Schema example, stock exchange data

[e3dio]

This is an example schema used by website ticker-trends.com for stock exchange data, reducing the data size from 210kB of JSON to 15kB binary

https://gist.github.com/e3dio/53018073c685b6c90125eae0a6b3fdb1

// https://github.com/e3dio/packBytes
import { bool, bits, string, array, PackBytes } from './packbytes.mjs';
import { deflateSync } from 'node:zlib';

const tickerNames = await fetch('https://ticker-trends.com/data.json').then(r => r.json()).then(data => data[Object.keys(data)[0]].map(t => t.ticker.split(':')[1])); 

const schema = {
	time: bits(32),
	tickers: array({
		exchange: string([ 'KRAKEN', 'NASDAQ', 'NYSE', 'OMXSTO', 'CBOE', 'AMEX', 'TVC', 'FX' ]),
		ticker: string(tickerNames), 
		since: bits(13), // range: 0 to 8192 days
		bullish: bool, 
		tradedCAGR: bits(12), // range: -200.0% to 200.0%
		CAGR: bits(12), // range: -200.0% to 200.0%
		age: bits(9), // range: 0.0 to 51.2 years
		prevAlert: bits(13), // range: 0 to 8192 days
	}),
};

const { encode, decode } = PackBytes(schema);

const data = await fetch('https://ticker-trends.com/data.json').then(r => r.json());
const encoded = encode(prepare(data));
const zipped = deflateSync(encoded);
const decoded = restore(decode(encoded));

console.log('encoded', encoded.byteLength);
console.log('zipped', zipped.byteLength);
console.log('decoded', decoded.tickers[0]);

function prepare(data) {
	const time = Object.keys(data)[0];
	const tickers = data[time];
	tickers.forEach(t => {
		const [ exchange, ticker ] = t.ticker.split(':');
		t.ticker = ticker;
		t.exchange = exchange;
		t.age *= 10;
		t.CAGR = (t.CAGR + 200) * 10;
		t.tradedCAGR = (t.tradedCAGR + 200) * 10;
	});
	return { time, tickers };
}

function restore(data) {
	data.tickers.forEach(t => {
		t.age /= 10;
		t.CAGR = t.CAGR / 10 - 200;
		t.tradedCAGR = t.tradedCAGR / 10 - 200;
	});
	return data;
}