<?php
// TimeZoneInfo.php
// Created: 2021-06-12
// Updated: 2022-02-27

namespace Index;

use DateTimeInterface;
use DateTimeZone;
use JsonSerializable;
use RuntimeException;
use Stringable;

/**
 * Represents a time zone.
 */
class TimeZoneInfo extends DateTimeZone implements JsonSerializable, Stringable, IComparable, IEquatable {
    private array|null $location = null;

    private static bool $constructed = false;
    private static TimeZoneInfo $utc;

    /**
     * Constructs a new TimeZoneInfo object.
     *
     * @param string $timeZone Time zone identifier.,
     * @return TimeZoneInfo New instance of TimeZoneInfo.
     */
    public function __construct(string $timeZone) {
        parent::__construct($timeZone);
    }

    /**
     * @internal
     */
    public static function construct(): void {
        if(self::$constructed)
            throw new RuntimeException('Static constructor was already called.');
        self::$constructed = true;
        self::$utc = new TimeZoneInfo('UTC');
    }

    /**
     * Gets a TimeZoneInfo instance representing the UTC (+00:00) time zone.
     *
     * @return TimeZoneInfo Instance representing UTC.
     */
    public static function utc(): TimeZoneInfo {
        return self::$utc;
    }

    /**
     * Gets the current default time zone.
     *
     * Uses date_default_timezone_get internally.
     *
     * @return TimeZoneInfo Instance representing the default time zone.
     */
    public static function default(): TimeZoneInfo {
        return new TimeZoneInfo(date_default_timezone_get());
    }

    /**
     * Sets the current default time zone.
     *
     * Uses date_default_timezone_set internally.
     *
     * @param DateTimeZone|string $timeZone Desired default time zone.
     * @throws RuntimeException If an invalid time zone was supplied.
     */
    public static function setDefault(DateTimeZone|string $timeZone): void {
        if($timeZone instanceof DateTimeZone)
            $timeZone = $timeZone->getName();

        if(!date_default_timezone_set($timeZone))
            throw new RuntimeException('Invalid default time zone specified.');
    }

    /**
     * Gets location info for a time zone.
     *
     * It makes more sense to use getCountryCode, getLatitude, getLongitude and getComments, if you can.
     *
     * @return array Location information.
     */
    public function getLocation(): array {
        if($this->location === null)
            $this->location = parent::getLocation();
        return $this->location;
    }

    /**
     * Gets the country code of the country which this time zone falls in.
     *
     * @return string Country code for this time zone.
     */
    public function getCountryCode(): string {
        return $this->getLocation()['country_code'];
    }

    /**
     * Gets the latitude of this time zone.
     *
     * @return float Latitude of this time zone.
     */
    public function getLatitude(): float {
        return $this->getLocation()['latitude'];
    }

    /**
     * Gets the longitude of this time zone.
     *
     * @return float Longitude of this time zone.
     */
    public function getLongitude(): float {
        return $this->getLocation()['longitude'];
    }

    /**
     * Gets location comments for this time zone.
     *
     * @return string Location comments.
     */
    public function getComments(): string {
        return $this->getLocation()['comments'];
    }

    /**
     * Gets the offset of this timezone relative to a given date/time instance.
     *
     * @param DateTimeInterface|null $dateTime Date/time to use as a base, null for UTC Now.
     * @return int Offset relative to given date/time.
     */
    public function getOffset(DateTimeInterface|null $dateTime = null): int {
        return parent::getOffset($dateTime ?? new DateTime('now', self::$utc));
    }

    /**
     * Creates a string representation of this object.
     *
     * @return string Representation of this object.
     */
    public function __toString(): string {
        $offset = $this->getOffset();
        return sprintf(
            '(UTC%s%s) %s',
            $offset < 0 ? '-' : '+',
            date('H:i', abs($offset)),
            $this->getName()
        );
    }

    /**
     * Returns the data which should be serialized as json.
     *
     * @see https://www.php.net/manual/en/jsonserializable.jsonserialize.php
     * @return mixed Data to be passed to json_encode.
     */
    public function jsonSerialize(): mixed {
        return $this->getName();
    }

    public function compare(mixed $other): int {
        if(!($other instanceof DateTimeZone))
            return -1;
        $other = self::cast($other);

        $diff = $this->getOffset() <=> $other->getOffset();
        if($diff) return $diff;

        return strcmp($this->getName(), $other->getName());
    }

    public function equals(mixed $other): bool {
        if(!($other instanceof DateTimeZone))
            return false;
        return $this->getName() === $other->getName()
            || $this->getOffset() === self::cast($other)->getOffset();
    }

    /**
     * Gets a list of all time zones.
     *
     * @param bool $ordered true if the list should be ordered, false if not.
     * @param int $timeZoneGroup ID of a group to filter the generated list.
     * @param string|null $countryCode Country to filter the generated list by.
     * @return array Array containing the time zones.
     */
    public static function all(bool $ordered = false, int $timeZoneGroup = DateTimeZone::ALL, string|null $countryCode = null): array {
        $timeZones = self::listIdentifiers($timeZoneGroup, $countryCode === null ? null : $countryCode);
        $timeZones = XArray::select($timeZones, fn($id) => new TimeZoneInfo($id));

        if($ordered)
            $timeZones = XArray::sort($timeZones, fn($a, $b) => $a->compare($b));

        return $timeZones;
    }

    /**
     * Makes sure a DateTimeZone inheriting object is a TimeZoneInfo instance.
     *
     * @param DateTimeZone $timeZone Input object.
     * @return TimeZoneInfo If the input was a TimeZoneInfo, the same instance will be returned.
     *                      If the input was something else, a new TimeZoneInfo instance will be returned based on the input.
     */
    public static function cast(DateTimeZone $timeZone): TimeZoneInfo {
        if($timeZone instanceof TimeZoneInfo)
            return $timeZone;
        return new TimeZoneInfo($timeZone->getName());
    }
}

TimeZoneInfo::construct();