// lib/markdown.ts：由 lib/utils.ts 按职责拆分（实现未改）
import { marked, Renderer, walkTokens } from 'marked';
import type { Tokens } from 'marked';
import katex from 'katex';
import { sanitizeHtml } from '/@/utils/markdownSafe';

const mdRenderer = new Renderer();

const defaultLinkRenderer = mdRenderer.link.bind(mdRenderer);
mdRenderer.link = (token: Tokens.Link): string => {
  const html = defaultLinkRenderer(token);
  return html.replace(/^<a\s/, '<a target="_blank" rel="noopener" ');
};

const renderLatexInHtml = (html: string): string => {
  // 匹配块级公式（$$...$$）
  html = html.replace(/\$\$(.*?)\$\$/gs, (_match, formula) => {
    return katex.renderToString(formula.trim(), {
      displayMode: true,
      throwOnError: false,
      strict: false,
      trust: true,
    });
  });
  // 匹配行内公式（$...$）
  html = html.replace(/\$(.*?)\$/g, (_match, formula) => {
    return katex.renderToString(formula.trim(), {
      displayMode: false,
      throwOnError: false,
      strict: false,
    });
  });
  return html;
};

const processFootnotes = (html: string, maxId?: number): string => {
  if (maxId === undefined) {
    // 无 citations 上下文，剥离所有 [^n] 标记
    return html.replace(/\[\^\d+\]/g, '');
  }
  // 有效编号范围 [1, maxId]，范围外的剥离
  return html.replace(/\[\^(\d+)\]/g, (_match, n) => {
    const id = parseInt(n, 10);
    if (id >= 1 && id <= maxId) {
      return `<sup class="footnote-ref" data-n="${id}">[${n}]</sup>`;
    }
    return '';
  });
};

export const renderMarkdown = (
  text: string,
  icons?: { copy: string; download: string; preview: string; copySuccess: string },
  maxCitationId?: number
): string => {
  if (!text) return '';
  const processed = text.replace(/<br\s*\/?>/gi, '  \n');
  let html = marked.parse(processed, { renderer: mdRenderer }) as string;
  html = processFootnotes(html, maxCitationId);
  html = renderLatexInHtml(html);
  // Sanitize HTML to prevent XSS attacks
  // [perf-base-v1] 卡6: 转调公共 sanitizeHtml（DOMPurify，ADD_TAGS:['img']），保留本模块额外交互属性白名单
  html = sanitizeHtml(html, ['target', 'data-action', 'data-table', 'data-icon', 'data-icon-success', 'data-n']);
  // 原始 HTML 锚点不经过 marked link renderer，统一补 target/rel
  html = html.replace(/<a\b[^>]*>/gi, (tag) => {
    let attrs = '';
    if (!/\btarget\s*=/i.test(tag)) attrs += ' target="_blank"';
    if (!/\brel\s*=/i.test(tag)) attrs += ' rel="noopener"';
    return attrs ? tag.replace(/^<a\b/i, '<a' + attrs) : tag;
  });
  return icons ? wrapTables(html, icons) : html;
};
// renderMarkdown 是纯函数（入参相同则输出相同），但 marked 解析 + KaTeX + DOMPurify 全流程开销大。
// 流式回答时每个 token 都会让消息列表重渲染，此时未变化的历史消息也会被重复解析，
// 这里按「引用上限 + 图标 + 原文」记忆化：命中缓存的直接返回上次结果。
// 内容每帧都在变的流式消息由调用方传 cacheable=false 排除，避免缓存被中间态刷满。

const MD_CACHE_MAX = 200;

const mdCache = new Map<string, string>();

export const renderMarkdownCached = (
  text: string,
  icons?: { copy: string; download: string; preview: string; copySuccess: string },
  maxCitationId?: number,
  cacheable = true
): string => {
  if (!cacheable || !text) return renderMarkdown(text, icons, maxCitationId);

  // \u0001 作分隔符：不会出现在正文与图标地址里，避免不同入参拼出同一个 key
  const iconKey = icons ? `${icons.copy}\u0001${icons.download}\u0001${icons.preview}\u0001${icons.copySuccess}` : '';
  const key = `${maxCitationId ?? -1}\u0001${iconKey}\u0001${text}`;
  const cached = mdCache.get(key);
  if (cached !== undefined) return cached;

  const html = renderMarkdown(text, icons, maxCitationId);
  // 简单 FIFO 淘汰，长会话下缓存条目数有上限
  if (mdCache.size >= MD_CACHE_MAX) {
    const oldestKey = mdCache.keys().next().value as string | undefined;
    if (oldestKey !== undefined) mdCache.delete(oldestKey);
  }
  mdCache.set(key, html);
  return html;
};
// 从 markdown 文本中提取链接（与 renderMarkdown 共用同一套 marked 解析，
// 仅收集 link token，代码块/图片等不会被误收）

