Bid share within a band

// The bid's share of resting size within a band around the mid.
indicator('Bid share within a band');

// The book the page shows reaches about 0.06% on BTC at its default 20 levels; show more levels for a wider band.
const band = input.float('Band (%)', 0.05, { min: 0.01, max: 10, step: 0.01 });

const chart = bars();
const book = depth({ bandsPct: [band] });
const share = plot.line('Bid share', { range: { min: 0, max: 1 } });
plot.level('Even', 0.5, { style: 'dashed' });

chart.onBar(() => {
  if (!book.available) return;
  const bid = book.bid(band);
  const ask = book.ask(band);
  share.set(bid + ask > 0 ? bid / (bid + ask) : na);
});