index.js

var vm = require("vm");
var Canvas = require("canvas");
var GifEncoder = require("gif-encoder");
var request = require("request");
var streams = require("memory-streams");

function getDweetCode() {
	return new Promise(function(resolve, reject) {
		request("https://www.dwitter.net/api/dweets/?limit=1", function(error, response, body) {
			var code = JSON.parse(body).results.code
			resolve(code);
		});
	});
}

function getFrames(cb) {
	return new Promise(function(resolve, reject) {
		getDweetCode().then(function(code) {
			var framestouse = 50;
			var can = new Canvas(1920, 1080);
			var ctx = can.getContext("2d");
			var frameArray = [];
			var sandbox = {
				S: Math.sin,
				C: Math.cos,
				T: Math.tan,
				R: function(r, g, b, a) {
					return "rgba(" + r + "," + g + "," + b + "," + a + ")";
				},
				c: can,
				x: ctx,
				t: 0
			};
			var script = new vm.Script(code);
			var context = vm.createContext(sandbox);
			var timesaround = 0;
			var intervalId = setInterval(function() {
				if (timesaround < framestouse) {
					script.runInContext(context);
					frameArray.push(ctx.getImageData(0, 0, can.width, can.height).data);
					context.t += 100;
					timesaround += 1;
				} else {
					clearInterval(intervalId);
					resolve(frameArray);
				}
			}, 100);
		});
	});
}

function start() {
	return new Promise(function(resolve, reject) {
		getFrames().then(function(frames) {
			var gif = new GifEncoder(1920, 1080);
			var writer = new streams.WritableStream();
			gif.pipe(writer);
			gif.setDelay(100);
			gif.setRepeat(0);
			frames.forEach(function(frame) {
				gif.addFrame(frame);
			});
			gif.finish();
			resolve(writer.toBuffer());
		});
	});
}

module.exports = start;