%% Copyright (c) 2011 Basho Technologies, Inc.  All Rights Reserved.
%%
%% This file is provided to you under the Apache License,
%% Version 2.0 (the "License"); you may not use this file
%% except in compliance with the License.  You may obtain
%% a copy of the License at
%%
%%   http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
%% KIND, either express or implied.  See the License for the
%% specific language governing permissions and limitations
%% under the License.

-module(lager_util).

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

-export([levels/0, level_to_num/1, num_to_level/1, open_logfile/2,
        ensure_logfile/4, rotate_logfile/2, format_time/0, format_time/1,
        localtime_ms/0, maybe_utc/1, parse_rotation_date_spec/1,
        calculate_next_rotation/1]).

-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
-endif.

levels() ->
    [debug, info, notice, warning, error, critical, alert, emergency].

level_to_num(debug)     -> 7;
level_to_num(info)      -> 6;
level_to_num(notice)    -> 5;
level_to_num(warning)   -> 4;
level_to_num(error)     -> 3;
level_to_num(critical)  -> 2;
level_to_num(alert)     -> 1;
level_to_num(emergency) -> 0.

num_to_level(7) -> debug;
num_to_level(6) -> info;
num_to_level(5) -> notice;
num_to_level(4) -> warning;
num_to_level(3) -> error;
num_to_level(2) -> critical;
num_to_level(1) -> alert;
num_to_level(0) -> emergency.

open_logfile(Name, Buffer) ->
    case filelib:ensure_dir(Name) of
        ok ->
            Options = [append, raw] ++
            if Buffer == true -> [delayed_write];
                true -> []
            end,
            case file:open(Name, Options) of
                {ok, FD} ->
                    case file:read_file_info(Name) of
                        {ok, FInfo} ->
                            Inode = FInfo#file_info.inode,
                            {ok, {FD, Inode, FInfo#file_info.size}};
                        X -> X
                    end;
                Y -> Y
            end;
        Z -> Z
    end.

ensure_logfile(Name, FD, Inode, Buffer) ->
    case file:read_file_info(Name) of
        {ok, FInfo} ->
            Inode2 = FInfo#file_info.inode,
            case Inode == Inode2 of
                true ->
                    {ok, {FD, Inode, FInfo#file_info.size}};
                false ->
                    %% delayed write can cause file:close not to do a close
                    file:close(FD),
                    file:close(FD),
                    case open_logfile(Name, Buffer) of
                        {ok, {FD2, Inode3, Size}} ->
                            %% inode changed, file was probably moved and
                            %% recreated
                            {ok, {FD2, Inode3, Size}};
                        Error ->
                            Error
                    end
            end;
        _ ->
            %% delayed write can cause file:close not to do a close
            file:close(FD),
            file:close(FD),
            case open_logfile(Name, Buffer) of
                {ok, {FD2, Inode3, Size}} ->
                    %% file was removed
                    {ok, {FD2, Inode3, Size}};
                Error ->
                    Error
            end
    end.

%% returns localtime with milliseconds included
localtime_ms() ->
    {_, _, Micro} = Now = os:timestamp(),
    {Date, {Hours, Minutes, Seconds}} = calendar:now_to_local_time(Now),
    {Date, {Hours, Minutes, Seconds, Micro div 1000 rem 1000}}.

maybe_utc({Date, {H, M, S, Ms}}) ->
    case lager_stdlib:maybe_utc({Date, {H, M, S}}) of
        {utc, {Date1, {H1, M1, S1}}} ->
            {utc, {Date1, {H1, M1, S1, Ms}}};
        {Date1, {H1, M1, S1}} ->
            {Date1, {H1, M1, S1, Ms}}
    end.

rotate_logfile(File, 0) ->
    file:delete(File);
rotate_logfile(File, 1) ->
    file:rename(File, File++".0"),
    rotate_logfile(File, 0);
rotate_logfile(File, Count) ->
    file:rename(File ++ "." ++ integer_to_list(Count - 2), File ++ "." ++
        integer_to_list(Count - 1)),
    rotate_logfile(File, Count - 1).

format_time() ->
    format_time(maybe_utc(localtime_ms())).

