@helia/verified-fetch
Version:
A fetch-like API for obtaining verified & trustless IPFS content on the web
93 lines • 3 kB
JavaScript
import { logger } from '@libp2p/logger';
import { fileTypeFromBuffer } from 'file-type';
const log = logger('helia:verified-fetch:content-type-parser');
export const defaultMimeType = 'application/octet-stream';
function checkForSvg(text) {
log('checking for svg');
return /^(<\?xml[^>]+>)?[^<^\w]+<svg/ig.test(text);
}
async function checkForJson(text) {
log('checking for json');
try {
JSON.parse(text);
return true;
}
catch (err) {
log('failed to parse as json', err);
return false;
}
}
function getText(bytes) {
log('checking for text');
const decoder = new TextDecoder('utf-8', { fatal: true });
try {
return decoder.decode(bytes);
}
catch (err) {
return null;
}
}
async function checkForHtml(text) {
log('checking for html');
return /^\s*<(?:!doctype\s+html|html|head|body)\b/i.test(text);
}
export async function contentTypeParser(bytes, fileName) {
log('contentTypeParser called for fileName: %s, byte size=%s', fileName, bytes.length);
const detectedType = (await fileTypeFromBuffer(bytes))?.mime;
if (detectedType != null) {
log('detectedType: %s', detectedType);
return detectedType;
}
log('no detectedType');
if (fileName == null) {
// it's likely text... no other way to determine file-type.
const text = getText(bytes);
if (text != null) {
// check for svg, json, html, or it's plain text.
if (checkForSvg(text)) {
return 'image/svg+xml';
}
else if (await checkForJson(text)) {
return 'application/json';
}
else if (await checkForHtml(text)) {
return 'text/html; charset=utf-8';
}
else {
return 'text/plain; charset=utf-8';
}
}
return defaultMimeType;
}
// no need to include file-types listed at https://github.com/SgtPooki/file-type#supported-file-types
switch (fileName.split('.').pop()) {
case 'css':
return 'text/css';
case 'html':
return 'text/html; charset=utf-8';
case 'js':
return 'application/javascript';
case 'json':
return 'application/json';
case 'txt':
return 'text/plain';
case 'woff2':
return 'font/woff2';
// see bottom of https://github.com/SgtPooki/file-type#supported-file-types
case 'svg':
return 'image/svg+xml';
case 'csv':
return 'text/csv';
case 'doc':
return 'application/msword';
case 'xls':
return 'application/vnd.ms-excel';
case 'ppt':
return 'application/vnd.ms-powerpoint';
case 'msi':
return 'application/x-msdownload';
default:
return defaultMimeType;
}
}
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