-module(ephp_datetime).

-author('manuel@altenwald.com').

-include("ephp.hrl").

-export([get_tz_version/0, get_tz/2, set_tz/1, get_abbr_weekday/1, get_abbr_month/1,
         get_timestamp/1, get_month/1, get_weekday/1, posix_time/0, posix_time_ms/0, timestamp/0,
         is_dst/2, to_zone/2, get_datetime/1, to_bmt/1, get_tz_time/3]).

-type month() :: 1..12.
-type daynum() :: 1..7.

get_tz_version(Name) when Name =:= "rebar3" orelse Name =:= undefined ->
    Filename = "tzdata/version",
    FullFilename =
        filename:join(
            code:priv_dir(ezic), Filename),
    {ok, Content} = file:read_file(FullFilename),
    Content;
get_tz_version(Name) ->
    {ok, Sections} = escript:extract(Name, []),
    Zip = proplists:get_value(archive, Sections),
    Opts = [{file_list, ["ezic/priv/tzdata/version"]}, memory],
    {ok, [{_, ZipContent}]} = zip:extract(Zip, Opts),
    ZipContent.

-spec get_tz_version() -> binary().
get_tz_version() ->
    try
        Name =
            filename:basename(
                escript:script_name()),
        get_tz_version(Name)
    catch
        error:{badmatch, []} ->
            get_tz_version(undefined)
    end.

-spec get_tz(ephp:context_id(), line()) -> binary().
get_tz(Context, Line) ->
    case ephp_config:get(<<"date.timezone">>) of
        undefined ->
            File = ephp_context:get_active_file(Context),
            ephp_error:handle_error(Context,
                                    {error, enotimezone, Line, File, ?E_WARNING, {<<"date">>}}),
            ?PHP_DEFAULT_TIMEZONE;
        Timezone ->
            Timezone
    end.

-spec set_tz(binary()) -> boolean().
set_tz(TZ) ->
    case ephp_timezone:is_valid(TZ) of
        true ->
            ephp_config:set(<<"date.timezone">>, TZ),
            true;
        false ->
            false
    end.

-spec get_timestamp(TS :: integer() | float()) -> erlang:timestamp().
get_timestamp(Timestamp) ->
    M = trunc(Timestamp) div 1000000,
    S = trunc(Timestamp) rem 1000000,
    U = trunc(Timestamp * 1000000) rem 1000000,
    {M, S, U}.

-spec get_abbr_month(month()) -> binary().
get_abbr_month(1) ->
    <<"Jan">>;
get_abbr_month(2) ->
    <<"Feb">>;
get_abbr_month(3) ->
    <<"Mar">>;
get_abbr_month(4) ->
    <<"Apr">>;
get_abbr_month(5) ->
    <<"May">>;
get_abbr_month(6) ->
    <<"Jun">>;
get_abbr_month(7) ->
    <<"Jul">>;
get_abbr_month(8) ->
    <<"Aug">>;
get_abbr_month(9) ->
    <<"Sep">>;
get_abbr_month(10) ->
    <<"Oct">>;
get_abbr_month(11) ->
    <<"Nov">>;
get_abbr_month(12) ->
    <<"Dec">>.

-spec get_month(month()) -> binary().
get_month(1) ->
    <<"January">>;
get_month(2) ->
    <<"February">>;
get_month(3) ->
    <<"March">>;
get_month(4) ->
    <<"April">>;
get_month(5) ->
    <<"May">>;
get_month(6) ->
    <<"June">>;
get_month(7) ->
    <<"July">>;
get_month(8) ->
    <<"August">>;
get_month(9) ->
    <<"September">>;
get_month(10) ->
    <<"October">>;
get_month(11) ->
    <<"November">>;
get_month(12) ->
    <<"December">>.

