import zlib from 'node:zlib';
const PREVIEWABLE_MIME_TYPES = new Set([
'text/html',
'text/plain',
'text/markdown',
'text/csv',
'application/pdf',
'image/png',
'image/jpeg',
'image/webp',
'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
]);
const PREVIEW_SHELL_STYLE = `
html,body{margin:0;padding:0;background:#f5f0e5;color:#1f2937;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}
body{padding:24px;box-sizing:border-box;line-height:1.6}
pre,code{font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
pre{white-space:pre-wrap;word-break:break-word;background:#fff;border:1px solid #e5e7eb;border-radius:12px;padding:16px}
table{border-collapse:collapse;width:100%;background:#fff;border-radius:12px;overflow:hidden}
th,td{border:1px solid #e5e7eb;padding:8px 10px;text-align:left;font-size:14px}
th{background:#faf7ef}
.docx-preview h1{font-size:1.5rem;margin:0 0 16px}
.docx-preview p{margin:0 0 12px;text-indent:2em}
.docx-preview .meta{color:#6b7280;font-size:13px;margin-bottom:20px;text-indent:0}
.pdf-frame,.image-frame{display:block;width:100%;min-height:calc(100vh - 48px);border:0;border-radius:12px;background:#fff}
.image-frame{object-fit:contain;max-height:calc(100vh - 48px);width:auto;max-width:100%;margin:0 auto}
`;
function escapeHtml(text) {
return String(text ?? '')
.replace(/&/g, '&')
.replace(//g, '>')
.replace(/"/g, '"');
}
function previewDocument(title, bodyHtml, { downloadUrl = null, extraHead = '' } = {}) {
const csp = [
"default-src 'none'",
"style-src 'unsafe-inline'",
"img-src 'self' data: https:",
"font-src 'self' data:",
"frame-src 'self'",
"object-src 'self'",
"base-uri 'none'",
"form-action 'none'",
"script-src 'none'",
].join('; ');
const downloadLink = downloadUrl
? `下载原文件
`
: '';
return `${escapeHtml(title)}${extraHead}${escapeHtml(title)}
${downloadLink}${bodyHtml}`;
}
function renderInlineMarkdown(text) {
let html = escapeHtml(text);
html = html.replace(/`([^`]+)`/g, '$1');
html = html.replace(/\*\*(.+?)\*\*/g, '$1');
html = html.replace(/\*(.+?)\*/g, '$1');
html = html.replace(/\[([^\]]+)]\(([^)]+)\)/g, '$1');
return html;
}
function renderMarkdownDocument(text) {
const lines = String(text ?? '').split('\n');
const blocks = [];
let inCode = false;
let code = [];
for (const line of lines) {
if (line.startsWith('```')) {
if (inCode) {
blocks.push(`${escapeHtml(code.join('\n'))}
`);
code = [];
inCode = false;
} else {
inCode = true;
}
continue;
}
if (inCode) {
code.push(line);
continue;
}
if (!line.trim()) continue;
const heading = line.match(/^(#{1,6})\s+(.+)$/);
if (heading) {
const level = heading[1].length;
blocks.push(`${renderInlineMarkdown(heading[2])}`);
continue;
}
blocks.push(`${renderInlineMarkdown(line)}
`);
}
if (inCode && code.length) {
blocks.push(`${escapeHtml(code.join('\n'))}
`);
}
return blocks.join('\n');
}
function parseCsvRows(text) {
const rows = [];
let row = [];
let cell = '';
let inQuotes = false;
for (let i = 0; i < text.length; i += 1) {
const ch = text[i];
const next = text[i + 1];
if (inQuotes) {
if (ch === '"' && next === '"') {
cell += '"';
i += 1;
} else if (ch === '"') {
inQuotes = false;
} else {
cell += ch;
}
continue;
}
if (ch === '"') {
inQuotes = true;
continue;
}
if (ch === ',') {
row.push(cell);
cell = '';
continue;
}
if (ch === '\n') {
row.push(cell);
rows.push(row);
row = [];
cell = '';
