<?php
namespace Zadex\Widgets;

defined('ABSPATH') || exit;

/**
 * Countdown widget helpers (T190): the due date (a wall-clock date in the site timezone) as a UTC timestamp,
 * the split of the remaining time over the shown units (mirrors widgets/countdown/countdown.ts) and the site
 * timezone for the editor preview (`window.ZADEX.data.timezone`, filter `zadex/editor/config`).
 */
final class Countdown
{
    public const UNITS = ['days' => 86400, 'hours' => 3600, 'minutes' => 60, 'seconds' => 1];

    public function register(): void
    {
        add_filter('zadex/editor/config', [self::class, 'editor_config'], 10, 1);
    }

    /**
     * @param mixed $config
     * @return mixed
     */
    public static function editor_config($config)
    {
        if (is_array($config)) {
            $tz = self::timezone()->getName();
            $config['data'] = is_array($config['data'] ?? null) ? $config['data'] : [];
            $config['data']['timezone'] = [['value' => $tz, 'label' => $tz]];
        }
        return $config;
    }

    public static function timezone(): \DateTimeZone
    {
        if (function_exists('wp_timezone')) {
            $tz = wp_timezone();
            if ($tz instanceof \DateTimeZone) {
                return $tz;
            }
        }
        return new \DateTimeZone('UTC');
    }

    /** `YYYY-MM-DD[T| ]HH:MM[:SS]` in the site timezone -> UTC timestamp (seconds); null when it does not parse. */
    public static function due_timestamp(string $value, ?\DateTimeZone $tz = null): ?int
    {
        if (!preg_match('/^(\d{4})-(\d{2})-(\d{2})(?:[T ](\d{2}):(\d{2})(?::(\d{2}))?)?$/', trim($value), $m)) {
            return null;
        }
        if (!checkdate((int) $m[2], (int) $m[3], (int) $m[1])) {
            return null;
        }
        $date = sprintf('%s-%s-%s %s:%s:%s', $m[1], $m[2], $m[3], $m[4] ?? '00', $m[5] ?? '00', ($m[6] ?? '') !== '' ? $m[6] : '00');
        $parsed = \DateTimeImmutable::createFromFormat('Y-m-d H:i:s', $date, $tz ?? self::timezone());
        return $parsed instanceof \DateTimeImmutable ? $parsed->getTimestamp() : null;
    }

    /**
     * Remaining seconds split over the shown units; the largest shown unit absorbs hidden larger ones.
     *
     * @param string[] $shown
     * @return array<string, int>
     */
    public static function breakdown(int $seconds, array $shown): array
    {
        $rest = max(0, $seconds);
        $out = [];
        foreach (self::UNITS as $key => $size) {
            if (!in_array($key, $shown, true)) {
                continue;
            }
            $out[$key] = intdiv($rest, $size);
            $rest -= $out[$key] * $size;
        }
        return $out;
    }

    public static function pad(int $n): string
    {
        return $n < 10 ? '0' . $n : (string) $n;
    }
}