<?php
namespace Relay\Support;

use Relay\Files\Fs;

/** How much this server can take in one request (spec §5.3). */
final class Limits
{
    public const MIN_BATCH = 262144;
    /** The smallest request SiteRelay sends when the other site's server refuses bigger ones (a web server or firewall limit). */
    public const MIN_REQUEST = 65536;
    public const MAX_BATCH = 25165824;

    /** The largest body this site accepts or builds: min(post_max_size, upload_max_filesize, memory_limit / 4) - 256 KB, within 256 KB–24 MB. */
    public static function max_body(): int
    {
        $limits = [];
        foreach (['post_max_size', 'upload_max_filesize'] as $setting) {
            $bytes = self::bytes((string) ini_get($setting));
            if ($bytes > 0) {
                $limits[] = $bytes;
            }
        }
        $memory = self::bytes((string) ini_get('memory_limit'));
        if ($memory > 0) {
            $limits[] = intdiv($memory, 4);
        }
        $limit = ($limits === [] ? self::MAX_BATCH : min($limits)) - 262144;
        return max(self::MIN_BATCH, min(self::MAX_BATCH, $limit));
    }

    /** Enough free disk space for $bytes of files: twice (staging plus restore point), once for uploads in low-disk mode. */
    public static function check_disk_space(int $bytes, bool $low_disk): void
    {
        $free = Fs::free_space(Paths::work_dir());
        $need = $low_disk ? $bytes : $bytes * 2;
        if ($free !== false && $free < $need) {
            throw new RelayError(
                'files.disk_space',
                /* translators: 1: site URL, 2: size needed, 3: size free */
                esc_html(sprintf(__('%1$s does not have enough free disk space for the files: %2$s needed, %3$s free.', 'siterelay'), home_url(), size_format($need), size_format((int) $free))),
                esc_html__('Free some space on that server, copy fewer files, or use low-disk mode for uploads.', 'siterelay')
            );
        }
    }

    /** "64M" → 67108864; "-1" or "0" (no limit) → 0. */
    public static function bytes(string $value): int
    {
        $value = trim($value);
        if ($value === '' || (int) $value <= 0) {
            return 0;
        }
        $unit = strtolower(substr($value, -1));
        $number = (int) $value;
        $factor = ['k' => 1024, 'm' => 1048576, 'g' => 1073741824][$unit] ?? 1;
        return $number * $factor;
    }
}