continue;
}
if (ch === '\r') continue;
cell += ch;
}
row.push(cell);
rows.push(row);
return rows.filter((item) => item.some((value) => String(value ?? '').trim()));
}
function renderCsvPreview(text) {
const rows = parseCsvRows(String(text ?? ''));
if (rows.length === 0) return '（空文件）
';
const [head, ...body] = rows;
const header = `${head.map((cell) => `| ${escapeHtml(cell)} | `).join('')}
`;
const content = body
.slice(0, 200)
.map((line) => `${line.map((cell) => `| ${escapeHtml(cell)} | `).join('')}
`)
.join('');
const tail = body.length > 200 ? `仅展示前 200 行
` : '';
return ``;
}
function extractZipEntry(buffer, targetName) {
let offset = 0;
while (offset + 30 <= buffer.length) {
if (buffer.subarray(offset, offset + 2).toString('ascii') !== 'PK') break;
const compressionMethod = buffer.readUInt16LE(offset + 8);
const compressedSize = buffer.readUInt32LE(offset + 18);
const nameLength = buffer.readUInt16LE(offset + 26);
const extraLength = buffer.readUInt16LE(offset + 28);
const name = buffer.subarray(offset + 30, offset + 30 + nameLength).toString('utf8');
const dataStart = offset + 30 + nameLength + extraLength;
if (name === targetName) {
const compressed = buffer.subarray(dataStart, dataStart + compressedSize);
if (compressionMethod === 0) return compressed;
if (compressionMethod === 8) return zlib.inflateRawSync(compressed);
return null;
}
offset = dataStart + compressedSize;
}
return null;
}
function extractDocxText(buffer) {
const xmlBuffer = extractZipEntry(buffer, 'word/document.xml');
if (!xmlBuffer) return '';
const xml = xmlBuffer.toString('utf8');
const paragraphs = [];
for (const block of xml.split('')) {
const texts = [...block.matchAll(/]*>([\s\S]*?)<\/w:t>/g)].map((match) =>
match[1]
.replace(/</g, '<')
.replace(/>/g, '>')
.replace(/&/g, '&')
.replace(/"/g, '"'),
);
const line = texts.join('');
if (line.trim()) paragraphs.push(line.trim());
}
return paragraphs.join('\n\n');
}
export function canPreviewAsset(mimeType) {
return PREVIEWABLE_MIME_TYPES.has(mimeType);
}
export function renderAssetPreviewHtml({ asset, buffer, downloadUrl }) {
const title = asset.displayName || asset.filename;
const mimeType = asset.mimeType;
if (mimeType === 'text/html') {
const csp =
'';
const html = buffer.toString('utf8');
if (/]*>/i.test(html)) {
return html.replace(/]*)>/i, `${csp}`);
}
return `${csp}${html}`;
}
if (mimeType === 'application/pdf') {
return previewDocument(
title,
``,
{ downloadUrl },
);
}
if (mimeType.startsWith('image/')) {
return previewDocument(
title,
`})
`,
{ downloadUrl },
);
}
if (mimeType === 'text/csv') {
return previewDocument(title, renderCsvPreview(buffer.toString('utf8')), { downloadUrl });
}
if (mimeType === 'text/markdown') {
return previewDocument(title, renderMarkdownDocument(buffer.toString('utf8')), { downloadUrl });
}
if (mimeType === 'text/plain') {
return previewDocument(title, `${escapeHtml(buffer.toString('utf8'))}`, { downloadUrl });
}
if (mimeType === 'application/vnd.openxmlformats-officedocument.wordprocessingml.document') {
const text = extractDocxText(buffer);
const body = text
? `${text
.split(/\n{2,}/)
.map((paragraph) => `${escapeHtml(paragraph)}
`)
.join('')}`
: '无法提取正文，请下载原文件查看。
';
return previewDocument(title, body, { downloadUrl });
}
throw Object.assign(new Error('该资产不支持预览'), { code: 'preview_not_supported' });
}