(This is used in description to keep text formatting).
 *
 * @param string $text input text.
 *
 * @return string formatted text.
 */
function space2nbsp($text)
{
    return preg_replace('/(^| ) /m', '$1 ', $text);
}

/**
 * Format Shaarli's description
 *
 * @param string $description shaare's description.
 * @param string $indexUrl    URL to Shaarli's index.
 * @param bool   $autolink    Turn on/off automatic linkifications of URLs and hashtags
 *
 * @return string formatted description.
 */
function format_description($description, $indexUrl = '', $autolink = true)
{
    if ($autolink) {
        $description = hashtag_autolink(text2clickable($description), $indexUrl);
    }

    return nl2br(space2nbsp($description));
}

/**
 * Generate a small hash for a link.
 *
 * @param DateTime $date Link creation date.
 * @param int      $id   Link ID.
 *
 * @return string the small hash generated from link data.
 */
function link_small_hash($date, $id)
{
    return smallHash($date->format(Bookmark::LINK_DATE_FORMAT) . $id);
}

/**
 * Returns whether or not the link is an internal note.
 * Its URL starts by `?` because it's actually a permalink.
 *
 * @param string $linkUrl
 *
 * @return bool true if internal note, false otherwise.
 */
function is_note($linkUrl)
{
    return isset($linkUrl[0]) && $linkUrl[0] === '?';
}

/**
 * Extract an array of tags from a given tag string, with provided separator.
 *
 * @param string|null $tags      String containing a list of tags separated by $separator.
 * @param string      $separator Shaarli's default: ' ' (whitespace)
 *
 * @return array List of tags
 */
function tags_str2array(?string $tags, string $separator): array
{
    // For whitespaces, we use the special \s regex character
    $separator = str_replace([' ', '/'], ['\s', '\/'], $separator);

    return preg_split('/\s*' . $separator . '+\s*/', trim($tags ?? ''), -1, PREG_SPLIT_NO_EMPTY) ?: [];
}

/**
 * Return a tag string with provided separator from a list of tags.
 * Note that given array is clean up by tags_filter().
 *
 * @param array|null $tags      List of tags
 * @param string     $separator
 *
 * @return string
 */
function tags_array2str(?array $tags, string $separator): string
{
    return implode($separator, tags_filter($tags, $separator));
}

/**
 * Clean an array of tags: trim + remove empty entries
 *
 * @param array|null $tags List of tags
 * @param string     $separator
 *
 * @return array
 */
function tags_filter(?array $tags, string $separator): array
{
    $trimDefault = " \t\n\r\0\x0B";
    return array_values(array_filter(array_map(function (string $entry) use ($separator, $trimDefault): string {
        return trim($entry, $trimDefault . $separator);
    }, $tags ?? [])));
}