format_time({utc, {{Y, M, D}, {H, Mi, S, Ms}}}) ->
    {io_lib:format("~b-~2..0b-~2..0b", [Y, M, D]),
        io_lib:format("~2..0b:~2..0b:~2..0b.~3..0b UTC", [H, Mi, S, Ms])};
format_time({{Y, M, D}, {H, Mi, S, Ms}}) ->
    {io_lib:format("~b-~2..0b-~2..0b", [Y, M, D]),
        io_lib:format("~2..0b:~2..0b:~2..0b.~3..0b", [H, Mi, S, Ms])};
format_time({utc, {{Y, M, D}, {H, Mi, S}}}) ->
    {io_lib:format("~b-~2..0b-~2..0b", [Y, M, D]),
        io_lib:format("~2..0b:~2..0b:~2..0b UTC", [H, Mi, S])};
format_time({{Y, M, D}, {H, Mi, S}}) ->
    {io_lib:format("~b-~2..0b-~2..0b", [Y, M, D]),
        io_lib:format("~2..0b:~2..0b:~2..0b", [H, Mi, S])}.

parse_rotation_day_spec([], Res) ->
    {ok, Res ++ [{hour, 0}]};
parse_rotation_day_spec([$D, D1, D2], Res) ->
    case list_to_integer([D1, D2]) of
        X when X >= 0, X =< 23 ->
            {ok, Res ++ [{hour, X}]};
        _ ->
            {error, invalid_date_spec}
    end;
parse_rotation_day_spec([$D, D], Res)  when D >= $0, D =< $9 ->
    {ok, Res ++ [{hour, D - 48}]};
parse_rotation_day_spec(_, _) ->
    {error, invalid_date_spec}.

parse_rotation_date_spec([$$, $W, W|T]) when W >= $0, W =< $6 ->
    Week = W - 48,
    parse_rotation_day_spec(T, [{day, Week}]);
parse_rotation_date_spec([$$, $M, L|T]) when L == $L; L == $l ->
    %% last day in month.
    parse_rotation_day_spec(T, [{date, last}]);
parse_rotation_date_spec([$$, $M, M1, M2|[$D|_]=T]) ->
    case list_to_integer([M1, M2]) of
        X when X >= 1, X =< 31 ->
            parse_rotation_day_spec(T, [{date, X}]);
        _ ->
            {error, invalid_date_spec}
    end;
parse_rotation_date_spec([$$, $M, M|[$D|_]=T]) ->
    parse_rotation_day_spec(T, [{date, M - 48}]);
parse_rotation_date_spec([$$, $M, M1, M2]) ->
    case list_to_integer([M1, M2]) of
        X when X >= 1, X =< 31 ->
            {ok, [{date, X}, {hour, 0}]};
        _ ->
            {error, invalid_date_spec}
    end;
parse_rotation_date_spec([$$, $M, M]) ->
    {ok, [{date, M - 48}, {hour, 0}]};
parse_rotation_date_spec([$$|X]) when X /= [] ->
    parse_rotation_day_spec(X, []);
parse_rotation_date_spec(_) ->
    {error, invalid_date_spec}.

calculate_next_rotation(Spec) ->
    Now = calendar:local_time(),
    Later = calculate_next_rotation(Spec, Now),
    calendar:datetime_to_gregorian_seconds(Later) -
      calendar:datetime_to_gregorian_seconds(Now).

