list(Config) ->
            Config;
        _ ->
            []
    end.

-spec log_path(proplists:proplist()) -> file:filename_all().
log_path(Config) ->
    Template = proplists:get_value(path, Config, ?DEFAULT_PATH_TEMPLATE),
    expand_path_template(Template).

-spec endpoint_root_dir() -> file:filename_all().
endpoint_root_dir() ->
    case application:get_env(endpoint, endpoints) of
        {ok, Endpoints} ->
            proplists:get_value(root_dir, Endpoints, ?DEFAULT_ENDPOINT_ROOT_DIR);
        undefined ->
            ?DEFAULT_ENDPOINT_ROOT_DIR
    end.

-spec config_pos_integer(atom(), proplists:proplist(), pos_integer()) -> pos_integer().
config_pos_integer(Key, Config, Default) ->
    case proplists:get_value(Key, Config, Default) of
        Value when is_integer(Value), Value > 0 ->
            Value;
        _ ->
            Default
    end.

-spec expand_path_template(file:filename_all()) -> file:filename_all().
expand_path_template(Template) ->
    TemplateBin = iolist_to_binary(Template),
    Vars = path_vars(),
    Expanded = lists:foldl(fun({Name, Value}, Acc) ->
        replace_path_var(Name, Value, Acc)
    end, TemplateBin, Vars),
    binary_to_list(Expanded).

-spec path_vars() -> [{binary(), binary()}].
path_vars() ->
    {{Year, Month, Day}, {Hour, _Minute, _Second}} = calendar:local_time(),
    [
        {<<"endpoint_root">>, iolist_to_binary(endpoint_root_dir())},
        {<<"date">>, format_date(Year, Month, Day)},
        {<<"year">>, integer_to_binary(Year)},
        {<<"month">>, two_digits(Month)},
        {<<"day">>, two_digits(Day)},
        {<<"hour">>, two_digits(Hour)},
        {<<"node">>, atom_to_binary(node(), utf8)}
    ].

-spec replace_path_var(binary(), binary(), binary()) -> binary().
replace_path_var(Name, Value, Template) ->
    Template0 = binary:replace(Template, <<"${", Name/binary, "}">>, Value, [global]),
    binary:replace(Template0, <<"{", Name/binary, "}">>, Value, [global]).

-spec encode_unmatched_publish(binary(), binary()) -> binary().
encode_unmatched_publish(RouteKey, Content) ->
    {LoggedContent, Truncated} = maybe_truncate(Content),
    iolist_to_binary([
        format_local_time(), <<"\t">>,
        <<"unmatched_publish">>, <<"\t">>,
        RouteKey, <<"\t">>,
        integer_to_binary(byte_size(Content)), <<"\t">>,
        boolean_to_binary(Truncated), <<"\t">>,
        base64:encode(LoggedContent), <<"\n">>
    ]).

-spec boolean_to_binary(boolean()) -> binary().
boolean_to_binary(true) ->
    <<"true">>;
boolean_to_binary(false) ->
    <<"false">>.

-spec format_local_time() -> binary().
format_local_time() ->
    MilliSeconds = erlang:system_time(millisecond) rem 1000,
    {{Year, Month, Day}, {Hour, Minute, Second}} = calendar:local_time(),
    iolist_to_binary(io_lib:format(
        "~4..0B-~2..0B-~2..0B ~2..0B:~2..0B:~2..0B.~3..0B",
        [Year, Month, Day, Hour, Minute, Second, MilliSeconds]
    )).

-spec format_date(integer(), integer(), integer()) -> binary().
format_date(Year, Month, Day) ->
    iolist_to_binary(io_lib:format("~4..0B-~2..0B-~2..0B", [Year, Month, Day])).

-spec two_digits(integer()) -> binary().
two_digits(Value) ->
    iolist_to_binary(io_lib:format("~2..0B", [Value])).

-spec maybe_truncate(binary()) -> {binary(), boolean()}.
maybe_truncate(Content) when byte_size(Content) =< ?MAX_LOG_CONTENT_BYTES ->
    {Content, false};
maybe_truncate(Content) ->
    MaxBytes = ?MAX_LOG_CONTENT_BYTES,
    <<LoggedContent:MaxBytes/binary, _/binary>> = Content,
    {LoggedContent, true}.