'use strict';

// 极简 Markdown → HTML（只覆盖 LLM 常用：粗体、链接、列表、段落、行内代码）。
// LibreDesk 的 live chat 消息按 HTML 渲染，直接发 Markdown 会显示成 ** 和 [text](url)。
function escapeHtml(text) {
  return String(text || '')
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;');
}

function inline(text) {
  const links = [];
  let out = text.replace(/\[([^\]]+)\]\((https?:\/\/[^\s)]+)\)/g, (_, label, url) => {
    links.push(`<a href="${url}" target="_blank" rel="noopener noreferrer">${label}</a>`);
    return `\u0000L${links.length - 1}\u0000`;
  });
  out = out.replace(/\*\*([^*]+)\*\*/g, '<strong>$1</strong>');
  out = out.replace(/`([^`]+)`/g, '<code>$1</code>');
  // 裸 URL 自动转链接（占位符里还没有 http，避免重复处理 href）
  out = out.replace(/(https?:\/\/[^\s<]+)/g, '<a href="$1" target="_blank" rel="noopener noreferrer">$1</a>');
  out = out.replace(/\u0000L(\d+)\u0000/g, (_, i) => links[Number(i)] || '');
  return out;
}

function markdownToHtml(markdown) {
  const escaped = escapeHtml(markdown);
  const lines = escaped.split(/\r?\n/);
  const html = [];
  let paragraph = [];
  let list = null; // 'ul' | 'ol'

  const flushParagraph = () => {
    if (!paragraph.length) return;
    html.push(`<p>${paragraph.map(inline).join('<br>')}</p>`);
    paragraph = [];
  };
  const closeList = () => {
    if (!list) return;
    html.push(`</${list}>`);
    list = null;
  };

  for (const rawLine of lines) {
    const line = rawLine.trim();
    if (!line) {
      flushParagraph();
      closeList();
      continue;
    }
    const bullet = /^[-*]\s+(.*)$/.exec(line);
    const numbered = /^\d+[.)]\s+(.*)$/.exec(line);
    if (bullet || numbered) {
      flushParagraph();
      const kind = bullet ? 'ul' : 'ol';
      if (list !== kind) {
        closeList();
        list = kind;
        html.push(`<${kind}>`);
      }
      html.push(`<li>${inline((bullet || numbered)[1])}</li>`);
      continue;
    }
    closeList();
    const heading = /^#{1,3}\s+(.*)$/.exec(line);
    if (heading) {
      flushParagraph();
      html.push(`<p><strong>${inline(heading[1])}</strong></p>`);
      continue;
    }
    paragraph.push(line);
  }
  flushParagraph();
  closeList();
  return html.join('');
}

module.exports = { markdownToHtml, escapeHtml };