/**
 * 标题行首序号：1 / 1.1 / 1.2.3 / 1. / 1) 等（不含 2024 这类四位年份）
 */
const HEADING_NUMBER_PREFIX_RE =
    /^\s*(?:(?:\d+\.)+\d+|\d{1,2}[\.\):：]|\d{1,2}(?=\s+[^\d]))[\.\):：]?\s+/;

export function stripHeadingNumberPrefix(text) {
    return String(text || '').replace(HEADING_NUMBER_PREFIX_RE, '');
}

export function hasHeadingNumberPrefix(text) {
    return HEADING_NUMBER_PREFIX_RE.test(String(text || ''));
}

function htmlToPlainText(html) {
    if (typeof document !== 'undefined') {
        const node = document.createElement('div');
        node.innerHTML = String(html || '');
        return (node.textContent || node.innerText || '').replace(/\u00a0/g, ' ');
    }
    return String(html || '')
        .replace(/<[^>]+>/g, '')
        .replace(/&nbsp;/g, ' ')
        .replace(/\s+/g, ' ')
        .trim();
}

export function headingHtmlHasNumberPrefix(html) {
    return hasHeadingNumberPrefix(htmlToPlainText(html));
}

/** 去掉 HTML 标题内容中首个非空文本节点前的序号 */
export function stripHeadingNumberFromHtml(html) {
    if (typeof document === 'undefined') {
        const plain = htmlToPlainText(html);
        if (!hasHeadingNumberPrefix(plain)) {
            return html;
        }
        return String(html || '').replace(HEADING_NUMBER_PREFIX_RE, '');
    }

    const div = document.createElement('div');
    div.innerHTML = html || '';
    const walker = document.createTreeWalker(div, NodeFilter.SHOW_TEXT, null);
    let node;
    while ((node = walker.nextNode())) {
        const raw = node.textContent || '';
        if (!raw.trim()) {
            continue;
        }
        const stripped = stripHeadingNumberPrefix(raw);
        if (stripped !== raw) {
            node.textContent = stripped;
        }
        break;
    }
    return div.innerHTML;
}

/** 从正文列表中收集需去掉序号的 H1/H2 标题 */
export function collectHeadingNumberStripUpdates(contentList) {
    const list = contentList || [];
    const updates = [];

    list.forEach(function (item) {
        if (!item || (item.is_h1 != 1 && item.is_h2 != 1)) {
            return;
        }
        const original = item.content || '';
        const next = stripHeadingNumberFromHtml(original);
        if (next !== original) {
            updates.push({
                am_id: item.am_id,
                content: next,
                original: original
            });
        }
    });

    return updates;
}