export const extractMarkdownLinks = (text: string): Array<{ title: string; href: string }> => {
  if (!text) return [];
  const links: Array<{ title: string; href: string }> = [];
  try {
    const tokens = marked.lexer(text);
    walkTokens(tokens, (token) => {
      if (token.type === 'link') {
        const linkToken = token as Tokens.Link;
        const href = linkToken.href || '';
        if (href) {
          links.push({ title: linkToken.text || href, href });
        }
      }
    });
  } catch {
    // 文本解析异常时返回已收集到的部分链接
  }
  return links;
};

export const wrapTables = (html: string, icons: { copy: string; download: string; preview: string; copySuccess: string }): string => {
  return html.replace(/<table>([\s\S]*?)<\/table>/g, (match) => {
    const encodedTable = encodeURIComponent(match);
    return `<div class="markdown-table-wrapper">
      <div class="table-actions">
        <span class="table-action-btn" data-action="copy" data-table="${encodedTable}" data-icon="${icons.copy}" data-icon-success="${icons.copySuccess}" title="复制Markdown">
          <img src="${icons.copy}" width="14" height="14" />
        </span>
        <span class="table-action-btn" data-action="csv" data-table="${encodedTable}" title="下载">
          <img src="${icons.download}" width="14" height="14" />
        </span>
        <span class="table-action-btn" data-action="preview" data-table="${encodedTable}" title="预览">
          <img src="${icons.preview}" width="14" height="14" />
        </span>
      </div>
      ${match}
    </div>`;
  });
};

const decodeHtmlEntities = (escaped: string): string => {
  const textarea = document.createElement('textarea');
  textarea.innerHTML = escaped;
  return textarea.value;
};
// 给渲染后 HTML 中的 ```markdown / ```md 代码块加上操作工具栏（复制/下载/预览）

export const wrapMarkdownCodeBlocks = (html: string, icons: { copy: string; download: string; preview: string; copySuccess: string }): string => {
  return html.replace(/<pre><code class="[^"]*language-(?:markdown|md)[^"]*">([\s\S]*?)<\/code><\/pre>/g, (match, escaped: string) => {
    const encoded = encodeURIComponent(decodeHtmlEntities(escaped));
    return `<div class="markdown-code-wrapper">
      <div class="table-actions">
        <span class="table-action-btn" data-action="copy-md" data-content="${encoded}" data-icon="${icons.copy}" data-icon-success="${icons.copySuccess}" title="复制内容">
          <img src="${icons.copy}" width="14" height="14" />
        </span>
        <span class="table-action-btn" data-action="download-md" data-content="${encoded}" title="下载.md文件">
          <img src="${icons.download}" width="14" height="14" />
        </span>
        <span class="table-action-btn" data-action="preview-md" data-content="${encoded}" title="预览渲染效果">
          <img src="${icons.preview}" width="14" height="14" />
        </span>
      </div>
      ${match}
    </div>`;
  });
};

export const tableHtmlToMarkdown = (tableHtml: string): string => {
  const parser = new DOMParser();
  const doc = parser.parseFromString(tableHtml, 'text/html');
  const table = doc.querySelector('table');
  if (!table) return tableHtml;

  const rows: string[][] = [];
  table.querySelectorAll('tr').forEach((tr) => {
    const cells: string[] = [];
    tr.querySelectorAll('th, td').forEach((cell) => {
      cells.push(cell.textContent?.trim() || '');
    });
    rows.push(cells);
  });

  if (rows.length === 0) return tableHtml;

  const colCount = Math.max(...rows.map((r) => r.length));
  const normalized = rows.map((r) => {
    while (r.length < colCount) r.push('');
    return r;
  });

  const lines: string[] = [];
  lines.push('| ' + normalized[0].join(' | ') + ' |');
  lines.push('| ' + normalized[0].map(() => '---').join(' | ') + ' |');
  for (let i = 1; i < normalized.length; i++) {
    lines.push('| ' + normalized[i].join(' | ') + ' |');
  }
  return lines.join('\n');
};

export const tableHtmlToCsv = (tableHtml: string): string => {
  const parser = new DOMParser();
  const doc = parser.parseFromString(tableHtml, 'text/html');
  const table = doc.querySelector('table');
  if (!table) return '';

  const rows: string[] = [];
  table.querySelectorAll('tr').forEach((tr) => {
    const cells: string[] = [];
    tr.querySelectorAll('th, td').forEach((cell) => {
      const text = (cell.textContent?.trim() || '').replace(/"/g, '""');
      cells.push(`"${text}"`);
    });
    rows.push(cells.join(','));
  });

  return '' + rows.join('\n');
};
// 大数字按「万」展示（上下文容量与今日用量共用）