my-links/src/pages/api/favicon.ts

import { NextApiRequest, NextApiResponse } from 'next';
import { createReadStream } from 'node:fs';
import { resolve } from 'node:path';
import {
  downloadImageFromUrl,
  getFavicon,
  makeRequestWithUserAgent,
} from 'lib/request';
import { Favicon } from 'types/types';
import { buildFaviconUrl, findFaviconPath } from 'lib/url';
import { convertBase64ToBuffer, isBase64Image, isImage } from 'lib/image';

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse,
) {
  const urlParam = (req.query?.urlParam as string) || '';
  if (!urlParam) {
    throw new Error('URL is missing');
  }

  const faviconRequestUrl = buildFaviconUrl(urlParam, '/favicon.ico');
  try {
    return sendImage(res, await getFavicon(faviconRequestUrl));
  } catch (error) {
    console.error(
      '[Favicon]',
      `[first: ${faviconRequestUrl}]`,
      'Unable to retrieve favicon from favicon.ico url',
    );
  }

  const requestDocument = await makeRequestWithUserAgent(urlParam);
  const documentAsText = await requestDocument.text();

  const faviconPath = findFaviconPath(documentAsText);
  if (!faviconPath) {
    console.error(
      '[Favicon]',
      `[first: ${faviconRequestUrl}]`,
      'No link/href attribute found',
    );
    return sendDefaultImage(res);
  }

  const finalUrl = buildFaviconUrl(requestDocument.url, faviconPath);
  try {
    if (!faviconPath) {
      throw new Error('Unable to find favicon path');
    }

    if (isBase64Image(faviconPath)) {
      console.log(
        '[Favicon]',
        `[second: ${faviconRequestUrl}]`,
        'info: base64, convert it to buffer',
      );
      const buffer = convertBase64ToBuffer(faviconPath);
      return sendImage(res, {
        buffer,
        type: 'image/x-icon',
        size: buffer.length,
        url: faviconPath,
      });
    }

    const finalUrl = faviconPath.startsWith('http')
      ? faviconPath
      : buildFaviconUrl(requestDocument.url, faviconPath);
    const favicon = await downloadImageFromUrl(finalUrl);
    if (!isImage(favicon.type)) {
      throw new Error('Favicon path does not return an image');
    }

    console.log('[Favicon]', `[second: ${finalUrl}]`, 'success: image found');
    return sendImage(res, favicon);
  } catch (error) {
    const errorMessage = error?.message || 'Unable to retrieve favicon';
    console.log('[Favicon]', `[second: ${finalUrl}], error:`, errorMessage);
    return sendDefaultImage(res);
  }
}

function sendImage(res: NextApiResponse, { buffer, type, size }: Favicon) {
  res.setHeader('Content-Type', type);
  res.setHeader('Content-Length', size);
  res.send(buffer);
}

function sendDefaultImage(res: NextApiResponse) {
  const readStream = createReadStream(
    resolve(process.cwd(), './public/empty-image.png'),
  );
  res.writeHead(206);
  readStream.pipe(res);
}