includes/login/src/getEmojiUrl.js

"use strict";

const util = require("util");

module.exports = function () {
	return function getEmojiUrl(c, size, pixelRatio) {
		/*
		 Resolves Facebook Messenger emoji image asset URL for an emoji character.
		 Supported sizes are 32, 64, and 128.
		 Supported pixel ratios are '1.0' and '1.5' (possibly more; haven't tested)
		 */
		const baseUrl = "https://static.xx.fbcdn.net/images/emoji.php/v8/z%s/%s";
		pixelRatio = pixelRatio || "1.0";

		const ending = util.format(
			"%s/%s/%s.png",
			pixelRatio,
			size,
			c.codePointAt(0).toString(16)
		);
		let base = 317426846;
		for (let i = 0; i < ending.length; i++) {
			base = (base << 5) - base + ending.charCodeAt(i);
		}

		const hashed = (base & 255).toString(16);
		return util.format(baseUrl, hashed, ending);
	};
};