my-links/pages/api/favicon.ts

import { NextApiRequest, NextApiResponse } from "next";
import { parse } from "node-html-parser";

const USER_AGENT =
	"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36 Edg/108.0.1462.54";

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

	try {
		const { favicon, type, size } = await downloadImageFromUrl(
			urlRequest + "/favicon.ico"
		);
		if (size === 0) {
			throw new Error("Empty favicon");
		}
		if (!isImage(type)) {
			throw new Error("Favicon path does not return an image");
		}
		return sendImage({
			content: favicon,
			res,
			type,
			size,
		});
	} catch (error) {
		console.error(error);
	}

	try {
		const requestDocument = await makeRequest(urlRequest);
		const text = await requestDocument.text();

		const faviconPath = findFaviconPath(text);
		if (!faviconPath) {
			throw new Error("Unable to find favicon path");
		}

		if (isBase64Image(faviconPath)) {
			console.log("base64, convert it to buffer");
			const buffer = convertBase64ToBuffer(faviconPath);
			return sendImage({
				content: buffer,
				res,
				type: "image/vnd.microsoft.icon",
				size: buffer.length,
			});
		}

		const pathWithoutFile = popLastSegment(requestDocument.url);
		const finalUrl = buildFaviconUrl(faviconPath, pathWithoutFile);

		const { favicon, type, size } = await downloadImageFromUrl(finalUrl);
		if (!isImage(type)) {
			throw new Error("Favicon path does not return an image");
		}

		return sendImage({
			content: favicon,
			res,
			type,
			size,
		});
	} catch (error) {
		console.error(error);
		res.status(404).send({ error: "Unable to retrieve favicon" });
	}
}

async function makeRequest(url: string) {
	const headers = new Headers();
	headers.set("User-Agent", USER_AGENT);

	const request = await fetch(url, { headers });
	return request;
}

async function downloadImageFromUrl(url: string): Promise<{
	favicon: Buffer;
	url: string;
	type: string;
	size: number;
}> {
	const request = await makeRequest(url);
	const blob = await request.blob();

	return {
		favicon: Buffer.from(await blob.arrayBuffer()),
		url: request.url,
		type: blob.type,
		size: blob.size,
	};
}

function sendImage({
	content,
	res,
	type,
	size,
}: {
	content: Buffer;
	res: NextApiResponse;
	type: string;
	size: number;
}) {
	res.setHeader("Content-Type", type);
	res.setHeader("Content-Length", size);
	res.send(content);
}

function findFaviconPath(text) {
	const document = parse(text);
	const links = document.querySelectorAll(
		'link[rel="icon"], link[rel="shortcut icon"]'
	);
	const link = links.find(
		(link) => !link.getAttribute("href").startsWith("data:image/")
	);
	if (!link) {
		return console.warn("nothing, exit");
	}

	return link.getAttribute("href") || "";
}

function popLastSegment(url = "") {
	const { href } = new URL(url);
	const pathWithoutFile = href.split("/");
	pathWithoutFile.pop();
	return pathWithoutFile.join("/") || "";
}

function buildFaviconUrl(faviconPath, pathWithoutFile) {
	if (faviconPath.startsWith("http")) {
		console.log("startsWith http, result", faviconPath);
		return faviconPath;
	} else if (faviconPath.startsWith("/")) {
		console.log("startsWith /, result", pathWithoutFile + faviconPath);
		return pathWithoutFile + faviconPath;
	} else {
		console.log("else, result", pathWithoutFile + "/" + faviconPath);
		return pathWithoutFile + "/" + faviconPath;
	}
}

function isImage(type: string) {
	return type.includes("image");
}

function isBase64Image(data) {
	return data.startsWith("data:image/");
}

function convertBase64ToBuffer(base64 = ""): Buffer {
	const buffer = Buffer.from(base64, "base64");
	return buffer;
}