-spec get_abbr_weekday(daynum()) -> binary().
get_abbr_weekday(1) ->
    <<"Mon">>;
get_abbr_weekday(2) ->
    <<"Tue">>;
get_abbr_weekday(3) ->
    <<"Wed">>;
get_abbr_weekday(4) ->
    <<"Thu">>;
get_abbr_weekday(5) ->
    <<"Fri">>;
get_abbr_weekday(6) ->
    <<"Sat">>;
get_abbr_weekday(7) ->
    <<"Sun">>.

-spec get_weekday(daynum()) -> binary().
get_weekday(1) ->
    <<"Monday">>;
get_weekday(2) ->
    <<"Tuesday">>;
get_weekday(3) ->
    <<"Wednesday">>;
get_weekday(4) ->
    <<"Thursday">>;
get_weekday(5) ->
    <<"Friday">>;
get_weekday(6) ->
    <<"Saturday">>;
get_weekday(7) ->
    <<"Sunday">>.

-spec posix_time() -> integer().
posix_time() ->
    {MS, S, _} = timestamp(),
    MS * 1000000 + S.

-spec posix_time_ms() -> integer().
posix_time_ms() ->
    {MS, S, MiS} = timestamp(),
    (MS * 1000000 + S) * 1000 + MiS div 1000.

-spec timestamp() -> erlang:timestamp().
-ifndef(TEST).

%% @doc Show timestamp. This function makes possible to overload the normal
%%      Erlang behaviour to make tests reliable.
%% @end
timestamp() ->
    os:timestamp().

-else.

%% @private
timestamp() ->
    {1474, 806235, 701464}.

-endif.

-spec normalize_tz(string() | binary()) -> string().
normalize_tz(TZ) when is_binary(TZ) ->
    normalize_tz(binary_to_list(TZ));
normalize_tz("UTC") ->
    "Etc/UTC";
normalize_tz("GMT") ->
    "Etc/GMT";
%% TODO: normalize more timezones and throw error...
normalize_tz(Zone) ->
    Zone.

-spec is_dst(calendar:datetime(), string() | binary()) -> boolean().
is_dst(Datetime, RawTZ) ->
    TZ = normalize_tz(RawTZ),
    ezic:has_dst_local(Datetime, TZ).

-spec to_zone(calendar:date(), string() | binary()) -> calendar:datetime().
to_zone(Date, RawTZ) ->
    TZ = normalize_tz(RawTZ),
    ezic:utc_to_local(
        calendar:now_to_universal_time(Date), TZ).

-spec get_datetime(pos_integer()) -> calendar:datetime().
get_datetime(Timestamp) when is_number(Timestamp) ->
    {_, _, _} = T = get_timestamp(Timestamp),
    calendar:now_to_datetime(T).

-spec to_bmt(calendar:datetime()) -> pos_integer().
to_bmt(DateTime) ->
    {_, {H, M, S}} = ezic:utc_to_local(DateTime, "Etc/GMT-1"),
    trunc(((H * 60 + M) * 60 + S) / 86.4).

-spec get_tz_time(calendar:datetime(), string() | binary(), binary()) -> binary().
get_tz_time(DateTime, TZ, Sep) ->
    UTCDateTime = ezic:local_to_utc(DateTime, normalize_tz(TZ)),
    UTCTime = calendar:datetime_to_gregorian_seconds(UTCDateTime),
    Time = calendar:datetime_to_gregorian_seconds(DateTime),
    case UTCTime - Time of
        Diff when Diff =< 0 ->
            <<"+",
              (ephp_data:pad_to_bin(abs(Diff div 3600), 2))/binary,
              Sep/binary,
              (ephp_data:pad_to_bin(abs(Diff rem 3600), 2))/binary>>;
        Diff when Diff > 0 ->
            <<"-",
              (ephp_data:pad_to_bin(Diff div 3600, 2))/binary,
              Sep/binary,
              (ephp_data:pad_to_bin(Diff rem 3600, 2))/binary>>
    end.