calculate_next_rotation([], Now) ->
    Now;
calculate_next_rotation([{hour, X}|T], {{_, _, _}, {Hour, _, _}} = Now) when Hour < X ->
    %% rotation is today, sometime
    NewNow = setelement(2, Now, {X, 0, 0}),
    calculate_next_rotation(T, NewNow);
calculate_next_rotation([{hour, X}|T], {{_, _, _}, _} = Now) ->
    %% rotation is not today
    Seconds = calendar:datetime_to_gregorian_seconds(Now) + 86400,
    DateTime = calendar:gregorian_seconds_to_datetime(Seconds),
    NewNow = setelement(2, DateTime, {X, 0, 0}),
    calculate_next_rotation(T, NewNow);
calculate_next_rotation([{day, Day}|T], {Date, _Time} = Now) ->
    DoW = calendar:day_of_the_week(Date),
    AdjustedDay = case Day of
        0 -> 7;
        X -> X
    end,
    case AdjustedDay of
        DoW -> %% rotation is today
            OldDate = element(1, Now),
            case calculate_next_rotation(T, Now) of
                {OldDate, _} = NewNow -> NewNow;
                {NewDate, _} ->
                    %% rotation *isn't* today! rerun the calculation
                    NewNow = {NewDate, {0, 0, 0}},
                    calculate_next_rotation([{day, Day}|T], NewNow)
            end;
        Y when Y > DoW -> %% rotation is later this week
            PlusDays = Y - DoW,
            Seconds = calendar:datetime_to_gregorian_seconds(Now) + (86400 * PlusDays),
            {NewDate, _} = calendar:gregorian_seconds_to_datetime(Seconds),
            NewNow = {NewDate, {0, 0, 0}},
            calculate_next_rotation(T, NewNow);
        Y when Y < DoW -> %% rotation is next week
            PlusDays = ((7 - DoW) + Y),
            Seconds = calendar:datetime_to_gregorian_seconds(Now) + (86400 * PlusDays),
            {NewDate, _} = calendar:gregorian_seconds_to_datetime(Seconds),
            NewNow = {NewDate, {0, 0, 0}},
            calculate_next_rotation(T, NewNow)
    end;
calculate_next_rotation([{date, last}|T], {{Year, Month, Day}, _} = Now) ->
    Last = calendar:last_day_of_the_month(Year, Month),
    case Last == Day of
        true -> %% doing rotation today
            OldDate = element(1, Now),
            case calculate_next_rotation(T, Now) of
                {OldDate, _} = NewNow -> NewNow;
                {NewDate, _} ->
                    %% rotation *isn't* today! rerun the calculation
                    NewNow = {NewDate, {0, 0, 0}},
                    calculate_next_rotation([{date, last}|T], NewNow)
            end;
        false ->
            NewNow = setelement(1, Now, {Year, Month, Last}),
            calculate_next_rotation(T, NewNow)
    end;
calculate_next_rotation([{date, Date}|T], {{_, _, Date}, _} = Now) ->
    %% rotation is today
    OldDate = element(1, Now),
    case calculate_next_rotation(T, Now) of
        {OldDate, _} = NewNow -> NewNow;
        {NewDate, _} ->
            %% rotation *isn't* today! rerun the calculation
            NewNow = setelement(1, Now, NewDate),
            calculate_next_rotation([{date, Date}|T], NewNow)
    end;
calculate_next_rotation([{date, Date}|T], {{Year, Month, Day}, _} = Now) ->
    PlusDays = case Date of
        X when X < Day -> %% rotation is next month
            Last = calendar:last_day_of_the_month(Year, Month),
            (Last - Day);
        X when X > Day -> %% rotation is later this month
            X - Day
    end,
    Seconds = calendar:datetime_to_gregorian_seconds(Now) + (86400 * PlusDays),
    NewNow = calendar:gregorian_seconds_to_datetime(Seconds),
    calculate_next_rotation(T, NewNow).

-ifdef(TEST).

parse_test() ->
    ?assertEqual({ok, [{hour, 0}]}, parse_rotation_date_spec("$D0")),
    ?assertEqual({ok, [{hour, 23}]}, parse_rotation_date_spec("$D23")),
    ?assertEqual({ok, [{day, 0}, {hour, 23}]}, parse_rotation_date_spec("$W0D23")),
    ?assertEqual({ok, [{day, 5}, {hour, 16}]}, parse_rotation_date_spec("$W5D16")),
    ?assertEqual({ok, [{date, 1}, {hour, 0}]}, parse_rotation_date_spec("$M1D0")),
    ?assertEqual({ok, [{date, 5}, {hour, 6}]}, parse_rotation_date_spec("$M5D6")),
    ?assertEqual({ok, [{date, 5}, {hour, 0}]}, parse_rotation_date_spec("$M5")),
    ?assertEqual({ok, [{date, 31}, {hour, 0}]}, parse_rotation_date_spec("$M31")),
    ?assertEqual({ok, [{date, 31}, {hour, 1}]}, parse_rotation_date_spec("$M31D1")),
    ?assertEqual({ok, [{date, last}, {hour, 0}]}, parse_rotation_date_spec("$ML")),
    ?assertEqual({ok, [{date, last}, {hour, 0}]}, parse_rotation_date_spec("$Ml")),
    ?assertEqual({ok, [{day, 5}, {hour, 0}]}, parse_rotation_date_spec("$W5")),
    ok.

parse_fail_test() ->
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$D")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$D24")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$W7")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$W7D1")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$M32")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$M32D1")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$D15M5")),
    ?assertEqual({error, invalid_date_spec}, parse_rotation_date_spec("$M5W5")),
    ok.

