/*
 * Copyright (c) 2021, Brian Gianforcaro <bgianf@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/StringView.h>
#include <LibTest/TestCase.h>
#include <time.h>

const auto expected_epoch = "Thu Jan  1 00:00:00 1970\n"sv;

class TimeZoneGuard {
public:
    TimeZoneGuard()
        : m_tz(getenv("TZ"))
    {
    }

    explicit TimeZoneGuard(char const* tz)
        : m_tz(getenv("TZ"))
    {
        setenv("TZ", tz, 1);
    }

    ~TimeZoneGuard()
    {
        if (m_tz)
            setenv("TZ", m_tz, 1);
        else
            unsetenv("TZ");
    }

private:
    char const* m_tz { nullptr };
};

TEST_CASE(asctime)
{
    TimeZoneGuard guard("UTC");

    time_t epoch = 0;
    auto result = asctime(localtime(&epoch));
    EXPECT_EQ(expected_epoch, StringView(result));
}

TEST_CASE(asctime_r)
{
    TimeZoneGuard guard("UTC");

    char buffer[26] {};
    time_t epoch = 0;
    auto result = asctime_r(localtime(&epoch), buffer);
    EXPECT_EQ(expected_epoch, StringView(result));
}

TEST_CASE(ctime)
{
    TimeZoneGuard guard("UTC");

    time_t epoch = 0;
    auto result = ctime(&epoch);

    EXPECT_EQ(expected_epoch, StringView(result));
}

TEST_CASE(ctime_r)
{
    TimeZoneGuard guard("UTC");

    char buffer[26] {};
    time_t epoch = 0;
    auto result = ctime_r(&epoch, buffer);

    EXPECT_EQ(expected_epoch, StringView(result));
}

TEST_CASE(tzset)
{
    TimeZoneGuard guard;

    auto set_tz = [](char const* tz) {
        setenv("TZ", tz, 1);
        tzset();
    };

    set_tz("UTC");
    EXPECT_EQ(timezone, 0);
    EXPECT_EQ(altzone, 0);
    EXPECT_EQ(daylight, 0);
    EXPECT_EQ(tzname[0], "UTC"sv);
    EXPECT_EQ(tzname[1], "UTC"sv);

    set_tz("America/New_York");
    EXPECT_EQ(timezone, 5 * 60 * 60);
    EXPECT_EQ(altzone, 4 * 60 * 60);
    EXPECT_EQ(daylight, 1);
    EXPECT_EQ(tzname[0], "EST"sv);
    EXPECT_EQ(tzname[1], "EDT"sv);

    set_tz("America/Phoenix");
    EXPECT_EQ(timezone, 7 * 60 * 60);
    EXPECT_EQ(altzone, 7 * 60 * 60);
    EXPECT_EQ(daylight, 0);
    EXPECT_EQ(tzname[0], "MST"sv);
    EXPECT_EQ(tzname[1], "MST"sv);

    set_tz("America/Asuncion");
    EXPECT_EQ(timezone, 4 * 60 * 60);
    EXPECT_EQ(altzone, 3 * 60 * 60);
    EXPECT_EQ(daylight, 1);
    EXPECT_EQ(tzname[0], "-04"sv);
    EXPECT_EQ(tzname[1], "-03"sv);

    set_tz("CET");
    EXPECT_EQ(timezone, -1 * 60 * 60);
    EXPECT_EQ(altzone, -2 * 60 * 60);
    EXPECT_EQ(daylight, 1);
    EXPECT_EQ(tzname[0], "CET"sv);
    EXPECT_EQ(tzname[1], "CEST"sv);
}