rotation_calculation_test() ->
    ?assertMatch({{2000, 1, 2}, {0, 0, 0}},
        calculate_next_rotation([{hour, 0}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 1}, {16, 0, 0}},
        calculate_next_rotation([{hour, 16}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 2}, {12, 0, 0}},
        calculate_next_rotation([{hour, 12}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 2, 1}, {12, 0, 0}},
        calculate_next_rotation([{date, 1}, {hour, 12}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 2, 1}, {12, 0, 0}},
        calculate_next_rotation([{date, 1}, {hour, 12}], {{2000, 1, 15}, {12, 34, 43}})),
    ?assertMatch({{2000, 2, 1}, {12, 0, 0}},
        calculate_next_rotation([{date, 1}, {hour, 12}], {{2000, 1, 2}, {12, 34, 43}})),
    ?assertMatch({{2000, 2, 1}, {12, 0, 0}},
        calculate_next_rotation([{date, 1}, {hour, 12}], {{2000, 1, 31}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 1}, {16, 0, 0}},
        calculate_next_rotation([{date, 1}, {hour, 16}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 15}, {16, 0, 0}},
        calculate_next_rotation([{date, 15}, {hour, 16}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 31}, {16, 0, 0}},
        calculate_next_rotation([{date, last}, {hour, 16}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 31}, {16, 0, 0}},
        calculate_next_rotation([{date, last}, {hour, 16}], {{2000, 1, 31}, {12, 34, 43}})),
    ?assertMatch({{2000, 2, 29}, {16, 0, 0}},
        calculate_next_rotation([{date, last}, {hour, 16}], {{2000, 1, 31}, {17, 34, 43}})),
    ?assertMatch({{2001, 2, 28}, {16, 0, 0}},
        calculate_next_rotation([{date, last}, {hour, 16}], {{2001, 1, 31}, {17, 34, 43}})),

    ?assertMatch({{2000, 1, 1}, {16, 0, 0}},
        calculate_next_rotation([{day, 6}, {hour, 16}], {{2000, 1, 1}, {12, 34, 43}})),
    ?assertMatch({{2000, 1, 8}, {16, 0, 0}},
        calculate_next_rotation([{day, 6}, {hour, 16}], {{2000, 1, 1}, {17, 34, 43}})),
    ?assertMatch({{2000, 1, 7}, {16, 0, 0}},
        calculate_next_rotation([{day, 5}, {hour, 16}], {{2000, 1, 1}, {17, 34, 43}})),
    ?assertMatch({{2000, 1, 3}, {16, 0, 0}},
        calculate_next_rotation([{day, 1}, {hour, 16}], {{2000, 1, 1}, {17, 34, 43}})),
    ?assertMatch({{2000, 1, 2}, {16, 0, 0}},
        calculate_next_rotation([{day, 0}, {hour, 16}], {{2000, 1, 1}, {17, 34, 43}})),
    ?assertMatch({{2000, 1, 9}, {16, 0, 0}},
        calculate_next_rotation([{day, 0}, {hour, 16}], {{2000, 1, 2}, {17, 34, 43}})),
    ?assertMatch({{2000, 2, 3}, {16, 0, 0}},
        calculate_next_rotation([{day, 4}, {hour, 16}], {{2000, 1, 29}, {17, 34, 43}})),

    ?assertMatch({{2000, 1, 7}, {16, 0, 0}},
        calculate_next_rotation([{day, 5}, {hour, 16}], {{2000, 1, 3}, {17, 34, 43}})),
    
    ?assertMatch({{2000, 1, 3}, {16, 0, 0}},
        calculate_next_rotation([{day, 1}, {hour, 16}], {{1999, 12, 28}, {17, 34, 43}})),
    ok.

rotate_file_test() ->
    file:delete("rotation.log"),
    [file:delete(["rotation.log.", integer_to_list(N)]) || N <- lists:seq(0, 9)],
    [begin
                file:write_file("rotation.log", integer_to_list(N)),
                Count = case N > 10 of
                    true -> 10;
                    _ -> N
                end,
                [begin
                            FileName = ["rotation.log.", integer_to_list(M)],
                            ?assert(filelib:is_regular(FileName)),
                            %% check the expected value is in the file
                            Number = list_to_binary(integer_to_list(N - M - 1)),
                            ?assertEqual({ok, Number}, file:read_file(FileName))
                end
                || M <- lists:seq(0, Count-1)],
                rotate_logfile("rotation.log", 10)
    end || N <- lists:seq(0, 20)].


-endif.